Science.gov

Sample records for iron garnets

  1. Unconventional Superfluidity in Yttrium Iron Garnet Films

    NASA Astrophysics Data System (ADS)

    Sun, Chen; Nattermann, Thomas; Pokrovsky, Valery L.

    2016-06-01

    We argue that the magnon condensate in yttrium iron garnet may display experimentally observable superfluidity at room temperature despite the 100 times dominance of the normal density over superfluid ones. The superfluidity has a more complicated nature than in known superfluids since the U(1) symmetry of the global phase shift is violated by the dipolar interaction leading to the exchange of spin moment between the condensate and the crystal lattice. It produces periodic inhomogeneity in the stationary superfluid flow. We discuss the manner of observation and possible applications of magnon superfluidity. It may strongly enhance the spin-torque effects and reduce the energy consumption of the magnonic devices.

  2. Unconventional Superfluidity in Yttrium Iron Garnet Films.

    PubMed

    Sun, Chen; Nattermann, Thomas; Pokrovsky, Valery L

    2016-06-24

    We argue that the magnon condensate in yttrium iron garnet may display experimentally observable superfluidity at room temperature despite the 100 times dominance of the normal density over superfluid ones. The superfluidity has a more complicated nature than in known superfluids since the U(1) symmetry of the global phase shift is violated by the dipolar interaction leading to the exchange of spin moment between the condensate and the crystal lattice. It produces periodic inhomogeneity in the stationary superfluid flow. We discuss the manner of observation and possible applications of magnon superfluidity. It may strongly enhance the spin-torque effects and reduce the energy consumption of the magnonic devices. PMID:27391750

  3. Thermochromism in yttrium iron garnet compounds.

    PubMed

    Serier-Brault, Hélène; Thibault, Lucile; Legrain, Magalie; Deniard, Philippe; Rocquefelte, Xavier; Leone, Philippe; Perillon, Jean-Luc; Le Bris, Stéphanie; Waku, Jean; Jobic, Stéphane

    2014-12-01

    Polycrystalline yttrium iron garnet (Y3Fe5O12, hereafter labeled YIG) has been synthesized by solid-state reaction, characterized by X-ray diffraction, Mössbauer spectroscopy, and UV-vis-NIR diffuse reflectance spectroscopy, and its optical properties from room temperature (RT) to 300 °C are discussed. Namely, its greenish color at RT is assigned to an O(2-) → Fe(3+) ligand-to-metal charge transfer at 2.57 eV coupled with d-d transitions peaking at 1.35 and 2.04 eV. When the temperature is raised, YIG displays a marked thermochromic effect; i.e., the color changes continuously from greenish to brownish, which offers opportunities for potential application as a temperature indicator for everyday uses. The origin of the observed thermochromism is assigned to a gradual red shift of the ligand-to-metal charge transfer with temperature while the positioning in energy of the d-d transitions is almost unaltered. Attempts to achieve more saturated colors via doping (e.g., Al(3+), Ga(3+), Mn(3+), ...) remained unsuccessful except for chromium. Indeed, Y3Fe5O12:Cr samples exhibit at RT the same color than the undoped garnet at 200 °C. The introduction of Cr(3+) ions strongly impacts the color of the Y3Fe5O12 parent either by an inductive effect or, more probably, by a direct effect on the electronic structure of the undoped material with formation of a midgap state.

  4. Combinatorial pulsed laser deposition of doped yttrium iron garnet films on yttrium aluminium garnet

    SciTech Connect

    Sposito, A. Eason, R. W.; Gregory, S. A.; Groot, P. A. J. de

    2014-02-07

    We investigate the crystalline growth of yttrium iron garnet (YIG) films doped with bismuth (Bi) and cerium (Ce) by combinatorial pulsed laser deposition, co-ablating a YIG target and either a Bi{sub 2}O{sub 3} or a CeO{sub 2} target, for applications in microwave and optical communications. Substrate temperature is critical for crystalline growth of YIG with simultaneous inclusion of Bi in the garnet lattice, whereas Ce is not incorporated in the garnet structure, but forms a separate CeO{sub 2} phase.

  5. Electromagnetic excitation of ultrasonic oscillations by yttrium iron garnet films on gallium gadolinium garnet substrates

    NASA Astrophysics Data System (ADS)

    Sarnatskii, V. M.; Mavlonazarov, I. O.; Lutsev, L. V.

    2014-07-01

    We have studied the phenomenon of contactless excitation of ultrasonic oscillations by thin yttrium iron garnet (YIG) films on gallium gadolinium garnet (GGG) substrates upon application of the superposition of a constant magnetic bias field and alternating magnetic field. Dimensional resonance effects that cannot be explained in the framework of existing theoretical notions have been discovered, in particular, in dependences of the amplitude of excited longitudinal oscillations on the YIG film thickness, frequency of ultrasound, and degree of homogeneity and strength of the magnetic bias field. It is suggested that the observed phenomenon is caused by resonant participation of the intrinsic oscillations of domain walls in the excitation of ultrasound.

  6. Magnetic anisotropies in ultrathin bismuth iron garnet films

    NASA Astrophysics Data System (ADS)

    Popova, Elena; Franco Galeano, Andres Felipe; Deb, Marwan; Warot-Fonrose, Bénédicte; Kachkachi, Hamid; Gendron, François; Ott, Frédéric; Berini, Bruno; Keller, Niels

    2013-06-01

    Ultrathin bismuth iron garnet Bi3Fe5O12 films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi3Fe5O12 films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization.

  7. Structure and thermodynamics of uranium-containing iron garnets

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; Engelhard, Mark H.; Lanzirotti, Antonio; Newville, Matthew; Ilton, Eugene S.; Sutton, Stephen R.; Xu, Hongwu

    2016-09-01

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2-xFe3O12 (x = 0.5-0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation states and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+. U substitution had a significant effect on local environments, the extent of U substitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were first time determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2-xFe3O12 as viable waste form phases for U and other actinides.

  8. Structure and thermodynamics of uranium-containing iron garnets

    DOE PAGESBeta

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; Engelhard, Mark H.; Lanzirotti, Antonio; Newville, Matthew; Ilton, Eugene S.; Sutton, Stephen R.; Xu, Hongwu

    2016-06-14

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2–xFe3O12 (x = 0.5–0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation statesmore » and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+. U substitution had a significant effect on local environments, the extent of U substitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were first time determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Furthermore, our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2–xFe3O12 as viable waste form phases for U and other actinides.« less

  9. FMR doublet in two-layer iron garnet films

    NASA Astrophysics Data System (ADS)

    Grishin, A. M.; Dellalov, V. S.; Nikolayev, E. I.; Shkar, V. F.; Yampolskii, S. V.

    1994-11-01

    Multilayer epitaxial iron garnet films have been investigated very intensively in the recent past. The dipole and exchange couplings of spins lying in different layers results in the existence of new types of oscillations in these structures and give rise to the characteristic resonance properties of them. Resonance microwave absorption in two-layer iron garnet films, of which one layer is in a saturated state and the other is in a demagnetized state, is investigated. The films were prepared by the epitaxial method on a gallium-gadolinium substrate with (111) orientation. The first layer on the substrate was the doped iron yttrium garnet with the easy plane magnetization. The second easy axis layer was the bubble domain layer. The resonant field of the first layer FMR line versus the external in-plane magnetic field was investigated. It was determined that the FMR doublet merge into a single line and the resonance intensity is doubled if the magnetic field is oriented in the zone axes (110) directions. It was established that the FMR line splitting is conditioned by the layer exchange interaction, the cubic anisotropy, and the domain dissipative field. The magnetic and anisotropy of the resonance fields agrees with the model of an isolated layer magnetized by domains of the neighboring layer.

  10. Features of optical anisotropy of europium and terbium iron garnets

    NASA Astrophysics Data System (ADS)

    Tsidaeva, N. I.; Abaeva, V. V.; Enaldieva, E. V.; Magkoev, T. T.; Ramonova, A. G.; Butkhuzi, T. G.; Kesaev, V. I.; Turiev, A. M.

    2013-08-01

    The results of investigation of magnetic linear birefringence (MLB) and magnetic linear dichroism of Tb3Fe5O12 (TbIG) iron garnet (IG) on 7F-7F and 7F-7F optical transitions and Eu3Fe5O12 (EuIG) iron garnet on 7F-7F at the variation of the directions of the magnetization vector I relative to the electric vector E linearly polarized light that propagates through single crystal iron garnets are presented. The measurements were made on Tb3Fe5О12 and Eu3Fe5O12 single-crystal samples in the form of plates 100 μm thick cut in the (1 1 0) and (1 0 0) plane a temperature of T = 82 K and in a magnetic field H = 22 kOe. The absorption spectra of the linearly polarized light were studied. It is shown that MLB and dichroism in the region of the 7F-7F and 7F-7F absorption bands reach values 10-3. The nonreciprocity of MLB spectra and dichroism with the change of the relative orientation of the magnetization vector I and the light wave vector is first experimentally discovered. This effect may be used as a base for the design of the different transducers such as a magnetooptical optical channels commutator.

  11. Ferroelectricity of domain walls in rare earth iron garnet films.

    PubMed

    Popov, A I; Zvezdin, K A; Gareeva, Z V; Mazhitova, F A; Vakhitov, R M; Yumaguzin, A R; Zvezdin, A K

    2016-11-16

    In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films. PMID:27620369

  12. Ferroelectricity of domain walls in rare earth iron garnet films

    NASA Astrophysics Data System (ADS)

    Popov, A. I.; Zvezdin, K. A.; Gareeva, Z. V.; Mazhitova, F. A.; Vakhitov, R. M.; Yumaguzin, A. R.; Zvezdin, A. K.

    2016-11-01

    In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.

  13. Ferroelectricity of domain walls in rare earth iron garnet films.

    PubMed

    Popov, A I; Zvezdin, K A; Gareeva, Z V; Mazhitova, F A; Vakhitov, R M; Yumaguzin, A R; Zvezdin, A K

    2016-11-16

    In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.

  14. Sublattice Magnetic Relaxation in Rare Earth Iron Garnets

    SciTech Connect

    McCloy, John S.; Walsh, Brian

    2013-07-08

    The magnetic properties of rare earth garnets make them attractive materials for applications ranging from optical communications to magnetic refrigeration. The purpose of this research was to determine the AC magnetic properties of several rare earth garnets, in order to ascertain the contributions of various sublattices. Gd3Fe5O¬12, Gd3Ga5O12, Tb3Fe5O12, Tb3Ga5O12, and Y3Fe5O12 were synthesized by a solid state reaction of their oxides and verified by x-ray diffraction. Frequency-dependent AC susceptibility and DC magnetization were measured versus temperature (10 – 340 K). Field cooling had little effect on AC susceptibility, but large effect on DC magnetization, increasing magnetization at the lowest temperature and shifting the compensation point to lower temperatures. Data suggest that interaction of the two iron lattices results in the two frequency dependent magnetic relaxations in the iron garnets, which were fit using the Vogel-Fulcher and Arrhenius laws.

  15. Vacuum annealed cerium-substituted yttrium iron garnet films on non-garnet substrates for integrated optical circuits

    SciTech Connect

    Goto, Taichi; Ross, C. A.; Eto, Yu; Kobayashi, Keiichi; Haga, Yoji; Inoue, Mitsuteru

    2013-05-07

    Polycrystalline cerium-substituted yttrium iron garnet (CeYIG) showing large Faraday rotation (FR) in the near-IR region was grown on non-garnet (synthetic fused silica, Si, and Si-on-insulator) substrates by sputtering followed by thermal annealing in vacuum. The FR of the films is comparable to the single crystal value. Structural characterization, magnetic properties, refractive index, extinction coefficient, surface topography, and FR vs. wavelength were measured and the magnetooptical figure of merit was compared with that of CeYIG films on garnet substrates.

  16. Enhanced spin pumping at yttrium iron garnet/Au interfaces

    SciTech Connect

    Burrowes, C.; Heinrich, B.; Kardasz, B.; Montoya, E. A.; Girt, E.; Sun Yiyan; Song, Young-Yeal; Wu Mingzhong

    2012-02-27

    Spin injection across the ferrimagnetic insulator yttrium iron garnet (YIG)/normal metal Au interface was studied using ferromagnetic resonance. The spin mixing conductance was determined by comparing the Gilbert damping parameter {alpha} in YIG/Au and YIG/Au/Fe heterostructures. The main purpose of this study was to correlate the spin pumping efficiency with chemical modifications of the YIG film surface using in situ etching and deposition techniques. By means of Ar{sup +} ion beam etching, one is able to increase the spin mixing conductance at the YIG/Au interface by a factor of 5 compared to the untreated YIG/Au interface.

  17. Synchronization of chaos in circular yttrium iron garnet films

    SciTech Connect

    Peterman, D.W.; Ye, M.; Wigen, P.E.

    1996-04-01

    The results of the synchronization of two ferromagnetic resonance signals are presented. In the experiment, a thin yttrium iron garnet (YIG) film was placed in the perpendicular resonance configuration and the bias field, rf power, and frequency were chosen so that the rf absorption of the YIG sample was chaotic. A segment of this chaotic signal was stored into memory. The goal was to induce the sample to synchronize to its prerecorded output through a perturbation applied to a system parameter. The results of these synchronization experiments were predicted by a numerical model. {copyright} {ital 1996 American Institute of Physics.}

  18. Current sensing using bismuth rare-earth iron garnet films

    NASA Astrophysics Data System (ADS)

    Ko, Michael; Garmire, Elsa

    1995-04-01

    Ferrimagnetic iron garnet films are investigated as current-sensing elements. The Faraday effect within the films permits measurement of the magnetic field or current by a simple polarimetric technique. Polarized diffraction patterns from the films have been observed that arise from the presence of magnetic domains in the films. A physical model for the diffraction is discussed, and results from a mathematical analysis are in good agreement with the experimental observations. A method of current sensing that uses this polarized diffraction is demonstrated.

  19. Structural and magnetic properties of yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrites prepared by microemulsion method

    NASA Astrophysics Data System (ADS)

    Akhtar, Majid Niaz; Bakar Sulong, Abu; Khan, Muhammad Azhar; Ahmad, Mukhtar; Murtaza, Ghulam; Raza, M. R.; Raza, R.; Saleem, M.; Kashif, M.

    2016-03-01

    Yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrite samples were synthesized by microemulsion method. The effect of sintering was examined by heating the samples at 900, 1000, and 1100 °C. The YIG and YAIG samples were then characterized using X-ray diffraction and field-emission scanning electron microscopy. Static and dynamic magnetic properties were measured by evaluating initial permeability, Q factor, and vibrating sample magnetometry properties of YIG and YAIG samples. YIG samples sintered at 1100 °C showed higher initial permeability and Q factor compared with YAIG samples. However, hysteresis loops also showed variations in the saturation magnetization, remanence, and coercivity of YIG and YAIG samples sintered at 900, 1000, and 1100 °C. The observed magnetic parameter such as saturation magnetization, coercivity and initial permeability are strongly affected by increasing temperature. The saturation magnetization and coercivity of YIG and YAIG nanoferrites were found in the range 11.56-19.92 emu/g and 7.30-87.70 Oe respectively. Furthermore, the decreasing trends in the static and magnetic properties of YAIG samples may be due to the introduction of Al ions in the YIG crystal lattice. Thus, YIG and YAIG sintered at 1100 °C can be used for wide-ranging frequency applications.

  20. RBS and XRD Characterization of Yttrium Iron Garnet Thin Films

    NASA Astrophysics Data System (ADS)

    Mansour, M.; Roumie, M.; Abdel Samad, B.; Basma, H.; Korek, M.

    2015-03-01

    Magnetic materials such as yttrium iron garnet (YIG or Y3Fe5O12) present a great importance for their magneto-optic properties. They are potential materials used for applications in the domain of optical telecommunications for example. In this work, we have investigated YIG thin films deposited on substrates of quartz and GGG (gadolinium gallium garnet or Gd3Ga5O12). Using Rutherford backscattering spectrometry (RBS) we characterized the performed layers (thickness and stoichiometry) in order to correlate the films preparation conditions with the quality of the final material. We determined the optimal energy of the alpha particles beam used for RBS measurements and we fitted the experimental spectra using the SIMNRA simulated code. Our RBS results showed that the films have a stoichiometry close to that of the starting material. In addition, we found that the film thickness is proportional to deposition time but inversely proportional to the substrate temperature. Moreover, using x-ray diffraction (XRD) we determined the annealing effect on the structure of the profile of our thin films.

  1. Ferromagnetic resonance of sputtered yttrium iron garnet nanometer films

    SciTech Connect

    Liu, Tao; Chang, Houchen; Sun, Yiyan; Kabatek, Michael; Wu, Mingzhong; Vlaminck, Vincent; Hoffmann, Axel; Deng, Longjiang

    2014-05-07

    Growth of nm-thick yttrium iron garnet (YIG) films by sputtering and ferromagnetic resonance (FMR) properties in the films were studied. The FMR linewidth of the YIG film decreased as the film thickness was increased from several nanometers to about 100 nm. For films with very smooth surfaces, the linewidth increased linearly with frequency. In contrast, for films with big grains on the surface, the linewidth-frequency response was strongly nonlinear. Films in the 7–26 nm thickness range showed a surface roughness between 0.1 nm and 0.4 nm, a 9.48-GHz FMR linewidth in the 6–10 Oe range, and a damping constant of about 0.001.

  2. Phase Diagram for Magnon Condensate in Yttrium Iron Garnet Film

    PubMed Central

    Li, Fuxiang; Saslow, Wayne M.; Pokrovsky, Valery L.

    2013-01-01

    Recently, magnons, which are quasiparticles describing the collective motion of spins, were found to undergo Bose-Einstein condensation (BEC) at room temperature in films of Yttrium Iron Garnet (YIG). Unlike other quasiparticle BEC systems, this system has a spectrum with two degenerate minima, which makes it possible for the system to have two condensates in momentum space. Recent Brillouin Light Scattering studies for a microwave-pumped YIG film of thickness d = 5 μm and field H = 1 kOe find a low-contrast interference pattern at the characteristic wavevector Q of the magnon energy minimum. In this report, we show that this modulation pattern can be quantitatively explained as due to unequal but coherent Bose-Einstein condensation of magnons into the two energy minima. Our theory predicts a transition from a high-contrast symmetric state to a low-contrast non-symmetric state on varying the d and H, and a new type of collective oscillation. PMID:23455849

  3. Observation of a cubical-like microstructure of strontium iron garnet and yttrium iron garnet prepared via sol-gel technique.

    PubMed

    Nasir, Nadeem; Yahya, Noorhana; Kashif, Muhammad; Daud, Hanita; Akhtar, Majid Niaz; Zaid, Hasnah Mohd; Shafie, Afza; Teng, Lee Chaw

    2011-03-01

    This is our initial response towards preparation of nano-inductors garnet for high operating frequencies strontium iron garnet (Sr3Fe5O12) denoted as SrIG and yttrium iron garnet (Y3Fe5O12) denoted as YIG. The garnet nano crystals were prepared by novel sol-gel technique. The phase and crystal structure of the prepared samples were identified by using X-ray diffraction analysis. SEM images were done to reveal the surface morphology of the samples. Raman spectra was taken for yttrium iron garnet (Y3Fe5O12). The magnetic properties of the samples namely initial permeability (micro), relative loss factor (RLF) and quality factor (Q-Factor) were done by using LCR meter. From the XRD profile, both of the Y3Fe5O12 and Sr3Fe5O12 samples showed single phase garnet and crystallization had completely occurred at 900 degrees C for the SrIG and 950 degrees C for the YIG samples. The YIG sample showed extremely low RLF value (0.0082) and high density 4.623 g/cm3. Interesting however is the high Q factor (20-60) shown by the Sr3Fe5O12 sample from 20-100 MHz. This high performance magnetic property is attributed to the homogenous and cubical-like microstructure. The YIG particles were used as magnetic feeder for EM transmitter. It was observed that YIG magnetic feeder with the EM transmitter gave 39% higher magnetic field than without YIG magnetic feeder.

  4. Longitudinal Spin Seebeck Effect in Bi-substituted Neodymium Iron Garnet on Gadolinium Gallium Garnet Substrate Prepared by MOD Method

    NASA Astrophysics Data System (ADS)

    Asada, H.; Kuwahara, A.; Sueyasu, K.; Ishibashi, T.; Liu, Q.; Lou, G.; Kishimoto, K.; Koyanagi, T.

    Bi-substituted Neodymium Iron Garnet (Nd3-xBixFe5O12, Bi:NIG) thin films with the Bi composition x=0-1.0 are prepared on both the (001) and (111) oriented gadolinium gallium garnet (GGG) substrates by a metal organic decomposition method. Crystalline qualities and magnetic properties of these films are examined by X-ray diffraction, atomic force microscopy and vibrating sample magnetometer. Longitudinal spin Seebeck effects (LSSEs) are investigated by means of the inverse spin Hall effect in a Pt film. The increase of LSSE voltage in Bi:NIG(x=0-1.0)/Pt bilayers on GGG(001) is observed with the increase of Bi composition. In the case of GGG(111), the LSSE voltage for Bi:NIG(x=1.0) is also larger than that for NIG.

  5. Magnetic and magnetodielectric properties of erbium iron garnet ceramic

    SciTech Connect

    Maignan, A.; Singh, K.; Simon, Ch.; Lebedev, O. I.; Martin, C.

    2013-01-21

    An Er{sub 3}Fe{sub 5}O{sub 12} ceramic has been sintered in oxygen atmosphere at 1400 Degree-Sign C for dielectric measurements. Its structural quality at room temperature has been checked by combining transmission electron microscopy and X-ray diffraction. It crystallizes in the cubic space group Ia3d with a = 12.3488(1). The dielectric permittivity ({epsilon} Prime ) and losses (tan {delta}) measurements as a function of temperature reveal the existence of two anomalies, a broad one between 110 K and 80 K, attributed to the Er{sup 3+} spin reorientation, and a second sharper feature at about 45 K associated to the appearance of irreversibility on the magnetic susceptibility curves. In contrast to the lack of magnetic field impact on {epsilon} Prime for the former anomaly, a complex magnetic field effect has been evidenced below 45 K. The isothermal {epsilon} Prime (H) curves show the existence of positive magnetodielectric effect, reaching a maximum of 0.14% at 3 T and 10 K. Its magnitude decreases as H is further increased. Interestingly, for the lowest H values, a linear regime in the {epsilon} Prime (H) curve is observed. From this experimental study, it is concluded that the {epsilon} Prime anomaly, starting above the compensation temperature T{sub c} (75 K) and driven by the internal magnetic field, is not sensitive to an applied external magnetic field. Thus, below 45 K, it is the magnetic structure which is responsible for the coupling between spin and charge in this iron garnet.

  6. Pulsed laser deposition and refractive index measurement of fully substituted bismuth iron garnet films

    NASA Astrophysics Data System (ADS)

    Tepper, T.; Ross, C. A.

    2003-08-01

    A systematic study of the pulsed-laser deposition of fully substituted bismuth iron garnet (BIG, or Bi 3Fe 5O 12) has been carried out. Garnet-structure BIG films grow epitaxially onto gallium gadolinium garnet substrates under deposition conditions that lead to a stoichiometric film. The variation of stoichiometry with deposition conditions is discussed. The refractive index, n, of BIG decreases from 2.819 at 633 nm to 2.584 at 1550 nm, with an imaginary part, k, less than 0.05.

  7. Semiconductor sensor for optically measuring polarization rotation of optical wavefronts using rare earth iron garnets

    DOEpatents

    Duncan, Paul G.

    2002-01-01

    Described are the design of a rare earth iron garnet sensor element, optical methods of interrogating the sensor element, methods of coupling the optical sensor element to a waveguide, and an optical and electrical processing system for monitoring the polarization rotation of a linearly polarized wavefront undergoing external modulation due to magnetic field or electrical current fluctuation. The sensor element uses the Faraday effect, an intrinsic property of certain rare-earth iron garnet materials, to rotate the polarization state of light in the presence of a magnetic field. The sensor element may be coated with a thin-film mirror to effectively double the optical path length, providing twice the sensitivity for a given field strength or temperature change. A semiconductor sensor system using a rare earth iron garnet sensor element is described.

  8. Electrically driven magnetization dynamics in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Jungfleisch, Matthias Benjamin

    Creation and manipulation of magnetization states by spin-orbital torques are important for novel spintronics applications. Magnetic insulators were mostly ignored for this particular purpose, despite their low Gilbert damping, which makes them outstanding materials for magnonic applications and investigation of nonlinear spin-wave phenomena. Here, we demonstrate the propagation of spin-wave modes in micro-structured yttrium iron garnet (Y3Fe5O12,YIG) stripes. Spin waves propagating along the long side of the stripe are detected by means of spatially-resolved Brillouin light scattering (BLS) microscopy. The propagation distance of spin waves is determined in the linear regime, where an exponential decay of 10 μm is observed. We also explored the possibility of driving magnetization dynamics with spin Hall effects (SHE) in bilayers of YIG/Pt microstructures. For this purpose we adopted a spin-transfer torque ferromagnetic resonance (ST-FMR) approach. Here a rf charge current is passed through the Pt layer, which generates a spin-transfer torque at the interface from an oscillating spin current via the SHE. This gives rise to a resonant excitation of the magnetization dynamics. In all metallic systems the magnetization dynamics is detected via the homodyne anisotropic magnetoresistance of the ferromagnetic layer. However, since there is no charge flowing through ferromagnetic insulators there is no anisotropic magnetoresistance. Instead, we show that for the case of YIG/Pt the spin Hall magnetoresistance can be used. Our measured voltage spectra can be well fitted to an analytical model evidencing that the ST-FMR concept can be extended to insulating systems. Furthermore, we employ spatially-resolved BLS spectroscopy to map the ST-FMR driven spin dynamics. We observe the formation of a strong, self-localized spin-wave intensity in the center of the sample. This spin-wave `bullet' is created due to nonlinear cross coupling of eigenmodes existing in the magnetic

  9. The nature of photoinduced changes in the magnetostriction of yttrium-iron garnet single crystals

    SciTech Connect

    Vorob'eva, N. V.

    2011-05-15

    A model of the occurrence of photoinduced changes in linear magnetostriction is proposed based on a complex experimental study of magnetostrictive strains in yttrium-iron garnets Y{sub 3}Fe{sub 5}O{sub 12} with low contents of different impurities. Analytical expressions for calculating the magnetostriction in yttrium-iron garnet single crystals with different types of doping are presented. The correlation of the photoinduced change in the magnetostriction with the crystallographic features of the samples is demonstrated. The changes in the magnetostriction constants are analyzed quantitatively for samples prepared in different ways.

  10. Temperature evolution of electromotive force from Pt on yttrium-iron-garnet under ferromagnetic resonance

    SciTech Connect

    Ohshima, Ryo; Emoto, Hiroyuki; Shinjo, Teruya; Ando, Yuichiro; Shiraishi, Masashi

    2015-05-07

    Temperature evolution of electromotive force from Pt due to the inverse spin Hall effect is studied. Pure spin current is injected from yttrium-iron-garnet by using spin pumping technique. The electromotive force from the Pt monotonically decreases with decreasing temperature, and it is showed that there is a deviation between the measured and the calculated electromotive forces.

  11. Epitaxial Growth of Atomically Flat Yttrium Iron Garnet Thin Films on Gadolinium Gallium Garnet by Pulse Laser Deposition

    NASA Astrophysics Data System (ADS)

    Lin, Tao; Tang, Chi; Shi, Jing

    2013-03-01

    Yttrium iron garnet (YIG) is a ferrimagnetic insulator which is useful for magneto-optical, microwave, and more recently spintronic devices. Pulsed laser deposition (PLD) has emerged as a preferred technique to deposit complex oxide thin films, heterostructures, and superlattices with high quality. Deposition of YIG films using PLD has been reported by several groups. The layer-by-layer growth mode has been achieved with a high laser repetition rate. No details about surface morphology were discussed. Here we report our approach to grow YIG films with thickness ranging from 10 to 100 nm on (110)- and (111)-oriented gadolinium gallium garnet (GGG) substrates. In both orientations, we have successfully grown epitaxial YIG thin films confirmed by the patterns of the reflection high-energy electron diffraction. The magnetic properties are measured by a vibrating sample magnetometer. The in-plane easy-axis coercivity is less than 1 Oe, while the perpendicular saturation field is ~ 2000 Oe. For both orientations, the atomic force microscopy images show that the YIG surface is extremely flat with roughness ~ 0.6Å. Flat terraces are found with the atomic step height in films with both orientations. This work paves the way to engineering anisotropy of the thin films for YIG-based magnetic devices. This work was supported in part by DMEA and DOE.

  12. Bonding mechanism of a yttrium iron garnet film on Si without the use of an intermediate layer

    SciTech Connect

    Pantzas, Konstantinos; Patriarche, Gilles; Talneau, Anne; Youssef, Jamal Ben

    2014-10-06

    Direct bonding of yttrium iron garnet (YIG) on silicon without the use of an intermediate bonding layer is demonstrated and characterized using scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy. During the bonding experiment, the garnet is reduced in the presence of oxide-free silicon. As a result, a 5 nm thick SiO{sub 2}/amorphous-YIG bilayer is formed and welds the garnet to silicon.

  13. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  14. Dynamic performance of magneto-optical Bi-substituted rare-earth iron garnet

    NASA Astrophysics Data System (ADS)

    Li, Shiguang; Yang, Changxi; Zhang, Enyao; Jin, Guofan

    2005-01-01

    The dynamic performances of magneto-optical Bi-substituted rare-earth iron garnet (BIG) under different external magnetic fields and at different frequencies are experimentally studied. The measurement data indicate that the Faraday rotation angle is almost proportional to the external magnetic field when the garnet is far less saturated, while there is good switch performance when it is saturated. The higher the working frequency is, the larger the saturation magnetic field and the phase delay of Faraday angle relative to the field. The saturation fields and the phase delays at different frequencies are measured. The dynamic performance of the BIG determines the performance of BIG-based optical devices. To get the better performance of such devices, the garnets with small dampness and large stiffness should be chosen elaborately.

  15. Group theory analysis of the rhombohedral magnetic structures in rare earth iron garnets revisited

    NASA Astrophysics Data System (ADS)

    Lahoubi, M.

    2015-01-01

    The representation analysis of Bertaut is used to enumerate all possible magnetic structures in rare earth iron garnets (RE3Fe5O12) for the RE and Fe ions on the 6e, 6e' and 12f, 2b, 6d Wyckoff positions respectively in the highest rhombohedral subgroup Rbar 3c of the cubic space group Iabar 3d. The basis vectors of the one-dimensional irreducible representation A2g lead to noncollinear magnetic structures of the RE moments which produce a better description than those based on the models of Wolf et al. Some results of the "double umbrella" structure found in our recent neutron powder diffraction studies of terbium iron garnet are reported.

  16. Generalized stochastic Landau-Lifshitz-Gilbert equation for yttrium-iron garnet films

    NASA Astrophysics Data System (ADS)

    Rückriegel, Andreas; Kopietz, Peter

    2015-03-01

    We derive a generalization of the well-known stochastic Landau-Lifshitz-Gilbert equation starting from a microscopic Heisenberg model coupled to the lattice degrees of freedom. By integrating out the phonons we obtain a non-Markovian, stochastic equation of motion for the spin degrees of freedom satisfying a Fluctuation-Dissipation theorem. We apply our theory to study the parametric pumping and thermalization of spin excitations in thin yttrium-iron garnet films.

  17. Spin wave localization in one-dimensional magnonic microcavity comprising yttrium iron garnet

    SciTech Connect

    Kanazawa, Naoki; Goto, Taichi Inoue, Mitsuteru

    2014-08-28

    We demonstrate the localization of magnetostatic surface waves, i.e., spin waves, in a one-dimensional magnonic microcavity substantialized with periodical conductivity modulation. The narrow localized state is observed inside band gaps and is responsible for a sharp transmission peak. The experimental results strongly agree with the theoretical prediction made with the shape magnetic anisotropy of the propagating medium composed of yttrium iron garnet taken into account.

  18. Observation of spin rectification in Pt/yttrium iron garnet bilayer

    SciTech Connect

    Rao, Jinwei; Fan, Xiaolong Zhou, Hengan; Zhao, Xiaobing; Zhao, Jing; Zhang, Fengzhen; Xue, Desheng; Ma, Li; Zhou, Shiming

    2015-05-07

    We used the ferromagnetic resonance (FMR) to study the dc voltage generation in Pt 20 nm layer deposited on yttrium iron garnet. Although the main contribution to the FMR voltage comes from the inverse spin Hall effect associated with spin pumping, the spin rectification would also contribute the resonance signal via the “new” magnetoresistance effect in Pt layer. Based on a symmetry consideration, we can separate those two effects through angular dependent resonance amplitude.

  19. Properties of epitaxial (210) iron garnet films exhibiting the magnetoelectric effect

    SciTech Connect

    Arzamastseva, G. V.; Balbashov, A. M.; Lisovskii, F. V. Mansvetova, E. G.; Temiryazev, A. G.; Temiryazeva, M. P.

    2015-04-15

    The properties of epitaxial magnetic (LuBi){sub 3}(FeGa){sub 5}O{sub 12} iron garnet films grown on (210) substrates, which exhibit the magnetoelectric effect, are experimentally studied. The induced anisotropy and the behavior of the domain structure in the films are investigated in uniform and nonuniform external fields. The existing hypotheses about the nature of the magnetoelectric coupling in such films are critically analyzed.

  20. Thickness- and temperature-dependent magnetodynamic properties of yttrium iron garnet thin films

    SciTech Connect

    Haidar, M. Ranjbar, M.; Balinsky, M.; Dumas, R. K.; Khartsev, S.; Åkerman, J.

    2015-05-07

    The magnetodynamical properties of nanometer-thick yttrium iron garnet films are studied using ferromagnetic resonance as a function of temperature. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition. First, we found that the damping coefficient increases as the temperature increases for different film thicknesses. Second, we found two different dependencies of the damping on film thickness: at room temperature, the damping coefficient increases as the film thickness decreases, while at T = 8 K, we find the damping to depend only weakly on the thickness. We attribute this behavior to an enhancement of the relaxation of the magnetization by impurities or defects at the surfaces.

  1. Exquisite growth control and magnetic properties of yttrium iron garnet thin films

    NASA Astrophysics Data System (ADS)

    Tang, Chi; Aldosary, Mohammed; Jiang, Zilong; Chang, Houchen; Madon, Benjamin; Chan, Kyle; Wu, Mingzhong; Garay, Javier E.; Shi, Jing

    2016-03-01

    A layer-by-layer epitaxial growth up to 227 atomic layers of ferrimagnetic insulator yttrium iron garnet (YIG) thin films is achieved on (110)-oriented gadolinium gallium garnet substrates using pulsed laser deposition. Atomically smooth terraces are observed on YIG films up to 100 nm in thickness. The root-mean-square roughness is as low as 0.067 nm. The easy-axis lies in the film plane, indicating the dominance of shape anisotropy. For (110)-YIG films, there is well-defined two-fold in-plane anisotropy, with the easiest axis directed along [001]. The Gilbert damping constant is determined to be 1.0 × 10-4 for 100 nm thick films.

  2. Platinum/yttrium iron garnet inverted structures for spin current transport

    NASA Astrophysics Data System (ADS)

    Aldosary, Mohammed; Li, Junxue; Tang, Chi; Xu, Yadong; Zheng, Jian-Guo; Bozhilov, Krassimir N.; Shi, Jing

    2016-06-01

    30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the presence of the intermediate Pt film. The YIG surface shows atomic steps with the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear in-plane uniaxial magnetic anisotropy with a well-defined easy axis along <001> and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz, similar to YIG epitaxially grown on GGG. Both spin Hall magnetoresistance and longitudinal spin Seebeck effects in the inverted bilayers indicate excellent Pt/YIG interface quality.

  3. Hybrid yttrium iron garnet-ferromagnet structures for spin-wave devices

    SciTech Connect

    Papp, A.; Porod, W. Csaba, G.

    2015-05-07

    We study coupled ferromagnetic layers, which could facilitate low loss, sub 100 nm wavelength spin-wave propagation and manipulation. One of the layers is a low-loss garnet film (such as yttrium iron garnet (YIG)) that enables long-distance, coherent spin-wave propagation. The other layer is made of metal-based (Permalloy, Co, and CoFe) magnetoelectronic structures that can be used to generate, manipulate, and detect the spin waves. Using micromagnetic simulations, we analyze the interactions between the spin waves in the YIG and the metallic nanomagnet structures and demonstrate the components of a scalable spin-wave based signal processing device. We argue that such hybrid-metallic ferromagnet structures can be the basis of potentially high-performance, ultra low-power computing devices.

  4. A shock-induced phase change in iron-silicate garnet.

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.; Graham, E. K.

    1972-01-01

    Hugoniot measurements on iron-silicate garnet demonstrate that above a shock pressure of about 205 kbar transition to a high-pressure phase(s), having an apparent zero-pressure density and bulk modulus of 4.44 g/cu cm and 3.3 Mbar, occurs. Crystal chemical systematics and Debye-Scherrer X-ray patterns of a recovered phase(s), which may be the shock-induced high-pressure form, suggest possible formation of a phase with a density of 4.48/cu cm. Occurrence of such a polymorph of garnet in the mantle would give rise to an increase in density and seismic velocity below 600 km in the earth.

  5. Large magneto-optic enhancement in ultra-thin liquid-phase-epitaxy iron garnet films

    SciTech Connect

    Levy, Miguel; Chakravarty, A.; Huang, H.-C.; Osgood, R. M.

    2015-07-06

    Significant departures from bulk-like magneto-optic behavior are found in ultra-thin bismuth-substituted iron-garnet films grown by liquid-phase-epitaxy. These changes are due, at least in part, to geometrical factors and not to departures from bulk-composition in the transient layer at the film-substrate interface. A monotonic increase in specific Faraday rotation with reduced thickness is the signature feature of the observed phenomena. These are traced to size-dependent modifications in the diamagnetic transition processes responsible for the Faraday rotation. These processes correspond to the electronic transitions from singlet {sup 6}S ground states to spin-orbit split excited states of the Fe{sup 3+} ions in the garnet. A measurable reduction in the corresponding ferrimagnetic resonance linewidths is found, thus pointing to an increase in electronic relaxation times and longer lived excitations at reduced thicknesses. These changes together with a shift in vibrational frequency of the Bi-O bonds in the garnet at reduced thicknesses result in greatly enhanced magneto-optical performance. These studies were conducted on epitaxial monocrystalline Bi{sub 0.8}Gd{sub 0.2}Lu{sub 2}Fe{sub 5}O{sub 12} films.

  6. Faraday effect of bismuth iron garnet thin film prepared by mist CVD method

    NASA Astrophysics Data System (ADS)

    Yao, Situ; Sato, Takafumi; Kaneko, Kentaro; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

    2015-06-01

    Metastable bismuth iron garnet (BIG, an abbreviation of Bi3Fe5O12), one kind of garnet-type ferrites, is known to manifest very large Faraday rotation as well as low optical absorption in the visible to infrared region. We report on successful synthesis of thin film composed of single-phase BIG epitaxially grown on single-crystalline gadolinium gallium garnet (Gd3Ga5O12, GGG) substrate by using mist chemical vapor deposition (CVD) method, which is an emerging technique for preparation of thin films. The crystal structure, surface morphology, and magnetic, optical and magneto-optical properties of the resultant thin films have been explored. The BIG thin film has a relatively flat surface free from roughness compared to those prepared by other vapor deposition methods. Saturation magnetization is about 1620 G at room temperature, which is close to that expected from the ideal magnetic structure of BIG. The maximum value of Faraday rotation angle reaches 54.3 deg/µm at a wavelength of 424 nm. This value is rather large when compared with those reported for BIG thin films prepared by other techniques. The wavelength dependence of Faraday rotation angle is analyzed well in terms of the crystal electric field (CEF) level schema. Our result suggests that the mist CVD method is a simple and effective technique to synthesize BIG thin film with excellent magneto-optical properties.

  7. Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet/Pt bilayers

    SciTech Connect

    Pirro, P.; Chumak, A. V.; Lägel, B.; Leven, B.; Hillebrands, B.; Brächer, T.; Dubs, C.; Surzhenko, O.; Görnert, P.

    2014-01-06

    We present an experimental study of spin-wave excitation and propagation in microstructured waveguides consisting of a 100 nm thick yttrium iron garnet/platinum (Pt) bilayer. The life time of the spin waves is found to be more than an order of magnitude higher than in comparably sized metallic structures, despite the fact that the Pt capping enhances the Gilbert damping. Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the spin-wave mode structure for different excitation frequencies. An exponential spin-wave amplitude decay length of 31 μm is observed which is a significant step towards low damping, insulator based micro-magnonics.

  8. Unidirectional anisotropy in the spin pumping voltage in yttrium iron garnet/platinum bilayers

    SciTech Connect

    Vilela-Leao, L. H.; Salvador, C.; Azevedo, A.; Rezende, S. M.

    2011-09-05

    Detailed measurements of the dc voltage generated in a thin Pt layer deposited on films of yttrium iron garnet (YIG) have been carried out to study the spin pumping effect produced by magnetostatic (MS) modes excited by a microwave field. In relatively thick YIG films the modes are far apart so that one can identify clearly the spin pumping voltage in V{sub SP} produced by each MS mode. We have discovered that when the sputter deposition of the thin Pt layer is made on the YIG film magnetized by a static magnetic field, V{sub SP} exhibits a strong unidirectional anisotropy.

  9. Growth and ferromagnetic resonance of yttrium iron garnet thin films on metals

    NASA Astrophysics Data System (ADS)

    Sun, Yiyan; Song, Young-Yeal; Wu, Mingzhong

    2012-08-01

    High-quality yttrium iron garnet (YIG) thin films were grown on a sandwich structure that consisted of a thick Cu layer and two thin cladding layers. The cladding layers were high entropy alloy nitrides (HEAN) and served as barriers to prevent Cu diffusion and oxidation during the YIG deposition. The Cu and HEAN layers were deposited by sputtering. The YIG films were grown by pulsed laser deposition. The YIG films had a thickness of several hundreds of nanometers, a surface roughness of several nanometers, and (111) orientation. The films showed a peak-to-peak ferromagnetic resonance linewidth of 1.1 Oe at 9.45 GHz.

  10. Ultrafast optical control of magnetization dynamics in polycrystalline bismuth doped iron garnet thin films

    SciTech Connect

    Deb, Marwan Vomir, Mircea; Rehspringer, Jean-Luc; Bigot, Jean-Yves

    2015-12-21

    Controlling the magnetization dynamics on the femtosecond timescale is of fundamental importance for integrated opto-spintronic devices. For industrial perspectives, it requires to develop simple growth techniques for obtaining large area magneto-optical materials having a high amplitude ultrafast Faraday or Kerr response. Here we report on optical pump probe studies of light induced spin dynamics in high quality bismuth doped iron garnet polycrystalline film prepared by the spin coating method. We demonstrate an ultrafast non-thermal optical control of the spin dynamics using both circularly and linearly polarized pulses.

  11. High temperature magneto-electric effect in yittrium iron garnet (YIG)

    NASA Astrophysics Data System (ADS)

    Saha, J.; Chaudhary, S.; Majumdar, P.; Kuanr, B. K.; Patnaik, S.

    2016-05-01

    We report a study on potential multiferroic characteristics of Yttrium Iron Garnet (YIG). The emergence of ferroelectricity in YIG is in debate but we provide evidence for strong magneto-electric coupling above room temperature from dielectric constant measurement with and without magnetic field. We find that the apparent pseudo-ferroelectric crossover temperature in YIG varies with frequency. For higher frequency the transition shifts towards higher temperature. This is indicative of relaxor behavior. We have also measured the dielectric constant in the presence of external magnetic field at high temperature that confirms interdependence of magnetic and dielectric properties.

  12. Magneto-optical properties of cerium substituted yttrium iron garnet films with reduced thermal budget for monolithic photonic integrated circuits.

    PubMed

    Goto, Taichi; Onbaşlı, Mehmet C; Ross, C A

    2012-12-17

    Thin films of polycrystalline cerium substituted yttrium iron garnet (CeYIG) were grown on an yttrium iron garnet (YIG) seed layer on Si and Si-on-insulator substrates by pulsed laser deposition, and their optical and magneto-optical properties in the near-IR region were measured. A YIG seed layer of ~30 nm thick processed by rapid thermal anneal at 800°C provided a virtual substrate to promote crystallization of the CeYIG. The effect of the thermal budget of the YIG/CeYIG growth process on the film structure, magnetic and magnetooptical properties was determined.

  13. Full spin polarization of complex ferrimagnetic bismuth iron garnet probed by magneto-optical Faraday spectroscopy

    NASA Astrophysics Data System (ADS)

    Deb, Marwan; Popova, Elena; Fouchet, Arnaud; Keller, Niels

    2013-06-01

    We investigate the spin-dependent electronic density of states near and above the Fermi level in bismuth iron garnet (BIG), Bi3Fe5O12, by magnetic circular dichroism and magneto-optical Faraday spectroscopy. BIG is a recently synthesized material, as its preparation requires special nonequilibrium conditions. Its scientific and applicative interest resides in huge specific Faraday rotation of the incident light, useful for magneto-optic applications. We show experimentally the presence of spin gaps in the conduction band as recently predicted theoretically by Oikawa [T. Oikawa, S. Suzuki, and K. Nakao, J. Phys. Soc. Jpn.JUPSAU0031-901510.1143/JPSJ.74.401 74, 401 (2005)]. In the range of photon energies, where full spin polarization is expected, completely asymmetric Faraday hysteresis loops were observed, similar to those observed in half-metals such as (Pr,La)0.7Ca0.3MnO3 and Fe3O4. These results were modeled using even and odd (with respect to magnetization) contributions into hysteresis loops. The odd contribution appears only in the energy ranges where the density of states is fully spin polarized and vanishes at the Curie temperature. These results open a new perspective for the use of bismuth iron garnet in optic spintronics at room temperature and above.

  14. Cerium Substitution in Yttrium Iron Garnet: Valence State, Structure, and Energetics

    SciTech Connect

    Guo, Xiaofeng; Tavakoli, Amir H.; Sutton, Steve; Kukkadapu, Ravi K.; Qi, Liang; Lanzirotti, Anthony; Newville, Mathew; Asta, Mark D.; Navrotsky, Alexandra

    2014-01-28

    The garnet structure is a promising nuclear waste form because it can accommodate various actinide elements. Y3Fe5O12 (YIG) is a model composition for such substitutions. Since cerium (Ce) can be considered an analogue of actinide elements such as thorium (Th), plutonium (Pu), and uranium (U), studying the local structure and thermodynamic stability of Ce-substituted YIG (Ce:YIG) can provide insights into the structural and energetic aspects of large ion substitution in garnets. Single phases of yttrium iron garnet with Ce substitution up to 20 mol % (Y3-xCexFe5O12 with 0 ≤ x ≤ 0.2) were synthesized through a citrate-nitrate combustion method. The oxidation state of cerium was examined by X-ray absorption near edge structure spectroscopy (XANES); the oxidation state and site occupancy of Fe as a function of Ce loading also was monitored by 57Fe-Mössbauer spectroscopy. These measurements establish that Ce is predominantly in the trivalent state at low substitution levels, while a mixture of trivalent and tetravalent states are observed at higher concentrations. Fe was predominately trivalent and exists in multiple environments. High temperature oxide melt solution calorimetry was used to determine the enthalpy of formation of these Ce-substituted YIG garnets. The thermodynamic analysis demonstrated that, although there is an entropic driving force for the substitution of Ce for Y, the substitution reaction is enthalpically unfavorable. The experimental results are complemented by electronic structure calculations performed within the framework of density functional theory (DFT) with Hubbard-U corrections, which reproduce the observed increase in the tendency for tetravalent Ce to be present with higher loading of Ce. The DFT+U results suggest that the energetics underlying the formation of tetravalent Ce involves a competition between an unfavorable energy to oxidize Ce and reduce Fe, and a favorable contribution due to strain-energy reduction. The structural

  15. Brillouin light scattering on yttrium iron garnet films in a magnetostatic wave device structure

    NASA Astrophysics Data System (ADS)

    Srinivasan, G.; Patton, C. E.; Emtage, P. R.

    1987-03-01

    Brillouin light scattering (BLS) has been used for the direct detection of magnetostatic wave (MSW) excitations in a MSW microwave device structure. The results are for a signal-to-noise enhancer device which consists of a yttrium iron garnet (YIG) film on a gadolinium gallium garnet substrate. The YIG film is in contact with a 30-micron wide stripline and the static magnetic field is parallel to the striline. MSW excitations were observed over the frequency range 2-4 GHz. At low power, magnetostatic surface waves (MSSW) were excited with propagation perpendicular to the stripline and field direction. At high power, parametric half-frequency magnons were also observed. The measured magnon dispersion for the MSSW excitations, determined using the wave vector selective capabilities of the BLS spectrometer, is in good agreement with theory. The measured intensity profiles for MSW excitations at low-power levels show strong MSSW excitations over the entire surface wave band. At high power, the scattering intensity for surface MSW excitations saturates and is accompanied by a strong parametric magnon signal.

  16. Giant Zeeman shifts in the optical transitions of yttrium iron garnet thin films

    NASA Astrophysics Data System (ADS)

    Vidyasagar, R.; Alves Santos, O.; Holanda, J.; Cunha, R. O.; Machado, F. L. A.; Ribeiro, P. R. T.; Rodrigues, A. R.; Mendes, J. B. S.; Azevedo, A.; Rezende, S. M.

    2016-09-01

    We report the observation of giant Zeeman shifts in the optical transitions of high-quality very thin films of yttrium iron garnet (YIG) grown by rf sputtering on gadolinium gallium garnet substrates. The optical absorption profile measured with magneto-optical absorption spectroscopy shows dual optical transition in the UV-visible frequency region attributed to transitions from the O-2p valence band to the Fe-3d conduction band and from the O-2p valence band to Fe-2p53d6 excitonic states at the Γ-symmetry point of the YIG band structure. The application of a static magnetic field of only 0.6 kOe produces giant Zeeman shifts of ˜100 meV in the YIG band structure and ˜60 meV in the excitonic states corresponding to effective g-factors on the order of 104. The giant Zeeman effects are attributed to changes in energy levels by the large exchange fields of the Fe-3d orbitals during the magnetization process.

  17. Growth and properties of High-quality metal/ yttrium iron garnet/metal sandwich structures

    NASA Astrophysics Data System (ADS)

    Aldosary, Mohammed; Li, Junxue; Tang, Chi; Xu, Yadong; Shi, Jing

    Sandwiched structures of magnetic insulators (e.g. yttrium iron garnet or YIG) between two normal metals are potentially useful for spintronics. In this work, we report our approach of growing a single crystalline YIG thin film on a Pt or Cu thin layer using the combination of sputtering and PLD. First, either 5 nm of Pt or Cu is deposited on (110)-oriented gadolinium gallium garnet (GGG) substrate using sputtering and then YIG is grown by PLD at intermediate temperatures followed by rapid thermal annealing at higher temperatures. Surprisingly, YIG films show a well-defined single-crystal reflection high energy electron diffraction (RHEED) pattern, despite that they are grown on polycrystalline Pt or Cu. TEM images show flat, clean and sharp interfaces between YIG/metals and metals/GGG. The magnetic properties show in-plane magnetic anisotropy. However, when thicker metallic layers (20 nm) or amorphous (metals/SiO2) substrate are used, only YIG polycrystalline phase is observed. We will show that by properly controlling the growth conditions the metal/YIG/ metal structures are not only of high structural quality, but also have desired properties for spin current transport. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

  18. Thermally induced transparency for short spin wave pulses in yttrium iron garnet (YIG) films

    NASA Astrophysics Data System (ADS)

    Ordonez Romero, Cesar Leonardo; Kolokoltsev, Oleg; Gomez Arista, Ivan; Qureshi, Naser; Monsiváis Galindo, Guillermo; Vargas Hernández, Hesiquio

    2014-03-01

    The compensation of spin wave propagation losses plays a very important role in the development of novel magnonic devices. Up to now, however, most of the known amplification methods present relative narrow frequency bandwidths due to their resonant nature. In this work, we present compensation of the propagation losses or pseudo-amplification of travelling spin waves by tailoring the bias magnetic field profile. The thermally-induced non-uniform profile of the magnetization introduced on an Yttrium Iron Garnet (YIG) thin film by a localized spot of a cw argon-ion laser creates the conditions to observe the complete compensation of the spin wave propagation losses. The spin wave evolution was mapped with a time and spaced resolved inductive magneto-dynamic prove system. The experiment was carried out using a uniform sample of single-crystal YIG film grown on a gallium-gadolinium garnet (GGG) substrate. The 2mm-wide, 20mm-long and 6microns-thick YIG strip was saturated with an external magnetic field enabling the set up for the propagation of magneto-static surface waves. This work was supported by the UNAM-DGAPA-PAPIIT IA100413.

  19. Integration of magneto-optical active bismuth iron garnet on nongarnet substrates

    NASA Astrophysics Data System (ADS)

    Körner, Timo; Heinrich, Andreas; Weckerle, Martin; Roocks, Patrick; Stritzker, Bernd

    2008-04-01

    For optical communication, high quality magneto-optical active iron garnet films such as Y3Fe5O12 are important ceramic systems with extensive applications, e.g., as optical isolators [H. Dötsch et al., J. Opt. Soc. Am. B 22, 240 (2005)], optical modulators, etc. Thereby, garnets stand out due to their high Faraday rotation and low optical losses in the near infrared. Currently, it is desirable to integrate such macroscopic optical components on a single chip (Si, SiO2, etc.) to build up optical circuits as in the case of microelectronics (integrated optics) or the use for magneto-optical imaging. Up to now, Bi3Fe5O12 shows the highest Faraday rotation over 20°/μm. Unfortunately, Bi3Fe5O12 forms in a nonthermodynamical way. Thus, it can only be grown on garnet substrates which prevent it from direct deposition on substrates such as Si or SiO2. In our present work, we studied the integration of Bi3Fe5O12 on different SiO2 substrates using the pulsed laser deposition method. Therefore, we deposited an Y3Fe5O12 buffer first which was optimized in a postannealing step above 900°C in order to form a polycrystalline garnet phase, which is needed for further Bi3Fe5O12 growth. We measured the Faraday rotation of the double layered films and intensely studied them with x-ray diffraction, Rutherford backscattering spectroscopy, environmental scanning electron microscopy, and high-resolution transmission electron microscopy. The attained Faraday rotation can be compared with epitaxial Bi3Fe5O12 films grown on Gd3Ga5O12 substrates or even overcome them due to interference effects in the double layer. So they are highly attractive for magneto-optical imaging. For the determination of the film thicknesses which is usually done by Rutherford backscattering or profilometry, we used another approach. We measured the transmission spectra of the stack which we also derived from a theoretical model that uses a transfer matrix formalism. The thickness of the multilayer can be

  20. Static and dynamic photoinduced magnetic effects in yttrium-iron garnet lightly doped with barium ions

    SciTech Connect

    Vorob'eva, N. V. Khalilov, R. Z.

    2012-04-15

    In yttrium-iron garnet lightly doped with barium, direct measurements of the photoinduced changes in magnetostrictive strains disagree with those in magnetostriction constants at 78-100 K. This is attributed to a considerable photoinduced modification of the initial state in this sample due to a redistribution of the charge (during illumination) between cations of the ferromagnetic octahedral sublattice. In the same sample, the temperature dependence of the photoinduced disaccomodation of magnetic permeability characterizing the initial demagnetized state is measured and calculated. A change in the electron mechanism of the phenomenon during the transition to room temperature is shown. The conclusion about the promising prospects for using such samples for remagnetization by light is advanced.

  1. Flux-gate magnetic field sensor based on yttrium iron garnet films for magnetocardiography investigations

    NASA Astrophysics Data System (ADS)

    Vetoshko, P. M.; Gusev, N. A.; Chepurnova, D. A.; Samoilova, E. V.; Syvorotka, I. I.; Syvorotka, I. M.; Zvezdin, A. K.; Korotaeva, A. A.; Belotelov, V. I.

    2016-08-01

    A new type of f lux-gate vector magnetometer based on epitaxial yttrium iron garnet films has been developed and constructed for magnetocardiography (MCG) investigations. The magnetic field sensor can operate at room temperature and measure MCG signals at a distance of about 1 mm from the thoracic cage. The high sensitivity of the sensor, better than 100 fT/Hz1/2, is demonstrated by the results of MCG measurements on rats. The main MCG pattern details and R-peak on a level of 10 pT are observed without temporal averaging, which allows heart rate anomalies to be studied. The proposed magnetic sensors can be effectively used in MCG investigations.

  2. Spin waves in micro-structured yttrium iron garnet nanometer-thick films

    SciTech Connect

    Jungfleisch, Matthias B. Zhang, Wei; Jiang, Wanjun; Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand; Hoffmann, Axel; Chang, Houchen; Wu, Mingzhong; Sklenar, Joseph; Ketterson, John B.

    2015-05-07

    We investigated the spin-wave propagation in a micro-structured yttrium iron garnet waveguide of 40 nm thickness. Utilizing spatially-resolved Brillouin light scattering microscopy, an exponential decay of the spin-wave amplitude of (10.06 ± 0.83) μm was observed. This leads to an estimated Gilbert damping constant of α=(8.79±0.73)×10{sup −4}, which is larger than damping values obtained through ferromagnetic resonance measurements in unstructured films. The theoretically calculated spatial interference of waveguide modes was compared to the spin-wave pattern observed experimentally by means of Brillouin light scattering spectroscopy.

  3. Nonlinear dynamics of three-magnon process driven by ferromagnetic resonance in yttrium iron garnet

    SciTech Connect

    Cunha, R. O.; Holanda, J.; Azevedo, A.; Rezende, S. M.; Vilela-Leão, L. H.; Rodríguez-Suárez, R. L.

    2015-05-11

    We report an investigation of the dynamics of the three-magnon splitting process associated with the ferromagnetic resonance (FMR) in films of the insulating ferrimagnet yttrium iron garnet (YIG). The experiments are performed with a 6 μm thick YIG film close to a microstrip line fed by a microwave generator operating in the 2–6 GHz range. The magnetization precession is driven by the microwave rf magnetic field perpendicular to the static magnetic field, and its dynamics is observed by monitoring the amplitude of the FMR absorption peak. The time evolution of the amplitude reveals that if the frequency is lowered below a critical value of 3.3 GHz, the FMR mode pumps two magnons with opposite wave vectors that react back on the FMR, resulting in a nonlinear dynamics of the magnetization. The results are explained by a model with coupled nonlinear equations describing the time evolution of the magnon modes.

  4. Epitaxial yttrium iron garnet film for fabrication of high frequency on-chip inductors

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Liu, Houfang; Wu, Hao; Li, Xiaoning; Qiu, Haochuan; Yang, Yi; Qu, Bingjun; Ren, Tian-Ling; Han, Xiufeng; Zhang, Ruyi; Wang, Hong

    2016-10-01

    The application of epitaxial yttrium iron garnet (YIG) thin film on high frequency on-chip spiral inductors is investigated. The YIG thin film with the thickness of 3.6 μm was grown on GGG(111) substrate using the liquid phase method, which exhibits relatively high saturation magnetization 4πMs of 1615 Oe close to the bulk value of 1750 Oe and low initial coercivity Hc of 0.5 Oe that minimizes the hysteretic losses. Subsequently, the spiral inductors were directly fabricated on the YIG/GGG(111) substrate. The results show substantial improvement in the optimum operating frequency and self-resonance frequency of the on-chip spiral inductor with the YIG thin film with an increase of 50% up to ˜7.5 GHz and 14.2 GHz, respectively, implying that on-chip spiral inductors with the YIG thin film can be applied to much higher frequency RF circuits.

  5. Spin valve effect of the interfacial spin accumulation in yttrium iron garnet/platinum bilayers

    SciTech Connect

    Jin, Lichuan; Zhang, Dainan; Zhang, Huaiwu Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong; Fan, Xin; Xiao, John Q.

    2014-09-29

    We report the spin valve effect in yttrium iron garnet/platinum (YIG/Pt) bilayers. The spin Hall effect (SHE) generates spin accumulation at the YIG/Pt interface and can be opened/closed by magnetization switching in the electrical insulator YIG. The interfacial spin accumulation was measured in both YIG/Pt and YIG/Cu/Pt structures using a planar Hall configuration. The spin valve effect remained, even after a 2 nm thick Cu layer was inserted between the YIG and Pt layers, which aimed to exclude the induced magnetization at the YIG/Pt interface. The transverse Hall voltage and switching field were dependent on the applied charge current density. The origin of this behavior can be explained by the SHE induced torque exerted on the domain wall, caused by the transfer of the spin angular momentum from the spin-polarized current to the YIG magnetic moment.

  6. Nanomechanical Detection of Magnetic Hysteresis of a Single-crystal Yttrium Iron Garnet Micromagnetic Disk

    NASA Astrophysics Data System (ADS)

    Losby, Joseph; Diao, Zhu; Burgess, Jacob; Compton, Shawn; Fani Sani, Fatemeh; Firdous, Tayyaba; Vick, Douglas; Belov, Miro; Hiebert, Wayne; Freeman, Mark

    2013-03-01

    A micromagnetic disk was milled from a monocrystalline yttrium iron garnet film using a focused ion beam and micromanipulated onto a nanoscale torsional resonator. Nanomechanical torque magnetometry results show a unipolar magnetic hysteresis characteristic of a magnetic vortex state. Landau-Lifshitz-Gilbert-based micromagnetic simulations of the disk show a rich, flux-enclosed, three-dimensional domain structure. On the top and bottom faces of the disk, a skewed vortex state exists with a very small core. The core region extends through the thickness of the disk with a smooth variation in core diameter reaching a maximum along the midplane of the disk. The single crystalline nature of the disk lends to an observed absence of Barkhausen-like steps in the magnetization-versus-field curves, qualitatively different in comparison to the magnetometry results of an individual polycrystalline permalloy microdisk. Prospects for the mechanical detection of spin dynamical modes in these structures will also be discussed.

  7. Spin wave excitation in yttrium iron garnet films with micron-sized antennas

    SciTech Connect

    Khivintsev, Y. V. Filimonov, Y. A.; Nikitov, S. A.

    2015-02-02

    In this paper, we explore spin waves excitation in monolithic structures based on yttrium iron garnet (YIG) films with micro-sized antennas. Samples based on plain and patterned YIG film were fabricated and tested for tangential bias field geometries. We observed spin wave excitation and propagation with wave numbers up to 3.5 × 10{sup 4} rad/cm. The corresponding wavelength is thus shorter more than by one order of magnitude compared to previous experiments with such films. For the sample with a periodic array of nanotrenches, we observed the effect of the shape anisotropy resulting in the shift of the spin wave propagation band in comparison to the unpatterned YIG film. Our results are very promising for the exploitation of short spin waves in YIG and provide great opportunity for significant miniaturization of YIG film based microwave devices.

  8. Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

    SciTech Connect

    Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu; Satoh, Takuya; Stupakiewicz, Andrzej; Maziewski, Andrzej

    2014-07-28

    A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm{sup 2}.

  9. Giant enhancement of Kerr rotation in two-dimensional Bismuth iron garnet/Ag photonic crystals

    NASA Astrophysics Data System (ADS)

    Liang, Hong; Liu, Huan; Zhang, Qiang; Fu, Shu-Fang; Zhou, Sheng; Wang, Xuan-Zhang

    2015-06-01

    Kerr effects of two-dimensional (2D) Bismuth iron garnet (BIG)/Ag photonic crystals (PCs) combined magnetic and plasmonic functionalities is investigated with the effective medium theory. An analytical expression of Kerr rotation angles is derived, in which the effects of the surface pasmons polaritons (SPP) on magneto-optical (MO) activities are reflected. The largest enhancement of Kerr rotation up to now is demonstrated, which is improved three orders of magnitude compared with that of BIG film. When λ < 750 nm all of the reflection are over 10% for the arbitrary filling ratio f1, in addition, the enhancement of Kerr rotation angles are at least one order of magnitude. Project supported by the National Natural Science Foundation of China (Grant Nos. 11104050, 10947168, 11204056, and 11304068).

  10. Nonlinear dynamics of three-magnon process driven by ferromagnetic resonance in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Cunha, R. O.; Holanda, J.; Vilela-Leão, L. H.; Azevedo, A.; Rodríguez-Suárez, R. L.; Rezende, S. M.

    2015-05-01

    We report an investigation of the dynamics of the three-magnon splitting process associated with the ferromagnetic resonance (FMR) in films of the insulating ferrimagnet yttrium iron garnet (YIG). The experiments are performed with a 6 μm thick YIG film close to a microstrip line fed by a microwave generator operating in the 2-6 GHz range. The magnetization precession is driven by the microwave rf magnetic field perpendicular to the static magnetic field, and its dynamics is observed by monitoring the amplitude of the FMR absorption peak. The time evolution of the amplitude reveals that if the frequency is lowered below a critical value of 3.3 GHz, the FMR mode pumps two magnons with opposite wave vectors that react back on the FMR, resulting in a nonlinear dynamics of the magnetization. The results are explained by a model with coupled nonlinear equations describing the time evolution of the magnon modes.

  11. Preparation of Bi Iron Garnet Film with a Two-Step Growth Technique

    NASA Astrophysics Data System (ADS)

    Mino, Shinji; Matsuoka, Morito; Shibukawa, Atsushi; Ono, Ken'ichi

    1990-10-01

    Completely Bi-substituted iron garnet (Bi3Fe5O12, BiIG) film with a smooth surface is synthesized by electron cyclotron resonance (ECR) sputtering using a two-step growth technique. Consequently, the waveguide propagation loss of BiIG film at a wavelength of 1.55 μm can be measured. The surface smoothness and the propagation loss can be improved with a buffer layer as thin as 2 nm, as the growth temperature Tb (400°C≤Tb≤600°C) is increased. This shows that buffer layer crystallinity plays an important role in making the BiIG film surface smooth and the propagation loss low.

  12. Nonlinear electric field tuning characteristics of yttrium iron garnet-lead zirconate titanate microwave resonators

    NASA Astrophysics Data System (ADS)

    Fetisov, Y. K.; Srinivasan, G.

    2008-07-01

    This report is on hysteresis and switching associated with electric field (E) tuning of ferromagnetic resonance in a bilayer of yttrium iron garnet (YIG)-lead zirconate titanate (PZT). The tuning is facilitated by piezoelectricity of PZT and mechanical bonding with YIG. For E <2kV/cm, the frequency shift δf is linear with E. For E <10kV/cm a pronounced hysteresis is seen in δf versus E. For E >10kV/cm, a butterflylike dependence of δf with an abrupt switch in the sign and magnitude of δf are measured. The observations are attributed to nonlinearities of the piezoelectric deformation.

  13. Studies on the growth of epitaxial bismuth-substituted iron garnet on gadolinium gallium garnet single crystals by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Leitenmeier, Stephan; Körner, Timo; Griesbauer, Josef; Herbort, Michael; Heinrich, Andreas; Stritzker, Bernd

    2008-12-01

    In this paper, we present extensive investigations of the growth of bismuth-substituted iron garnet Bi 3Fe 5O 12 (BIG) on (0 0 1)-, (1 1 1)- and (1 1 0)-oriented gadolinium gallium garnet Gd 3Ga 5O 12 (GGG) and doped GGG (SGGG, S*GGG) substrates by pulsed laser deposition. The growth has been studied by the use of in-situ reflecting high-energy electron diffraction, atomic force microscopy, scanning electron microscopy and X-ray diffraction. We found 3D island growth to be the dominant growth mode for the BIG films. Additionally, we present a special technique to create very large BIG growth islands. This method involves the use of a metallic bismuth iron ablation target and partially shielding the substrate during deposition. The growth islands have a characteristic geometry depending on the cut of the substrate. We could explain their shapes by the assumption that growing BIG tends to form {1 1 0} facets.

  14. Swift heavy ion-beam induced amorphization and recrystallization of yttrium iron garnet.

    PubMed

    Costantini, Jean-Marc; Miro, Sandrine; Beuneu, François; Toulemonde, Marcel

    2015-12-16

    Pure and (Ca and Si)-substituted yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers and amorphous films on gadolinium gallium garnet (Gd3Ga5O12, or GGG) single crystal substrates were irradiated by 50 MeV (32)Si and 50 MeV (or 60 MeV) (63)Cu ions for electronic stopping powers larger than the threshold value (~4 MeV μm(-1)) for amorphous track formation in YIG crystals. Conductivity data of crystalline samples in a broad ion fluence range (10(11)-10(16) cm(-2)) are modeled with a set of rate equations corresponding to the amorphization and recrystallization induced in ion tracks by electronic excitations. The data for amorphous layers confirm that a recrystallization process takes place above ~10(14) cm(-2). Cross sections for both processes deduced from this analysis are discussed in comparison to previous determinations with reference to the inelastic thermal-spike model of track formation. Micro-Raman spectroscopy was also used to follow the related structural modifications. Raman spectra show the progressive vanishing and randomization of crystal phonon modes in relation to the ion-induced damage. For crystalline samples irradiated at high fluences (⩾10(14) cm(-2)), only two prominent broad bands remain like for amorphous films, thereby reflecting the phonon density of states of the disordered solid, regardless of samples and irradiation conditions. The main band peaked at ~660 cm(-1) is assigned to vibration modes of randomized bonds in tetrahedral (FeO4) units.

  15. Swift heavy ion-beam induced amorphization and recrystallization of yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Costantini, Jean-Marc; Miro, Sandrine; Beuneu, François; Toulemonde, Marcel

    2015-12-01

    Pure and (Ca and Si)-substituted yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers and amorphous films on gadolinium gallium garnet (Gd3Ga5O12, or GGG) single crystal substrates were irradiated by 50 MeV 32Si and 50 MeV (or 60 MeV) 63Cu ions for electronic stopping powers larger than the threshold value (~4 MeV μm-1) for amorphous track formation in YIG crystals. Conductivity data of crystalline samples in a broad ion fluence range (1011-1016 cm-2) are modeled with a set of rate equations corresponding to the amorphization and recrystallization induced in ion tracks by electronic excitations. The data for amorphous layers confirm that a recrystallization process takes place above ~1014 cm-2. Cross sections for both processes deduced from this analysis are discussed in comparison to previous determinations with reference to the inelastic thermal-spike model of track formation. Micro-Raman spectroscopy was also used to follow the related structural modifications. Raman spectra show the progressive vanishing and randomization of crystal phonon modes in relation to the ion-induced damage. For crystalline samples irradiated at high fluences (⩾1014 cm-2), only two prominent broad bands remain like for amorphous films, thereby reflecting the phonon density of states of the disordered solid, regardless of samples and irradiation conditions. The main band peaked at ~660 cm-1 is assigned to vibration modes of randomized bonds in tetrahedral (FeO4) units.

  16. Swift heavy ion-beam induced amorphization and recrystallization of yttrium iron garnet.

    PubMed

    Costantini, Jean-Marc; Miro, Sandrine; Beuneu, François; Toulemonde, Marcel

    2015-12-16

    Pure and (Ca and Si)-substituted yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers and amorphous films on gadolinium gallium garnet (Gd3Ga5O12, or GGG) single crystal substrates were irradiated by 50 MeV (32)Si and 50 MeV (or 60 MeV) (63)Cu ions for electronic stopping powers larger than the threshold value (~4 MeV μm(-1)) for amorphous track formation in YIG crystals. Conductivity data of crystalline samples in a broad ion fluence range (10(11)-10(16) cm(-2)) are modeled with a set of rate equations corresponding to the amorphization and recrystallization induced in ion tracks by electronic excitations. The data for amorphous layers confirm that a recrystallization process takes place above ~10(14) cm(-2). Cross sections for both processes deduced from this analysis are discussed in comparison to previous determinations with reference to the inelastic thermal-spike model of track formation. Micro-Raman spectroscopy was also used to follow the related structural modifications. Raman spectra show the progressive vanishing and randomization of crystal phonon modes in relation to the ion-induced damage. For crystalline samples irradiated at high fluences (⩾10(14) cm(-2)), only two prominent broad bands remain like for amorphous films, thereby reflecting the phonon density of states of the disordered solid, regardless of samples and irradiation conditions. The main band peaked at ~660 cm(-1) is assigned to vibration modes of randomized bonds in tetrahedral (FeO4) units. PMID:26580459

  17. Integration of bulk-quality thin film magneto-optical cerium-doped yttrium iron garnet on silicon nitride photonic substrates.

    PubMed

    Onbasli, Mehmet C; Goto, Taichi; Sun, Xueyin; Huynh, Nathalie; Ross, C A

    2014-10-20

    Cerium substituted yttrium iron garnet (Ce:YIG) films were grown on yttrium iron garnet (YIG) seed layers on silicon nitride films using pulsed laser deposition. Optimal process conditions for forming garnet films on silicon nitride are presented. Bulk or near-bulk magnetic and magneto-optical properties were observed for 160 nm thick Ce:YIG films grown at 640 °C on rapid thermal annealed 40 nm thick YIG grown at 640 °C and 2 Hz pulse rate. The effect of growth temperature and deposition rate on structural, magnetic and magneto-optical properties has been investigated.

  18. Identification of spin wave modes in yttrium iron garnet strongly coupled to a co-axial cavity

    SciTech Connect

    Lambert, N. J.; Ferguson, A. J.; Haigh, J. A.

    2015-02-07

    We demonstrate, at room temperature, the strong coupling of the fundamental and non-uniform magnetostatic modes of an yttrium iron garnet ferrimagnetic sphere to the electromagnetic modes of a co-axial cavity. The well-defined field profile within the cavity yields a specific coupling strength for each magnetostatic mode. We experimentally measure the coupling strength for the different magnetostatic modes and, by calculating the expected coupling strengths, we are able to identify the modes themselves.

  19. Spin dynamics in patterned nanometer-thick yttrium iron garnet films

    NASA Astrophysics Data System (ADS)

    Jungfleisch, Matthias Benjamin; Zhang, Wei; Jiang, Wanjun; Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand; Hoffmann, Axel; Sklenar, Joseph; Ketterson, John B.; Chang, Houchen; Wu, Mingzhong

    2015-03-01

    We present experimental investigations on the propagation of spin-wave modes in micro-structured yttrium iron garnet (YIG) stripes.1 The stripes were patterned by photo-lithography from high-quality 40-nm-thick YIG films grown by sputtering.2 Magnetization dynamics is driven by the rf field of a shorted coplanar waveguide patterned onto the YIG stripes. The propagation of spin waves are detected by means of spatially-resolved Brillouin light scattering microscopy. The propagation distance of spin waves is determined in the linear regime, where an exponential decay of 10 μm is observed. The estimated Gilbert damping parameter extracted from the spin-wave decay length is 3 times larger than that obtained through ferromagnetic resonance measurements in unstructured films, which is possibly due to enhanced two-magnon scattering in the patterned films. Furthermore, studies on the spin dynamics driven by spin-torque ferromagnetic resonance in YIG/Pt bilayers and the corresponding spatially-resolved spin-wave distribution are presented. This work was supported by Department of Energy, Office of Science, Materials Science and Engineering Division, the Army Research Office, and National Science Foundation.

  20. Scanning magnetic resonance microscopy: Spatially resolved imaging of ferromagnetic resonance on yttrium iron garnet disk.

    NASA Astrophysics Data System (ADS)

    An, Toshu; Eguchi, Toyoaki; Hasegawa, Yukio

    2009-03-01

    We developed a radio frequency (RF) probe which can be implemented into scanning probe microscope aiming for its spatially resolved imaging. The probe is composed of a sharp tip attached at the end of a semi-rigid coaxial cable which transmits RF over 10 GHz. To measure ferromagnetic resonance (FMR) of a sample, the probe is set close to the sample, and the S11 parameter was measured by using a network analyzer. As a test magnetic sample, a 10 mm-diameter and 1 mm-thickness polycrystalline YIG (yttrium iron garnet) disk was used. By locating the RF probe at the center of the YIG disk, FMR signal was detected as an absorption dip at 2.8 GHz in the S11 measurements under in-plane static magnetic field of 458 Oe. The detected FMR signal has a sharper dip compared with that obtained in the coplanar wave guide method, and by moving the RF probe to the edge of the YIG disk, two different frequencies of FMR signal appears depending on the moving direction parallel or perpendicular to the applied magnetic field. The detected spatially dependent FMR signals are well explained by the magnetostatic waves.

  1. Yttrium Iron Garnet Thin Films with Very Low Damping Obtained by Recrystallization of Amorphous Material

    PubMed Central

    Hauser, Christoph; Richter, Tim; Homonnay, Nico; Eisenschmidt, Christian; Qaid, Mohammad; Deniz, Hakan; Hesse, Dietrich; Sawicki, Maciej; Ebbinghaus, Stefan G.; Schmidt, Georg

    2016-01-01

    We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10−5 is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10−5 is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials. PMID:26860816

  2. Optical spectroscopy of sputtered nanometer-thick yttrium iron garnet films

    SciTech Connect

    Jakubisova-Liskova, Eva Visnovsky, Stefan; Chang, Houchen; Wu, Mingzhong

    2015-05-07

    Nanometer (nm)-thick yttrium iron garnet (Y{sub 3}Fe{sub 5}O{sub 12}, YIG) films present interest for spintronics. This work employs spectral ellipsometry and magneto-optic Kerr effect (MOKE) spectra to characterize nm-thick YIG films grown on single-crystal Gd{sub 3}Ga{sub 5}O{sub 12} substrates by magnetron sputtering. The thickness (t) of the films ranges between 10 nm and 40 nm. Independent on t, the polar MOKE hysteresis loops saturate in the field of about 1.8 kOe, consistent with the saturation magnetization in bulk YIG (4πM{sub s} ≈ 1.75 kG). The MOKE spectrum measured at photon energies between 1.3 eV and 4.5 eV on the 38-nm-thick film agrees with that measured on single-crystal YIG bulk materials. The MOKE spectrum of the 12-nm-thick film still preserves the structure of the bulk YIG but its amplitude at lower photon energies is modified due to the fact that the radiation penetration depth exceeds 20 nm. The t dependence of the MOKE amplitude is consistent with MOKE calculations. The results indicate that the films are stoichiometric, strain free, without Fe{sup 2+}, and preserve bulk YIG properties down to t ≈ 10 nm.

  3. Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition.

    PubMed

    Johnson, Scooter D; Glaser, Evan R; Kub, Fritz J; Eddy, Charles R

    2015-05-15

    Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 µm thick yttrium iron garnet films that are  > 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

  4. Preparing magnetic yttrium iron garnet nanodot arrays by ultrathin anodic alumina template on silicon substrate

    SciTech Connect

    Zheng, Hui; Han, Mangui Deng, Longjiang; Zheng, Liang; Zheng, Peng; Qin, Huibin; Wu, Qiong

    2015-08-10

    Ultrahigh density periodically ordered magnetic yttrium iron garnet (Y{sub 3}Fe{sub 5}O{sub 12}, YIG) nanodot arrays have been prepared by pulsed laser deposition through an ultrathin alumina mask (UTAM). UTAM having periodically ordered circularly shaped holes with 350 nm in diameter, 450 nm in inter-pore distance, and 700 nm in height has been prepared on silicon substrate. Furthermore, the microstructure and magnetic properties of YIG nanodot arrays have been characterized. Nanodot arrays with a sharp distribution in diameter centered at 340 nm with standard deviation of 10 nm have been fabricated. Moreover, typical hysteresis loops and ferromagnetic resonance spectra in in-plane and out-of-plane revealed that this unique structure greatly influences the magnetics properties of YIG. First, coercivity of YIG nanodot arrays in in-plane was increased about from 15 Oe of YIG films to 500 Oe. Then, the degree of uniformity about nanodot height decided that two or more resonance peaks in out-of-plane were detected in the spectra. The peak-to-peak linewidth values were about 94 Oe and 40 Oe in the parallel and perpendicular directions, respectively, which indicated that the values were larger by the two-magnon scattering. Consequently, this pattering method creates opportunities for studying physics in oxide nanomagnets and may be applied in spin-wave devices.

  5. Excitation and propagation of exchange spin waves in films of yttrium iron garnet

    SciTech Connect

    Zil`berman, P.E.; Temiryazev, A.G.; Tikhomirova, M.P.

    1995-07-01

    We investigate resonant microwave absorption in films of yttrium iron garnet (YIG) with magneetic properties varying through the film thickness. Using measurements of the spin-wave resonant absorption spectra for two different directions of the external magnetic field, we calculate the profile of this nonuniformity. In our investigation of the response of nonuniform films to a pulsed microwave signal, we observed the appearance of delayed pulses, which we interpret to be the result of propagation of exchange spin waves transversely through the film. We analyze the dependence of the time delay on frequency for various nonuniformity profiles, and compare the data obtained with the results of experiment. Our investigation of the spin-wave resonance spectra, as well as the results of our pulsed measurements, show that propagation of spin waves is accompanied by the excitation of acoustic waves. We conclude that ferrite films that vary in the transverse direction can on the one hand be used to efficiently excite short-wavelength exchange spin waves with wave numbers 1{approximately}3 {center_dot}10{sup 5} cm{sup {minus}1}, and on the other hand to excite very high-frequency acoustic waves. 25 refs., 15 figs.

  6. Observation of auto-oscillations and chaos in subsidiary absorption in yttrium iron garnet

    SciTech Connect

    Srinivasan, G.; Chen, M.; Patton, C.E.

    1988-11-15

    Auto-oscillations of the dynamic magnetization and routes to chaos for the first-order transverse pump spin-wave instability have been studied in single-crystal yttrium-iron-garnet (YIG) films. The measurements reported here were made on a 20.8-..mu..m-thick YIG film at 9.4 GHz with the static and microwave fields in the plane of the film. Auto-oscillations at 100--400 kHz were observed in the power absorbed by the film over a relatively narrow static field range of 1100--1460 Oe, compared to the first-order instability (FOI) range of 0--1630 Oe. The auto-oscillation frequency and threshold microwave field amplitude were both strongly field dependent. The threshold amplitudes were about a factor of 2 larger than the FOI threshold amplitudes. At even higher power levels and for an even narrower field range of 1300--1380 Oe, the auto-oscillations showed frequency changes indicative of chaotic behavior. Several different subharmonic bifurcation routes to chaos were observed for different fields within the chaotic region.

  7. Non-local thermal spin injection to study spin diffusion in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Giles, Brandon; Yang, Zihao; Jamison, John; Myers, Roberto

    Understanding the generation, detection, and manipulation of spin current is critical for the development of devices that depend on spin transport for information processing and storage. Recent studies have shown that spin transport over long distances is possible in the magnetic insulator yttrium iron garnet (YIG) through the diffusion of non-equilibrium magnons. Electrically excited magnons have been shown to diffuse up to 40um at room temperature, while thermally injected magnons were detected at ranges greater than 125um at 23K. However, much work is still required to fully understand the processes responsible for magnon diffusion. Here, we present an in-depth study of the diffusion of magnons in YIG. By using the non-local thermal spin detection method, we analyze spin transport as a function of temperature. Spin diffusion maps, which can be used to experimentally determine the spin diffusion length in YIG as a function of temperature, are presented Work supported by the Army Research Office MURI W911NF-14-1-0016.

  8. Synthesis of nanocrystalline yttrium iron garnet by low temperature solid state reaction

    SciTech Connect

    Yu Hongtao Zeng Liwen; Lu Chao; Zhang Wenbo; Xu Guangliang

    2011-04-15

    In this work, nanocrystalline yttrium iron garnet powders were produced by low temperature solid state reaction. The phase evolution during the procedure was determined from the thermogravimetric and differential thermal analysis, and the x-ray diffraction patterns. The results of transmission electron microscopy indicated that the prepared powders exhibited grain size at the nano-level of 20 {approx} 40 nm. Dense ceramics with a theoretical density of around 98% were obtained from the prepared powders after sintering at 1280 deg. C, a relative low sintering temperature compared with conventional ceramic processes, and the saturation magnetizations of sintered samples were also determined. - Research Highlights: {yields}No sol or gel form during the synthesis processing using nitrates and citric acid as raw materials. {yields}The synthesis method needs a low heating temperature (700 deg. C) compared with conventional solid state reaction. {yields}The product is a single phase with homogeneous size distribution and nano grains (20 {approx} 40 nm) confirmed by TEM. {yields}Dense YIG ceramic can be sintered at a low temperature (1280 deg. C) compared with that in conventional processing.

  9. Thermal properties of magnons in yttrium iron garnet at elevated magnetic fields

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; López Ortiz, J. C.

    2015-03-01

    The ferrimagnetic insulator yttrium iron garnet (YIG) has become an important material in the emergent field of spin caloritronics. Despite this and the fact that this material has been studied for over half a century, the thermal properties of magnons in YIG have not been sufficiently characterized, mainly because at not very low temperatures, they are overwhelmed by the contribution of phonons. Experimental attempts to characterize the magnon specific heat and thermal conductivity in YIG make use of large magnetic fields to freeze the magnon contributions and isolate those of phonons relative to their behavior at zero field. Here we present calculations of the magnon thermal properties in YIG under elevated magnetic fields using spin-wave theory. We show that at a temperature of 10 K , a field of at least 300 kOe is necessary to decrease the magnon contributions to 10% of their zero-field values. With the results of the calculations, we reinterpret recent measurements of the magnon thermal properties in YIG at temperatures up to 20 K and a field of 70 kOe, and suggest a procedure to determine their values at room temperature with the use of a field of 300 kOe.

  10. Evolution of properties of epitaxial bismuth iron garnet films with increasing thickness

    NASA Astrophysics Data System (ADS)

    Kahl, S.; Grishin, A. M.

    2004-07-01

    Bismuth iron garnet (BIG) films of thicknesses from 470 to 2560 nm were prepared by pulsed laser deposition under identical deposition conditions. All films are epitaxial, bismuth deficient, and show rms surface roughnesses between 15 and 40 nm. X-ray coherence lengths decrease with increasing film thickness. Films below approximately 1 μm are free of cracks, thicker films possess a network of cracks. From fits of optical transmission spectra, real and imaginary parts of the refractive indices were found for wavelengths from 500 to 850 nm. The effects of thin film interference and surface roughness were included. With these data as input information, each of our experimental Faraday rotation spectra was described by a single diamagnetic line in visible light. The measured spectra could be reproduced and parameters of the magneto-optical transition were obtained. We observed a broadening of the transition with increasing film thickness and a red shift of the center frequency. This corresponds to our experimental observation that the wavelength of maximum Faraday rotation for BIG films in visible light shifts to longer wavelengths by almost 40 nm for a 2560-nm-thick film as compared to a 470-nm-thick film. As BIG is not thermodynamically stable, aging is a crucial question. We found that careful annealing in oxygen below the deposition temperature increases the angle of Faraday rotation, while film properties deteriorate during long annealing times at the deposition temperature.

  11. Yttrium Iron Garnet Thin Films with Very Low Damping Obtained by Recrystallization of Amorphous Material.

    PubMed

    Hauser, Christoph; Richter, Tim; Homonnay, Nico; Eisenschmidt, Christian; Qaid, Mohammad; Deniz, Hakan; Hesse, Dietrich; Sawicki, Maciej; Ebbinghaus, Stefan G; Schmidt, Georg

    2016-01-01

    We have investigated recrystallization of amorphous Yttrium Iron Garnet (YIG) by annealing in oxygen atmosphere. Our findings show that well below the melting temperature the material transforms into a fully epitaxial layer with exceptional quality, both structural and magnetic. In ferromagnetic resonance (FMR) ultra low damping and extremely narrow linewidth can be observed. For a 56 nm thick layer a damping constant of α = (6.15 ± 1.50) · 10(-5) is found and the linewidth at 9.6 GHz is as small as 1.30 ± 0.05 Oe which are the lowest values for PLD grown thin films reported so far. Even for a 20 nm thick layer a damping constant of α = (7.35 ± 1.40) · 10(-5) is found which is the lowest value for ultrathin films published so far. The FMR linewidth in this case is 3.49 ± 0.10 Oe at 9.6 GHz. Our results not only present a method of depositing thin film YIG of unprecedented quality but also open up new options for the fabrication of thin film complex oxides or even other crystalline materials.

  12. Interface effects in nanometer-thick yttrium iron garnet films studied by magneto-optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Jakubisova, Eva Liskova; Visnovsky, Stefan; Chang, Houchen; Wu, Mingzhong

    2016-02-01

    The properties of nanometer-thick yttrium iron garnet (YIG) films are strongly influenced by interfaces. This work employs spectral ellipsometry (SE) and magneto-optic polar Kerr rotation (PKR) to characterize YIG films with thickness, t, from 6 nm to 30 nm grown on Gd3Ga5O12 (GGG) substrates oriented parallel to (111) plane. The films display a surface roughness of 0.35 nm or lower. The analysis of the SE data at the photon energies of 1 eV < E < 6.5 eV provided the t and permittivity values. The PKR at 1.3 eV < E < 4.5 eV is reasonably explained with the optical model for the YIG film/GGG substrate system. Even better agreement is achieved by assuming a 1.07-nm-thick layer sandwiched between YIG and GGG that has Fe3+ sublattice magnetization opposite to that in the YIG volume. This suggests the existence of antiferromagnetic coupling between the Gd3+ and tetrahedral Fe3+.

  13. Spin-to-charge-current conversion in yttrium iron garnet-graphene hybrid structure

    NASA Astrophysics Data System (ADS)

    Mendes, Joaquim; Alves Santos, Obed; Meireles, Leonel; Lacerda, Rodrigo; Vilela-Leão, Luis; Machado, Fernando; Rodríguez-Suárez, Roberto; Azevedo, Antonio; Rezende, Sergio

    The use of graphene in spintronic devices depends, among other things, on its ability to convert a spin excitation into an electric charge signal, a phenomenon that requires a spin-orbit coupling (SOC). In this work we report the observation of two effects that show the existence of SOC in large-area CVD grown single-layer graphene (SLG) deposited on a single crystal film of the ferrimagnetic insulator yttrium iron garnet (YIG). The first is a magnetoresistance of graphene induced by the magnetic proximity effect with YIG. The second is the detection of a DC voltage along the graphene layer resulting from the conversion of the spin current generated by spin pumping from microwave driven FMR into charge current. We interpret the spin-to-charge conversion as arising from the inverse Rashba-Edelstein effect (IREE) made possible by the extrinsic spin-orbit coupling in graphene. These observations show that spin orbit coupling can be extrinsically enhanced in graphene by the proximity effect with a ferromagnetic layer. This result opens new possibilities for the use of graphene in spintronic devices with unique functionalities. Research supported in Brazil by the agencies CNPq, CAPES, FINEP, FAPEMIG, FACEPE, and in Chile by FONDECYT No. 1130705.

  14. Magnetic properties of the magnetophotonic crystal based on bismuth iron garnet

    NASA Astrophysics Data System (ADS)

    Popova, Elena; Magdenko, Liubov; Niedoba, Halina; Deb, Marwan; Dagens, Béatrice; Berini, Bruno; Vanwolleghem, Mathias; Vilar, Christèle; Gendron, François; Fouchet, Arnaud; Scola, Joseph; Dumont, Yves; Guyot, Marcel; Keller, Niels

    2012-11-01

    This article reports on the magnetism of continuous and patterned bismuth iron garnet (Bi3Fe5O12 or BIG) thin films for magnetophotonic crystal (MPC) applications. The exact knowledge of the magnetic properties is crucial for the design of fully functional MPC. BIG thin films were grown on several types of isostructural substrates by pulsed laser deposition. The growth conditions and bismuth transfer were optimized to obtain good quality magneto-optically active films compatible with nanostructuring process. MPC were successfully fabricated from BIG/GGG(001) films with low roughness and high Faraday rotation. Magnetic characteristics (magnetization, anisotropy, magnetic domains, magnetization reversal) of the continuous BIG films and MPC were extensively studied and compared to the results of the micromagnetic simulations performed for MPC with different anisotropy. The present study shows that the fabrication of the MPC structure lowers the magnetocrystalline and uniaxial in-plane anisotropies and induces a partial out-of-plane magnetization. External field smaller than 2000 G is sufficient to ensure the out-of-plane saturation of magnetization for optimum device operation, in agreement with micromagnetic calculations. The experimentally determined magnetic properties of MPC are fully compatible with the device operation.

  15. Pulsed laser deposition of epitaxial yttrium iron garnet films with low Gilbert damping and bulk-like magnetization

    SciTech Connect

    Onbasli, M. C. Kim, D. H.; Ross, C. A.; Kehlberger, A.; Jakob, G.; Kläui, M.; Chumak, A. V.; Hillebrands, B.

    2014-10-01

    Yttrium iron garnet (YIG, Y {sub 3}Fe{sub 5}O{sub 12}) films have been epitaxially grown on Gadolinium Gallium Garnet (GGG, Gd{sub 3}Ga{sub 5}O{sub 12}) substrates with (100) orientation using pulsed laser deposition. The films were single-phase, epitaxial with the GGG substrate, and the root-mean-square surface roughness varied between 0.14 nm and 0.2 nm. Films with thicknesses ranging from 17 to 200 nm exhibited low coercivity (<2 Oe), near-bulk room temperature saturation moments (∼135 emu cm{sup −3}), in-plane easy axis, and damping parameters as low as 2.2 × 10{sup −4}. These high quality YIG thin films are useful in the investigation of the origins of novel magnetic phenomena and magnetization dynamics.

  16. Pulsed laser deposition of epitaxial yttrium iron garnet films with low Gilbert damping and bulk-like magnetization

    NASA Astrophysics Data System (ADS)

    Onbasli, M. C.; Kehlberger, A.; Kim, D. H.; Jakob, G.; Kläui, M.; Chumak, A. V.; Hillebrands, B.; Ross, C. A.

    2014-10-01

    Yttrium iron garnet (YIG, Y 3Fe5O12) films have been epitaxially grown on Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) substrates with (100) orientation using pulsed laser deposition. The films were single-phase, epitaxial with the GGG substrate, and the root-mean-square surface roughness varied between 0.14 nm and 0.2 nm. Films with thicknesses ranging from 17 to 200 nm exhibited low coercivity (<2 Oe), near-bulk room temperature saturation moments (˜135 emu cm-3), in-plane easy axis, and damping parameters as low as 2.2 × 10-4. These high quality YIG thin films are useful in the investigation of the origins of novel magnetic phenomena and magnetization dynamics.

  17. Low-relaxation spin waves in laser-molecular-beam epitaxy grown nanosized yttrium iron garnet films

    NASA Astrophysics Data System (ADS)

    Lutsev, L. V.; Korovin, A. M.; Bursian, V. E.; Gastev, S. V.; Fedorov, V. V.; Suturin, S. M.; Sokolov, N. S.

    2016-05-01

    Synthesis of nanosized yttrium iron garnet (Y3Fe5O12, YIG) films followed by the study of ferromagnetic resonance (FMR) and spin wave propagation in these films is reported. The YIG films were grown on gadolinium gallium garnet substrates by laser molecular beam epitaxy. It has been shown that spin waves propagating in YIG deposited at 700 °C have low damping. At the frequency of 3.29 GHz, the spin-wave damping parameter is less than 3.6 × 10-5. Magnetic inhomogeneities of the YIG films give the main contribution to the FMR linewidth. The contribution of the relaxation processes to the FMR linewidth is as low as 1.2%.

  18. Optical transmission and Faraday rotation spectra of a bismuth iron garnet film

    NASA Astrophysics Data System (ADS)

    Kahl, S.; Popov, V.; Grishin, A. M.

    2003-11-01

    We prepared an epitaxial 530-nm-thick bismuth iron garnet (BIG) film on a Gd3Ga5O12(GGG) (111) substrate by pulsed laser deposition and measured spectra of optical transmission and magneto-optical Faraday rotation θF(λ) in visible light. Both spectra are shaped by the dispersion relations of the dielectric tensor and the effects of multiple-beam interference in the thin film. From fitting of the transmission spectrum, dispersion relations of the real and imaginary parts of the refractive index were found for the wavelength range from 515 to 1000 nm, n(λ)=2.36+(413 nm/λ)2 and k(λ)=(λ/4π nm)×exp[(1660 nm/λ)2-15.2]. With these data as input information, a single diamagnetic line centered at λ=486 nm was fitted to the experimentally recorded magneto-optical spectrum. The effects of thin film interference and surface roughness were included in order to closely reproduce the measured spectrum. The roughness determined from spectral analysis was compared to the rms roughness measured by atomic force microscopy. The values agree within a deviation of less than 20% and are approximately 3% of film thickness. The magneto-optical figure of merit 2|θF|/α (α is the absorption coefficient) of our film increases strongly with wavelength and exceeds 100° at 740 nm. The optical efficiency for magneto-optical visualization |exp(-2αd)sin(4θFd)| (d is film thickness) possesses a maximum value of 29% at 600 nm. Both quantities were calculated using the obtained dispersion relations for absorption and Faraday rotation.

  19. Anomalous magnetic reordering in magnetodielectric terbium iron garnet at low temperatures

    NASA Astrophysics Data System (ADS)

    Lahoubi, Mahieddine; Ouladdiaf, Bachir

    2015-01-01

    The paper deals with five topics: i) the single three-dimensional irreductible representation (D4g=T1g) of the paramagnetic space group Ia 3 bar d No. 230 is chosen according to the representation analysis of Bertaut for the interpretation of the neutron powder diffraction experiments performed on terbium iron garnet (Tb3Fe5O12); ii) the use of the method of the "symmetry lowering device" of Bertaut in order to select the appropriate rhombohedral subgroup of Ia 3 bar d which allows to deal with the case where the cubic description provides an incomplete answer to the changes observed below 160 K in the ferrimagnetic structure around the [1 1 1] axis from the Néel model toward the "double umbrella" observed at 13 K; iii) the magnetic modes belonging to the one-dimensional irreductible representation A2g of the highest rhombohedral subgroup R 3 bar c No. 167 are able to describe the occurrence of its anisotropic character which steeply increases below 160 K due to the concomitant anisotropic effects; iv) the broad anomaly observed near 54 K in the temperature dependences of the components of both sublattices of the Tb3+ ions in the Wyckoff positions (6e) and (6e‧) is explained partially on the basis of the concept of Belov of the strong paraprocess which has been termed "exchange-enhanced paramagnetism" at the so-called "low-temperature point" (TB); v) the results are related to the magnetodielectric effect in low magnetic field and to the significant coupling between exchange magnons and ligand-field excitations reported recently in this compound.

  20. Curie temperature, exchange integrals, and magneto-optical properties in off-stoichiometric bismuth iron garnet epitaxial films

    NASA Astrophysics Data System (ADS)

    Vertruyen, B.; Cloots, R.; Abell, J. S.; Jackson, T. J.; da Silva, R. C.; Popova, E.; Keller, N.

    2008-09-01

    We have studied the influence of the stoichiometry on the structural, magnetic, and magneto-optical properties of bismuth iron garnet (Bi3Fe5O12) thin films grown by pulsed laser deposition. Films with different stoichiometries have been obtained by varying the Bi/Fe ratio of the target and the oxygen pressure during deposition. Stoichiometry variations influence the Curie temperature TC by tuning the (Fe)-O-[Fe] geometry: TC increases when the lattice parameter decreases, contrary to what happens in the case of stoichiometric rare-earth iron garnets. The thermal variation of the magnetization, the Faraday rotation, and the Faraday ellipticity have been analyzed in the frame of the Néel two-sublattice magnetization model giving energies of -48K (4.1 meV), -29K (2.5 meV), and 84 K (7.3 meV) for the three magnetic exchange integrals jaa , jdd , and jad , respectively. Magneto-optical spectroscopy linked to compositional analysis by Rutherford backscattering spectroscopy shows that Bi and/or Fe deficiencies also affect the spectral variation (between 1.77 and 3.1 eV). Our results suggest that bismuth deficiency has an effect on the magneto-optical response of the tetrahedral Fe sublattice, whereas small iron deficiencies affect predominantly the magneto-optical response of the octahedral sublattice.

  1. Laser MBE-grown yttrium iron garnet films on GaN: characterization of the crystal structure and magnetic properties

    NASA Astrophysics Data System (ADS)

    Kaveev, A. K.; Bursian, V. E.; Gastev, S. V.; Krichevtsov, B. B.; Suturin, S. M.; Volkov, M. P.; Sokolov, N. S.

    2016-07-01

    Yttrium iron garnet (YIG) films were grown on GaN substrates using the laser molecular beam epitaxy method. X-ray diffraction data showed polycrystalline YIG layers without additional structural modifications. The magnetic properties of the YIG films were studied at room temperature with the aid of a vibration sample magnetometer, the magneto-optical Kerr effect and ferromagnetic resonance methods. ‘Easy-plane’-type magnetic anisotropy was found in the films. The gyromagnetic ratio and 4 πMS value were calculated.

  2. Study of the branching domain structures in epitaxial films of yttrium iron garnet by end face magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Lisovskii, F. V.; Mansvetova, E. G.; Temiryazeva, M. P.; Temiryazev, A. G.

    2013-01-01

    The distribution of the magnetization vector on the free surface and end (cleaved facet) of thick epitaxial yttrium iron garnet films has been studied by the scanning magnetic-force microscopy method. Volume fractal-like branching of the domain structure has been found at the interface of the film and the free space with the refinement of the formed partial branches of the stripe (labyrinth) domains. Triangular closing domains have been observed at the interface between the film and the substrate. Direct experimental proof of the existence of the static horizontal Bloch lines within the stripe domain walls has been obtained.

  3. Sign of inverse spin Hall voltages generated by ferromagnetic resonance and temperature gradients in yttrium iron garnet platinum bilayers

    NASA Astrophysics Data System (ADS)

    Schreier, Michael; Bauer, Gerrit E. W.; Vasyuchka, Vitaliy I.; Flipse, Joost; Uchida, Ken-ichi; Lotze, Johannes; Lauer, Viktor; Chumak, Andrii V.; Serga, Alexander A.; Daimon, Shunsuke; Kikkawa, Takashi; Saitoh, Eiji; van Wees, Bart J.; Hillebrands, Burkard; Gross, Rudolf; Goennenwein, Sebastian T. B.

    2015-01-01

    We carried out a concerted effort to determine the absolute sign of the inverse spin Hall effect voltage generated by spin currents injected into a normal metal. We focus on yttrium iron garnet (YIG)∣platinum bilayers at room temperature, generating spin currents by microwaves and temperature gradients. We find consistent results for different samples and measurement setups that agree with theory. We suggest a right-hand-rule to define a positive spin Hall angle corresponding to the voltage expected for the simple case of scattering of free electrons from repulsive Coulomb charges.

  4. On-chip waveguide isolator based on bismuth iron garnet operating via nonreciprocal single-mode cutoff.

    PubMed

    Drezdzon, Samuel M; Yoshie, Tomoyuki

    2009-05-25

    We analyze an on-chip optical isolator based on direction dependent single-mode cutoff, which is described in 1D and 2D momentum space. Isolation is shown using 3D finite difference time domain (FDTD) where the magnetization is represented by imaginary off-diagonal permittivity tensor elements. The isolator designs are optimized using perturbation theory, which successfully predicts increased isolation for rib waveguides and structures with non-magnetic dielectric layers. Our isolators are based on bismuth iron garnet and its compatible substrates; an isolation ratio of 10.7 dB/mm is achieved for TM modes.

  5. An antidot array as an edge for total non-reflection of spin waves in yttrium iron garnet films

    SciTech Connect

    Gieniusz, R. Guzowska, U.; Maziewski, A.; Bessonov, V. D.; Stognii, A. I.

    2014-02-24

    An array of antidots has been used as an edge to create the phenomenon of total non-reflection of spin waves in yttrium iron garnet films. At the critical angle between the line of antidots and the magnetic field, we observe a high-intensity beam of spin waves moving along the line of antidots. The properties of these waves are investigated experimentally by Brillouin light scattering spectroscopy. The conditions required for the occurrence of this phenomenon based on an analysis of the properties of the isofrequency dependencies are presented. The numerical simulations are in good agreement with those of the experimental measurements.

  6. Negative permittivity and permeability spectra of Cu/yttrium iron garnet hybrid granular composite materials in the microwave frequency range

    SciTech Connect

    Tsutaoka, Takanori Fukuyama, Koki; Kinoshita, Hideaki; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2013-12-23

    The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.

  7. Spin Seebeck effect and spin Hall magnetoresistance at high temperatures for a Pt/yttrium iron garnet hybrid structure.

    PubMed

    Wang, Shuanhu; Zou, Lvkuan; Zhang, Xu; Cai, Jianwang; Wang, Shufang; Shen, Baogen; Sun, Jirong

    2015-11-14

    Based on unique experimental setups, the temperature dependences of the longitudinal spin Seebeck effect (LSSE) and spin Hall magnetoresistance (SMR) of the Pt/yttrium iron garnet (Pt/YIG) hybrid structure are determined in a wide temperature range up to the Curie temperature of YIG. From a theoretical analysis of the experimental relationship between the SMR and temperature, the spin mixing conductance of the Pt/YIG interface is deduced as a function of temperature. Adopting the deduced spin mixing conductance, the temperature dependence of the LSSE is well reproduced based on the magnon spin current theory. Our research sheds new light on the controversy about the theoretical models for the LSSE.

  8. Ferric iron contents of clinopyroxene from cratonic mantle and partitioning behaviour with garnet

    NASA Astrophysics Data System (ADS)

    Woodland, A. B.

    2009-11-01

    Together with garnet and spinel, clinopyroxene is known to be an important carrier of Fe 3+ in mantle-derived peridotites. The systematics of Fe 3+ incorporation in clinopyroxene and the Fe 3+-partitioning behaviour between clinopyroxene and garnet have been investigated from a large suite of garnet peridotite xenoliths (> 50) mostly originating from the upper mantle beneath the Kaapvaal craton (Southern Africa). A correlation between Na and Fe 3+ is apparent that is not observed for clinopyroxene from spinel peridotites. This indicates a change in how Fe 3+ substitutes into clinopyroxene when going from the spinel to the garnet peridotite facies in the upper mantle. A general decrease in Fe 3+/∑Fe with increasing temperature is also observable, however, when considered in terms of Fe 3+ cations per formula unit this negative correlation with temperature disappears. This partial decoupling Fe 3+/∑Fe values from the actual Fe 3+ contents can be understood in terms of two factors: 1) Fe 3+ incorporation is controlled by a number of parameters, including ƒO 2, the degree of depletion of a given sample, as well as the composition of the clinopyroxene itself, and 2) Fe 3+/∑Fe in clinopyroxene can also be directly influenced by changes in Fe 2+ content, which is known to be temperature dependent in the presence of opx and garnet. The partitioning of Fe 3+ between clinopyroxene and garnet can be considered in terms of two different Fe 3+-Al exchange equilibria involving Na-bearing components in clinopyroxene and either Ca-bearing or Fe 2+-bearing components in the coexisting garnet. Results from the natural samples suggest a temperature dependence, with Fe 3+ being progressively partitioned into garnet with increasing temperature. However, the magnitude of this effect remains open due to uncertainties in available thermodynamic data. Analysis of the two exchange equilibria point to an error in the tabulated standard enthalpy of formation of NaFe 3+Si 2O 6 aegerine

  9. Iron site populations from Mössbauer spectroscopy in Ti-bearing garnets from Mt Vulture (Italy)

    NASA Astrophysics Data System (ADS)

    Ortalli, I.; Pedrazzi, G.; Schingaro, E.; Scordari, F.

    1994-12-01

    The present work concerns the determination of the cation site populations and crystal chemical formulae of some Ti-rich silicate garnets. The samples come from Mt. Vulture, a volcanic complex located on the east side of the Lucania Apennines (south Italy). Mössbauer spectroscopy (MS) has been used in order to obtain the iron site occupancies. Two different models for interpreting the Fe2+ peak positions in the Mössbauer spectra are compared, and some methodological aspects are discussed. The derived iron distributions have then been combined with the data obtained by electron probe microanalysis (EPMA) and single-crystal X-ray diffraction analysis (XRD) to obtain consistent crystal chemical formulae for these compounds.

  10. Growth of high-quality nanometre-thick yittrium iron garnet by sputtering and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Mitra, Arpita; Cespedes, Oscar; Ali, Mannan; Hickey, B. J.; University Of Regensburg Collaboration

    2015-03-01

    Observation of Spin Seebeck effect(SSE) in magnetic insulators has led to dramatic advances in spin currents research and its applications for thermo-spintronics devices. Here we report deposition of high quality nm-thick yittrium iron garnet(YIG) film on gadolinium gallium garnet(GGG) by RF magnetron sputtering. The morphology and magnetic properties of the films were studied by using AFM and SQUID VSM respectively. 10-60 nm thick films have surface roughness of 1-3Å,and (111) orientation. Our results show that magnetic properties of YIG depend strongly on thickness: magnetic moment has linear dependence at room temperature. The saturation magnetization and coercive field observed in thick films are 136 emu/cc and 0.50 Oe, respectively. Temperature dependence of magnetization of nm-thick YIG films has revealed an interesting result,which can be attributed to an additional magnetic phase at the YIG/GGG interface. The reduction in magnetization at low temperatures up to now has not been reported, but has significant relevance to the spin hall magnetoresistance(SMR) at low temperature.Our results on the temperature dependence of Gilbert damping factor of YIG and YIG/Pt films will lead to new physics, to understand its effect on spin mixing conductance and SMR in magnetic insulators

  11. Preparation and structural and magnetic characterization of yttrium-iron garnets by sol-gel techniques and microemulsions

    NASA Astrophysics Data System (ADS)

    Rodriguez, Paz Vaqueiro

    Yttrium iron garnet (YIG) has been synthesized by five different techniques. First, the garnet was prepared by solid-state reaction; furthermore the material was prepared by two sol-gel techniques: the citrate gel method and the malonate gel method, and by two techniques in microemulsion: sol-gel in microemulsion and coprecipitation in microemulsion. The properties of the material as obtained by solid-state reaction are those typical of the bulk material. By the two sol-gel techniques one obtain a fine divided material, composed of small particles. Depending on the annealing time and temperature, the mean particle size of the particles range from 30 to 500 nm. The lattice parameter of the material synthesized by sol-gel techniques is larger than that of the bulk material, and a lattice expansion occurs when the mean crystallite size decreases. The magnetic properties of the nanoparticles depend also on the mean particle size. The coercive field depends on the particle size, and at room temperature a maximum value occurs for a particle size around 150 nm. The saturation magnetization of the material decreases with the mean particle size, due to the existence of a noncollinear spin arrangement at the surface of the particles. Using microemulsion as a reaction medium, we hoped to improve the control on the particle size and on the particle size distribution. However, we did not obtain a material with a good quality (pure material and with a short particle size distribution).

  12. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    NASA Astrophysics Data System (ADS)

    Sokolov, N. S.; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Maksimova, K. Yu.; Grunin, A. I.; Bursian, V. E.; Lutsev, L. V.; Tabuchi, M.

    2016-01-01

    Pulsed laser deposition has been used to grow thin (10-84 nm) epitaxial layers of Yttrium Iron Garnet Y3Fe5O12 (YIG) on (111)-oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  13. Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

    SciTech Connect

    Sadovnikov, A. V. Nikitov, S. A.; Beginin, E. N.; Bublikov, K. V.; Grishin, S. V.; Sheshukova, S. E.; Sharaevskii, Yu. P.

    2015-11-28

    Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

  14. Tuning of the spin pumping in yttrium iron garnet/Au bilayer system by fast thermal treatment

    SciTech Connect

    Jin, Lichuan E-mail: hwzhang@uestc.edu.cn; Zhang, Huaiwu E-mail: hwzhang@uestc.edu.cn; Yang, Qinghui; Tang, Xiaoli; Zhong, Zhiyong; Zhang, Dainan; Xiao, John Q.

    2014-05-07

    In this Letter, we investigated the influence of the fast thermal treatment on the spin pumping in ferromagnetic insulator yttrium iron garnet (YIG)/normal metal Au bilayer system. The YIG/Au bilayer thin films were treated by fast annealing process with different temperatures from 0 to 800 °C. The spin pumping was studied using ferromagnetic resonance. The surface evolution was investigated using a high resolution scanning microscopy and an atomic force microscopy. A strong thermal related spin pumping in YIG/Au bilayer system has been revealed. It was found that the spin pumping process can be enhanced by using fast thermal treatment due to the thermal modifications of the Au surface. The effective spin-mixing conductance of the fast thermal treated YIG/Au bilayer has been obtained.

  15. Domain structure of a thin single-crystal plate of terbium iron garnet near the magnetic compensation point

    NASA Astrophysics Data System (ADS)

    Sokolov, B. Yu.; Talabov, M. D.; Sharipov, M. Z.

    2013-02-01

    The domain structure of a thin single-crystal plate of the iron garnet Tb3Fe5O12 has been investigated using the magneto-optical method in the temperature range near the magnetic compensation point of this ferrimagnet T c = 248.6 K. It has been shown that, when the temperature of the sample approaches the magnetic compensation point, the domain width significantly increases, but remains finite at T = T c . The magnetic H- T phase diagram, which determines the boundary between the multidomain and domain-free (uniformly magnetized) states of the sample, has been constructed using the data on visual observations of the transformation of the domain structure with variations in the temperature and external magnetic field. The results obtained have been interpreted in terms of the thermodynamic theory of stability of different magnetic phases of a two-sublattice cubic ferrimagnet near T c .

  16. Reflection and Transmission Coefficient of Yttrium Iron Garnet Filled Polyvinylidene Fluoride Composite Using Rectangular Waveguide at Microwave Frequencies

    PubMed Central

    Soleimani, Hassan; Abbas, Zulkifly; Yahya, Noorhana; Shameli, Kamyar; Soleimani, Hojjatollah; Shabanzadeh, Parvaneh

    2012-01-01

    The sol-gel method was carried out to synthesize nanosized Yttrium Iron Garnet (YIG). The nanomaterials with ferrite structure were heat-treated at different temperatures from 500 to 1000 °C. The phase identification, morphology and functional groups of the prepared samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. The YIG ferrite nanopowder was composited with polyvinylidene fluoride (PVDF) by a solution casting method. The magnitudes of reflection and transmission coefficients of PVDF/YIG containing 6, 10 and 13% YIG, respectively, were measured using rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in X-band frequencies. The results indicate that the presence of YIG in polymer composites causes an increase in reflection coefficient and decrease in transmission coefficient of the polymer. PMID:22942718

  17. One-dimensional photonic crystals with highly Bi-substituted iron garnet defect in reflection polar geometry

    NASA Astrophysics Data System (ADS)

    Mikhailova, T. V.; Berzhansky, V. N.; Karavainikov, A. V.; Shaposhnikov, A. N.; Prokopov, A. R.; Lyashko, S. D.

    2016-08-01

    It is represented the results of modelling of magnetooptical properties in reflection polar geometry of one-dimensional photonic crystal, in which highly Bi-substituted iron garnet defect of composition Bi1.0Y0.5Gd1.5Fe4.2Al0.8O12 / Bi2.8Y0.2Fe5Oi2 is located between the dielectric Bragg mirrors (SiO2 / TiO2)m (were m is number of layer pairs) and buffer SiO2 and gold top layers of different thicknesses is placed on structure. The modification of spectral line- shapes of microcavity and Tamm plasmon-polariton modes depending on m is found.

  18. Spin-Current to Charge-Current Conversion and Magnetoresistance in a Hybrid Structure of Graphene and Yttrium Iron Garnet

    NASA Astrophysics Data System (ADS)

    Mendes, J. B. S.; Alves Santos, O.; Meireles, L. M.; Lacerda, R. G.; Vilela-Leão, L. H.; Machado, F. L. A.; Rodríguez-Suárez, R. L.; Azevedo, A.; Rezende, S. M.

    2015-11-01

    The use of graphene in spintronic devices depends, among other things, on its ability to convert a spin excitation into an electric charge signal, a phenomenon that requires a spin-orbit coupling (SOC). Here we report the observation of two effects that show the existence of SOC in large-area CVD grown single-layer graphene deposited on a single crystal film of the ferrimagnetic insulator yttrium iron garnet (YIG). The first is a magnetoresistance of graphene induced by the magnetic proximity effect with YIG. The second is the detection of a dc voltage along the graphene layer resulting from the conversion of the spin current generated by spin pumping from microwave driven ferromagnetic resonance into a charge current, which is attributed to the inverse Rashba-Edelstein effect.

  19. Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque.

    PubMed

    Collet, M; de Milly, X; d'Allivy Kelly, O; Naletov, V V; Bernard, R; Bortolotti, P; Ben Youssef, J; Demidov, V E; Demokritov, S O; Prieto, J L; Muñoz, M; Cros, V; Anane, A; de Loubens, G; Klein, O

    2016-01-01

    In recent years, spin-orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin-orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin-orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current.

  20. Thermal properties of magnons and the spin Seebeck effect in yttrium iron garnet/normal metal hybrid structures

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; Rodríguez-Suárez, R. L.; Lopez Ortiz, J. C.; Azevedo, A.

    2014-04-01

    In the study of the spin Seebeck effect (SSE) in structures with a ferromagnetic insulator (FMI) in contact with a normal metal it is important to know the distributions of the temperatures of the magnon, phonon, and electron systems. Studies of the SSE in yttrium iron garnet (YIG) have relied on the thermal properties of magnons in YIG calculated with expressions valid for low temperatures. Here we present a calculation of the magnon specific heat and thermal conductivity in YIG and show that the values at room temperature are very discrepant from numbers used in the literature. With our values we calculate the temperature profiles of the magnon and phonon systems in a FMI subject to a temperature gradient in the configurations used to study the transverse and longitudinal SSE. In both cases the results are quite different from those obtained in previous studies.

  1. Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

    NASA Astrophysics Data System (ADS)

    Sadovnikov, A. V.; Beginin, E. N.; Bublikov, K. V.; Grishin, S. V.; Sheshukova, S. E.; Sharaevskii, Yu. P.; Nikitov, S. A.

    2015-11-01

    Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

  2. Radiotherapeutic bandage based on electrospun polyacrylonitrile containing holmium-166 iron garnet nanoparticles for the treatment of skin cancer.

    PubMed

    Munaweera, Imalka; Levesque-Bishop, Daniel; Shi, Yi; Di Pasqua, Anthony J; Balkus, Kenneth J

    2014-12-24

    Radiation therapy is used as a primary treatment for inoperable tumors and in patients that cannot or will not undergo surgery. Radioactive holmium-166 ((166)Ho) is a viable candidate for use against skin cancer. Nonradioactive holmium-165 ((165)Ho) iron garnet nanoparticles have been incorporated into a bandage, which, after neutron-activation to (166)Ho, can be applied to a tumor lesion. The (165)Ho iron garnet nanoparticles ((165)HoIG) were synthesized and introduced into polyacrylonitrile (PAN) polymer solutions. The polymer solutions were then electrospun to produce flexible nonwoven bandages, which are stable to neutron-activation. The fiber mats were characterized using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and inductively coupled plasma mass spectrometry. The bandages are stable after neutron-activation at a thermal neutron-flux of approximately 3.5 × 10(12) neutrons/cm(2)·s for at least 4 h and 100 °C. Different amounts of radioactivity can be produced by changing the amount of the (165)HoIG nanoparticles inside the bandage and the duration of neutron-activation, which is important for different stages of skin cancer. Furthermore, the radioactive bandage can be easily manipulated to irradiate only the tumor site by cutting the bandage into specific shapes and sizes that cover the tumor prior to neutron-activation. Thus, exposure of healthy cells to high energy β-particles can be avoided. Moreover, there is no leakage of radioactive material after neutron activation, which is critical for safe handling by healthcare professionals treating skin cancer patients.

  3. Radiotherapeutic bandage based on electrospun polyacrylonitrile containing holmium-166 iron garnet nanoparticles for the treatment of skin cancer.

    PubMed

    Munaweera, Imalka; Levesque-Bishop, Daniel; Shi, Yi; Di Pasqua, Anthony J; Balkus, Kenneth J

    2014-12-24

    Radiation therapy is used as a primary treatment for inoperable tumors and in patients that cannot or will not undergo surgery. Radioactive holmium-166 ((166)Ho) is a viable candidate for use against skin cancer. Nonradioactive holmium-165 ((165)Ho) iron garnet nanoparticles have been incorporated into a bandage, which, after neutron-activation to (166)Ho, can be applied to a tumor lesion. The (165)Ho iron garnet nanoparticles ((165)HoIG) were synthesized and introduced into polyacrylonitrile (PAN) polymer solutions. The polymer solutions were then electrospun to produce flexible nonwoven bandages, which are stable to neutron-activation. The fiber mats were characterized using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and inductively coupled plasma mass spectrometry. The bandages are stable after neutron-activation at a thermal neutron-flux of approximately 3.5 × 10(12) neutrons/cm(2)·s for at least 4 h and 100 °C. Different amounts of radioactivity can be produced by changing the amount of the (165)HoIG nanoparticles inside the bandage and the duration of neutron-activation, which is important for different stages of skin cancer. Furthermore, the radioactive bandage can be easily manipulated to irradiate only the tumor site by cutting the bandage into specific shapes and sizes that cover the tumor prior to neutron-activation. Thus, exposure of healthy cells to high energy β-particles can be avoided. Moreover, there is no leakage of radioactive material after neutron activation, which is critical for safe handling by healthcare professionals treating skin cancer patients. PMID:25396281

  4. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2001-01-01

    A general overview of the industrial garnet industry is provided. About 20 percent of global industrial garnet production takes place in the U.S. During 2000, an estimated 300 kt of industrial garnets were produced worldwide. The U.S. is the world's largest consumer of industrial garnet, consuming 56.9 kt in 2000.

  5. Magnetic and electrical properties of Ti-substituted yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Parkash, Om; Bahadur, D.

    1982-11-01

    We have investigated the possibility of formation of a garnet phase and the magnetic and electrical properties of the systems (a) Y2O3-CaO-Fe2O3-TiO2 and (b) Y2O3-Fe2O3-NiO- TiO2. X-ray data show the formation of single phase up to x=0.7, in the system (a) while the garnet phase could not be prepared in the system (b). Magnetization measurements indicated canting of spins on the tetrahedral sites in the system (a). Curie temperature decreased with increase in x in this system. Change in the activation energy for conduction has been observed near the Curie temperature. Seebeck coefficients were positive and essentially independent of temperature. Electrical properties have been explained on the basis of the model suggested by Austin and Mott. According to this model electron hopping in the octahedral sites may occur by jumping indirectly through tetrahedral site.

  6. Morphology and magnetic characterisation of aluminium substituted yttrium-iron garnet nanoparticles prepared using sol gel technique.

    PubMed

    Yahya, Noorhana; Al Habashi, Ramadan Masoud; Koziol, Krzysztof; Borkowski, Rafal Dunin; Akhtar, Majid Niaz; Kashif, Muhammad; Hashim, Mansor

    2011-03-01

    Aluminum substituted yttrium iron garnet nano particles with compositional variation of Y(3.0-x) A1(x)Fe5O12, where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 were prepared using sol gel technique. The X-ray diffraction results showed that the best garnet phase appeared when the sintering temperature was 800 degrees C. Nano-crystalline particles with high purity and sizes ranging from 20 to 100 nm were obtained. It was found that the aluminum substitution had resulted in a sharp fall of the d-spacing when x = 2, which we speculated is due to the preference of the aluminum atoms to the smaller tetrahedron and octahedron sites instead of the much larger dodecahedron site. High resolution transmission electron microscope (HRTEM) and electron diffraction (ED) patterns showed single crystal nanoparticles were obtained from this method. The magnetic measurement gave moderate values of initial permeability; the highest value of 5.3 was shown by sample Y3Fe5O12 at more than 100 MHz which was attributed to the morphology of the microstructure which appeared to be homogeneous. This had resulted in an easy movement of domain walls. The substitution of aluminum for yttrium is speculated to cause a cubic to rhombodedral structural change and had weakened the super-exchange interactions thus a fall of real permeability was observed. This might have created a strain in the sub-lattices and had subsequently caused a shift of resonance frequencies to more than 1.8 GHz when x > 0.5.

  7. The effect of gallium substitution on the microstructure and magnetic properties of yttrium iron garnet

    SciTech Connect

    Zaini, N. Z. M. Ibrahim, N. B.

    2015-09-25

    Y{sub 3}Fe{sub (5-y)}Ga{sub y}O{sub 12} (y = 0, 0.4, 1.4 and 2,4) thin films were prepared by sol-gel method and annealed for 2h in oxygen. The thin film’s characteristic were studied by an X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM) and a vibration sample magnetometer (VSM). The XRD show that all films have the garnet phase structure. The grain size particles measured using FESEM were between 45.08 nm to 51.58 nm, and the thickness were between 42 nm to 90 nm. The magnetic properties measured using VSM showed that result was shown with hysteresis loop. The magnetization saturation decreased from 144.26 to 2.76 emu/cm{sup 3} with the increasing substitution gallium. The substitution for y = 2.4 was shown the saturation magnetization was very low. The coercivity increased 35 to 75 Oe due the the increasing grain size.

  8. Indium-substitution and indium-less case effects on structural and magnetic properties of yttrium-iron garnet

    NASA Astrophysics Data System (ADS)

    Nazlan, Rodziah; Hashim, Mansor; Ibrahim, Idza Riati; Idris, Fadzidah Mohd; Ismail, Ismayadi; Ab Rahman, Wan Norailiana Wan; Abdullah, Nor Hapishah; Zulkimi, Muhammad Misbah Muhammad; Mustaffa, Muhammad Syazwan

    2015-10-01

    The effect of indium (In) substitution in the dynamics of structure and ferrimagnetism of yttrium iron garnet (YIG) employing sintering temperature as a temporary agent of composition and structural changes was reported in this study. The nanoparticles of YIG powder samples with various In content (x=0.0-0.4) were prepared via the mechanical alloying (MA) technique. A brief, yet revealing characterization of the samples was carried out via transmission electron microscope, X-ray diffraction, Raman spectroscopy, B-H Hysteresisgraph, and LCR-metre. The X-ray diffraction analysis of the samples prepared via the MA indicates the formation of single phase YIG structure at much lower sintering temperature than that in the conventional ceramic technique. The lattice constant increases as In content increases which obeys Vegard's Law due to the larger In3+ ions replacing the smaller Fe3+ ions. The saturation induction increased reaching about 699.1 G for x=0.3 and decreased with further In substitution. Three stages of ordered magnetism formation were identified which attributed to development of crystallinity and larger grains for magnetic domain accommodation. The Curie temperature shows a decrement in their values with In content due to weakening of superexchange interactions. Raman shifts from 268.1 to 272.2 cm-1 with increasing In content were observed due to stress developed in the YIG crystal structure.

  9. Observation of magnon-mediated current drag in Pt/yttrium iron garnet/Pt(Ta) trilayers

    PubMed Central

    Li, Junxue; Xu, Yadong; Aldosary, Mohammed; Tang, Chi; Lin, Zhisheng; Zhang, Shufeng; Lake, Roger; Shi, Jing

    2016-01-01

    Pure spin current, a flow of spin angular momentum without flow of any accompanying net charge, is generated in two common ways. One makes use of the spin Hall effect in normal metals (NM) with strong spin–orbit coupling, such as Pt or Ta. The other utilizes the collective motion of magnetic moments or spin waves with the quasi-particle excitations called magnons. A popular material for the latter is yttrium iron garnet, a magnetic insulator (MI). Here we demonstrate in NM/MI/NM trilayers that these two types of spin currents are interconvertible across the interfaces, predicated as the magnon-mediated current drag phenomenon. The transmitted signal scales linearly with the driving current without a threshold and follows the power-law Tn with n ranging from 1.5 to 2.5. Our results indicate that the NM/MI/NM trilayer structure can serve as a scalable pure spin current valve device which is an essential ingredient in spintronics. PMID:26932316

  10. Mean field analysis of the high temperature magnetic properties of terbium iron garnet in strong DC fields

    NASA Astrophysics Data System (ADS)

    Lahoubi, Mahieddine; Wang, Wei

    2015-11-01

    This paper is devoted to the description of the magnetic phase diagrams (MPD) together with a special interest to the determination of more precise values of some reliable parameters at the compensation point, Tcomp=243.5±0.5 K of the terbium iron garnet, Tb3Fe5O12 or TbIG. Using isothermal magnetizations performed on single crystal in strong DC magnetic fields up to 200 kOe applied along the <111>, <110> and <100> directions within the temperature range 128-295 K, field-induced phase transitions between collinear and canted phases are observed in the vicinity of Tcomp at critical fields, Hc2. In comparison with the measurement at zero external magnetic field, the specific heat, Cp(T) at 80 kOe along <111> shows an excess around Tcomp characterized by an anomaly which has a width in the boundaries of the canted phase and a maximum at 252 K, the more accurate value of the critical temperature, TC* of the MPD in the (Hc2-T) plane. Better determinations of the molecular field coefficients which represent the magnetic interactions on the Tb sublattice are obtained by an improved molecular field model based on the saturation effects of the Tb sublattice and the differential susceptibility contribution due to the Fe sublattices to the total magnetic susceptibility of TbIG. The results are discussed in terms of the previous theoretical studies of the MPD predicted for weakly anisotropic ferrimagnets.

  11. Significant reduction in spin pumping efficiency in a platinum/yttrium iron garnet bilayer at low temperature

    NASA Astrophysics Data System (ADS)

    Shigematsu, Ei; Ando, Yuichiro; Ohshima, Ryo; Dushenko, Sergey; Higuchi, Yukio; Shinjo, Teruya; Jürgen von Bardeleben, Hans; Shiraishi, Masashi

    2016-05-01

    The temperature evolution of a direct-current electromotive force (EMF) generated by spin pumping and the inverse-spin Hall effect in a platinum (Pt)/yttrium iron garnet (YIG) bilayer was investigated down to 80 K. The magnitude of the EMF decreased significantly with decreasing temperature and disappeared at approximately 80 K. 40-nm-thick YIG films fabricated by a metal organic decomposition method exhibited single-peak ferrimagnetic resonance (FMR) spectra without any spin wave resonance, which allowed us to precisely analyze the FMR spectra. We determined that the temperature evolution of the Gilbert damping constant is the dominant factor in the temperature dependence of the EMF. The comparison of the FMR linewidth between the X- and Q-bands revealed that an increase in Gilbert damping constant at low temperatures is not due to the enhancement of the spin pumping efficiency but due to an additional spin relaxation in the YIG film itself, which reduces the precession angle of the magnetization under the FMR conditions.

  12. Observation of magnon-mediated current drag in Pt/yttrium iron garnet/Pt(Ta) trilayers

    DOE PAGESBeta

    Li, Junxue; Xu, Yadong; Aldosary, Mohammed; Tang, Chi; Lin, Zhisheng; Zhang, Shufeng; Lake, Roger; Shi, Jing

    2016-03-02

    Pure spin current, a flow of spin angular momentum without flow of any accompanying net charge, is generated in two common ways. One makes use of the spin Hall effect in normal metals (NM) with strong spin–orbit coupling, such as Pt or Ta. The other utilizes the collective motion of magnetic moments or spin waves with the quasi-particle excitations called magnons. A popular material for the latter is yttrium iron garnet, a magnetic insulator (MI). Here we demonstrate in NM/MI/NM trilayers that these two types of spin currents are interconvertible across the interfaces, predicated as the magnon-mediated current drag phenomenon.more » The transmitted signal scales linearly with the driving current without a threshold and follows the power-law Tn with n ranging from 1.5 to 2.5. Lastly, our results indicate that the NM/MI/NM trilayer structure can serve as a scalable pure spin current valve device which is an essential ingredient in spintronics.« less

  13. Investigation of the unidirectional spin heat conveyer effect in a 200 nm thin Yttrium Iron Garnet film.

    PubMed

    Wid, Olga; Bauer, Jan; Müller, Alexander; Breitenstein, Otwin; Parkin, Stuart S P; Schmidt, Georg

    2016-01-01

    We have investigated the unidirectional spin wave heat conveyer effect in sub-micron thick yttrium iron garnet (YIG) films using lock-in thermography (LIT). Although the effect is small in thin layers this technique allows us to observe asymmetric heat transport by magnons which leads to asymmetric temperature profiles differing by several mK on both sides of the exciting antenna, respectively. Comparison of Damon-Eshbach and backward volume modes shows that the unidirectional heat flow is indeed due to non-reciprocal spin-waves. Because of the finite linewidth, small asymmetries can still be observed when only the uniform mode of ferromagnetic resonance is excited. The latter is of extreme importance for example when measuring the inverse spin-Hall effect because the temperature differences can result in thermovoltages at the contacts. Because of the non-reciprocity these thermovoltages reverse their sign with a reversal of the magnetic field which is typically deemed the signature of the inverse spin-Hall voltage. PMID:27311931

  14. Investigation of the unidirectional spin heat conveyer effect in a 200 nm thin Yttrium Iron Garnet film

    NASA Astrophysics Data System (ADS)

    Wid, Olga; Bauer, Jan; Müller, Alexander; Breitenstein, Otwin; Parkin, Stuart S. P.; Schmidt, Georg

    2016-06-01

    We have investigated the unidirectional spin wave heat conveyer effect in sub-micron thick yttrium iron garnet (YIG) films using lock-in thermography (LIT). Although the effect is small in thin layers this technique allows us to observe asymmetric heat transport by magnons which leads to asymmetric temperature profiles differing by several mK on both sides of the exciting antenna, respectively. Comparison of Damon-Eshbach and backward volume modes shows that the unidirectional heat flow is indeed due to non-reciprocal spin-waves. Because of the finite linewidth, small asymmetries can still be observed when only the uniform mode of ferromagnetic resonance is excited. The latter is of extreme importance for example when measuring the inverse spin-Hall effect because the temperature differences can result in thermovoltages at the contacts. Because of the non-reciprocity these thermovoltages reverse their sign with a reversal of the magnetic field which is typically deemed the signature of the inverse spin-Hall voltage.

  15. Sub-THz dielectric resonance in single crystal yttrium iron garnet and magnetic field tuning of the modes

    NASA Astrophysics Data System (ADS)

    Popov, M. A.; Zavislyak, I. V.; Srinivasan, G.

    2011-07-01

    The observation of dielectric resonance over the frequency range 40-110 GHz in single crystal yttrium iron garnet (YIG) and its magnetic field tuning characteristics are reported. The dimensions of YIG are appropriately chosen in order to have the dielectric resonance occur at a much higher frequency than the ferromagnetic resonance and avoid any hybrid spin-electromagnetic modes. The dielectric modes are magnetically tunable by 1 GHz with a magnetic field of ˜1.75 kOe. The tuning range and required bias magnetic fields, however, can be controlled with the sample dimensions (or the demagnetization factor Nzz). Theoretical calculations on magnetic field tuning characteristics for the dielectric modes are in reasonable agreement with the data. The theory also predicts a similar magnetic tuning of the dielectric modes in the sub-THz frequency range as well. The dielectric modes that can be tuned with a magnetic field are of importance for the realization of low-loss tunable devices, including resonators, isolators, and phase shifters operating in the sub-THz region.

  16. Investigation of the unidirectional spin heat conveyer effect in a 200 nm thin Yttrium Iron Garnet film

    PubMed Central

    Wid, Olga; Bauer, Jan; Müller, Alexander; Breitenstein, Otwin; Parkin, Stuart S. P.; Schmidt, Georg

    2016-01-01

    We have investigated the unidirectional spin wave heat conveyer effect in sub-micron thick yttrium iron garnet (YIG) films using lock-in thermography (LIT). Although the effect is small in thin layers this technique allows us to observe asymmetric heat transport by magnons which leads to asymmetric temperature profiles differing by several mK on both sides of the exciting antenna, respectively. Comparison of Damon-Eshbach and backward volume modes shows that the unidirectional heat flow is indeed due to non-reciprocal spin-waves. Because of the finite linewidth, small asymmetries can still be observed when only the uniform mode of ferromagnetic resonance is excited. The latter is of extreme importance for example when measuring the inverse spin-Hall effect because the temperature differences can result in thermovoltages at the contacts. Because of the non-reciprocity these thermovoltages reverse their sign with a reversal of the magnetic field which is typically deemed the signature of the inverse spin-Hall voltage. PMID:27311931

  17. Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin–orbit torque

    PubMed Central

    Collet, M.; de Milly, X.; d'Allivy Kelly, O.; Naletov, V. V.; Bernard, R.; Bortolotti, P.; Ben Youssef, J.; Demidov, V. E.; Demokritov, S. O.; Prieto, J. L.; Muñoz, M.; Cros, V.; Anane, A.; de Loubens, G.; Klein, O.

    2016-01-01

    In recent years, spin–orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin–orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin–orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current. PMID:26815737

  18. Q factor of dual-tunable microwave resonators based on yttrium iron garnet and barium strontium titanate layered structures

    NASA Astrophysics Data System (ADS)

    Ustinov, A. B.; Kalinikos, B. A.; Tiberkevich, V. S.; Slavin, A. N.; Srinivasan, G.

    2008-03-01

    Q factor of dual-tunable ferrite-ferroelectric hybrid wave microwave resonator was studied as a function of bias electric voltage U and bias magnetic field H. The resonator consisted of a thin (7μm) ferromagnetic resonator made of a single-crystal yttrium iron garnet film and a dielectric resonator made of relatively thick (500μm) plate of ceramic barium strontium titanate having similar in-plane sizes. A frequency spectrum of the resonator consisted of two hybridized modes: a quasiferromagnetic mode and a quasidielectric mode. Maximum electric tuning band of 5% of the resonance frequency has been observed for H values corresponding to maximum hybridization of the modes. The Q factor of the resonator was varied from 30-300 depending on both U and H. In general, Q factor decreases with increasing level of modes' hybridization and electric tuning interval. Thus, Q factor and electric tunability are competing characteristics of hybrid ferrite-ferroelectric microwave resonators.

  19. Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque.

    PubMed

    Collet, M; de Milly, X; d'Allivy Kelly, O; Naletov, V V; Bernard, R; Bortolotti, P; Ben Youssef, J; Demidov, V E; Demokritov, S O; Prieto, J L; Muñoz, M; Cros, V; Anane, A; de Loubens, G; Klein, O

    2016-01-01

    In recent years, spin-orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin-orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin-orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current. PMID:26815737

  20. Effects of off-stoichiometry and density on the magnetic and magneto-optical properties of yttrium iron garnet films by magnetron sputtering method

    SciTech Connect

    Yang Qinghui; Zhang Huaiwu; Wen Qiye; Liu Yingli

    2010-10-15

    Yttrium iron garnet films were deposited on Si and Si/CeO{sub 2} substrates by magnetron sputtering method followed by postannealing. By varying the fabrication parameters such as sputtering atmosphere, sputtering power, and annealing atmosphere, single phase garnet films were obtained with different off-stoichiometry and film density. The dependence of cation ratio, magnetic and magneto-optical characteristics, and absorption coefficient were systemically investigated. The results reveal that a proper oxygen pressure in both sputtering and annealing process give rise to a small cation ratio of (Fe{sup 2+} or Fe{sup 4+})/Fe{sup 3+}, thus is beneficial to obtain large saturation magnetization, large Faraday rotation, and small optical absorption. The sputtering power can also affect the properties of the film through changing the film density. Our results indicate that the properties of sputtering deposited yttrium iron garnet (YIG) film can be easily tuned and optimized by modifying the off-stoichiometry and density of the film, thus provides flexibility to fabricate YIG film for extensive applications.

  1. Garnet polycrystals

    NASA Astrophysics Data System (ADS)

    Whitney, Donna; Seaton, Nca

    2010-05-01

    Electron backscattered diffraction (EBSD) studies have revealed complex microstructures in garnet, including features developed during crystal growth and/or deformation. New data show that garnets commonly grow as clusters of grains (polycrystals) juxtaposed by high-angle boundaries. Garnet polycrystals may form at any stage of metamorphism following nucleation of garnet: polycrystals may form early as a result of close spacing of nuclei, or later via impingement of larger grains. EBSD analysis of garnets in metamorphic rocks from 9 localities in the US, Canada, Turkey, Iran, and Colombia detected polycrystals at every site. Evidence for internal deformation of garnet was observed in only one sample, a calc-pelite dominated by plagioclase; all other samples are mica schists. Three sites displayed garnet shape-preferred orientation, but none had a crystallographic preferred orientation of garnet. In some samples, polycrystals comprise ~20-30% of garnets analyzed. Some early-coalescing polycrystals exhibit growth zoning concentric about the geometric center of the polycrystal; i.e., zoning is unrelated to the location of internal grain boundaries. In other polycrystals, Fe-Mn-Mg zoning has a different pattern than that of Ca. Some polycrystals are characterized by high-angle misorientation boundaries in special orientations, indicating that these polycrystals are not random clusters of grains. Special boundaries were detected in 0-60% of garnets analyzed. Polycrystal formation may relate to the presence of chemical or textural heterogeneities (e.g. precursor phases, deformation features) that allowed close spacing of garnet nuclei. It is important to recognize polycrystals because internal grain boundaries may affect diffusion pathways and length scales and may facilitate communication of garnet interiors with matrix phases, thereby influencing reaction history and garnet composition and zoning.

  2. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2010-01-01

    In 2009, U.S. production of crude garnet concentrate for industrial use was estimated to be 56.5 kt (62,300 st), valued at about $8.85 million. This was a 10-percent decrease in quantity compared with 2008 production. Refined garnet material sold or used was 28 kt (31,000 st) valued at $7.96 million.

  3. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2011-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet's angular fractures, relatively high hardness and specific gravity, chemical inertness and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  4. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2012-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet's angular fractures, relatively high hardness and specific gravity, chemical inertness, and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  5. Domain self-organization in iron garnet films in pulsed magnetic fields with a frequency between 0.001 and 25 Hz

    NASA Astrophysics Data System (ADS)

    Osadchenko, V. Kh.; Kandaurova, G. S.; Pashko, A. G.

    2007-04-01

    The results of studying processes of self-organization in a domain structure of highly anisotropic iron garnet films with perpendicular anisotropy in an ac magnetic field of a symmetrical meander type (with rectangular pulses with a frequency of 0.001-25 Hz and an amplitude H 0 = 0-70 Oe are reported for the first time. In the frequency range from 0.01 to 25 Hz, there has been observed an anger (excited) state, which is characterized by the formation of a close packing of spiral dynamic domains.

  6. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2006-01-01

    In 2005, US production of crude garnet concentrate for industrial use was 28.4 kt valued at $3.05 million. Refined garnet material sold or used was 30.4 kt valued at $10 million. For the year, the US was one of the world's leading consumers of industrial garnet. Domestic values for crude concentrates for different applications ranged from about $53 to $120/t. In the short term, excess production capacity, combined with suppliers that vary in quality, grain size and mineral type, will keep prices down.

  7. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2000-01-01

    The state of the global industrial garnet industry in 1999 is discussed. Industrial garnet mined in the U.S., which accounts for approximately one-third of the world's total, is usually a solid-solution of almandine and pyrope. The U.S. is the largest consumer of industrial garnet, using an estimated 47,800 st in 1999 as an abrasive and as a filtration medium in the petroleum industry, filtration plants, aircraft and motor vehicle manufacture, shipbuilding, wood furniture finishing operations, electronic component manufacture, ceramics manufacture, and glass production. Prices for crude concentrates ranged from approximately $50 to $110/st and refined garnet from $50 to $215/st in 1999, depending on type, source, quantity purchased, quality, and application.

  8. Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

    PubMed Central

    Onbasli, Mehmet C.; Beran, Lukáš; Zahradník, Martin; Kučera, Miroslav; Antoš, Roman; Mistrík, Jan; Dionne, Gerald F.; Veis, Martin; Ross, Caroline A.

    2016-01-01

    Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices. PMID:27025269

  9. Red Shift of Faraday Rotation in Thin Films of Completely Bismuth-Substituted Iron Garnet Bi3Fe5O12

    NASA Astrophysics Data System (ADS)

    Chern, Ming-Yau; Lo, Fang-Yuh; Liu, Da-Ren; Yang, Kuang; Liaw, Juin-Sen

    1999-12-01

    The magnetooptical Faraday rotations of epitaxial films of BixY3-xFe5O12 (Bi:YIG) grown on [111]-oriented gadolinium gallium garnet (GGG) substrates by pulsed laser deposition (PLD) were studied with bismuth content x = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0. The Faraday rotation angles, θF, of the films were measured by the method of rotating analyzer ellipsometry (RAE) with the photon energy varied from 1.5 to 3.5 eV. It was shown that in addition to the increase of the Faraday rotation with increasing x, the peaks of θF shifted toward the red region as x changed from 1.0 to 1.5. The peak positions of θF for the completely Bi-substituted iron garnet, Bi3Fe5O12 (BIG), were found at 2.4 and 2.8 eV with peak values as large as -23 deg/µm and 44 deg/µm, respectively

  10. Active tuning of a microstrip hairpin-line microwave bandpass filter on a polycrystalline yttrium iron garnet substrate using small magnetic fields

    NASA Astrophysics Data System (ADS)

    Gillette, S. M.; Geiler, A. L.; Chen, Z.; Chen, Y.; Arruda, T.; Xie, C.; Wang, L.; Zhu, X.; Liu, M.; Mukerjee, S.; Vittoria, C.; Harris, V. G.

    2011-04-01

    Active magnetic tuning of a microstrip hairpin-line coupled resonator bandpass filter fabricated on a polycrystalline yttrium iron garnet substrate has been demonstrated. The filter exhibits a five-pole Chebyshev response with passband center frequency tunability from 8.3 to 9 GHz under low applied H fields of 50-200 Oe. The instantaneous bandwidth was measured to be approximately 1 GHz. During tuning, passband center frequency insertion loss varies between 1 and 1.4 dB. Good agreement between simulated and measured device performance was demonstrated. Advantages of the proposed filter design include planar geometry, compact size, low insertion loss, and low field tunability. The proposed design approach lends itself to the implementation of a wide range of filter responses, including low pass, high pass, bandpass, and band stop, as well as passband characteristics, including center frequency, fractional bandwidth, passband ripple, out-of-band rejection, etc.

  11. A comparative transport study of Bi{sub 2}Se{sub 3} and Bi{sub 2}Se{sub 3}/yttrium iron garnet

    SciTech Connect

    Jiang, Zilong; Tang, Chi; Shi, Jing; Katmis, Ferhat; Wei, Peng; Moodera, Jagadeesh S.

    2014-06-02

    Bilayers of 20 quintuple layer Bi{sub 2}Se{sub 3} on 30 nm thick yttrium iron garnet (YIG) have been grown with molecular beam epitaxy in conjunction with pulsed laser deposition. The presence of the ferri-magnetic insulator YIG causes additional scattering to the surface states of the Bi{sub 2}Se{sub 3} topological insulator layer, as indicated by the temperature dependence of the resistivity. From the two-channel analysis of the Hall data, we find that the surface contribution in the bilayer samples is greatly reduced. Furthermore, the weak antilocalization effect from the surface states is clearly suppressed due to the presence of the YIG layer.

  12. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2013-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet’s angular fractures, relatively high hardness and specific gravity, chemical inertness and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  13. Enhancement of the electron electric dipole moment in gadolinium garnets

    SciTech Connect

    Mukhamedjanov, T.N.; Dzuba, V.A.; Sushkov, O.P.

    2003-10-01

    Effects caused by the electron electric dipole moment (EDM) in gadolinium garnets are considered. Experimental studies of these effects could improve the current upper limit on the electron EDM by several orders of magnitude. We suggest a consistent theoretical model and perform calculations of observable effects in gadolinium gallium garnet and gadolinium iron garnet. Our calculation accounts for both direct and exchange diagrams.

  14. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2007-01-01

    World production of industrial garnet was about 326 kt in 2006, with the U.S. producing about 11 percent of this total. U.S. consumption, imports, and exports were estimated at 74.3 kt, 52.3 kt, and 13.2 kt, respectively. The most important exporters are Australia, China, and India. Although demand is expected to rise over the next 5 years, prices are expected to remain low in the short term.

  15. 50 MeV, Li3+ - ion irradiation effect on magnetic ordering of Y3+ - substituted yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Sharma, P. U.; Zankat, K. B.; Dolia, S. N.; Modi, K. B.

    2016-05-01

    This communication presents the effect of non-magnetic Y3+ ions substitution for magnetic Fe3+ ions and 50 MeV, Li3+ ion irradiation (fluence: 5 × 1013 ions/cm2) on magnetic ordering and Neel temperature of Y3+xFe5-xO12 (x = 0.0, 0.2, 0.4 and 0.6) garnet system, studied by means of X-ray powder diffractometry and thermal variation of low field (0.5 Oe) ac susceptibility measurements. The un-irradiated compositions exhibit normal ferrimagnetic behavior with decrease in transition temperature (TN) on increasing Y3+-concentration (x). The irradiated counterparts are characterized by tailing effect indicative of non-uniform effect of irradiation and lower value of TN. The results have been discussed based on the weakening of magnetic exchange interactions and cumulative effect of redistribution of cations and fractional creation of localized paramagnetic centers resulting from swift heavy ion irradiation. The Neel temperatures and exchange integrals have been calculated theoretically.

  16. Localized excitation of magnetostatic surface spin waves in yttrium iron garnet by shorted coaxial probe detected via spin pumping and rectification effect

    SciTech Connect

    Soh, Wee Tee Ong, C. K.; Peng, Bin

    2015-04-21

    We demonstrate the localized excitation and dc electrical detection of magnetostatic surface spin waves (MSSWs) in yttrium iron garnet (YIG) by a shorted coaxial probe. Thin films of NiFe and Pt are patterned at different regions onto a common bulk YIG substrate. A shorted coaxial probe is used to excite spin precession locally near various patterned regions. The dc voltages across the corresponding regions are recorded. For excitation of the Pt regions, the dc voltage spectra are dominated by the spin pumping of MSSWs from YIG, where various modes can be clearly distinguished. For the NiFe region, it is also found that spin pumping from MSSWs generated in YIG dominated the spectra, indicating that the spin pumped currents are dissipated into charge currents via the inverse Spin Hall effect (ISHE) in NiFe. For all regions, dc signals from YIG MSSWs are observed to be much stronger than the ferromagnetic resonance (FMR) uniform mode, likely due to the nature of the microwave excitation. The results indicate the potential of this probe for microwave imaging via dc detection of spin dynamics in continuous and patterned films.

  17. Non-local detection of spin dynamics via spin rectification effect in yttrium iron garnet/SiO{sub 2}/NiFe trilayers near simultaneous ferromagnetic resonance

    SciTech Connect

    Soh, Wee Tee Ong, C. K.; Peng, Bin

    2015-08-15

    The spin rectification effect (SRE), a phenomenon that generates dc voltages from ac microwave fields incident onto a conducting ferromagnet, has attracted widespread attention due to its high sensitivity to ferromagnetic resonance (FMR) as well as its relevance to spintronics. Here, we report the non-local detection of yttrium iron garnet (YIG) spin dynamics by measuring SRE voltages from an adjacent conducting NiFe layer up to 200 nm thick. In particular, we detect, within the NiFe layer, SRE voltages stemming from magnetostatic surface spin waves (MSSWs) of the adjacent bulk YIG which are excited by a shorted coaxial probe. These non-local SRE voltages within the NiFe layer that originates from YIG MSSWs are present even in 200 nm-thick NiFe films with a 50 nm thick SiO{sub 2} spacer between NiFe and YIG, thus strongly ruling out the mechanism of spin-pumping induced inverse spin Hall effect in NiFe as the source of these voltages. This long-range influence of YIG dynamics is suggested to be mediated by dynamic fields generated from YIG spin precession near YIG/NiFe interface, which interacts with NiFe spins near the simultaneous resonance of both spins, to generate a non-local SRE voltage within the NiFe layer.

  18. Determination of the easy axis of magnetization in terbium-yttrium iron garnet Tb1Y2Fe5O12 at low temperatures

    NASA Astrophysics Data System (ADS)

    Lahoubi, Mahieddine; Wang, Wei; Pu, Shengli

    2015-11-01

    Experimental investigations have been carried out on a spherical single crystal of terbium yttrium iron garnet (Tb1Y2Fe5O12) by means of magnetization measurements in strong dc magnetic fields up to 200 kOe applied along the <111>, <110> and <100> crystallographic directions at low temperatures (T<20 K) with a high degree of resolution both in field and temperature. The strong anisotropic magnetic behavior which appears at 4.2 K is due to the competition between <111> and <100> directions to be the easy axis of spontaneous magnetization while the <110> direction remains the more difficult axis. The magnetization measurement at 4.2 K leaving the sample to rotate freely on itself suggests that the easy axis of spontaneous magnetization is along the <100> direction. However, due to the magnetic anisotropy energies associated with both <100> and <111> directions which are close to each other, the phase <111> becomes more stable as soon as the magnetic field exceeds 10 kOe or the temperature is higher than 10 K. The results are compared with previous works.

  19. Electric-field-induced reorientation and flip in domain magnetization and light diffraction in an yttrium-iron-garnet/lead-zirconate-titanate bilayer

    NASA Astrophysics Data System (ADS)

    Zavislyak, I. V.; Sohatsky, V. P.; Popov, M. A.; Srinivasan, G.

    2013-04-01

    A continuous reorientation and an abrupt flip to a canted structure in the magnetization of stripe domains are observed under the influence of an electric field in an yttrium-iron-garnet (YIG)/lead-zirconate-titanate (PZT) bilayer. Magneto-optic techniques have been utilized for the observation of the domain structure and the magnetization flip. It is found that electrically generated mechanical stress in PZT induces an uniaxial anisotropy field in YIG, which is large enough to initially cause a gradual change in the domain magnetization and then a transition from out-of-plane orientation to a canted state for a threshold electric field. Additional evidence for the spin flip has been obtained from data on the modulation of intensity of linearly polarized light due to diffraction by the stripe domains. A comprehensive theory for the voltage-induced magnetization flip is discussed and compared with the data. The magnetic transitions and the theory discussed here are of interests for electric-field-controlled magneto-optic and spintronic devices.

  20. Mössbauer Spectral Properties of Yttrium Iron Garnet, Y3Fe5O12, and Its Isovalent and Nonisovalent Yttrium-Substituted Solid Solutions.

    PubMed

    Long, Gary J; Grandjean, Fernande; Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K

    2016-04-01

    Several high-resolution Mössbauer spectra of yttrium iron garnet, Y3Fe5O12, have been fit as a function of temperature with a new model based on a detailed analysis of the spectral changes that result from a reduction from the cubic Ia3̅d space group to the trigonal R3̅ space group. These spectral fits indicate that the magnetic sextet arising from the 16a site in cubic symmetry is subdivided into three sextets arising from the 6f, the 3d, 3d, and the 1a, 1b, 2c sites in rhombohedral-axis trigonal symmetry. The 24d site in cubic Ia3̅d symmetry is subdivided into four sextets arising from four different 6f sites in R3̅ rhombohedral-axis trigonal symmetry, sites that differ only by the angles between the principal axis of the electric field gradient tensor and the magnetic hyperfine field assumed to be parallel with the magnetic easy axis. This analysis, when applied to the potential nuclear waste storage compounds Y(3-x)Ca(0.5x)Th(0.5x)Fe5O12 and Y(3-x)Ca(0.5x)Ce(0.5x)Fe5O12, indicates virtually no perturbation of the structural, electronic, and magnetic properties upon substitution of small amounts of calcium(II) and thorium(IV) or cerium(IV) onto the yttrium(III) 24c site as compared with Y3Fe5O12. The observed broadening of the four different 6f sites derived from the 24d site results from the substitution of yttrium(III) with calcium(II) and thorium(IV) or cerium(IV) cations on the next-nearest neighbor 24c site. In contrast, the same analysis applied to Y(2.8)Ce(0.2)Fe5O12 indicates a local perturbation of the magnetic exchange pathways as a result of the presence of cerium(IV) in the 24c next-nearest neighbor site of the iron(III) 24d site. PMID:26998613

  1. Mössbauer Spectral Properties of Yttrium Iron Garnet, Y3Fe5O12, and Its Isovalent and Nonisovalent Yttrium-Substituted Solid Solutions.

    PubMed

    Long, Gary J; Grandjean, Fernande; Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K

    2016-04-01

    Several high-resolution Mössbauer spectra of yttrium iron garnet, Y3Fe5O12, have been fit as a function of temperature with a new model based on a detailed analysis of the spectral changes that result from a reduction from the cubic Ia3̅d space group to the trigonal R3̅ space group. These spectral fits indicate that the magnetic sextet arising from the 16a site in cubic symmetry is subdivided into three sextets arising from the 6f, the 3d, 3d, and the 1a, 1b, 2c sites in rhombohedral-axis trigonal symmetry. The 24d site in cubic Ia3̅d symmetry is subdivided into four sextets arising from four different 6f sites in R3̅ rhombohedral-axis trigonal symmetry, sites that differ only by the angles between the principal axis of the electric field gradient tensor and the magnetic hyperfine field assumed to be parallel with the magnetic easy axis. This analysis, when applied to the potential nuclear waste storage compounds Y(3-x)Ca(0.5x)Th(0.5x)Fe5O12 and Y(3-x)Ca(0.5x)Ce(0.5x)Fe5O12, indicates virtually no perturbation of the structural, electronic, and magnetic properties upon substitution of small amounts of calcium(II) and thorium(IV) or cerium(IV) onto the yttrium(III) 24c site as compared with Y3Fe5O12. The observed broadening of the four different 6f sites derived from the 24d site results from the substitution of yttrium(III) with calcium(II) and thorium(IV) or cerium(IV) cations on the next-nearest neighbor 24c site. In contrast, the same analysis applied to Y(2.8)Ce(0.2)Fe5O12 indicates a local perturbation of the magnetic exchange pathways as a result of the presence of cerium(IV) in the 24c next-nearest neighbor site of the iron(III) 24d site.

  2. The influence of the iron content on the reductive decomposition of A{sub 3−x}Fe{sub x}Al{sub 2}Si{sub 3}O{sub 12} garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

    SciTech Connect

    Aparicio, Claudia Filip, Jan Mashlan, Miroslav Zboril, Radek

    2014-10-27

    Thermally-induced reductive decomposition of natural iron-bearing garnets of the almandine-pyrope and almandine-spessartine series were studied at temperatures up to 1200 °C (heating rate of 10 °C/min) under atmosphere of forming gas (10% of H{sub 2} in N{sub 2}). Crystallochemical formula of the studied garnet was calculated as {sup VIII}(A{sub 3−x}Fe{sub x}{sup 2+}){sup VI}(Al,Fe{sup 3+}){sub 2}Si{sub 3}O{sub 12}, where the amount of Fe{sup 3+} in the octahedral sites is negligible with the exception of pyrope, A = Mg, Mn, and 0.47 ≤ x ≤ 2.85. The observed decomposition temperature, determined from differential scanning calorimetry and thermogravimetry, is greater than 1000 °C in all cases and showed almost linear dependence on the iron content in the dodecahedral sites of the studied garnets, with the exception of garnet with a near-pyrope composition (Prp{sub 80}Alm{sub 20}). The initial garnet samples and decomposition products were characterized in details by means of X-ray powder diffraction and {sup 57}Fe Mössbauer spectroscopy. We found that all studied garnets have common decomposition products such as metallic iron (in general, rounded particles below 4 μm) and Fe-spinel; the other identified decomposition products depend on starting chemical composition of the garnet: Fe-cordierite, olivine (fayalite or tephroite), cristobalite, pyroxene (enstatite or pigeonite), and anorthite. Anorthite and pigeonite were only present in garnets with Ca in the dodecahedral site. All the identified phases were usually well crystallized.

  3. Empirical garnet muscovite geothermometry in metapelites

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Ming; Wang, Xin-She; Yang, Chong-Hui; Geng, Yuan-Sheng; Liu, Fu-Lai

    2002-05-01

    Two empirical garnet-muscovite geothermometers, assuming no ferric iron (Model A) and 50% ferric iron (Model B) in muscovite, respectively, were calibrated under the physical conditions of P=3.0-14.0 kbar and T=530-700 °C. The input temperatures and pressures were determined by simultaneously applying the garnet-biotite thermometer [Am. Mineral. 85 (2000) 881.] and the GASP geobarometer [Am. Mineral. 86 (2001) 1117.] to natural metapelites. To confirm internal thermodynamic consistency, Holdaway's [Am. Mineral. 85 (2000) 881.] garnet mixing properties were adopted. Muscovite was treated as a symmetric Fe-Mg-Al VI ternary solid solution, and its Margules parameters were derived in this work. The resulting two formulae reproduced the input garnet-biotite temperatures well within ±50 °C, and gave identical results for a great body of natural samples. Moreover, they successfully distinguished the systematic changes of temperatures of different grade rocks from a prograde sequence, inverted metamorphic zone, and thermal contact aureole. Pressure estimation has almost no effect on the two formalisms of the garnet-muscovite geothermometer. Assuming analytical error of ±5% for the relevant components of both garnet and muscovite, the total random uncertainty of the two formulations will generally be within ±5 °C. The two thermometers derived in this work may be used as practical tools to metamorphic pelites under the conditions of 480 to 700 °C, low- to high-pressure, in the composition ranges Xalm=0.51-0.82, Xpyr=0.04-0.22, and Xgros=0.03-0.24 in garnet, and Fe tot=0.03-0.17, and Mg=0.04-0.14 atoms p.f.u. in muscovite.

  4. Specific features of spontaneous reorientation of the magnetic moment in a single-crystal thin plate of the iron garnet Tb0.2Y2.8Fe5O12

    NASA Astrophysics Data System (ADS)

    Niyazov, L. N.; Sokolov, B. Yu.; Sharipov, M. Z.

    2012-09-01

    The Faraday effect, light scattering, and changes in the domain structure of a single-crystal thin plate of the iron garnet Tb0.2Y2.8Fe5O12 cut parallel to the (110) crystallographic plane have been experimentally investigated in the temperature range of the spontaneous magnetic orientational phase transition. It has been established that the transformation of the domain structure of the studied sample due to the orientational phase transition is accompanied by a significant temperature hysteresis. A model of the spontaneous reorientation of the magnetic moment vector of the crystal has been proposed by analyzing the results of visual observations of the domain structure and the temperature dependences of the Faraday effect and light scattering. In the proposed model, preference is given to the spin wave mechanism of nucleation of domains of the equilibrium magnetic phases.

  5. Wide frequencies range of spin excitations in a rare-earth Bi-doped iron garnet with a giant Faraday rotation

    NASA Astrophysics Data System (ADS)

    Parchenko, Sergii; Stupakiewicz, Andrzej; Yoshimine, Isao; Satoh, Takuya; Maziewski, Andrzej

    2013-10-01

    Ultrafast magnetization dynamics of a rare-earth Bi-doped garnet were studied using an optical pump-probe technique via the inverse Faraday effect. We observed a wide range of frequency modes of the magnetization precession, covering two orders of magnitude. The excitation efficiency of low-frequency precessions in the GHz range, together with a significant beating effect, strongly depended on the amplitude of the external magnetic field. On the contrary, high-frequency precession was independent of the external magnetic field. The obtained results may be exploited in the development of wide class of microwave and magneto-optical devices.

  6. Highly luminescent garnets for magneto-optical photonic crystals

    NASA Astrophysics Data System (ADS)

    Grishin, A. M.; Khartsev, S. I.

    2009-09-01

    We compare luminescent properties of several Er-doped garnets as building blocks in all-garnet heteroepitaxial magneto-optical photonic crystals. Pulsed laser deposited La3Ga5O12, Gd3Ga5O12, Y3Fe5O12, and rf-magnetron sputtered Bi3Fe5O12 were chosen to host Er3+ ions on dodecahedral lattice sites. Er substituents with the concentration of 0.5 at. % (0.1 garnet formula units) do not decrease giant Faraday rotation in Bi2.9Er0.1Fe5O12 garnet; meanwhile providing intense room temperature C-band photoluminescence (PL). Fe3+ ion works as a sensitizer for Er resulting in fivefold PL enhancement in iron garnets compared to gallium ones. PL lifetime in gallium garnets is in millisecond range reaching almost 6 ms in Gd2.9Er0.1Ga5O12. We conclude Er substitution in gallium and iron garnet layers used both as Bragg mirrors and microcavities promises magneto-optical photonic crystals to become an active lasing medium.

  7. Mercury'S Radar Bright Region C: Mg-rich Orthopyroxene And Olivine, K-spar, Iron-free Tio2, Ca- And Mg-garnet Indicate Possible Deep Crust Or Mantle Rock Exposures

    NASA Astrophysics Data System (ADS)

    Kozlowski, Richard W.; Donaldson Hanna, K. L.; Sprague, A. L.; Helbert, J.; Maturilli, A.

    2008-09-01

    We identify mineral phases and approximate abundances on Mercury's surface for a large (600 by 600 km) region at and around radar bright region C (Harmon, 1997, Adv. Space Res.). Our results are obtained by fitting spectra obtained with the Mid-Infrared Spectrometer and Imager (MIRSI) at the Infrared Telescope Facility (IRTF) using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR). We have assembled several laboratory mineral spectral libraries (JHU, Salisbury et al. 1987, Open-File Report 87-263, USGS; JPL, http://speclib.jpl.nasa.gov; RELAB, http://www.planetary.brown.edu/relab; ASU, Christensen et al. 2000, JGR; BED, Helbert et al. 2007, Adv. Space Res.; USGS, Clark et al. 2007, USGS digital spectral library) with a wide range of known mineral compositions with grain sizes ranging from the finest separates, 0 - 45 µm, incrementally increasing to 250 - 400 µm. For the region 110° to 130° E longitude and 0° to 20° N latitude we find enstatite and Mg-rich hypersthene, K-spar (either sanidine or orthoclase), intermediate plagioclase compositions, Mg-rich olivine, an iron-free opaque phase of either (TiO2) or perovskite (CaTiO3). Small abundances of Mg- and Ca- rich garnet are also apparently present. These minerals are indicative of possible excavated upper mantle material that may be causing the high radar backscatter at this location. This work was funded by NSF AST0406796.

  8. The effect of Ce doping on the structure, surface morphology and magnetic properties of Dy doped-yttrium iron garnet films prepared by a sol-gel method

    NASA Astrophysics Data System (ADS)

    Arsad, A. Z.; Ibrahim, N. B.

    2016-07-01

    Cerium substitute Y2.8-xDy0.2CexFe5O12 (x=0, 0.2, 0.25, 0.3, 0.35) films have been prepared on quartz substrates by a simple sol-gel method and followed by a spin-coating technique. The crystalline structures, surface and magnetic properties of the films has been investigated by an X-ray diffractometer (XRD), a field emission scanning electron microscope (FESEM), an atomic force microscope (AFM) and a vibrating sample magnetometer (VSM). The XRD analysis revealed that the films have garnet structure. The lattice parameter increased as Ce content was increased up to 0.25 due to the Ce3+ ions completely substituted for Y3+ ions. For films x≥0.3, the lattice parameter decreased. The FESEM results showed that the average grains were small, ranging from 11 to 14 nm and the thickness of films increased with the increment of Ce contents. VSM results for both in and out-plane magnetic measurement showed the film with x=0 has the highest saturation magnetization (Ms) values. With the increment of Ce contents, the Ms of films decreased due to the substitution of Ce3+, Dy3+ ions in the c-site. For films x≥0.3 the reduction of Ms values was due to the presence of CeO2 in the film. The films with x=0-0.25 exhibited increases in Hc values. The improvement of coercivity value, small grain size and high crystalline structure of film with x=0.25 has a potential to be used in magneto optical (MO) memory storage applications.

  9. Mineral of the month: garnet

    USGS Publications Warehouse

    Olson, Donald

    2005-01-01

    Garnet is the general name given to a group of complex silicate minerals, all with isometric crystal structure, similar properties and chemical compositions. Garnet occurs in every color of the spectrum except blue, but it is most commonly red, purple, brown and green. Garnet necklaces dating from the Bronze Age have been found in graves and also among the ornaments adorning the oldest Egyptian mummies.

  10. Iron

    MedlinePlus

    ... cereals and breads. White beans, lentils, spinach, kidney beans, and peas. Nuts and some dried fruits, such as raisins. Iron in food comes in two forms: heme iron and nonheme iron. Nonheme iron is found in plant foods and iron-fortified food products. Meat, seafood, ...

  11. Phase stable rare earth garnets

    DOEpatents

    Kuntz, Joshua D.; Cherepy, Nerine J.; Roberts, Jeffery J.; Payne, Stephen A.

    2013-06-11

    A transparent ceramic according to one embodiment includes a rare earth garnet comprising A.sub.hB.sub.iC.sub.jO.sub.12, where h is 3.+-.10%, i is 2.+-.10%, and j is 3.+-.10%. A includes a rare earth element or a mixture of rare earth elements, B includes at least one of aluminum, gallium and scandium, and C includes at least one of aluminum, gallium and scandium, where A is at a dodecahedral site of the garnet, B is at an octahedral site of the garnet, and C is at a tetrahedral site of the garnet. In one embodiment, the rare earth garment has scintillation properties. A radiation detector in one embodiment includes a transparent ceramic as described above and a photo detector optically coupled to the rare earth garnet.

  12. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  13. Micromorphology, microstructure and magnetic properties of sputtered garnet multilayers

    SciTech Connect

    Marcelli, R.; Padeletti, G.; Gambacorti, N.; Simeone, M.G.; Fiorani, D.

    1998-12-31

    The growth technique, the micromorphological and microstructural characterization by means of atomic force microscopy (AFM) and secondary ions mass spectrometry (SIMS) as well as the magnetic properties of a novel class of magnetic multilayers, based on radio frequency (RF) sputtered thin amorphous garnet films, are presented. One, three and five thin film multilayers composed by amorphous pure yttrium iron garnet (a:YIG) and amorphous gadolinium gallium garnet (a:GGG) have been grown on GGG single crystal substrates. The multilayer interfaces have been found to be comparable in both, the three and five-layers structure. Low field susceptibility measurements, showed a paramagnetic behavior for the single layer YIG film. For the three and five layers samples, irreversibility effects were observed, giving evidence of magnetic clusters at the interface YIG/GGG.

  14. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

  15. Water content of mantle garnets

    NASA Astrophysics Data System (ADS)

    Aines, Roger D.; Rossman, George R.

    1984-12-01

    Garnet megacrysts from Colorado Plateau diatremes (Green Knobs, Garnet Ridge) and the Wesselton kimberlite, South Africa, commonly contain a structural hydrous component. The Colorado Plateau samples range from 0.0 to 0.26 wt% H2O, and the Wesselton samples contain from 0.01 to 0.07%. Concentrations were measured using P2O5 cell coulometry, H2 gas manometry, and thermogravimetry. These were used to calibrate infrared integrated absorbance in the 3-μm region, which is a more sensitive measure of total O-H content than the other analytical methods. Infrared absorbance patterns were also used to differentiate structural hydrous component from water contained in alteration and included phases. The structure of the hydrous component in these garnets appears to be the classic H4O44- = SiO44-. Profiles at 100-μm intervals across these samples show flat concentration profiles or slightly increasing concentration toward the center. A large range of water content among samples appears to represent real differences in water fugacity at the point where the garnets equilibrated. Garnets in eclogite nodules from South Africa and the Solomon Islands were also studied but were either anhydrous or too badly altered to determine the content of structurally bound water. The high concentration of hydrous component in the Colorado Plateau samples is consistent with other indicators of high volatile content in that region of the mantle. The water content of mantle garnets may prove to be an accurate indicator of mantle-water fugacities.

  16. Mineral resource of the month: garnet

    USGS Publications Warehouse

    Olson, Donald W.

    2011-01-01

    Garnet, the birthstone for the month of January, has been used as a gemstone for centuries. Garnet necklaces dating from the Bronze Age have been found in graves, and garnet is found among the ornaments adorning the oldest Egyptian mummies. However, garnet’s characteristics, such as its relatively high hardness and chemical inertness, make it ideal for many industrial applications.

  17. Faraday polarisation mode conversion in semiconductor waveguides incorporating periodic garnet claddings

    NASA Astrophysics Data System (ADS)

    Hutchings, David C.; Zhang, Cui; Holmes, Barry M.; Dulal, Prabesh; Block, Andrew D.; Stadler, Bethanie J. H.

    2016-02-01

    We report on our progress towards the integration of nonreciprocal optical elements in, for example, an integrated optical waveguide isolator on conventional semiconductor photonic platforms. Our approach uses an evanescent interaction with a magneto-optic iron garnet upper cladding. Specifically, cerium- and bismuth- substituted yttrium and terbium iron garnets were investigated. Device fabrication incorporates RF sputtering, mask lift-off to form a grating for a quasi-phase-matched interaction and thermal anneal. A non-reciprocal polarisation-mode conversion was observed.

  18. Investigate the doped magnetic garnets and their applications to ultrafast switching

    NASA Astrophysics Data System (ADS)

    Kang, Shaoying; Yin, Shizhuo; Zhu, Yong; Li, Qi; Adyam, Venimadhav

    2006-08-01

    Bismuth Iron Gallium Garnet (BI 3Fe 5-xGa xO 12, BIGG) has been synthesized by pulsed laser deposition method and their comprehensive characterizations are reported. X-ray diffraction analyses have proved that the BIGG films are of good epitaxial quality. Faraday experiments verify the BIGG's high Faraday rotation. BIGG film is more transparent than Bismuth Iron Garnet film especially at wavelengths shorter than 550nm. Figure of merit of BIGG films θ F/-log (T)are greatly improved than that of original BIG films. High speed pulse response experiments of our BIGG films have reached 5ns.

  19. Garnet Random-Access Memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R.

    1995-01-01

    Random-access memory (RAM) devices of proposed type exploit magneto-optical properties of magnetic garnets exhibiting perpendicular anisotropy. Magnetic writing and optical readout used. Provides nonvolatile storage and resists damage by ionizing radiation. Because of basic architecture and pinout requirements, most likely useful as small-capacity memory devices.

  20. Chapter L: U.S. Industrial Garnet

    USGS Publications Warehouse

    Evans, James G.; Moyle, Phillip R.

    2006-01-01

    The United States presently consumes about 16 percent of global production of industrial garnet for use in abrasive airblasting, abrasive coatings, filtration media, waterjet cutting, and grinding. As of 2005, domestic garnet production has decreased from a high of 74,000 t in 1998, and imports have increased to the extent that as much as 60 percent of the garnet used in the United States in 2003 was imported, mainly from India, China, and Australia; Canada joined the list of suppliers in 2005. The principal type of garnet used is almandite (almandine), because of its specific gravity and hardness; andradite is also extensively used, although it is not as hard or dense as almandite. Most industrial-grade garnet is obtained from gneiss, amphibolite, schist, skarn, and igneous rocks and from alluvium derived from weathering and erosion of these rocks. Garnet mines and occurrences are located in 21 States, but the only presently active (2006) mines are in northern Idaho (garnet placers; one mine), southeastern Montana (garnet placers; one mine), and eastern New York (unweathered bedrock; two mines). In Idaho, garnet is mined from Tertiary and (or) Quaternary sedimentary deposits adjacent to garnetiferous metapelites that are correlated with the Wallace Formation of the Proterozoic Belt Supergroup. In New York, garnet is mined from crystalline rocks of the Adirondack Mountains that are part of the Proterozoic Grenville province, and from the southern Taconic Range that is part of the northern Appalachian Mountains. In Montana, sources of garnet in placers include amphibolite, mica schist, and gneiss of Archean age and younger granite. Two mines that were active in the recent past in southwestern Montana produced garnet from gold dredge tailings and saprolite. In this report, we review the history of garnet mining and production and describe some garnet occurrences in most of the Eastern States along the Appalachian Mountains and in some of the Western States where

  1. The origin of garnet in the anorthosite-charnockite suite of the Adirondacks

    USGS Publications Warehouse

    McLelland, J.M.; Whitney, P.R.

    1977-01-01

    Detailed analysis of textural and chemical criteria in rocks of the anorthosite-charnockite suite of the Adirondack Highlands suggests that development of garnet in silica-saturated rocks of the suite occurs according to the reaction: {Mathematical expression}, where ?? is a function of the distribution of Fe and Mg between the several coexisting ferromagnesian phases. Depending upon the relative amounts of Fe and Mg present, quartz may be either a reactant or a product. Using an aluminum-fixed reference frame, this reaction can be restated in terms of a set of balanced partial reactions describing the processes occurring in spatially separated domains within the rock. The fact that garnet invariably replaces plagioclase as opposed to the other reactant phases indicates that the aluminum-fixed model is valid as a first approximation. This reaction is univariant and produces unzoned garnet. It differs from a similar equation proposed by de Waard (1965) for the origin of garnet in Adirondack metabasic rocks, i.e. 6 Orthopyroxene+2 Anorthite = Clinopyroxene+Garnet+2 Quartz, the principle difference being that iron oxides (ilmenite and/or magnetite) are essential reactant phases in the present reactions. The product assemblage (garnet+clinopyroxene+plagioclase ?? orthopyroxene ?? quartz) is characteristic of the clinopyroxene-almandine subfacies of the granulite facies. ?? 1977 Springer-Verlag.

  2. High-pressure behavior of Fe-bearing silicate garnets up to 100 GPa

    NASA Astrophysics Data System (ADS)

    Ismailova, L.; Bykov, M.; Cerantola, V.; Bykova, E.; Vasyukov, D.; Bobrov, A.; McCammon, C. A.; Dubrovinskaia, N.; Dubrovinsky, L. S.

    2015-12-01

    Silicate garnets are key phases not only because of their petrological importance in thermobarometry and oxybarometry, but also due to the intriguing relationship between their structure and physico-chemical properties. Natural silicate garnets can accommodate a variety of divalent and trivalent cations in their crystal structure and form many solid solutions. While most major cations in garnet occur in only a single oxidation state (Al3+, Ca2+, Mg2+, Si4+), iron occurs as both Fe2+ and Fe3+. Skiagite garnet (Fe2+3Fe3+2Si3O12) contains iron in two oxidation states and as a component in peridotitic garnet, it can be used as a redox sensor to determine mantle ƒO2 from Fe3+/∑Fe. With increasing pressure/depth the Fe3+/∑Fe ratio increases due to the higher solubility of Fe3+ in garnet, hence expanding the stability field of skiagite. At greater depth skiagite garnet is expected to accommodate an excess of Si, forming a solid solution with the iron majorite endmember (Fe4Si4O12). Studying the high-pressure behavior and redox relations of Fe-bearing silicate garnet can therefore provide important insight into the chemical composition and physical properties of the Earth's mantle. Single-crystals of skiagite-majorite solid solution were synthesized at 9.5 GPa and 1100 °C in a multianvil apparatus and found to have the composition Fe2+3(Fe2+0.234(2)Fe3+1.53(1)Si0.234(2))Si3O12. We performed a room temperature investigation of the equation of state up to 100 GPa using synchrotron single crystal XRD at ESRF, Grenoble. Fitting the data to a 3rd order BM EoS gives K0 = 166(3) GPa with K`=3.8(1) and V0 = 1606.9(8) Å3. In the pressure range between 50 and 60 GPa the overall unit cell volume drops by about 4 % and we observe a collapse of about 7 % in FeO6 octahedral volume. Synchrotron Mössbauer source spectra at ambient pressure show two doublets assigned to dodecahedral Fe2+ and octahedral Fe3+ that remain essentially unchanged up to 50 GPa. However at ~52 GPa the

  3. Effects of high-temperature annealing on ESR properties of solid solutions of garnet minerals

    NASA Astrophysics Data System (ADS)

    Gundu Rao, T. K.; Cano, Nilo F.; Chubaci, Jose F. D.; Watanabe, S.

    2016-04-01

    A garnet (G7) silicate mineral belonging to pyralspite subgroup was studied using the technique of electron spin resonance (ESR). This study shows that iron is present in G7 as isolated species as well as species coupled by dipolar interactions. The ESR data shows a gradual increase of cluster of Fe3+ ions accompanied by decrease of dipolar interactions and increase of possible exchange interactions at high temperature. The Fe2+→Fe3+ oxidation process occurs in the garnets as a function of annealing temperature. Thermoluminescence (TL) peaks at approximately 190 and 340 °C are observed in the irradiated G7 garnet. Investigations using the technique of ESR were carried out to identify the centers involved in the TL process.

  4. Raman spectroscopy of garnet-group minerals

    USGS Publications Warehouse

    Mingsheng, P.; Mao, Ho-kwang; Dien, L.; Chao, E.C.T.

    1994-01-01

    The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the internal modes, translational and rotatory modes of SiO4 tetrahedra, as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe garnet series. ?? 1994 Institute of Geochemistry, Chinese Academy of Sciences.

  5. Rare Earth Garnet Selective Emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional

  6. Intercomparison of garnet barometers and implications for garnet mixing models

    SciTech Connect

    Anovitz, L.M.; Essene, E.J.

    1985-01-01

    Several well-calibrated barometers are available in the system Ca-Fe-Ti-Al-Si-O, including: Alm+3Ru-3Ilm+Sil+2Qtz (GRAIL), 2Alm+Grreverse arrow6Ru=6Ilm+3An+3Qtz (GRIPS); 2Alm+Gr=3Fa+3An (FAG); 3AnGr+Ky+Qtz (GASP); 2Fs-Fa+Qtz (FFQ); and Gr+Qtz=An+2Wo (WAGS). GRIPS, GRAIL and GASP form a linearly dependent set such that any two should yield the third given an a/X model for the grossular/almandine solid-solution. Application to barometry of garnet granulite assemblages from the Grenville in Ontario yields average pressures 0.1 kb lower for GRIPS and 0.4 kb higher for FAGS using our mixing model. Results from Parry Island, Ontario, yield 8.7 kb from GRAIL as opposed to 9.1 kb using Ganguly and Saxena's model. For GASP, Parry Island assemblages yield 8.4 kb with the authors calibration. Ganguly and Saxena's model gives 5.4 kb using Gasparik's reversals and 8.1 kb using the position of GASP calculated from GRIPS and GRAIL. These corrections allow GRIPS, GRAIL, GASP and FAGS to yield consistent pressures to +/- 0.5 kb in regional metamorphic terranes. Application of their mixing model outside of the fitted range 700-1000 K is not encouraged as extrapolation may yield erroneous results.

  7. Experimental Constraints on the Partitioning and Valence of V and Cr in Garnet and Coexisting Glass

    NASA Technical Reports Server (NTRS)

    Righter, K.; Sutton, S.; Berthet, S.; Newville, M.

    2008-01-01

    A series of experiments with garnet and coexisting melt have been carried out across a range of oxygen fugacities (near hematite-magnetite (HM) to below the iron-wustite (IW) buffers) at 1.7 GPa to study the partitioning and valence of Cr and V in both phases. Experiments were carried out in a non end loaded piston cylinder apparatus, and the run products were analyzed with electron microprobe and xray absorption near edge structure (XANES) analysis at beamline 13-ID at the Advanced Photon Source of Argonne National Lab. The valence of vanadium and chromium were determined using the position and intensity of the Ka pre-edge peaks, calibrated on a series of Cr and Vbearing standard glasses. This technique has been applied to V and Cr in glasses and V in spinels previously, and in these isotropic phases there are no orientational effects on the XANES spectra (Righter et al., 2006, Amer. Mineral. 91, 1643-1656). We also now demonstrate this to be true for V and Cr in garnet. Also, previous work has shown that V has a higher valence in the glass (or melt) than in the coexisting spinel. This is also true for V in garnet-glass pairs in this study. Vanadium valence in garnets varies from 2.7 below the IW buffer to 3.7 near HM, and for coexisting glass it varies from 3.2 to 4.3. Vanadium valence measured in some natural garnets from mantle localities indicates V in the more reduced range at 2.5. Comparisons will be made between fO2 estimated from V valence and other methods for garnet-bearing mantle samples. In contrast, Cr valence measured in garnet and coexisting glass for all experimental and natural samples is 2.9- 3.0, suggesting that the valence of Cr does not vary within either phase across a large fO2 range. These results demonstrate that while V varies from 2+ to 3+ to 4+ in garnet-melt systems, Cr does not, and this will ultimately affect the partitioning behavior of these two elements in natural systems. Garnet/melt D(Cr) are between 12 and 17 across this range

  8. Polycrystalline magnetic garnet films comprising weakly coupled crystallites for piezoelectrically-driven magneto-optic spatial light modulators

    SciTech Connect

    Mito, S.; Sakurai, H.; Takagi, H.; Inoue, M.; Baryshev, A. V.

    2012-04-01

    We have investigated the magnetization process of the polycrystalline magnetic garnet films in order to determine the most suitable composition of garnet films for piezoelectrically-driven magneto-optic spatial light modulators (MOSLMs). For experiment, the bismuth-dysprosium-aluminum-substituted yttrium iron (Bi{sub 1.3}Dy{sub 0.7}Y{sub 1.0}Fe{sub 3.1}Al{sub 1.9}O{sub 12}) garnet films were deposited by an RF magnetron sputter and annealed at 700 deg. C in air. The annealing time was varied in a range of several minutes to control the grain size. The saturation magnetization, the remanent magnetization and the composition of the fabricated garnet films slightly changed versus the annealing time. Experiments showed that the coercivity and the grain size increased at longer annealing; the coercivity was larger for films with bigger grains. This work shows that garnet films with smaller coercivity are most suitable for controlling the magnetization of garnet and, correspondingly, the magneto-optical rotation of MOSLM pixels driven by piezoelectrics.

  9. Garnet ships in a quartzite sea

    NASA Astrophysics Data System (ADS)

    Rogowitz, Anna; Rice, A. Hugh N.; Grasemann, Bernhard; Huet, Benjamin

    2016-04-01

    During progressive deformation, a strong inclusion in a weaker matrix causes a stress concentration that may result in strain localization, seen in a matrix grain-size reduction. A superb example of this phenomena, but rather more complex, has been observed in north Norwegian Caledonides. A probably subvertical metadolerite dyke has been rotated to lie parallel to the penetrative regional low-angled foliation during the emplacement of the overlying nappe. The metadolerite, now only ~1.4 cm thick and lying between two quartzite layers has been retrogressed to a biotite schist with an assemblage of biotite, titanite, epidote group, garnet and quartz. Garnets are from 0.2 mm to 4 cm in size, subhedral and have two growth zones, with inclusions of predominantly titanite and rare amphibole. The country-rock metasedimentary schists contain staurolite, indicating mid-amphibolite-facies conditions (~550 °C and 6 kbar). During late deformation, some garnets were forced into the quartzite, resulting in the development of pronounced gouges (tectoglyphs), up to 70 mm long, 14 mm wide and 14 mm deep, deepening in the direction of movement. Quartz was pushed up at the sides of the gouges and forms a pronounced bow-wave at the front of the garnets. Where garnets are gouged into the quartzite, intense strain localization occurs. Both in front of and under the garnet, a up to 18 mm wide zone of quartz mylonite developed. The mylonitic foliation curves around the garnet, with a relatively sharp boundary to the adjacent quartzite that preserves an older random fabric. Deformation in the mylonite, which shows a strong crystallographic preferred orientation, seems to have occurred by (1) intense dislocation glide followed by (2) subgrain rotation resulting in an almost foam-like fabric. The grain size of the mylonite (at the quartzite-biotite schist interface) increases with increasing distance behind the present position of the garnets. This observation is consistent with an expected

  10. Rare earth garnet selective emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approximately equal to 0.74, ((4)l(sub 15/2)) - ( (4)l(sub13/2)), for Er-YAG and epsilon(sub lambda) approximately equal to 0.65, ((5)l(sub 7))-((5)l(sub 8)) for Ho-YAG) at excellent candidates for high efficiency selective emitters in the thermophotovoltaics (TPV) systems operating at moderate temperatures (1200-1500K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium (Ho), and erbium (Er) doped YAG thin film selective emitters at 1500 K, and compares those results with the theoretical spectral emittance.

  11. Water contents of garnets from the Garnet Ridge, northern Arizona: H2O behavior underneath the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Ogasawara, Y.; Sakamaki, K.; Sato, Y.

    2013-12-01

    Kimberlitic volcanism at the Garnet Ridge delivered a wide variety of garnets and garnet-associated rocks in large vertical range from the deep mantle to shallow depths underneath the Colorado Plateau (Smith et al., 2004). Koga and Ogasawara (2012) classified the garnets at the Garnet Ridge into the following nine groups; (a) Cr and pyrope-rich garnet, (b) pyrope-rich reddish brown garnet, (c) reddish brown garnet, (d) garnet in eclogite, (e) garnet in metasomatized eclogite, (f) garnet aggregate, (g) garnet megacryst, (h) garnet in metasomatic rock I, (i) garnet in metasomatic rock II. They regarded these garnets as the four origins: mantle peridotite (a, b), subducted oceanic crust (d, e), high-pressure metasomatism (c, f, g), low-pressure metasomatism (h, i). On the garnets (a, b, d), Sakamaki et al. (2012) preliminary reported OH qualitatively using micro FT-IR spectroscopy. In garnets (a, b), OH was detected clearly, but in garnet (d) OH was below detection limit because the thickness of a doubly polished section of garnet (d) was too small (thickness: ~70 μm) and the concentration was too low. Using micro FT-IR method, this study conducted the quantitative analysis of H2O for 20 grains of group (a), 18 grains of group (b) and 6 grains of group (d). The garnet samples were prepared as doubly polished thick sections (thicknesses of 0.1-1.3 mm). An IR absorption coefficient of 8770 L/mol/cm2 (Katayama et al., 2005) for garnets was used. Significant amounts of hydroxyl were detected in garnets (a, b, d); clear OH bands were identified in garnets (a, b), but very week and extremely broad OH bands in garnet (d). In the analyzed garnets, no zonal distribution of OH was identified. Garnet (a): the IR spectra have a main OH band at 3575 cm-1 and often with a week band at 3675 cm-1. The resultant H2O contents range from the below detection limit to 119 ppm wt. and are distributed at 0~10 and at ca. 100 ppm wt., bimodally. Garnet (b): the IR spectra have a main OH band

  12. Formation of Garnet Granulite in the Lower Crust of a paleo-Island Arc

    NASA Astrophysics Data System (ADS)

    Garrido, Carlos J.; Padrón-Navarta, José Alberto; López Sánchez-Vizcaíno, Vicente; Bodinier, Jean-Louis; Bosch, Delphine; Marchesi, Claudio; Hidas, Károly

    2016-04-01

    The Jijal complex (Kohistan paleo-island arc complex, NW Pakistan) is a unique occurrence of high-pressure (HP), mafic, opx-free, garnet granulite formed in the lower crust of an island arc. The upper part of the Jijal Granulitic Gabbro Unit (GGU) records the arrested transformation of hornblende gabbronorite to garnet granulite, involving the coeval breakdown of amphibole and orthopyroxene, and the formation of garnet and quartz. Close to the transformation front (2-3 cm), clinopyroxene from the granulite displays a strong Ca-tschermak zoning with lower Al-contents at rims. REE zoning of clinopyroxene and pseudosection diagrams indicate that only clinopyroxene rims reflect chemical equilibrium with garnet in the reaction front (P = 1.1 ± 0.1 GPa, T = 800 ± 50 °C), whereas the cores retained high-Al contents inherited from precursor gabbronorite clinopyroxene and remained in chemical disequilibrium within a few centimeters of the garnet granulite assemblage. Clinopyroxene of garnet granulites from the Jijal lower GGU are completely re-equilibrated with garnet (P = 1.5 ± 0.1 GPa, T = 800 ± 50 °C). If ferric iron corrections are disregarded, equilibration pressure and temperature are highly overestimated yielding exceedingly high pressures for an island arc setting. The pressure difference between the upper and lower Jijal GGU granulites (~0.4 GPa) and its current thickness (<5 km) implies delamination of the denser parts of Jijal crust. Thermodynamically computed phase diagram sections for upper GGU bulk compositions show that, at the equilibration conditions of Jijal garnet granulite, the equilibrium assemblage is orthopyroxene-free and amphibole-free garnet granulite coexisting with melt or a fluid phase, depending on the water activity at the onset of amphibole breakdown. Pseudosections indicate that hornblende gabbronorite assemblages are highly metastable at lower arc crust depths. The transformation to garnet granulite was therefore substantially

  13. Cryptic Calcium Zoning in Garnets from the Nufenen Pass Area and its Implication for Garnet Growth

    NASA Astrophysics Data System (ADS)

    Gauchat, K.; Baumgartner, L. P.

    2006-12-01

    Garnets from graphite rich metamarls of the Nufenen Pass area in the Swiss Alps display textural and chemical sector zoning, and irregular birefringent lamellae normal to the sector growth direction. Garnets range size of 0.6 mm to 4.8 mm. All garnets display two distinct zones; the outer zone is graphite rich and has clinozoisite, calcite, ankerite, and quartz inclusions. The central zone shows 6 sectors without graphite inclusions radiating from the centre of the crystal separated by zones which are inclusions rich. The sectors contain a few quartz rods oriented normal to the garnet growth face along with irregular birefringent lamellae with identical orientation. The width of the lamellae varies from one to twenty microns and their length can reach up to 500 microns. Element X-ray maps and profiles were made on centrally cut garnets of different sizes. Compositional profiles show a decrease of Mn and an increase of Fe and Mg from core to rim. Mn X- Ray maps and profiles document a chemical sector zoning in agreement with the inclusion sector zoning. Ca X-ray maps shows within sectors anomalous Ca richer lamellae oriented normal to the garnet faces corresponding to the anomalous birefringent lamellae. These lamellae do probably not represent exsolution, since the composition of the garnet (sector and into sector zones) are similar but they only occur within the six sectors. The most likely explanation is that these Ca-rich lamellae are growth structures linked to the interaction of the garnet surface with the graphite rich matrix. This implies that garnet composition is, on a second order, influenced by surface kinetics.

  14. Magnetic volumetric hologram memory with magnetic garnet.

    PubMed

    Nakamura, Yuichi; Takagi, Hiroyuki; Lim, Pang Boey; Inoue, Mitsuteru

    2014-06-30

    Holographic memory is a promising next-generation optical memory that has a higher recording density and a higher transfer rate than other types of memory. In holographic memory, magnetic garnet films can serve as rewritable holographic memory media by use of magneto-optical effect. We have now demonstrated that a magnetic hologram can be recorded volumetrically in a ferromagnetic garnet film and that the signal image can be reconstructed from it for the first time. In addition, multiplicity of the magnetic hologram was also confirmed; the image could be reconstructed from a spot overlapped by other spots.

  15. Major element chemistry and inclusion/lamella mineralogy of garnets from the Garnet Ridge in the Colorado Plateau, northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Koga, I.; Ogasawara, Y.

    2014-12-01

    Various garnets with diverse features and origins occur in the Garnet Ridge. These were transported from upper mantle to crustal depths underneath the Colorado Plateau by a kimberlitic diatreme (ca. 30 Ma) as xenocrysts and xenoliths. On the basis of major element chemistry, inclusion/lamella mineralogy, color, and host rocks of garnets, the Garnet Ridge garnets were classified into the following ten groups (Table) using 495 analyzed grains: A. Cr and pyrope-rich garnet, B. pyrope-rich reddish brown garnet, C. garnet aggregate, D. garnet megacryst, E. garnet in eclogite, F. garnet in metasomatized eclogite, G. quartz lamellae-bearing garnet, H. garnet in metasomatic rock I, I. garnet in metasomatic rock II, J. almandine-rich garnet. A and B are of mantle peridotite origins. Both garnets were characterized by Cr-Spl lamellae for A, and Cpx/Amp lamellae for B, respectively. B is subdivided into 2 types by lamellae and inclusions: (Prp 49-66, Grs 16-26 mol%) lamellae of Rt, Ilm, Cpx, Amp, and Chl, and (Prp 47-66, Grs 11-24 mol%) lamellae of Ilm and fluid inclusions. C and D have similar chemistry and inclusion/lamella mineralogy. The chemistry (Prp 22-53, Grs 11-41, Alm 26-50 mol%) and the wide variation suggest metasomatism at mantle depths. E includes Rt, Omp, Zrn, Ap, Kfs, and simplectite of Zo + Ab. F contains Rt, Omp, and Ap. Both E and F have chemical zonation from core to rim in Alm component. These garnets are of subducted oceanic slab origins, probably Fallaron plate. G includes Cpx, Zrn, and fluid, and oriented lamellae of Rt, Ap, and Qtz. Oriented Qtz lamellae characterize this group. The host rock of H is of metasomatism origin at crustal depths. H has Grs-rich composition and inclusions of Mt, Zo, Ttn, Ap and fluid. I has lamellae of Rt and crichtonites, and includes Qtz and Zrn. The host rock of I was strongly altered. J shows chemical zonation from core to rim in Alm component. This garnet includes Pl, Qtz, Ilm with Mt lamellae, and Rt lamella. The

  16. Inhibitors in LPE growth of garnets

    NASA Astrophysics Data System (ADS)

    De Roode, W. H.; Robertson, J. M.

    1983-09-01

    The growth rate of LPE growth garnets can be reduced considerably by the addition of small amounts of group II oxides. This effect can be helpful for the controlled growth of very thin garnet films for sub-micron bubbles and optical devices. The largest effect was found with the addition of Mg 2+ and Ca 2+, resulting in a maximum decrease of the growth rate of approximately 70%. A semi-empirical formula was used to describe the growth rate as a function of the dipping temperature. The change in the growth rate on the addition of the inhibitor ion at constant temperature was found to be proportional to ( aMO)/( aMO+2 Ln 2O 3), where M is a group II element, Ln 2O 2 is the sum of the yttrium and RE oxides in the melt, and a is the inhibitor factor. The value of the inhibitor factor depends on both the inhibitor ion as well as the composition of the garnet. The lowering of the growth rate on the addition of an inhibitor ion is explained by the introduction of an extra growth resistance due to the charge compensation mechanism of the divalent ions. The influence of the different charge compensation possibilities in the garnet system is examined and the relative importance of these possibilities for charge compensation is discussed.

  17. Experimental tests of garnet peridotite oxygen barometry

    NASA Astrophysics Data System (ADS)

    Gudmundsson, G.; Wood, B. J.

    1995-02-01

    We have performed experiments aimed at testing the calibration of oxygen barometers for the garnet peridotite [garnet (Gt)-olivine (Ol)-orthopyroxene (Opx)] phase assemblage. These involved equilibrating a thin layer of garnet sandwiched between layers of olivine and orthopyroxene at 1300° C and 25 35 kbar for 1 7 days. Oxygen fugacity was controlled (but not buffered) by using inner capsules of Fe Pt alloy or graphite or molybdenum sealed in welded Pt outer capsules. Post-experiment measurement of f O2 was made by determining the compositions of Pt Fe alloy sensors at the interface between garnet and olivine+orthopyroxene layers. The composition of alloy in equilibrium with olivine+orthopyroxene was approached from Fe-oversaturated and Fe-undersaturated conditions in the same experiment with, in general, excellent convergence. Product phase compositions were determined by electron microprobe and a piece of the garnet layer saved for 57Fe Mössbauer spectroscopy. The latter gave the Fe3+ content of the garnet at the measured P-T-f O2 conditions. Approach to equilibrium was checked by observed shifts in Fe3+ content and by the approach of garnet-olivine Fe Mg partitioning to the expected value. The compositions of the phases were combined with mixing properties and thermodynamic data to calculate an apparent f O2 from two possible garnet oxybarometers:- 2Ca3Fe2Si3O12Gt1+2Mg3Al2Si3O12Gt+4FeSiO3Opx=2Ca3Al2Si3O12Gt+8FeSi0.5O2Ol+6MgSiO3Opx+O2 (1) and 2Fe3Fe2Si3O12Gt=8FeSi0.5O2Ol+2FeSiO3Opx+O2(2) Comparison of calculated f O2s with those measured by the Pt-Fe sensors demonstrated that either barometer gives the correct answer within the expected uncertainty. Data from the first (Luth et al. 1990) has an uncertainty of about 1.6 log f O2 units, however, while that from equilibrium (2) (Woodland and O’Neill 1993) has an error of +/- 0.6 log units, comparable to that of the spinel peridotite oxybarometer. We therefore conclude that equilibrium (2) may be used to

  18. A generalized garnet-forming reaction for metaigneous rocks in the Adirondacks

    USGS Publications Warehouse

    McLelland, J.M.; Whitney, P.R.

    1980-01-01

    A generalized reaction is presented to account for garnet formation in a variety of Adirondack metaigneous rocks. This reaction, which is the sum of five partial reactions written in aluminum-fixed frames of reference, is given by: 4(y+1+w)Anorthite+4 k(y+1+2 w)Olivine +4(1-k)(y+1+2 w)Fe-oxide+(8(y+1) -4 k(y+1+2 w))Orthopyroxene = 2(y+1)Garnet +2(y+1+2 w)Clinopyroxene+4 wSpinel where y is a function of plagioclase composition, k refers to the relative amounts of olivine and Fe-oxide participating in the reaction, and w is a measure of silicon mobility. When mass balanced for Mg and Fe, this reaction is found to be consistent with analyzed mineral compositions in a wide range of Adirondack metaigneous rocks. The reaction applies equally well whether the garnets were formed directly from the rectants given above or went through an intermadiate stage involving the formation of spinel, orthopyroxene, and clinopyroxene. The actual reactions which have produced garnet in both undersaturated and quartz-bearing rocks are special cases of the above general reaction. The most important special cases appear to be those in which the reactants include either olivine alone (k=1) or Fe-oxide alone (k=0). Silicon is relatively immobile (w =2) in olivine bearing, magnesium-rich rocks (k???1), and this correlates with the increased intensity in spinel clouding of plagioclase in these rocks. Silicon mobility apparently increases in the more iron-rich rocks, which also tend to contain clear or lightly clouded plagioclase. In all the rocks studied the most common composition of metamorphic plagioclase is close to An33 (i.e., y=1). Plagioclase of lower anorthite content may be too sodic to participate in garnet formation at the P-T conditions involved. ?? 1980 Springer-Verlag.

  19. Purplish-red almandine garnets with alexandrite-like effect: causes of colors and color-enhancing treatments

    NASA Astrophysics Data System (ADS)

    Krambrock, K.; Guimarães, F. S.; Pinheiro, M. V. B.; Paniago, R.; Righi, A.; Persiano, A. I. C.; Karfunkel, J.; Hoover, D. B.

    2013-07-01

    Fine gem-quality, purplish-red garnets from the Tocantins State, Brazil, were investigated for their crystal chemistry and optical properties by several spectroscopic techniques, including electron microprobe analysis, Mössbauer, Raman spectroscopy and optical absorption. Although most garnets are purplish-red, some specimens show color zoning, with deep red color in the core and purple in the outer parts. Electron microprobe analysis showed that these garnets are principally almandine-pyrope solid solution at the rim. However, at the red core, they contain also up to 7 % of spessartine. Mössbauer spectroscopy reveals that the iron content is predominantly Fe2+ (>99 %) in the natural garnets. The optical absorption spectra are dominated by spin-allowed and unusual high-intense spin-forbidden transitions from eightfold coordinated Fe(II) in the near infrared and visible spectral region, respectively. For the red core, in addition, three sharp bands centered in the blue part of the visible spectral range and a broad charge transfer band in the near-UV region are observed. All garnets with purplish colors show also a remarkable color-changing effect from purple in daylight light to red in incandescent light called alexandrite-like effect. Heat treatments in the 700-900 °C temperature range in oxidizing and reducing atmospheres lead to reversible and irreversible color changes which are discussed based on the microscopic changes in the Fe ion coordination and valence states.

  20. Valid garnet biotite (GB) geothermometry and garnet aluminum silicate plagioclase quartz (GASP) geobarometry in metapelitic rocks

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Ming; Cheng, Ben-He

    2006-06-01

    At present there are many calibrations of both the garnet-biotite (GB) thermometer and the garnet-aluminum silicate-plagioclase-quartz (GASP) barometer that may confuse geologists in choosing a reliable thermometer and/or barometer. To test the accuracy of the GB thermometers we have applied the various GB thermometers to reproduce the experimental data and data from natural metapelitic rocks of various prograde sequences, inverted metamorphic zones and thermal contact aureoles. We have concluded that the four GB thermometers (Perchuk, L.L., Lavrent'eva, I.V., 1983. Experimental investigation of exchange equilibria in the system cordierite-garnet-biotite. In: Saxena, S.K. (ed.) Kinetics and equilibrium in mineral reactions. Springer-Verlag New York, Berlin, Heidelberg. pp. 199-239.; Kleemann, U., Reinhardt, J., 1994. Garnet-biotite thermometry revised: the effect of Al VI and Ti in biotite. European Journal of Mineralogy 6, 925-941.; Holdaway, M.J., 2000. Application of new experimental and garnet Margules data to the garnet-biotite geothermometer. American Mineralogist 85, 881-892., Model 6AV; Kaneko, Y., Miyano, T., 2004. Recalibration of mutually consistent garnet-biotite and garnet-cordierite geothermometers. Lithos 73, 255-269. Model B) are the most valid and reliable of this kind of thermometer. More specifically, we prefer the Holdaway (Holdaway, M.J., 2000. Application of new experimental and garnet Margules data to the garnet-biotite geothermometer. American Mineralogist 85, 881-892.) and the Kleemann and Reinhardt (Kleemann, U., Reinhardt, J., 1994. Garnet-biotite thermometry revised: the effect of Al VI and Ti in biotite. European Journal of Mineralogy 6, 925-941.) calibrations due to their small errors in reproducing the experimental temperatures and good accuracy in successfully discerning the systematic temperature changes of the different sequences. In addition, after applying the GASP barometer to 335 natural metapelitic samples containing one kind

  1. Garnets from the Camafuca-Camazambo kimberlite (Angola).

    PubMed

    Correia, Eugénio A; Laiginhas, Fernando A T P

    2006-06-01

    This work presents a geochemical study of a set of garnets, selected by their colors, from the Camafuca-Camazambo kimberlite, located on northeast Angola. Mantle-derived garnets were classified according to the scheme proposed by Grütter et al. (2004) and belong to the G1, G4, G9 and G10 groups. Both sub-calcic (G10) and Ca-saturated (G9) garnets, typical, respectively, of harzburgites and lherzolites, were identified. The solubility limit of knorringite molecule in G10D garnets suggests they have crystallized at a minimum pressure of about 40 to 45 kbar (4-4.5 GPa). The occurrence of diamond stability field garnets (G10D) is a clear indicator of the potential of this kimberlite for diamond. The chemistry of the garnets suggests that the source for the kimberlite was a lherzolite that has suffered a partial melting that formed basaltic magma, leaving a harzburgite as a residue.

  2. Polycrystalline Garnet Porphyroblasts, an EBSD Study

    NASA Astrophysics Data System (ADS)

    Seaton, N. C.; Whitney, D. L.; Anderson, C.; Alpert, A.

    2008-12-01

    Polycrystalline garnet porphyroblasts (PGP's) are significant because their formation provides information about metamorphic crystalline mechanisms, in particular during early stages of crystal growth, which may differ from those governing later stages; and because their existence may affect the chemical and structural evolution of metamorphic rocks. For example, the extent of element exchange between the garnet interior and the matrix may be affected by the presence of grain boundaries within PGP's. There have been several previous studies of PGP's but important questions about them remain; e.g. whether early coalescence is a common method by which garnets crystallize, whether grains rotate during growth to attain an energetically favorable grain-grain contact, and whether deformation and/or precursor minerals or other chemical or mechanical heterogeneities influence the formation of PGP's. PGP's have been detected by us in several different localities including; micaschist from SE Vermont (USA), including locality S35j of Rosenfeld (1968); the Solitude Range (British Columbia, Canada); the Southern Menderes Massif (Turkey); and three zones (garnet, staurolite, kyanite) from the Dutchess County Barrovian sequence in NY (USA). We have identified two types of PGP: cryptic and morphologically distinct. Cryptic PGP have no obvious morphological expression of the high angle boundaries within them and appear to be a single crystal. Morphologically distinct PGP have an obvious depression in the outer grain boundary where it is intersected by the internal grain boundary. Most PGP's contain inclusion trails and the high angle grain boundaries crosscut the trend of these as well as the inclusions themselves. PGP also show major element growth zoning that is not influenced by the internal grain boundaries except in rare cases. PGP's comprise ~ 5-35% of the garnet populations analyzed. More than 95% of the PGP's we have analyzed are comprised of 2-3 domains; the rest contain

  3. Inclusion/lamella mineralogy and chemical characteristics of garnets from the Garnet Ridge in the Colorado Plateau, northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Ogasawara, Y.

    2013-12-01

    A wide variety of garnets as xenocrysts and those in xenoliths, come from kimberlitic diatreme (Smith et al. 2004), occurs at the Garnet Ridge. Koga and Ogasawara (2012) classified these garnets into 9 groups: (a) Cr and pyrope-rich garnet, (b) pyrope-rich reddish brown garnet, (c) reddish brown garnet, (d) garnet in eclogite, (e) garnet in metasomatized eclogite, (f) garnet aggregate, (g) garnet megacryst, (h) garnet in metasomatic rock I, (i) garnet in metasomatic rock II. They divided genetically these groups into four: mantle peridotite (a, b), subducted oceanic crust (d, e), high-pressure metasomatism (c, f, g), low-pressure metasomatism (h, i).In this study, the following 4 groups (a, b, f, g) were chose for inclusion mineralogy by laser Raman spectroscopy. Groups (a) and (b): pyrope-rich garnets (a: 45-82, b: 61-80 Prp mol%) both Cr-rich and Cr-poor (a: 1.0-5.9, b: 0.0-1.0 wt.% Cr2O3) are Ca-poor (1.5-7.0 wt.% CaO) and single-crystals of 5-15 mm in diameter. Group (a) is identical to chrome-pyrope based on the classification of kimberlitic garnets by Dawson and Stephens (1975). CaO-Cr2O3 ratio of (a, b) indicates lherzorite origin (Turkin and Sobolev 2009). Wang et al. (1999) have reported the detailed inclusion and lamella mineralogy of pyrope-rich garnets from the Garnet Ridge. We identified inclusions of Chl (OH: 3450, 3582, 3679 cm-1), Amp (OH: 3685, 3711 cm-1), Ol, Opx, Cpx, Rt (OH: 3295 cm-1), Mgs, Dol, Cal, sulfides, fluid (OH: 3445 cm-1) and spherical composite inclusions of Amp, Ap, Dol, Mgs, Rt and sulfides, and oriented lamellae (presumable exsolution) of Qz, Ol, Opx, Cpx, Amp, Chl, Rt, Ilm, crichtonite (6-7 Peaks at 120-820 cm-1), carmichaelite (710-782 cm-1, OH: 3340 cm-1), Ap (OH: 3570 cm-1) and Ti-Chn (OH: 3404, 3527, 3564 cm-1) adjacent to the oriented Ol. The mineral assemblages of the inclusion and lamella show a correlation with the host garnet compositions; inclusions: (a, b) Ol + Opx + Cpx × composite, (b, low Mg) Opx + Cpx + Amp

  4. Coexisting cummingtonite and aluminous hornblende from garnet amphibolite, Boehls Butte area, Idaho, USA

    USGS Publications Warehouse

    Hietanen, A.

    1973-01-01

    Electron microprobe analyses of green hornblende and coexisting cummingtonite from garnet amphibolite show identical Fe/Mg ratios ( = 0.9). Cummingtonite is iron-magnesium silicate with very little calcium and aluminum and practically no alkalies. In contrast, the hornblende has 1.5 tetrahedral Al, 0.9 octahedral Al and a considerable amount of Ca and alkalies. Comparison with the hornblendes from the Sierra Nevada shows a higher relative amount of tschemakite molecule in the hornblendes from Idaho where pressures during the recrystallization were higher. ?? 1973.

  5. Atomistic simulation of trace element incorporation into garnets - comparison with experimental garnet-melt partitioning data

    NASA Astrophysics Data System (ADS)

    van Westrenen, W.; Allan, N. L.; Blundy, J. D.; Purton, J. A.; Wood, B. J.

    2000-05-01

    We have studied the energetics of trace element incorporation into pure almandine (Alm), grossular (Gros), pyrope (Py) and spessartine (Spes) garnets (X 3Al 2Si 3O 12, with X = Fe, Ca, Mg, Mn respectively), by means of computer simulations of perfect and defective lattices in the static limit. The simulations use a consistent set of interatomic potentials to describe the non-Coulombic interactions between the ions, and take explicit account of lattice relaxation associated with trace element incorporation. The calculated relaxation (strain) energies Urel are compared to those obtained using the Brice (1975) model of lattice relaxation, and the results compared to experimental garnet-melt trace element partitioning data interpreted using the same model. Simulated Urel associated with a wide range of homovalent (Ni, Mg, Co, Fe, Mn, Ca, Eu, Sr, Ba) and charge-compensated heterovalent (Sc, Lu, Yb, Ho, Gd, Eu, Nd, La, Li, Na, K, Rb) substitutions onto the garnet X-sites show a near-parabolic dependence on trace element radius, in agreement with the Brice model. From application of the Brice model we derived apparent X-site Young's moduli EX(1+, 2+, 3+) and the 'ideal' ionic radii r0(1+, 2+, 3+), corresponding to the minima in plots of Urel vs. radius. For both homovalent and heterovalent substitutions r0 increases in the order Py-Alm-Spes-Gros, consistent with crystallographic data on the size of garnet X-sites and with the results of garnet-melt partitioning studies. Each end-member also shows a marked increase in both the apparent EX and r0 with increasing trace element charge ( Zc). The increase in EX is consistent with values obtained by fitting to the Brice model of experimental garnet-melt partitioning data. However, the increase in r0 with increasing Zc is contrary to experimental observation. To estimate the influence of melt on the energetics of trace element incorporation, solution energies ( Usol) were calculated for appropriate exchange reactions between

  6. Significance of hydrous silicate lamellae in pyrope-rich garnets from the Garnet Ridge in the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Ogasawara, Y.; Sakamaki, K.; Sato, Y.

    2014-12-01

    Pyrope-rich garnets originated from the upper mantle underneath the Colorado Plateau occur at the Garnet Ridge. These garnets contain the following lamellae of hydrous and anhydrous minerals; Rt, Ilm, crichtonites, Cr-Spl, Amp, Cpx, Chl, rarely Apt, srilankite and carmichealite. The origin of these lamellae in the garnets is controversial; exsolved origin or epitaxial growth. We emphasize here the close relations between the presence of hydrous lamellae and the OH concentrations in the host garnets. Lamella phases were identified with a standard-less quantitative EDS system and a laser Raman spectrometer with Ar+ laser (514.5 nm). OH concentrations in garnets were quantitated on the basis of IR absorption spectra of garnet by micro FT-IR method using IR absorption coefficient (8770 L/mol/cm2, Katayama et al., 2006). Pyrope-rich reddish brown garnet (group B by Sato et al., AGU2014F) has large variations of major chemical compositions (Prp: 49-76, Alm: 6-43, Grs: 6-26 mol%), and OH contents (2-177 ppm wt. H2O). Among this group garnets, Ca-rich ones (Prp: 49-66; Alm: 18-28; Grs: 16-26 mol%) have lamellae of both hydrous (Amp and Chl) and anhydrous (Rt, Ilm, and Cpx) minerals. Amp and Chl lamellae are pargasitic amphibole and clinochlore, respectively, and their host garnets contain significantly low amounts of OH (2-42 ppm). Cr and pyrope-rich garnet (group A by Sato et al., AGU2014F) has chemical compositions of Prp: 67-74, Alm: 13-18, Grs: 7-11 mol% with Cr2O3 up to 5.9 wt.%, and contains lamellae of anhydrous minerals (Rt, Ilm, crichtonites, and Cr-Spl). The host garnet with these anhydrous lamellae contains a little higher OH ranging 24 to 115 ppm. Summarizing the present results, the OH contents of the host garnets depend on the presence of hydrous silicate lamella phase; OH in the garnet with hydrous silicate lamellae is lower than that in the garnet with anhydrous lamellae. The precursor OH incorporated in the host garnet structure was exsolved as hydrous

  7. Interface Engineering of Garnet Solid Electrolytes

    NASA Astrophysics Data System (ADS)

    Cheng, Lei

    Solid lithium ion conductors represent a promising class of materials for next generation high energy density batteries, with the potential for enabling use of high capacity Li metal anodes and providing opportunities for novel lithium-free cathode materials. However, highly resistive interfaces stymie their practical use. This urgent scientific challenge requires mechanistic understanding of ion transport at interfaces, as well as development of novel processes to achieve low interfacial resistances. The goal of this PhD dissertation was to generate fundamental understandings of garnet-structured Al substituted Li7La3Zr2O 12 (LLZO) electrolyte surfaces and interfaces with lithium metal electrodes. Specifically in this research, the topmost surface microstructure, local chemical environment, and surface chemistry were carefully studied. The ceramic processing of garnet is discussed and ways to control the sintering behavior and microstructures were explored and successfully demonstrated. Factors contributing to high interfacial resistance were systematically studied. The source of the high interfacial impedance has been traced to the presence of Li2CO 3 on pellet surfaces resulting from air exposure after processing. In addition, it was discovered that surface grain boundaries are surprisingly fast ion transport pathways and surface microstructure is critically important to lithium ion transport at interfaces. Complex homo- and heterostructured LLZO solid electrolytes with controllable surface and bulk microstructures were successfully fabricated, which allowed the comparison and separation of the contribution from the surface and the bulk. Engineered pellet surfaces allowed us to achieve the lowest interfacial resistance ever reported for this composition, resulting in significantly improved cycling behavior. Lastly, it was found that LLZO surfaces can be effectively stabilized under air exposure conditions, preventing Li2CO3 formation and maintaining low

  8. Elastic moduli of pyrope rich garnets

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Pandey, A. K.; Singh, C. K.

    2013-06-01

    The elastic properties of minerals depend on its composition, crystal structure, temperature and level of defects. The elastic parameters are important for the interpretation of the structure and composition of the garnet rich family. In present work we have calculated the elastic moduli such as isothermal bulk modulus, Young's modulus and Shear modulus over a wide range of temperature from 300 K to 1000 K by using Birch EOS and Poirrier Tarantola equation of state. The obtained results are compared with the experimental results obtained by measuring the elastic moduli of single crystal. The calculated results show that the logarithmic isothermal EOS does not cooperate well with experimental results.

  9. Very high-pressure orogenic garnet peridotites

    PubMed Central

    Liou, J. G.; Zhang, R. Y.; Ernst, W. G.

    2007-01-01

    Mantle-derived garnet peridotites are a minor component in many very high-pressure metamorphic terranes that formed during continental subduction and collision. Some of these mantle rocks contain trace amounts of zircon and micrometer-sized inclusions. The constituent minerals exhibit pre- and postsubduction microstructures, including polymorphic transformation and mineral exsolution. Experimental, mineralogical, petrochemical, and geochronological characterizations using novel techniques with high spatial, temporal, and energy resolutions are resulting in unexpected discoveries of new phases, providing better constraints on deep mantle processes. PMID:17519341

  10. The Garnet to Majorite Transformation in Mafic Compositions

    NASA Technical Reports Server (NTRS)

    Xirouchakis, D.; Draper, David S.; Agee, C. B.

    2002-01-01

    The garnet to majorite transformation in mafic compositions is controlled by bulk composition and the presence of silicate melt, clinopyroxene, and silicate perovskite as well as pressure. Thus, the use of empirical geobarometers based on garnet Si(4+) and/or [Al(3+) +/- Cr(3+)] (p.f.u) seems unjustified. Additional information is contained in the original extended abstract.

  11. Garnet and pyroxene compositions in some diamondiferous eclogites

    NASA Technical Reports Server (NTRS)

    Reid, A. M.; Brown, R. W.; Dawson, J. B.; Whitfield, G. G.; Siebert, J. C.

    1976-01-01

    Analyses are reported for garnet and pyroxene from 17 eclogites that contain diamond. The garnets contain small but significant contents of Na, Ti and P and the pyroxenes contain traces of K. The diamond-bearing eclogites do not constitute a unique compositional group but show a range of mineral compositions consistent with a very high P-T environment.

  12. Garnet megacrysts of the Williams diatremes, north-central Montana.

    USGS Publications Warehouse

    McGee, E.S.

    1986-01-01

    The physical characteristics of garnet megacrysts from the Williams diatremes are described, analysed and compared with other garnet megacryst suites. The only correlation found between the physical characteristics and the composition of the megacrysts related deep-red colour to high Cr content.-J.A.Z.

  13. Crystal plasticity of natural garnet: New microstructural evidence

    NASA Astrophysics Data System (ADS)

    Prior, David J.; Wheeler, John; Brenker, Frank E.; Harte, Ben; Matthews, Mike

    2000-11-01

    Scanning electron microscope (SEM) orientation contrast images of mantle nodules show that garnets contain cellular domains of different crystallographic orientation. Electron backscatter diffraction shows small crystallographic mismatches (<3°) across cell boundaries. A transmission electron microscope examination of an area containing these substructures shows that the cell boundaries comprise arrays of dislocations and are subgrain boundaries. The observed garnet substructures relate to high-temperature dislocation creep and recovery. This is the first time that subgrains have been shown to occur in a significant volume of an individual garnet. Wider application of new SEM techniques may enable us to use garnet microstructures to determine deformation conditions more exactly and will aid interpretation of garnet microchemical data.

  14. Chemistry and mineralogy of garnet pyroxenites from Sabah, Malaysia

    USGS Publications Warehouse

    Morgan, B.A.

    1974-01-01

    Garnet pyroxenites and corundum-garnet amphibolites from the Dent peninsula of eastern Sabah (North Borneo) occur as blocks in a slump breccia deposit of late Miocene age. The earliest formed minerals include pyrope-almandine garnet, tschermakitic augite, pargasite, and rutile. Cumulate textures are present in two of the six specimens studied. The earlier fabric has been extensively brecciated and partly replaced by plagioclase, ilmenite, and a fibrous amphibole. The bulk composition and mineralogy of these rocks are similar to those of garnet pyroxenite lenses within ultramafic rocks. Estimated temperature and pressure for the origin of the Sabah garnet pyroxenites is 850??150?? C and 19??4 kbar. ?? 1974 Springer-Verlag.

  15. ESCA studies of yttrium aluminum garnets

    SciTech Connect

    Pawlak, D.A. |; Wozniak, K.; Frukacz, Z.; Barr, T.L.; Fiorentino, D.; Seal, S.

    1999-03-04

    X-ray photoelectron spectroscopy (XPS/ESCA) has been employed to investigate pure single crystals and powdered samples of yttrium aluminum garnet, Y{sub 3}Al{sub 5}O{sub 12} (YAG), and YAG crystals doped with several rare earth elements (Ln = Pr, Er, Ho, Tm) and a transition metal (Cr). Core level XPS peak shapes of the main elements forming the garnet structure can be rationalized due to different structural environments of particular ions modified by doping. The change of dopant oxidation state also results in variation of XPS peaks and helps to identify the sites in which it takes place. Single-crystal and powder samples give different XPS spectra. Possible sources of these differences are discussed. Similarities and differences between simple and mixed oxides are shown. The structure of YAG suggests the presence of only one independent oxygen ion; however the O(1s) spectra of all YAG systems exhibit two readily discerned peaks. An explanation for this dichotomy is discussed, involving the possible polarization of the oxygen valence electron density between the aluminum and yttrium. Alternative explanations are also considered.

  16. Chemical zonation in garnet: kinetics or chemical equilibrium?

    NASA Astrophysics Data System (ADS)

    Ague, Jay; Chu, Xu; Axler, Jennifer

    2015-04-01

    Chemical zonation in garnet is widely used to reconstruct the pressure (P), temperature (T), time (t), and fluid (f) histories of mountain belts. Zonation is thought to result largely from changing P - T - t - f conditions during growth as well as post-growth intracrystalline diffusion. Chemical zonation is conventionally interpreted to mean that at least some of the garnet interior was out of chemical equilibrium with the matrix during metamorphism. In this case, thermally-activated diffusion in garnet is too slow to equalize chemical potentials. However, in their groundbreaking paper, Tajčmanová et al. (2014) postulate that in high-grade rocks, chemical zonation may actually reflect attainment of equilibrium. In this scenario, diffusion is fast but viscous relaxation is slow such that the zonation patterns directly mirror internal pressure gradients within garnet. Such zoning would likely be very different than typical concentric growth zonation. Furthermore, Baumgartner et al. (2010) hypothesize that given significant variations in the molar volumes of garnet endmembers, diffusional relaxation may produce internal pressure gradients if the garnet behaves as a near constant-volume system. Consequently, growth zoning could be preserved by pressure variations within the garnet that equalize chemical potentials and slow or stop diffusion (i.e., the garnet is chemically heterogeneous but maintains internal chemical equilibrium due to the pressure variations). This mechanism predicts that areas of garnet with small compositional contrasts would undergo more diffusional relaxation than areas with large contrasts. Moreover, generation of large internal pressure gradients approaching 1 GPa would be expected to induce deformation (e.g., fracturing) in regions of large compositional gradients. Strongly growth-zoned amphibolite facies garnet from the Barrovian zones, Scotland (Ague and Baxter, 2007) shows neither of these features. The sharp compositional gradients are

  17. Optical properties of gadolinium gallium garnet.

    PubMed

    Wood, D L; Nassau, K

    1990-09-01

    The refractive index, the temperature coefficient of the refractive index, and the optical transparency of gadolinium gallium garnet are reported as a function of wavelength from the near UV to the middle IR. The materialis transparent enough for good optical components between 0.36 and 6.0 microm, and the refractive index ranges from 2.0 at the UV end to 1.8 at the IR end of the spectrum. The wavelength dependence of index is expressed as a three-term Sellmeier formula with agreement better than two parts in the fourth decimal between calculated and experimental values. Variations in composition depending on growth from various melts (e.g., stoichiometric vs congruent) have no effect on the optical parameters at this level of precision.

  18. Terbium photoluminescence in yttrium aluminum garnet xerogels

    SciTech Connect

    Maliarevich, G. K.; Gaponenko, N. V. Mudryi, A. V.; Drozdov, Yu. N.; Stepikhova, M. V.; Stepanova, E. A.

    2009-02-15

    Based on a colloidal solution containing terbium, yttrium, and aluminum metal ions, a powder was synthesized and films of terbium-doped yttrium aluminum garnet Tb{sub 0.15}Y{sub 2.85}Al{sub 5}O{sub 12} were grown on single-crystal silicon and porous anodic alumina. Annealing of the sample in a temperature range from 200-1100 deg. C results in an increase in the photoluminescence intensity in the wavelength range from 480-640 nm, which is caused by Tb{sup 3+} ion intra-atomic transitions {sup 5}D{sub 4}{sup {yields}}{sup 7}F{sub j} (j = 3, 4, 5, 6). Annealing at 900 deg. C and higher temperatures gives rise to low-intensity photoluminescence bands in the region of 667 and 681 nm, which correspond to transitions {sup 5}D{sub 4}{sup {yields}}{sup 7}F{sub 0}, {sup 5}D{sub 4}{sup {yields}}{sup 7}F{sub 1}, and room-temperature Stark term splitting, which suggests the existence of a crystalline environment of Tb{sup 3+} ions. The FWHM of spectral lines in the region of 543 nm decreases from {approx}10 to {approx}(2-3) nm as the xerogel annealing temperature is increased from 700 to 900 deg. C and higher. Three bands with maxima at 280, 330, and 376 nm, which correspond to Tb{sup 3+} ion transitions {sup 7}F{sub 6}{sup {yields}}{sup 5}I{sub 8}, {sup 5}L{sub 6}, {sup 5}G{sub 6}, {sup 5}D{sub 3}, are observed in the photoluminescence excitation spectra of the studied structures for the emission wavelength at 543 nm. X-ray diffraction detected the formation of a crystalline phase for a terbium-doped yttrium aluminum garnet powder after annealing at 1100 deg. C.

  19. Garnet: featured mineral group at the 1993 Tucson Show

    USGS Publications Warehouse

    Modreski, P.J.

    1993-01-01

    The garnets are a common but complex group of minerals. They are perhaps the mineral kingdom's best example of solid solution: a relationship in which minerals have chemical compositions that are intermediate between two or more ideal end-member species. In garnet, we deal with a complex group of solid-solution series between as many as 14 end-member minerals. The varying intergradations of solid solution between these different end-members help to explain the garnet group's variety of color, environment of occurrence, gem use, and variation in such physical properties as specific gravity, refractive index, and hardness. -from Author

  20. Ce-doped single crystal and ceramic garnets for γ ray detection

    SciTech Connect

    Hull, G; Roberts, J; Kuntz, J; Fisher, S; Sanner, R; Tillotson, T; Drobshoff, A; Payne, S; Cherepy, N

    2007-07-30

    Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.

  1. Magneto-Optical Experiments on Rare Earth Garnet Films.

    ERIC Educational Resources Information Center

    Tanner, B. K.

    1980-01-01

    Describes experiments in which inexpensive or standard laboratory equipment is used to measure several macroscopic magnetic properties of thin rare earth garnet films used in the manufacture of magnetic bubble devices. (Author/CS)

  2. Indus Basin sediment provenance constrained using garnet geochemistry

    NASA Astrophysics Data System (ADS)

    Alizai, Anwar; Clift, Peter D.; Still, John

    2016-08-01

    The chemical and mineralogical diversity of western Himalayan rivers is the result of each of them draining different tectonic and lithologic units, whose character is partly transferred to the sediments carried by those rivers. Garnet geochemistry was employed to discriminate provenance in the Indus River system. We characterized the geochemistry of garnet sediment grains from the modern Indus and all its major tributaries, as well as the related but ephemeral Ghaggar-Hakra River and dune sand from the Thar Desert. Garnet geochemistry displays a unique signature for the Himalayan rivers on the east of the Indus drainage compared to those in the western drainage. The trunk Indus remains distinct because of the dominant arc-type pyrope-garnet derived from Kohistan and the Karakoram. The Jhellum, which lies just east of the modern Indus has modest concentrations of arc-type pyrope garnets, which are more depleted in the other eastern tributaries. Their presence in the Jhellum reflects recycling of trunk Indus garnets through the Miocene Siwalik Group foreland sedimentary rocks. The Thar Desert dune sample contains significant numbers of grains similar to those in the trunk Indus, likely reworked by monsoon winds from the SW. Our data further indicate the presence of a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. Sands from this channel cannot be distinguished from the Indus on the basis of their garnet geochemistry alone but we favour their sedimentation from an Indus channel rather than reworking of desert sands by another stream. The garnet geochemistry shows some potential as a provenance tool, but cannot be used alone to uniquely discriminate Indus Basin provenance.

  3. Garnet polycrystals and the significance of clustered crystallization

    NASA Astrophysics Data System (ADS)

    Whitney, Donna L.; Seaton, Nicholas C. A.

    2010-10-01

    Polycrystalline garnets are common in metamorphic rocks and may form as a result of close spacing of nuclei (if clustering is early) or impingement of larger grains (if clustering occurs later in the growth history). The timing of clustering relative to garnet growth is relevant to understanding the formation and evolution of porphyroblasts and evaluating the significance (if any) of clustering. Electron backscattered diffraction (EBSD) analysis of garnet-bearing metamorphic rocks reveals the presence of polycrystalline garnet in nine localities examined in this study: the northern Appalachians (Vermont, Maine, New York, USA); North American Cordillera (North Cascades Range, Washington; Snake Range, Nevada, USA); western Rocky Mountains (British Columbia, Canada); southern Menderes Massif (Turkey); Santander Massif (Colombia); and the Sanandaj-Sirjan zone (Hamadan, Iran). In some samples, polycrystals comprise ~20-30% of garnets analyzed, and chemical and textural evidence suggests that early coalescence of garnet polycrystals is common. Some early-coalescing polycrystals exhibit growth zoning that is concentric about the geometric center of the polycrystal. In thin section, these garnets may be undetectable as polycrystals based on morphology or zoning. In some polycrystals, zoning is unrelated to the location of internal grain boundaries; in others, Fe-Mn-Mg zoning has a different pattern than that of Ca; zoning patterns may vary on the scale of a single thin section. In addition, some polycrystals are characterized by high-angle misorientation boundaries that may be in special (non-random) orientations, an observation that indicates that these polycrystals are not random clusters of grains. The presence of internal grain boundaries may affect diffusion pathways and length scales, and may facilitate communication of porphyroblast interiors with matrix phases, thereby influencing reaction history of the rock and the composition/zoning of garnet.

  4. Garnet--An Essential Industrial Mineral and January's Birthstone

    USGS Publications Warehouse

    Evans, James G.; Moyle, Phillip R.; Frank, David G.; Olson, Donald W.

    2006-01-01

    Garnet is one of the most common minerals in the world. Occurring in almost any color, it is most widely known for its beauty as a gem stone. Because of its hardness and other properties, garnet is also an essential industrial mineral used in abrasive products, non-slip surfaces, and filtration. To help manage our Nation's resources of such essential minerals, the U.S. Geological Survey (USGS) provides crucial data and scientific information to industry, policymakers, and the public.

  5. Garnets from the Camafuca-Camazambo kimberlite (Angola).

    PubMed

    Correia, Eugénio A; Laiginhas, Fernando A T P

    2006-06-01

    This work presents a geochemical study of a set of garnets, selected by their colors, from the Camafuca-Camazambo kimberlite, located on northeast Angola. Mantle-derived garnets were classified according to the scheme proposed by Grütter et al. (2004) and belong to the G1, G4, G9 and G10 groups. Both sub-calcic (G10) and Ca-saturated (G9) garnets, typical, respectively, of harzburgites and lherzolites, were identified. The solubility limit of knorringite molecule in G10D garnets suggests they have crystallized at a minimum pressure of about 40 to 45 kbar (4-4.5 GPa). The occurrence of diamond stability field garnets (G10D) is a clear indicator of the potential of this kimberlite for diamond. The chemistry of the garnets suggests that the source for the kimberlite was a lherzolite that has suffered a partial melting that formed basaltic magma, leaving a harzburgite as a residue. PMID:16710568

  6. Multistep sintering to synthesize fast lithium garnets

    NASA Astrophysics Data System (ADS)

    Xu, Biyi; Duan, Huanan; Xia, Wenhao; Guo, Yiping; Kang, Hongmei; Li, Hua; Liu, Hezhou

    2016-01-01

    A multistep sintering schedule is developed to synthesize Li7La3Zr2O12 (LLZO) doped with 0.2 mol% Al3+. The effect of sintering steps on phase, relative density and ionic conductivity of Al-doped LLZO has been evaluated using powder X-Ray diffraction (XRD), scanning electron microscopy (SEM), 27Al magic spinning nuclear magnetic resonance (NMR) spectroscopy and electrochemical impedance spectroscopy (EIS). The results show that by holding the sample at 900 °C for 6 h, the mixture of tetragonal and cubic garnet phases are obtained; by continuously holding at 1100 °C for 6 h, the tetragonal phase completely transforms into cubic phase; by holding at 1200 °C, the relative density increases without decomposition of the cubic phase. The Al-LLZO pellets after multistep sintering exhibit cubic phase, relative density of 94.25% and ionic conductivity of 4.5 × 10-4 S cm-1 at room temperature. Based on the observation, a sintering model is proposed and discussed.

  7. Evaluation of thermobarometers for garnet peridotites

    NASA Technical Reports Server (NTRS)

    Finnerty, A. A.; Boyd, F. R.

    1984-01-01

    Twenty-one geothermometers and six geobarometers are evaluated for accuracy and precision for garnet lherzolites, with a suite of well-equilibrated xenoliths from kimberlites of northern Lesotho. Accuracy was tested by comparison of P-T estimates for a diamond-bearing and a graphite-bearing xenolith with the experimentally determined diamond-graphite univariant curve and by comparison of P-T estimates for phlogopite-bearing xenoliths to the high-temperature stability limit of phlogopite. Precision was evaluated by measuring the scatter of P-T estimates for each of four xenoliths from a wide range of P and T when many point analyses of the constituent minerals are used for P-T estimation. Most satisfactory is a thermobarometer composed of the uncorrected diopside-enstatite miscibility gap of Lindsley and Dixon (1976), combined with the uncorrected isopleths for aluminum in enstatite coexisting with pyrope of MacGregor (1974). The inflection observed in the northern Lesotho paleogeotherm cannot be an artifact of the method of temperature estimation.

  8. Magnetic and electronic properties of nanocrystalline Gd{sub 3}Fe{sub 5}O{sub 12} garnet

    SciTech Connect

    Lassri, H.; Hlil, E.K.; Prasad, S.; Krishnan, R.

    2011-12-15

    The Gd{sub 3}Fe{sub 5}O{sub 12} nanocrystalline Gadolinium Iron Garnet (GdIG) obtained from a sintered block was milled in a high energy ball mill. We measured the magnetization at 5 K under applied fields up to 12 T. We report here our study of approach to saturation magnetization. The results have been interpreted within the framework of random anisotropy model. From an analysis of the approach to saturation magnetization some fundamental parameters have been extracted. We have determined the anisotropy field H{sub r} and the local magnetic anisotropy constant K{sub L}. In addition, first-principles spin-density functional calculations, using the Full potential Linear Augmented Plane Waves (FLAPW) method are performed to investigate electronic and magnetic structures. All computed parameters are discussed and compared to available experimental data. - Graphical abstract: Random anisotropy fields, random anisotropy constant, substantial interstitial magnetism as well as magnetic quadrupolar feature on oxygen are determined from magnetization, theoretical random magnetic anisotropy model and FLAPW calculations in nanocrystalline Gadolinium Iron Garnet (GdIG). Highlights: Black-Right-Pointing-Pointer Nanocrystalline Gadolinium Iron Garnet (GdIG) prepared by a high energy ball mill. Black-Right-Pointing-Pointer Random magnetic anisotropy model developed for amorphous is used for Nanocrystalline GdIG. Black-Right-Pointing-Pointer Random anisotropy fields and random anisotropy constant are determined. Black-Right-Pointing-Pointer FLAPW calculations performed to investigate both magnetic and electronic structures. Black-Right-Pointing-Pointer Substantial interstitial magnetism and magnetic quadrupolar feature on oxygen are revealed.

  9. Garnet-rich Rocks and their Genetic Relationship to the Broken Hill Lead-Zinc-Silver Deposit, New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Spry, P. G.; Plimer, I. R.; Teale, G. S.; Heimann, A.

    2004-05-01

    The stratiform Paleoproterozoic Broken Hill deposit, Australia, is the largest accumulation of lead-zinc-silver in the world (280 million tons of 10% Pb, 8.5% Zn, and 148 g/t Ag). It is located within a rift in an upward-coarsening sequence of clastic metasediments into which Paleoproterozoic mafic and felsic melts have intruded, probably while the sediments were wet. The deposit was metamorphosed to granulite facies conditions (750-800oC and 5-6 kb) and was subjected to at least five periods of deformation (D1-D5). Garnet occurs in a variety of rock types, including sillimanite-bearing pelitic schist, felsic gneisses (e.g. feldspar-quartz-garnet-biotite rock [Potosi Gneiss]), pegmatite, banded iron formation, and the stratigraphic equivalents of sulfide rocks, as a hanging wall syn- to late-D2 halo to sulfides. Garnet also occurs as discordant halos on the margins (up to 50 cm wide) of post-D3 epidotized dolerite dikes, lode pegmatite, quartz veins (so-called garnet envelope), and massive sulfides. However, the garnet-rich rocks that are the best indicator to each of the six main orebodies sulfides are quartz-garnetite and garnetite. Quartz-garnetite and garnetite are massive or banded and contain a variety of accessory silicates, sulfides, phosphates, and oxides. Laminae in these rocks are predominantly coplanar with S0 and S1 and garnetite is also associated with F2 and F3 sulfide projections (droppers). Some droppers contain epidotized dolerite clasts suggesting post-D3 formation. Coarse garnets (up to 1 cm in diameter) in one massive metasomatic variety of quartz garnetite cross-cut laminated fine-grained massive quartz garnetite and garnetite. This remobilized variety, as well as discordant gahnite-bearing quartz garnetite, likely formed during D2 or D3. Retrograde shear zones (D4, D5 and possibly later deformation events) contain transposed cataclastic sulfide masses with a quartz-garnet rim thereby showing that sulfide mobilization and formation of quartz-garnet

  10. Charge-coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Anthony; Newville, Mathew; Engelhard, Mark H.; Sutton , Steven R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce), and thorium (Th), incorporated by a charge-coupled substitution with calci-um (Ca) for yttrium (Y) in YIG, namely 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single phase garnets Y3-xCa0.5xM0.5xFe5O12, synthesized by the citrate-nitrate combustion method, were obtained up to x = 0.7. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe-Mössbauer spectroscopy indicated that the samples are single phase, M4+ and Ca2+ cations are restricted to the c-site, the nature of M4+ has only a minor effect on the structure, and the local environments of both the tetrahedral and octahedral Fe3+ are systematically affected by the extent of substitution, especially on the tetrahedral sublattice. The charge coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases, compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature. These structural and thermodynamic findings shed light on possible incorporation of U in this garnet system.

  11. Presumed Multiple Metasomatism underneath the Colorado Plateau; Decoding from Chemistry and Inclusion/Lamella Mineralogy of Diverse Garnets from the Garnet Ridge, Northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Ogasawara, Y.

    2015-12-01

    Various garnets containing the information on mantle petrology and related metasomatism occur at the Garnet Ridge, Colorado Plateau. The origins of garnets range from deep mantle to shallow continental crust. These garnets were delivered by kimberlitic diatreme of 30 Ma (Smith et al. 2004). We have classified the garnets into 10 groups (A to J, see figure) by naked eye observation, major chemistry, minor Na-Ti-P, inclusion/lamella mineralogy. Among them, groups A to D are of mantle origin, E to G of subducted oceanic crust origin, and H to J of continental crust origin. We summarized results as in the followings. A: Cr and pyrope-rich garnet has Cr2O3(0.8-6.3 wt.%) and inclusions of Ol, Cpx, Opx, Ti-Chu/Chn and carbonates, indicating carbonated garnet lherzolites as host. Cr contents negatively correlates with Na-Ti-P contents and occurrence of exsolved Rt, Ilm and crichtonite. This indicates Cr-rich end-member is the most "primitive" mantle garnet before metasomatism. B: Pyrope-rich reddish brown garnet of peridotitic origins was subdivided into 4 subgroups (B1 to B4, see figure). Compositional range in Ca-Mg-Fe triangle expands to Fe-rich side from group A. Exsolved Na-bearing amphibole and inclusions of Ap, carbonates and fluid were identified. These indicate metasomatism of group A. C: Garnet megacryst is coarse-grained garnet (2-10 cm across) with crystal faces. This garnet has wide chemical variation plotted in the center area of Ca-Mg-Fe triangle. D: Garnet aggregate has similar chemistry of group C and is composed of several grains. Grain boundaries of garnet were recognized by Rt, Ilm and other minerals and oscillatory zonings of Ca, Mg, Fe and Na-Ti-P. Fluid inclusions of groups C and D suggest these garnets might crystalized from fluid. E: Garnet in eclogite and F: Garnet in metasomatized eclogite are xenolith samples (the Fallaron Plate origin?). Aggregate of Zo+Ab contained in group E indicates decomposed precursor lawsonite inclusion. G: Quartz

  12. Discovery of a New Garnet Mineral, Hutcheonite, in the Allende Meteorite

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2013-09-01

    A new titanium-rich garnet mineral has been found in a FUN CAI (a rare type of calcium-aluminum-rich inclusion, CAI) from the Allende carbonaceous chondrite, as reported by the discovery team of Chi Ma (CalTech) and Alexander Krot (University of Hawaii). The mineral, IMA 2013-029, was officially approved in June 2013 by the Commission on New Minerals, Nomenclature, and Classification of the International Mineralogical Association as hutcheonite. The mineral's name honors Ian D. Hutcheon, a researcher at Lawrence Livermore National Laboratory, who is a leading authority in the chronology of the early Solar System, especially known for his significant contributions to the development of instrumentation and techniques for isotopic and elemental microanalysis. Researchers Ma and Krot say hutcheonite in Allende is likely an alteration phase formed by iron-alkali-halogen metasomatism of the primary phases in the FUN CAI.

  13. The metapelitic garnet biotite muscovite aluminosilicate quartz (GBMAQ) geobarometer

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Ming; Zhao, Guochun C.

    2007-09-01

    In this contribution we have empirically calibrated the garnet-biotite-muscovite-aluminosilicate-quartz (GBMAQ) barometer using low- to medium-high-pressure, mid-grade metapelites. Application of the barometer suggests that the GBMAQ and GASP barometers show quite similar pressure estimates. Furthermore, metapelites within thermal contact aureole or very limited geographic area show no meaningful pressure diversity determined by the GBMAQ and GASP barometers which is the geological reality. The random error of the GBMAQ barometer is expected to be around ± 0.8 kbar, and this barometer shows no systematic bias with respect to either pressure, or temperature, or Al VI in muscovite, or Fe in biotite, or Fe in garnet. The GBMAQ barometer is thermodynamically consistent with the garnet-biotite geothermometer because they share the same activity models of both garnet and biotite. This barometer is especially useful for assemblages with Ca-poor garnet or Ca-poor plagioclase or plagioclase-absent metapelites. Application of this barometer beyond the calibration ranges, i.e., P- T range and chemical ranges of the minerals, is not encouraged.

  14. Iron Test

    MedlinePlus

    ... detect and help diagnose iron deficiency or iron overload. In people with anemia , these tests can help ... also be ordered when iron deficiency or iron overload is suspected. Early iron deficiency often goes unnoticed. ...

  15. Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Pal, AnnaMarie T.; Patton, Martin O.; Jenkins, Phillip P.

    1999-01-01

    As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K.

  16. Ti in garnet: complex substitutions and their implications for understanding crustal metamorphism

    NASA Astrophysics Data System (ADS)

    Ackerson, M. R.; Watson, E. B.; Tailby, N. D.

    2015-12-01

    The nature of Ti incorporation into garnet (substitution mechanisms, site occupancy) has been a matter of interest for decades. Most crustal garnets contain minor to trace quantities of Ti, yet crystallographically-aligned rutile needles in some high grade crustal and mantle garnets suggest Ti solubility can reach major-element concentrations (>1%TiO2) under certain conditions. Understanding Ti incorporation into garnet holds promise for evaluating and interpreting the history and evolution of metamorphic systems. In this study we will demonstrate that Ti is incorporated into garnets via at least three substitution mechanisms on multiple crystallographic sites. Garnets were grown in piston cylinder apparatuses at eclogite and granulite facies conditions in multiple bulk compositions. Chemical trends in the experimentally-grown garnets suggest Ti incorporation occurs on the octahedral crystallographic site (VITi) via at least two substitution mechanisms. Furthermore, Ti partitioning between garnets and their corresponding melts increases with decreasing temperature and increasing melt polymerization. Ti Kα X-ray Absorption Near Edge Struture (XANES) pre-edge analysis was used to observe Ti coordination in experimental and natural garnets (contact metamorphic grade up to eclogite and granulite facies). XANES analyses confirm the observation of VITi in experimental garnets. However, natural garnets contain both VITi and IVTi (from ~90% IVTi to 100% VITi). Microprobe analyses of Ti in garnet were combined with the XANES analyses to determine VITi and IVTi concentrations. Increasing VITi is strongly correlated with increasing Ca content in garnet, while IVTi behaves similar to IVTi in other silicate minerals (e.g. quartz, zircon). The complex nature of Ti incorporation into garnet diminishes the utility of a single-mineral Ti-in-garnet thermobarometer, but partitioning of Ti between garnet, clinopyroxene and melt could be useful for the development of novel empirical

  17. Garnet compositions and their use as indicators of peraluminous granitoid petrogenesis - southeastern Arabian Shield

    USGS Publications Warehouse

    du Bray, E.A.

    1988-01-01

    Garnet, an uncommon accessory mineral in igneous rocks, occurs in seven small peraluminous granitoid plutons in the southeastern Arabian Shield; textural equilibrium between garnet and other host granitoid minerals indicates that the garnets crystallized from their host magmas. Compositions of the garnets form three groups that reflect host-granitoid compositions, which in turn reflect source compositions and tectonic regimes in which the host magmas were generated. Garnets from the seven plutons have almandine-rich cores and spessartine-rich rims. This reverse zoning depicts host magma compositional evolution; i.e. rimward spessartine enrichment resulted from progressive, host-magma manganese enrichment. The garnets are heavy rare-earth element enriched; (Lu/La)N ranges from 13 to 355 and one of the garnets contains spectacularly elevated abundances of Y, Ta, Th, U, Zn, Zr, Hf, Sn, and Nb. Involvement of garnets with these trace element characteristics in magma genesis or evolution can have dramatic effects on trace element signatures of the resulting magmas. Other researchers suggest that Mn-enriched magmas are most conducive to garnet nucleation. Although the garnetiferous granitoids discussed here are slightly Mn enriched, other genetically similar peraluminous Arabian granitoids lack garnet; Mn enrichment alone does not guarantee garnet nucleation. The presence of excess alumina in the magma may be a prerequisite for garnet nucleation. ?? 1988 Springer-Verlag.

  18. Lu-Hf geochronology on cm-sized garnets using microsampling: New constraints on garnet growth rates and duration of metamorphism during continental collision (Menderes Massif, Turkey)

    NASA Astrophysics Data System (ADS)

    Schmidt, Alexander; Pourteau, Amaury; Candan, Osman; Oberhänsli, Roland

    2015-12-01

    This study shows Lu-Hf geochronology of zoned garnet crystals contained in mica schists from the southern Menderes Massif, Turkey. Selected samples are four 3-5 cm large garnet megacrysts of which several consecutive garnet shells have been sampled with a micro-saw and analyzed for dating. The results are used to extract growth rates of garnet, and also to improve the time constraint for Alpine-aged overprint of the Pan-African basement in the Menderes Massif. Lu-Hf ages of the sampled garnet shells are determined by two-point garnet-only isochrons using the garnets' Lu-depleted rim compositions. This yields a consistent decrease of age information from core to rim segments of individual garnet crystals and the calculated isochron ages propose a time frame of growth between 42.6 ± 1.9 and 34.8 ± 3.1 Ma. Major element profiles in the investigated garnets characterize zoning patterns indicative of prograde conditions: Rayleigh fractionated bell-shaped Mn and decreasing Fe/(Fe + Mg) are recorded by the garnets' core to rim compositions. Therefore the obtained Lu-Hf ages record timing of early prograde growth for the cores of the garnets. Two of the large garnet crystals also yield isochron ages of 58.83 ± 0.69 and 50.16 ± 0.84 Ma in their innermost cores, which appear to record an early nucleation event. This view, however, is not in concordance with the observed major element profiles of these garnets, and therefore is interpreted with caution. Termination of the garnet growth period is determined through the calculation of radial growth rates based on the size of the garnets and the Lu-Hf ages obtained for consecutive shells. Extrapolation of these rates potentially constrains the total duration for garnet growth terminating at 31 ± 6 Ma. Comparison of the growth rates calculated for individual crystals shows a variety of slow and fast growing garnets, and similar results have been previously obtained with the Rb-Sr and Sm-Nd isotope systems. The new data

  19. Charge-coupled substituted garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): structure and stability as crystalline nuclear waste forms.

    PubMed

    Guo, Xiaofeng; Kukkadapu, Ravi K; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H; Sutton, Stephen R; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y(3+) = Ca(2+) + M(4+), where M(4+) = Ce(4+) or Th(4+). Single-phase garnets Y3-xCa0.5xM0.5xFe5O12 (x = 0.1-0.7) were synthesized by the citrate-nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and (57)Fe-Mössbauer spectroscopy indicated that M(4+) and Ca(2+) cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe(3+) are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  20. Charge-coupled substituted garnets (Y 3–x Ca 0.5x M 0.5x )Fe₅O₁₂ (M = Ce, Th): Structure and stability as crystalline nuclear waste forms

    DOE PAGESBeta

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y³⁺ = Ca²⁺ + M⁴⁺, where M⁴⁺ = Ce⁴⁺ or Th⁴⁺. Single-phase garnets Y3–xCa0.5xM0.5xFe₅O₁₂ (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffractionmore » and ⁵⁷Fe–Mössbauer spectroscopy indicated that M⁴⁺ and Ca²⁺ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe³⁺ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high-temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.« less

  1. William Herschel and the 'garnet' stars: μ Cephei and more

    NASA Astrophysics Data System (ADS)

    Steinicke, Wolfgang

    2015-07-01

    Although William Herschel's 'Garnet Star' (μ Cephei) is a prominent object, the story of the discovery of this famous red star is not well documented. Prior to and after Herschel, the identification of this star was the subject of confusion in various catalogues and atlases. The case is complex and involves other stars in southern Cepheus, including double stars, found by Herschel in the course of his star surveys. It is also fascinating to learn that μ Cephei is not the only star called 'garnet' by him. This study reveals that there are 21 in all, resulting in a 'Herschel Catalogue of Garnet Stars' - the first historical catalogue of red stars. Among them are prominent objects, which in the literature are credited to later observers. This misconception is corrected here, for Herschel was the true discoverer of all of them. The most interesting cases are Hind's 'Crimson Star', Secchi's 'La Superba', John Herschel's 'Ruby Star' and Schmidt's V Aquilae. Finally, we discussed whether Herschel speculated about the physical nature of his garnet stars, many of which are now known to be variable.

  2. Thermodynamic consistencies and anomalies among end-member silicate garnets.

    PubMed

    Glasser, Leslie

    2014-09-01

    Materials with the garnet crystal structure include silicate minerals of importance both in geology, on account of their use in geothermobarometry, and industrially as abrasives. As a consequence of the former, there is considerable published thermodynamic information concerning them. We here examine this thermodynamic information for end-member silicate garnets (some of which are synthetic since not all occur in nature) for consistencies and anomalies, using thermodynamic relations between thermodynamic properties that we have established over recent years. The principal properties of interest are formula volume, heat capacity, entropy, formation enthalpy (from which the Gibbs energy may be obtained), and isothermal compressibility. A significant observation is that the ambient-temperature heat capacities of the silicate garnets are rather similar, whereas their ambient-temperature entropies are roughly proportional to their formula volumes. Evaluation of their Debye temperatures implies that their vibrational contributions to heat capacity are fully excited at ambient temperatures. The relatively small isothermal compressibilities of these garnets is related to the rigidity of their constituent silicate tetrahedra. We here establish additive single-ion values for each of the thermodynamic properties, which may be applied in estimating corresponding values for related materials.

  3. Isomorphism of actinides and REE in synthetic ferrite garnets

    NASA Astrophysics Data System (ADS)

    Livshits, T. S.

    2010-02-01

    The reprocessing of spent nuclear fuel (SNF) is accompanied by the formation of liquid high-level radioactive waste (HLW). To increase the safety of handling HLW, it is proposed to extract actinide isotopes (An) and REE from them. These elements may be incorporated into crystalline matrices, e.g., based on ferrites with garnet structure, and then disposed in a geologic repository. The actinide-REE fraction is characterized by a complex composition. In addition to major components (An and REE), Al, Si, Na, and Sn occur therein in small amounts (a few wt %). Possible incorporation of the admixtures into ferrite garnets, as well as their effect on the phase composition of matrices and Th, Ce, Gd, and La contents were studied. It was shown that admixtures enter into garnet by means of isomorphic replacement. The properties of samples change only when admixtures are added in amounts exceeding their concentrations in HLW. The ability of ferrite garnets to accumulate significant amounts of An, REE, and admixture elements makes them suitable for use as matrices in immobilizing actinide-REE HLW of complex composition.

  4. Elasticity of some mantle crystals structures. III - Spessartite-almandine garnet

    NASA Technical Reports Server (NTRS)

    Wang, H.; Simmons, G.

    1974-01-01

    Measurements of the pressure dependence of the elastic constants of spessartite-almandine garnet are given. The basis for velocity systematics among the available natural and synthetic garnet data is then examined. As for any dense oxide, the natural anion in garnet is dominant in size. The ionic sizes of the cations in the various sites are used to determine the extent to which it might be expected that garnets of different chemical formulas are analogous in elastic properties. The results are used to predict that the elastic velocities in garnet-transformed MgSiO3 are the same as those in pyrope (Mg3Al2Si3O12).

  5. Iron Chelation

    MedlinePlus

    ... iron overload and need treatment. What is iron overload? Iron chelation therapy is used when you have ... may want to perform: How quickly does iron overload happen? This is different for each person. It ...

  6. Garnet-filled trails associated with carbonaceous matter mimicking microbial filaments in Archean basalt.

    PubMed

    Lepot, K; Philippot, P; Benzerara, K; Wang, G-Y

    2009-09-01

    The study of the earliest traces of life on Earth can be complicated by abiotically formed biomorphs. We report here the finding of clustered micrometer-sized filaments of iron- and calcium-rich garnets associated with carbonaceous matter in an agate amygdale from a 2.7-billion-year-old basalt of the Maddina Formation, Western Australia. The distribution of carbonaceous matter and the mineral phases composing the filaments were analyzed using a combination of confocal laser scanning microscopy, laser-Raman micro-spectroscopy, focused ion beam sectioning and transmission electron microscopy. The results allow consideration of possible biogenic and abiotic processes that produced the filamentous structures. The filaments have a range of sizes, morphologies and distributions similar to those of certain modern iron-mineralized filamentous bacteria and some ancient filamentous structures interpreted as microfossils. They also share a high morphological similarity with tubular structures produced by microbial boring activity. However, the microstructures and the distribution of carbonaceous matter are more suggestive of an abiotic origin for the filaments. They are characteristic features of trails produced by the displacement of inclusions associated with local dissolution of their silica matrix. Organic compounds found in kerogen or bitumen inclusions may have contributed significantly to the dissolution of the quartz (or silica gel) matrix driving filamentous growth. Discriminating the products of such abiotic organic-mediated processes from filamentous microfossils or microbial borings is important to the interpretation of the scarce Precambrian fossil record and requires investigation down to the nanoscale.

  7. Garnet-filled trails associated with carbonaceous matter mimicking microbial filaments in Archean basalt.

    PubMed

    Lepot, K; Philippot, P; Benzerara, K; Wang, G-Y

    2009-09-01

    The study of the earliest traces of life on Earth can be complicated by abiotically formed biomorphs. We report here the finding of clustered micrometer-sized filaments of iron- and calcium-rich garnets associated with carbonaceous matter in an agate amygdale from a 2.7-billion-year-old basalt of the Maddina Formation, Western Australia. The distribution of carbonaceous matter and the mineral phases composing the filaments were analyzed using a combination of confocal laser scanning microscopy, laser-Raman micro-spectroscopy, focused ion beam sectioning and transmission electron microscopy. The results allow consideration of possible biogenic and abiotic processes that produced the filamentous structures. The filaments have a range of sizes, morphologies and distributions similar to those of certain modern iron-mineralized filamentous bacteria and some ancient filamentous structures interpreted as microfossils. They also share a high morphological similarity with tubular structures produced by microbial boring activity. However, the microstructures and the distribution of carbonaceous matter are more suggestive of an abiotic origin for the filaments. They are characteristic features of trails produced by the displacement of inclusions associated with local dissolution of their silica matrix. Organic compounds found in kerogen or bitumen inclusions may have contributed significantly to the dissolution of the quartz (or silica gel) matrix driving filamentous growth. Discriminating the products of such abiotic organic-mediated processes from filamentous microfossils or microbial borings is important to the interpretation of the scarce Precambrian fossil record and requires investigation down to the nanoscale. PMID:19656217

  8. Combined external-beam PIXE and /μ-Raman characterisation of garnets used in Merovingian jewellery

    NASA Astrophysics Data System (ADS)

    Calligaro, T.; Colinart, S.; Poirot, J.-P.; Sudres, C.

    2002-04-01

    Red garnets were the dominant gemstones used for jewels in Europe during the Early Middle Ages. We have studied over 350 garnets set on 12 jewels unearthed in the royal necropolis of the Saint-Denis Basilica, close to Paris. This famous collection of "cloisonné" style artefacts dates from the Merovingian period (late fifth century AD to early seventh century AD). The archaeological issue addressed is the identification of the geographical origin of these garnets, in view to establish the gem trading routes during the Dark Ages. External beam PIXE was used to determine the major constituents (Mg, Al, Si, Ca, Mn, Fe), specifying the garnet type (composition in various mineralogical end-members, e.g. almandine, pyrope, spessartite, …), and the trace element content (Cr, Y). Three sorts of garnets were identified. Ten jewels are adorned with almandine garnets (Fe-rich). One jewel has intermediate almandine-pyrope garnets ("rhodolite"). The last and most recent jewel is inlaid with pyrope (Mg-rich) garnets. Trace element content and slight differences in major composition allowed to distinguish five different sources: two sources for pyrope garnets (with and without chromium), and two sources for almandine garnets (distinctive calcium, magnesium and yttrium contents). A preliminary comparison with literature data suggested that almandine garnets may have been mined from India while the "rhodolite" garnets may have been imported from Sri Lanka. The sources of pyrope garnets could be the Bohemian deposits (Czech republic). In addition, μ-Raman spectrometry was used to identify most of the mineral inclusions (apatite, zircon, ilmenite, monazite, calcite, quartz) present in almandine garnets. Even if two specific types of inclusions were not identified, due to the lack of corresponding reference spectra in our database, the Raman spectra collected provided an interesting inclusion fingerprint.

  9. Applying Lu-Hf garnet geochronology and inverse phase equilibria modeling to migmatites

    NASA Astrophysics Data System (ADS)

    Yakymchuk, C.; Brown, M.; Vervoort, J. D.

    2013-12-01

    Garnet-bearing assemblages are common in HT metamorphic rocks and are widely used to determine P-T conditions. Garnet is also a host for accessory minerals that may be used to determine the timing of garnet growth or breakdown. However, using accessory minerals to date garnet in HT metamorphic rocks may produce ambiguous or erroneous age results if these minerals were grown or modified subsequently due to fluid or melt infiltration along microfractures. Direct dating of garnet using the Sm-Nd and/or Lu-Hf isotope systems potentially avoids these problems. However, at temperatures above the solidus, the Sm-Nd isotope composition of garnet may become homogenized during post-peak cooling and evidence of prograde growth may be removed. The Lu-Hf isotope system in garnet is more robust and less susceptible to diffusion-controlled re-equilibration. Therefore, Lu-Hf dating of garnet has the potential to constrain the period of prograde garnet growth in HT metamorphic rocks. In the Fosdick migmatite-granite complex of West Antarctica, two episodes of HT garnet growth have been proposed based on U-Pb monazite ages from garnet-bearing migmatitic paragneisses and orthogneisses and U-Pb zircon ages from spatially associated peraluminous granites. Cores of monazite inclusions in garnet yield Carboniferous ages whereas the rims yield Cretaceous ages, and the garnet itself records Cretaceous Sm-Nd ages. The Sm-Nd ages were interpreted to represent diffusional resetting during the Cretaceous of garnet that grew in the Carboniferous. In this study, Lu-Hf garnet geochronology is used to test the hypothesis that garnet in the migmatitic paragneisses and orthogneisses is Carboniferous in age. We also assess the utility of the Lu-Hf system for dating garnet growth in rocks that have experienced superimposed HT metamorphic events. In addition, inverse phase equilibria modeling of open system melting is used to constrain the P-T conditions of garnet growth in migmatitic paragneisses and

  10. Garnet-melt Trace Element Partitioning From 5 to 9 GPa: Onset of Garnet to Majorite Transformation

    NASA Astrophysics Data System (ADS)

    Draper, D. S.; Xirouchakis, D.; Agee, C. B.

    2002-05-01

    Garnet (Gt) and its higher-pressure form, majorite (Mj), are thought to play important roles in the generation of terrestrial Archaean komatiites and of Martian meteorite compositions. Earlier work by Ohtani, Kato, and coworkers on majoritic Gt partitioning at 16-24 GPa showed that DHREE for Mj were somewhat lower, and DLREE somewhat higher, than those for lower-pressure Gt. Thus, REE signatures of Mj fractionation are less pronounced than those for ordinary Gt, and because DHf is less affected, Lu/Hf will be less strongly perturbed by Mj fractionation than by Gt fractionation. In this study, we were motivated to measure Gt-melt trace element partitioning in more iron-rich systems than were used in these earlier studies, which are more relevant to early Martian magmatism. However, our results have general applicability and form a useful comparison with the studies of van Westrenen and coworkers (e.g. 2001, CMP 142:219), who developed predictive relationships for 3+ cation partitioning into the X sites of lower-pressure Gt. We doped a synthetic ultramafic composition, based on the silicate portion of Homestead L5 ordinary chondrite, with various subsets of Nd, Sm, Tb, Yb, Lu, Y, Sc, Zr, and Hf (max total dopant ~2 wt%) for multianvil experiments between 5 and 9 GPa. Gt begins to exhibit the transformation to Mj at 5 GPa, a lower pressure than has been previously reported. This transformation is evidenced by decreasing Al and excess Si per formula unit (e.g. 3.1 to 3.2 Si per 12 oxygens), becoming progressively more majoritic (increasing Si, decreasing Al) with increasing pressure to ~3.3 Si per 12 oxygens at 9 GPa. We have reported elsewhere (Xirouchakis et al., 2002, XXXIII LPSC, 1316) that the Mj transformation is favored at these lower pressures by the presence of silicate melt and the absence of clinopyroxene. We find that DHREE,Y and DTb decrease markedly as Gt begins the transformation to Mj, but that the LREE are less affected. DHf,Zr undergo almost no change

  11. Intercalibration of FTIR and SIMS for Hydrogen Measurements in Garnets

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Rossman, G.; Guan, Y.; Ma, C.

    2008-12-01

    The importance of understanding the hydrogen incorporated in nominally anhydrous minerals (NAMs) that influences their physical and chemical properties significantly is well accepted, however, quantitatively experimental constraints between hydrogen concentration and physical and chemical properties are only meaningful if hydrogen concentration can be accurately determined. Fourier Transform Infrared Spectroscopy (FTIR) may be the most powerful technique since it provides information about both bulk concentration and local bonding environments, while Secondary Ion Mass Spec-trometry (SIMS) has held promise as an ideal method for hydrogen analyses for its advantages of high spatial resolution and insensitivity to crystal orientation. Great efforts have been made to establish experimental standards for these two techniques since they have no rigorous self-calibration. We here present new Fourier Transform Infrared Spectroscopy (FTIR) and Secondary Ion Mass Spectrometry (SIMS) analyses of 1H in 11 natural garnets (grossular, spessartite and pyrope). This set of garnets extends to a wider range of H2O contents (~4 to 6790 wt. ppm H2O) than previous studies and can be more reliable if more garnets can be investigated. We routinely achieve a less than 5 ppm by weight H2O with high vacuum quality, the use of a Cs+ primary beam, and carefully prepared samples using a resin-free mounting technique (described in Aubaud C. et al., 2007. Intercalibration of FTIR and SIMS for hydrogen measurements in glasses and nominally anhydrous minerals. American Mineralogist, 92, 811-828). Although some scatter is observed, the straight line with a slope of 0.0722 defined by all garnets in a plot of (H)FTIR vs. (H+/Si+)SIMS* (SiO2)EMP suggests small matrix effects, while some previous efforts demonstrated the existence of such matrix effects. Discrepancies between FTIR and SIMS measurements can be partially distributed to the impurities, which have different hydrogen concentration as the

  12. Upconversion luminescence in Yb 3+-doped yttrium aluminum garnets

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Zhao, Zhiwei; Song, Pingxin; Jiang, Benxue; Zhou, Guoqing; Xu, Jun; Deng, Peizhen; Bourdet, Gilbert; Christophe Chanteloup, Jean; Zou, Ji-Ping; Fulop, Annabelle

    2005-03-01

    In this paper, we present results on upconversion luminescence performed on Yb 3+-doped yttrium aluminum garnets under 940 nm excitation. The upconversion luminescence was ascribed to Yb 3+ cooperative luminescence and the presence of rare earth impurity ions. The cooperative luminescence spectra as a function of Yb concentration were measured and the emission intensity variation with Yb concentration was discussed. Yb 3+ energy migration quenched the cooperative luminescence of Yb:YAG crystals with doping level over 15 at%.

  13. Wear performance of garnet aluminium composites at high contact pressure

    NASA Astrophysics Data System (ADS)

    Sharma, Anju; Arora, Rama; Kumar, Suresh; Singh, Gurmel; Pandey, O. P.

    2016-05-01

    To satisfy the needs of the engineering sector, researchers and material scientists in this area adopted the development of composites with tailor made properties to enhance efficiency and cost savings in the manufacturing sector. The technology of the mineral industry is shaping the supply and demand of minerals derived materials. The composites are best classified as high performance materials have high strength-to-weight ratios, and require controlled manufacturing environments for optimum performance. Natural mineral garnet was used as the reinforcement of composite because of satisfactory mechanical properties as well as an attractive ecological alternative to others ceramics. For this purpose, samples have been prepared with different sizesof the garnet reinforcement using the mechanical stirring method to achieve the homogeneously dispersed strengthening phase. A systematic study of the effect of high contact pressure on the sliding wear behaviour of garnet reinforced LM13 alloy composites is presented in this paper. The SEM analysis of the worn samples and debris reveals the clues about the wear mechanism. The drastic improvement in the wear resistance of the composites at high contact pressure shows the high potential of the material to be used in engineering applications.

  14. Lattice and Magnetic Effects on Multiferroic Transitions in Garnets

    NASA Astrophysics Data System (ADS)

    Louca, Despina; Kamazawa, K.; Proffen, T.

    2007-03-01

    The possible presence of ferroelectricity in a magnetically ordered state has attracted considerable attention particularly in ABO3 and AB2O5 systems with B = Mn. Evidence for strong coupling of the two order parameters has been provided in the so-called multiferroics, where the field-induced polarization leads to a giant magnetoelectric effect and a magneto-dielectric effect. It was recently shown that the ferrimagnetic garnet crystal of Tb3Fe5O12 exhibits a large magnetodielectric response as well when a very small magnetic field is applied (1). To understand the origin of the high sensitivity of the dielectric effect in garnets, we investigated the crystal and magnetic structures of Tb3(Fe/Ga)5O12 using pulsed neutron diffraction. The garnet crystal appears to be very close to a lattice instability and high-resolution diffraction showed that the lattice gradually changes symmetry from cubic to rhombohedral with cooling over a wide temperature range. At the same time, magnetic diffuse scattering is observed that goes away by 15 K. The role of the lattice and of local distortions in the magnetic polarization and the coupling of the magnetostriction to the dielectric effect will be discussed. (1) N. Hur et al, Appl. Phys. Lett. 87, 042901 (2005).

  15. Overstepping the garnet isograd: a comparison of QuiG barometry and thermodynamic modeling

    NASA Astrophysics Data System (ADS)

    Spear, Frank S.; Thomas, Jay B.; Hallett, Benjamin W.

    2014-09-01

    The consequences of overstepping the garnet isograd reaction have been investigated by comparing the composition of garnet formed at overstepped P-T conditions (the overstep or "OS" model) with the P-T conditions that would be inferred by assuming garnet nucleated in equilibrium with the matrix assemblage at the isograd (the equilibrium or "EQ" model). The garnet nucleus composition formed at overstepped conditions is calculated as the composition that produces the maximum decrease in Gibbs free energy from the equilibrated, garnet-absent, matrix assemblage for the bulk composition under study. Isopleths were then calculated for this garnet nucleus composition assuming equilibrium with the matrix assemblage (the EQ model). Comparison of the actual P-T conditions of nucleation (the OS model) with those inferred from the EQ model reveals considerable discrepancy between the two. In general, the inferred garnet nucleation P-T conditions (the EQ model) are at a lower temperature and higher or lower pressure (depending on the coexisting calcic phase(s)) than the actual (OS model) nucleation conditions. Moreover, the degree of discrepancy increases with the degree of overstepping. Independent estimates of the pressure of nucleation of garnet were made using the Raman shift of quartz inclusions in garnet (quartz-in-garnet or QuiG barometry). To test the validity of this method, an experimental synthesis of garnet containing quartz inclusions was made at 800 °C, 20 kbar, and the measured Raman shift reproduced the synthesis conditions to within 120 bars. Raman band shifts from three natural samples were then used to calculate an isochore along which garnet was presumed to have nucleated. Model calculations were made at several temperatures along this isochore (the OS model), and these P-T conditions were compared to those computed assuming equilibrium nucleation (the EQ model) to estimate the degree of overstepping displayed by these samples. A sample from the garnet

  16. Timing and duration of garnet granulite metamorphism in magmatic arc crust, Fiordland, New Zealand

    USGS Publications Warehouse

    Stowell, H.; Tulloch, A.; Zuluaga, C.; Koenig, A.

    2010-01-01

    Pembroke Granulite from Fiordland, New Zealand provides a window into the mid- to lower crust of magmatic arcs. Garnet Sm-Nd and zircon U-Pb ages constrain the timing and duration of high-P partial melting that produced trondhjemitic high Sr/Y magma. Trace element zoning in large, euhedral garnet is compatible with little post growth modification and supports the interpretation that garnet Sm-Nd ages of 126.1??2.0 and 122.6??2.0. Ma date crystal growth. Integration of the garnet ages with U-Pb zircon ages elucidates a history of intrusion(?) and a protracted period of high-temperature metamorphism and partial melting. The oldest zircon ages of 163 to 150. Ma reflect inheritance or intrusion and a cluster of zircon ages ca. 134. Ma date orthopyroxene-bearing mineral assemblages that may be magmatic or metamorphic in origin. Zircon and garnet ages from unmelted gneiss and garnet reaction zones record garnet granulite facies metamorphism at 128 to 126. Ma. Peritectic garnet and additional zircon ages from trondhjemite veins and garnet reaction zones indicate that garnet growth and partial melting lasted until ca. 123. Ma. Two single fraction garnet ages and young zircon ages suggest continued high-temperature re-equilibration until ca. 95. Ma. Phase diagram sections constrain orthopyroxene assemblages to <0.6 GPa @ 650??C, peak garnet granulite facies metamorphic conditions to 680-815??C @ 1.1-1.4. GPa, and a P-T path with a P increase of???0.5. GPa. These sections are compatible with water contents???0.28wt.%, local dehydration during garnet granulite metamorphism, and <0.3. GPa P increases during garnet growth. Results demonstrate the utility of integrated U-Pb zircon and Sm-Nd garnet ages, and phase diagram sections for understanding the nature, duration, and conditions of deep crustal metamorphism and melting. Geochronologic and thermobarometric data for garnet granulite indicate that thickening of arc crust, which caused high-pressure metamorphism in northern

  17. Distribution of garnet grain sizes and morphologies across the Moine Supergroup, northern Scottish Caledonides

    NASA Astrophysics Data System (ADS)

    Ashley, Kyle T.; Thigpen, J. Ryan; Law, Richard D.

    2016-04-01

    Garnet is used in a wide range of geologic studies due to its important physical and chemical characteristics. While the mineral is useful for thermobarometry and geochronology constraints and can often be correlated to deformation and fabric development, difficulties remain in making meaningful interpretations of such data. In this study, we characterize garnet grain sizes and crystal morphologies from 141 garnet-bearing metasedimentary rock samples collected from the northern part of the Moine Supergroup in the Scottish Caledonides. Larger, euhedral crystals are indicative of prograde metamorphic growth and are typically associated with the most recent phase of orogenesis (Scandian, ˜430 Ma). Small, rounded ("pin-head") garnets are interpreted as detrital in origin. A subhedral classification is more subjective and is used when garnets contains portions of straight boundaries but have rounded edges or rims that have been altered through retrograde metamorphic reactions. From our collection, 88 samples contain anhedral garnets (maximum measured grain size d = 0.46 ± 0.21 mm), 34 bear subhedral garnets (d = 2.0 ± 1.0 mm), and the remaining 19 samples contain garnets with euhedral grains (d = 4.4 ± 2.6 mm). Plotting the distribution of garnets relative to the mapped thrust contacts reveals an abrupt change in morphology and grain size when traced from the Moine thrust sheet across the Ben Hope and Sgurr Beag thrusts into the higher-grade, more hinterland-positioned thrust sheets. The dominance of anhedral garnets in the Moine thrust sheet suggests that these grains should not be used for peak P - T estimation associated with relatively low temperature (<500 ° C) Scandian metamorphism, as they are likely detrital in origin and contain protolith chemical signatures that would not have been reset due to sluggish diffusivities at greenschist facies temperatures. However, chemical and isotopic data from these grains may provide information into the provenance of

  18. OH and H2O of garnets in diamond-bearing and diamond-free garnet-clinopyroxene rocks from the Kumdy-kol area, Kokchetav Massif

    NASA Astrophysics Data System (ADS)

    Sakamaki, K.; Ogasawara, Y.

    2013-12-01

    Garnet-clinopyroxene (Grt-Cpx) rocks consisting mainly of Grt + Na-poor Cpx + calcite with various proportions, occur in the Kumdy-kol area. Diamond-bearing Grt-Cpx rock was first reported by Sobolev and Shatsky (1990) and has been well-known as one of the Kokchetav diamond-bearing rocks. UHP evidence, e.g., coesite exsolution from supersilicic titanite, was discovered also in the diamond-free Grt-Cpx rock (Inoue and Ogasawara, 2003). Presence/lack of diamond in Grt-Cpx rocks is one of important features to understand the stability of diamond in the Kokchetav UHP calcsilicate and carbonate rocks. We focused on OH and H2O in garnets in two types of Grt-Cpx rock to clarify fluid conditions during UHP metamorphism. One of the samples, the diamond-bearing Grt-Cpx rock (sample no. 25018; provided by Prof. H.-P. Schertl) is composed of two monomineralic layers, Grt-layer and Cpx-layer, with minor amounts of rutile and calcite. Coarse-grained diamond (up to 0.15 mm across) is included in garnet. Another Grt-Cpx rock, diamond-free one (sample no. XX16) shows a glanoblastic texture, and consists of Grt (30 %) + Cpx (30 %) + calcite (30 %) × titanite (5 %) with exsolved coesite-needles and plates. The precursor supersilicic compositions of titanite indicate six-coordinated Si at UHP conditions (Ogasawara et al, 2002; Sakamaki and Ogasawara, IGR in press). To understand the fluid environments during the formation of these two calcsilicate rocks, we chose garnets and conducted micro FT-IR spectroscopy. IR spectra of garnets in the diamond-bearing Grt-Cpx rock showed OH bands at 3430 and 3570 cm-1, sometimes with a week band at 3675 cm-1. The absorption band at 3570 cm-1 is the strongest and is sharp, whereas the band at 3430 cm-1 is broad. IR spectra of garnets in diamond-free one show strong OH bands at 3400 and 3555 cm-1, sometimes with week bands at 3590 and 3640 cm-1. The OH band at 3555 cm-1 is the strongest and is sharp, whereas the band at 3400 cm-1 is broad. IR

  19. Magneto-optical rotation of a one-dimensional all-garnet photonic crystal in transmission and reflection

    NASA Astrophysics Data System (ADS)

    Kahl, S.; Grishin, A. M.

    2005-05-01

    We present spectra of transmittance, reflectance, and Faraday rotation of transmitted and reflected light for a periodic garnet multilayer structure with a central defect layer. The multilayer consists of alternating layers of bismuth and yttrium iron garnet, is 1.5μm thick, and was prepared by pulsed laser deposition. For the reflection measurements, a silver mirror was evaporated on top of the multilayer. Faraday rotation is strongly enhanced at resonances in transmission and reflection. The peak value obtained at 748 nm in transmission is 5.3° and at 733 nm in reflection is 18°. A single layer BIG film of equivalent thickness shows 2.2° Faraday rotation at 748 nm. We find rather good agreement between measured and calculated spectra. Using calculations of the distributions of light intensities at different wavelengths inside the multilayer, we are able to give consistent qualitative explanations for the enhancement of Faraday rotation. We also find numerically that—at moderate strengths of the optical resonances—a linear relation exists between Faraday rotation and the intensity integrated over all magneto-optically active layers, if absorption is neglected.

  20. Garnet-bearing granite from the Třebíč pluton, Bohemian Massif (Czech Republic)

    NASA Astrophysics Data System (ADS)

    René, M.; Stelling, J.

    2007-09-01

    Garnet occurs as a significant mineral constituent of felsic garnet-biotite granite in the southern edge of the Třebíč pluton. Two textural groups of garnet were recognized on the basis of their shape and relationship to biotite. Group I garnets are 1.5-2.5 mm, euhedral grains which have no reaction relationship with biotite. They are zoned having high XMn at the rims and are considered as magmatic. Group II garnets form grain aggregates up to 2.5 cm in size, with anhedral shape of individual grains. The individual garnet II grains are usually rimmed by biotite and have no compositional zoning. The core of group I garnets and group II garnets contains 67-80 mol% of almandine, 5-19 mol% of pyrope, 7-17 mol% of spessartine and 2-4 mol% of grossular. Biotite occurs in two generations; both are magnesian siderophyllites with Fe/(Fe + Mg) = 0.50-0.69. The matrix biotite in granites (biotite I) has high Ti content (0.09-0.31 apfu) and Fe/(Fe + Mg) ratio between 0.50 and 0.59. Biotite II forms reaction rims around garnet, is poor in Ti (0.00-0.06 apfu) and has a Fe/(Fe + Mg) ratio between 0.61 and 0.69. The textural relationship between biotite and garnet indicates that garnet reacted with granitic melt to form Ti-poor biotite and a new granitic melt, depleted in Ti and Mg and enriched in Fe and Al. In contrast to the host durbachites (hornblende-biotite melagranites), which originated by mixing of crustal melts and upper mantle melts, the origin of garnet-bearing granites is related to partial melting of the aluminium-rich metamorphic series of the Moldanubian Zone.

  1. Magnetooptical and crystalline properties of sputtered garnet ferrite film on spinel ferrite buffer layer

    NASA Astrophysics Data System (ADS)

    Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Kagami, Osamu; Tanabe, Takaya

    2016-09-01

    The purpose of this study is to provide garnet films for volumetric magnetic holography. Volumetric magnetic holography usually employs an easily obtainable short-wavelength laser (visible light, not infrared light) with a large diffraction intensity. Bi-substituted garnet ferrite with a large Faraday rotation is promising for volumetric magnetic holography applications in the visible light region. However, a garnet film without a deteriorated layer must be obtained because a deteriorated layer (minute polycrystalline grains containing an amorphous phase) is formed during the initial deposition on a glass substrate. In particular, the required magnetooptical properties have not been obtained in a thin garnet film (100 nm or less) after annealing (1 h, 700 °C, oxygen atmosphere). Therefore, there is a need for excellent garnet films with the required magnetooptical (MO) properties even if the films are thin. By using a spinel ferrite buffer layer for garnet film deposition, we could obtain a thin garnet film with excellent MO properties. We determined the effect of the initial buffer layer on the crystallinity of the deposited garnet films by observing the film cross section. In addition, we undertook a qualitative estimation of the influence of the crystallinity and optical properties of the garnet film on a glass substrate with a spinel ferrite buffer layer.

  2. 176Lu-176Hf geochronology of garnet I: experimental determination of the diffusion kinetics of Lu3+ and Hf4+ in garnet, closure temperatures and geochronological implications

    NASA Astrophysics Data System (ADS)

    Bloch, Elias; Ganguly, Jibamitra; Hervig, Richard; Cheng, Weiji

    2015-02-01

    The 176Lu-176Hf and 147Sm-143Nd decay systems are routinely used to determine garnet (Grt)-whole-rock (WR) ages; however, the 176Lu-176Hf age of garnet is typically older than the 147Sm-143Nd age determined from the same aliquots. Here we present experimental data for Lu3+ and Hf4+ diffusion in garnet as functions of temperature, pressure and oxygen fugacity and show that the diffusivity of Hf4+ in almandine/spessartine garnet is significantly slower than that of Lu3+. The diffusive closure temperature ( T C) of Hf4+ is significantly higher than that of Nd3+, and although this property is partly responsible for the observed 176Lu-176Hf and 147Sm-143Nd Grt-WR age discrepancies, the difference between the T C-s of Lu3+ and Hf4+ could lead to apparent Grt-WR 176Lu-176Hf ages that are skewed from the age of Hf4+ closure in garnet. In addition, the slow diffusivity of Hf4+ indicates that the bulk of metamorphic garnets retain a substantial fraction of prograde radiogenic 176Hf throughout peak metamorphic conditions, a phenomenon that further complicates the interpretation of 176Lu-176Hf garnet ages and invalidates the use of analytical T C expressions. We argue that the diffusion of trivalent rare earth elements in garnet becomes much faster when their concentration level falls below a few hundred ppm, as in the experiments of Tirone et al. (Geochim Cosmochim Acta 69: 2385-2398, 2005), and further argue that this low-concentration mechanism is appropriate for modeling the susceptibility of 147Sm-143Nd garnet ages to diffusive resetting.

  3. A Calorimetric Study of Almandine: Are the Thermodynamic Properties of the End-Member Aluminosilicate Garnets Finally Known Quantitatively?

    NASA Astrophysics Data System (ADS)

    Dachs, E.; Geiger, C. A.; Benisek, A.

    2012-12-01

    The aluminosilicate garnets (E3Al2Si3O12 with E = Fe2+, Mn2+, Ca, Mg) form an important rock-forming mineral group. Much study has been directed toward determining their thermodynamic properties. The iron end-member almandine (Fe3Al2Si3O12) is a key phase in many petrologic investigations. As part of an ongoing calorimetric and thermodynamic study of the aluminosilicate garnets, the heat capacity of three synthetic well-characterized polycrystalline almandine garnets and one natural almandine-rich single crystal was measured. The various garnets were characterized by optical microscopy, electron-microprobe analysis, X-ray powder diffraction and 57Fe Mössbauer spectroscopy. Heat capacity measurements were performed in the temperature range 3 to 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. From the former, So values between 336.7 ± 0.8 and 337.8 ± 0.8 J/molK are calculated for the different samples. The smaller value is considered the best So for end-member stoichiometric almandine, because it derives from the "best" Fe3+-free synthetic sample. The Cp behavior for almandine at T > 298 K is given by the polynomial (in J/molK): Cp = 649.06(±4) - 3837.57(±122)T-0.5 - 1.44682(±0.06)107T-2 + 1.94834(±0.09)109T-3, which is calculated using DSC data together with one published heat-content datum determined by transposed-drop calorimetry along with a new determination that gives H1181K - H302K = 415.0 ± 3.2 kJ/mole. Almandine shows a λ-type heat-capacity anomaly at low temperatures resulting from a paramagnetic-antiferromagnetic phase transition at about 9 K. The lattice heat capacity was calculated using the single-parameter phonon dispersion model of Komada and Westrum (1997), which allows the non-lattice heat capacity (Cex) behavior to be modelled. An analysis shows the presence of an electronic heat-capacity contribution (Cel - Schottky anomaly) around 17 K that is superimposed on a larger magnetic heat-capacity effect (Cmag

  4. Computational modelling of Er(3+): Garnet laser materials

    NASA Technical Reports Server (NTRS)

    Spangler, Lee H.

    1994-01-01

    The Er(3+) ion has attracted a lot of interest for four reasons: (1) Its (4)I(sub 13/2) yields (4)I(sub 15/2) transition lases in the eyesafe region near 1.5 micron; (2) the (4)I(sub 13/2) transition lases near 2.8 micron, an important wavelength for surgical purposes; (3) it displays surprisingly efficient upconversion with lasing observed at 1.7, 1.2, 0.85, 0.56, 0.55, and 0.47 micron following 1.5 micron pumping; and (4) it has absorption bands at 0.96 and 0.81 micron and thus can be diode pumped. However, properties desirable for upconversion reduce the efficiency of 1.5 and 3 micron laser operation and vice versa. Since all of the processes are influenced by the host via the crystal field induced stark splittings in the Er levels, this project undertook modelling of the host influence on the Er lasinng behavior. While growth and measurement of all ten Er(3+) doped garnets is the surest way of identifying hosts which maximize upconversion (or conversly, 1.5 and 3 micron performance), it is also expensive - costing approximately $10,000/material or approximately $100,000 for the materials computationally investigated here. The calculations were performed using a quantum mechanical point charge model developed by Clyde Morrison at Harry Diamond Laboratories. The programs were used to fit the Er:YAG experimental energy levels so that the crystal field parameters, B(sub nm) could be extracted. From these radial factors, rho (sub n) were determined for Er(3+) in garnets. These, in combination with crystal field components, Anm, available from X-ray data, were used to predict energy levels for Er in the other nine garnet hosts. The levels in Er:YAG were fit with an rms error of 12.2/cm over a 22,000/cm range. Predicted levels for two other garnets for which literature values were available had rms errors of less than 17/cm , showing the calculations to be reliable. Based on resonances between pairs of calculated stark levels, the model predicts GSGG as the best host

  5. The compression mechanism of garnets based on in situ observations

    NASA Astrophysics Data System (ADS)

    Dymshits, Anna; Sharygin, Igor; Litasov, Konstantin; Shatskiy, Anton

    2014-05-01

    Previously it was showed that the bulk modulus of garnet is strongly affected by the bulk modulus of the dodecahedra, while compressibility of other individual polyhedra displays no correlation with the compressibility of the structure as a whole (Milman et al., 2001). If so, Na-majorite (Na-maj) would have the smallest bulk modulus of all silicate garnets, as a phase with a predicted dodecahedral bulk modulus of approximately 70 GPa (Hazen et al., 1994). In fact Na-maj has the largest bulk modulus among the silicate garnets. This behavior must reflect the all-mineral framework of Na-maj with very small cell volume and silicon in the octahedral position. Thus, we conclude that not only the dodecahedral sites, but also the behavior of the garnet framework and relative sizes of the 8- and 6-coordinated cations, control garnet compression. The octahedral site in Na-maj is quite small (1.79 Å) and contains only silicon in comparison to the pyrope (1.85 Å) or majorite (1.88 Å). The small and highly charged octahedra shares four edges with the dodecahedra and thus restrict the volume of the large and low charged dodecahedra. In spite Na-maj has a large average X-cation radius (RNa = 1.07 Å) its dodecahedral volume is relatively small (V = 21.23 and 21.26 Å3). Pacalo et al. (1992) suggested that XO8 polyhedra act as braces and controls the amount of rotation between tetrahedra and octahedra within the corner-linked chains. In case of pyrope XO8 cite is not filled up and polyhedra within the corner-linked chains can rotate freely to accommodate applied stress. In case of Na-maj the dodecahedral site is filled up and rotational freedom is minimized. The dodecahedral site in knorringite (Knr) contains cation with a small radius (Mg-O = 2.22 and 2.34 Å), so XO8 polyhedra is not filled up and can rotate freely to accommodate applied stress. In case of uvarovite not only octahedral but the dodecahedral site is also large (Ca-O = 2.35 and 2.51 Å), so the rotational

  6. Crystallization of pegmatites: Insights from chemistry of garnet, Jacumba pegmatites, San Diego County, California

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Sirbescu, M. C.

    2013-12-01

    Systematic mineral and textural variations from the border zone to the core of a zoned pegmatite sheet may reflect the kinetic or equilibrium fractionation processes that occurred during sequential crystallization of the pegmatite magma. Rhythmic layering, also named 'line rock', is a salient textural feature of world famous San Diego Co. pegmatites, that consists of alternating garnet × tourmaline layers and albite - quartz layers, mm's to cm's thick. Slowly diffusing, incompatible elements in the felsic magma including B, Fe, and Mn may become enriched in boundary layers formed ahead of rapidly crystallized quartzo-felspathic assemblages. This study explores whether the chemistry of garnet concentrated in the border and foot-wall zones and dispersed in the graphic feldspar, core, and pocket zones of Garnet Ledge pegmatite, Jacumba district, might fingerprint the diffusion-controlled oscillatory boundary layers. The lithium-cesium-tantalum (LCT) Jacumba pegmatite district, late product of the Eastern Peninsular Ranges Batholith, consists of numerous subparallel dikes, 3 to 7 m thick, intruding pre-batholitic metasedimentary rocks. The composite aplite-pegmatite dikes are texturally diverse. Comb-textured tourmaline, other unidirectional textures, garnet × tourmaline 'line rock', and coarse graphic K-feldspar crystals occur in the outer zones, followed by massive feldspar-quartz cores, vuggy cleavlandite- euhedral garnet, and miarolitic cavities. The Jacumba pegmatites have produced gem spodumene, beryl, and garnet from several open cuts such as the Beebe Hole and Pack Rat - Garnet Ledge workings. Systematic mineralogical and textural variations, and SEM-EDS garnet compositions were recorded from border to core at Garnet Ledge outcrop and thin section scale, focusing on continuous traverses across the line rock. Garnet from Garnet Ledge belongs to the spessartine-almandine series (Sp42 to Sp65) with minor contents of Mg, Ca, and Ti, consistent with garnet

  7. Native iron in the continental lower crust: petrological and geophysical implications.

    PubMed

    Haggerty, S E; Toft, P B

    1985-08-16

    Lower crustal granulite xenoliths recovered from a kimberlite pipe in western Africa contain native iron (Fe(0)) as a decomposition product of garnet and ilmenite. Magnetic measurements show that less than 0.1 percent (by volume) of iron metal is present. Data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron-wüstite and magnetite-wüstite buffers, which may represent the oxidation state of the continental lower crust, and the depleted lithospheric upper mantle. Ferromagnetic native iron could be stable to a depth of approximately 95 kilometers and should be considered in the interpretation of long-wavelength static magnetic anomalies.

  8. Native iron in the continental lower crust - Petrological and geophysical implications

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E.; Toft, P. B.

    1985-01-01

    Lower crustal granulite xenoliths recovered from a kimberlite pipe in western Africa contain native iron (Fe) as a decomposition product of garnet and ilmenite. Magnetic measurements show that less than 0.1 percent (by volume) of iron metal is present. Data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron-wuestite and magnetite-wuestite buffers, which may represent the oxidation state of the continental lower crust, and the depleted lithospheric upper mantle. Ferromagnetic native iron could be stable to a depth of about 95 kilometers and should be considered in the interpretation of long-wavelength static magnetic anomalies.

  9. Native iron in the continental lower crust - petrological and geophysical implications

    SciTech Connect

    Haggerty, S.E.; Toft, P.B.

    1985-08-01

    Lower crustal granulite xenoliths recovered from a kimberlite pipe in western Africa contain native iron (Fe) as a decomposition product of garnet and ilmenite. Magnetic measurements show that less than 0.1 percent (by volume) of iron metal is present. Data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron-wuestite and magnetite-wuestite buffers, which may represent the oxidation state of the continental lower crust, and the depleted lithospheric upper mantle. Ferromagnetic native iron could be stable to a depth of about 95 kilometers and should be considered in the interpretation of long-wavelength static magnetic anomalies. 32 references.

  10. Garnet Yield Strength at High Pressures and Implications for Upper Mantle and Transition Zone Rheology

    SciTech Connect

    Kavner,A.

    2008-01-01

    Garnet helps control the mechanical behavior of the Earth's crust, mantle, and transition zone. Here, measurements are presented suggesting that garnet, long considered to be a high-viscosity phase, is actually weaker than the other dominant components in the transition zone. The mechanical behavior of garnet at high pressures was examined using radial diffraction techniques in the diamond anvil cell. The yield strength of grossular garnet was inferred from synchrotron X-ray measurements of differential lattice strains. The differential stress was found to increase from 1.3 ({+-}0.6) GPa at a hydrostatic pressure 5.8 ({+-}1.1) GPa to 4.1 ({+-}0.4) GPa at 15.7 ({+-}1.0) GPa, where it was level to 19 GPa. The strength results are consistent with inferred strength values for majorite garnet from measurements in the diamond cell normal geometry, bolstering the idea that garnet-structured materials may all have similar strengths. In this low-temperature, high differential stress regime, garnet is shown to be significantly weaker than anhydrous ringwoodite and to have a strength similar to hydrous ringwoodite. This result suggests that the presence of water in the transition zone may not be required to explain a weak rheology, and therefore models of transition zone behavior built assuming that garnet is the high-strength phase may need to be revised.

  11. Empirical calibration of the clinopyroxene-garnet magnesium isotope geothermometer and implications

    NASA Astrophysics Data System (ADS)

    Li, Wang-Ye; Teng, Fang-Zhen; Xiao, Yilin; Gu, Hai-Ou; Zha, Xiang-Ping; Huang, Jian

    2016-07-01

    The large equilibrium Mg isotope fractionation between clinopyroxene and garnet observed in eclogites makes it a potential high-precision geothermometer, but calibration of this thermometer by natural samples is still limited. Here, we report Mg isotopic compositions of eclogite whole rocks as well as Mg and O isotopic compositions of clinopyroxene and garnet separates from 16 eclogites that formed at different temperatures from the Dabie orogen, China. The whole-rock δ26Mg values vary from -1.20 to +0.10 ‰. Among them, 11 samples display limited δ26Mg variations from -0.36 to -0.17 ‰, similar to those of their protoliths. The mineral separates exhibit very different δ26Mg values, from -0.39 to +0.39 ‰ for clinopyroxenes and from -1.94 to -0.81 ‰ for garnets. The clinopyroxene-garnet Mg isotope fractionation (Δ26Mgclinopyroxene-garnet = δ26Mgclinopyroxene-δ26Mggarnet) varies from 1.05 to 2.15 ‰. The clinopyroxene-garnet O isotope fractionation (Δ18Oclinopyroxene-garnet = δ18Oclinopyroxene-δ18Ogarnet) varies from -1.01 to +0.98 ‰. Equilibrium Mg isotope fractionation between clinopyroxene and garnet in the investigated samples is selected based on both the δ26Mgclinopyroxene versus δ26Mggarnet plot and the state of O isotope equilibrium between clinopyroxene and garnet. The equilibrium Δ26Mgclinopyroxene-garnet and corresponding temperature data obtained in this study, together with those available so far in literatures for natural eclogites, are used to calibrate the clinopyroxene-garnet Mg isotope thermometer. This yields a function of Δ26Mgclinopyroxene-garnet = (0.99 ± 0.06) × 106/ T 2, where T is temperature in Kelvin. The refined function not only provides the best empirically calibrated clinopyroxene-garnet Mg isotope thermometer for precise constraints of temperatures of clinopyroxene- and garnet-bearing rocks, but also has potential applications in high-temperature Mg isotope geochemistry.

  12. The provenance of garnet: constraints provided by studies of coastal sediments from southern India

    NASA Astrophysics Data System (ADS)

    Sabeen, H. M.; Ramanujam, N.; Morton, Andrew C.

    2002-10-01

    The provenance of sediment with heavy mineral suites containing garnets with low-grossular and high-pyrope contents is enigmatic. Such garnet assemblages characterise sediments in many basins worldwide. They are especially common in the sedimentary basins around northern Britain, but their source cannot be identified in adjacent basement rocks. This paper documents garnet populations in beach, dune and river sands from southern India, which almost exclusively comprise low-grossular, high-pyrope garnets. These are derived from the high-grade (granulite facies) metasedimentary and charnockitic rocks that form the basement in this area. By analogy, similar lithologies are inferred to source sediments with low-grossular, high-pyrope garnet assemblages seen elsewhere. In the case of the sandstones of northern Britain, the most likely location of such material is considered to be Greenland.

  13. Optical and scintillation properties of Nd-doped complex garnet

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Sato, Hiroki

    2014-12-01

    Nd 1% doped complex garnet scintillators were prepared by Furukawa and their optical and scintillation properties were investigated on a comparison with previously reported Nd-doped YAG. Chemical compositions of newly developed complex garnets were Lu2Y1Al5O12, Lu2Y1Ga3Al2O12, Lu2Gd1Al5O12, Lu2Gd1Ga3Al2O12, Gd1Y2Al5O12, Gd1Y2Ga3Al2O12, and Gd3Ga3Al2O12. They all showed 50-80% transmittance from ultraviolet to near infrared wavelengths with several absorption bands due to Gd3+ or Nd3+ 4f-4f transition. In X-ray induced radioluminescence spectra, all samples exhibited intense lines at 310 nm due to Gd3+ or 400 nm due to Nd3+ depending on their chemical composition. Among them, the highest scintillation light yield was achieved by Lu2Y1Al5O12. Typical scintillation decay times of them resulted 1.5-3 μs. Thermally stimulated glow curve after 1 Gy exposure and X-ray induced afterglow were also investigated.

  14. Iron deficiency.

    PubMed

    Scrimshaw, N S

    1991-10-01

    The world's leading nutritional problem is iron deficiency. 66% of children and women aged 15-44 years in developing countries have it. Further, 10-20% of women of childbearing age in developed countries are anemic. Iron deficiency is identified with often irreversible impairment of a child's learning ability. It is also associated with low capacity for adults to work which reduces productivity. In addition, it impairs the immune system which reduces the body's ability to fight infection. Iron deficiency also lowers the metabolic rate and the body temperature when exposed to cold. Hemoglobin contains nearly 73% of the body's iron. This iron is always being recycled as more red blood cells are made. The rest of the needed iron does important tasks for the body, such as binds to molecules that are reservoirs of oxygen for muscle cells. This iron comes from our diet, especially meat. Even though some plants, such as spinach, are high in iron, the body can only absorb 1.4-7% of the iron in plants whereas it can absorb 20% of the iron in red meat. In many developing countries, the common vegetarian diets contribute to high rates of iron deficiency. Parasitic diseases and abnormal uterine bleeding also promote iron deficiency. Iron therapy in anemic children can often, but not always, improve behavior and cognitive performance. Iron deficiency during pregnancy often contributes to maternal and perinatal mortality. Yet treatment, if given to a child in time, can lead to normal growth and hinder infections. However, excess iron can be damaging. Too much supplemental iron in a malnourished child promotes fatal infections since the excess iron is available for the pathogens use. Many countries do not have an effective system for diagnosing, treating, and preventing iron deficiency. Therefore a concerted international effort is needed to eliminate iron deficiency in the world.

  15. The use of trace element zoning patterns in garnet to infer reaction paths of metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Konrad-Schmolke, Matthias; Witte, Clemens; Dohmen, Ralf; O'Brien, Patrick; Erpel, Lars; Halama, Ralf; Schmidt, Alexander; Ditterova, Hana

    2015-04-01

    Garnet is one of the most versatile minerals in metamorphic petrology. It is stable over a large pressure and temperature range and thus occurs in many metamorphic environments. Garnet has a wide range of chemical compositions and its major and trace element composition well reflects the pressure (P), temperature (T) and chemical conditions (X) as well as the element transport kinetic properties of the host rock during growth. Hence, compositional growth zonations in garnet contain information about most geochemical, mineralogical and petrological properties of metamorphic rocks. However, detailed interpretation of complex zoning patterns in metamorphic garnet was hindered mainly by the lack of knowledge about the various contributions of kinetic and equilibrium effects to the trace element incorporation into garnet. In this contribution we combine thermodynamic equilibrium calculations together with mass balanced trace element distribution among coexisting phases with diffusion models that simulate kinetically controlled element transport in a reacting host rock. Comparison of the model results with natural garnets enables detailed interpretation of commonly observed major and trace element patterns in high-pressure (HP) and ultra-high pressure (UHP) garnets in terms of reaction paths and physico-chemical properties of the host rock. The comparison of our numerical models with a series of well-investigated (U)HP samples shows that the kinetic influence on rare earth element incorporation into garnet is limited in most rocks at the early stages of garnet growth and increases with increasing grade of rock transformation. We show that REE zoning patterns can be used to distinguish between cold (lawsonite-stable) and warm (epidote-stable) prograde reaction paths. REE liberation along a warm P-T trajectory occurs in three breakdown reactions involving chlorite, epidote and amphibole. All three reactions result in characteristic heavy (HREE) and medium (MREE) REE growth

  16. Charge-coupled substituted garnets (Y 3–x Ca 0.5x M 0.5x )Fe₅O₁₂ (M = Ce, Th): Structure and stability as crystalline nuclear waste forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y³⁺ = Ca²⁺ + M⁴⁺, where M⁴⁺ = Ce⁴⁺ or Th⁴⁺. Single-phase garnets Y3–xCa0.5xM0.5xFe₅O₁₂ (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and ⁵⁷Fe–Mössbauer spectroscopy indicated that M⁴⁺ and Ca²⁺ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe³⁺ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high-temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  17. Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra

    2015-06-08

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single-phase garnets Y3–xCa0.5xM0.5xFe5O12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe–Mössbauer spectroscopy indicated that M4+ and Ca2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  18. The effect of chromium ions on the formation of color centers in crystals with the structure of garnet

    NASA Astrophysics Data System (ADS)

    Ashurov, M. Kh.; Zharikov, E. V.; Laptev, V. V.; Nasyrov, I. N.; Osiko, V. V.

    Experiments have been carried out on crystals of gadolinium-gallium garnet, gadolinium-scandium garnet, yttrium-scandium-gallium garnet, and yttrium-aluminum garnet to investigate the effect of chromium ions on the formation of color centers in these highly efficient laser materials. It is found that following gamma irradiation at 300 K, all chromium-free specimens become colored, whereas specimens activated by Cr(3+) ions do not acquire any additional color at wavelengths greater than 300 nm. It is concluded that chromium ions enhance the radiation stability of crystals with the structure of garnet.

  19. Ilmenite Exsolution in Xenolithic Garnets From the Hawaiian Hot Spot: Evidence for the Existance of High-titanium Garnets in the Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Keshav, S.; Sowerby, J. R.; Sen, G.

    2001-12-01

    Oxide inclusions in a pyrope host were discovered in a single garnet clinopyroxenite xenolith (sample 115954-20 B; Jackson Collection, Smithsonian) from Salt Lake Crater, Oahu, Hawaii. These inclusions, ~ 5-6 μ m thick and 10 μ m long, appear to radiate from a point, rather than align along the <111> direction, as found previously by other authors (e.g., Haggerty, 1991b). In the same section there are other garnet grains that have ilmenite of the same morphology but along <111>. Electron microprobe analysis and Raman spectroscopy show that both types of inclusions are ilmenite (FeTiO3) with a large geikelite (MgTiO3) component, and minor amounts of Al3+, Cr3+, and Fe3+. Note that ilmenite does not occur as a discrete phase in the xenolith. Inclusions of ilmenite and rutile, have previously been found in host garnets from eclogitic and lherzolitic xenoliths in kimberlites and ultra-high pressure terrains. This is the first report of such occurrence from an oceanic hot spot source. Based on texture, we suggest that the ilmenite inclusions in garnet in the Hawaiian xenolith are of exsolution origin as opposed to an origin by epitaxal precipitation (as proposed by Wang et al, 1999). At the present time, because of the lack of appropriate experimental study it is difficult to speculate on the P,T conditions under which ilmenite exsolved from the garnet host. However, Van Roermund et al (2000) have hypothesized on crystal chemical grounds that such inclusions are the result of the break down of a high P,T `super-titanic' garnet to a lower P,T pyrope with exsolved ilmenite, in a similar fashion to the breakdown of `super-silicic' or majoritic garnet to pyrope with exsolved pyroxene.

  20. Investigation of the growth of garnet films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Moody, J. W.; Shaw, R. W.; Sandfort, R. M.

    1974-01-01

    Liquid phase expitaxy was investigated to determine its applicability to fabricating magnetic rare earth garnet films for spacecraft data recording systems. Two mixed garnet systems were investigated in detail: (1) Gd-Y and (2) Eu-Yb-Y. All films were deposited on Gd3Ga5012 substrates. The uniaxial anisotropy of the Gd-Y garnets is primarily stress-induced. These garnets are characterized by high-domain wall mobility, low coercivity and modest anisotropy. Characteristic length was found to be relatively sensitive to temperature. The Eu-Yb-Y garnets exhibit acceptable mobilities, good temperature stability and reasonable quality factors. The uniaxial anisotropy of these garnets is primarily growth-induced. The system is well suited for compositional "tailoring" to optimize specific desirable properties. Liquid phase epitaxy can be used to deposit Gd3Ga5012 spacing layers on magnetic garnet films and this arrangement possesses certain advantages over more conventional magnetic filmspacing layer combinations. However, it cannot be used if the magnetic film is to be ion implanted.

  1. Lithospheric roots beneath western Laurentia: The geochemical signal in mantle garnets

    USGS Publications Warehouse

    Canil, D.; Schulze, D.J.; Hall, D.; Hearn, B.C.; Milliken, S.M.

    2003-01-01

    This study presents major and trace element data for 243 mantle garnet xenocrysts from six kimberlites in parts of western North America. The geochemical data for the garnet xenocrysts are used to infer the composition, thickness, and tectonothermal affinity of the mantle lithosphere beneath western Laurentia at the time of kimberlite eruption. The garnets record temperatures between 800 and 1450??C using Ni-in-garnet thermometry and represent mainly lherzolitic mantle lithosphere sampled over an interval from about 110-260 km depth. Garnets with sinuous rare-earth element patterns, high Sr, and high Sc/V occur mainly at shallow depths and occur almost exclusively in kimberlites interpreted to have sampled Archean mantle lithosphere beneath the Wyoming Province in Laurentia, and are notably absent in garnets from kimberlites erupting through the Proterozoic Yavapai Mazatzal and Trans-Hudson provinces. The similarities in depths of equilibration, but differing geochemical patterns in garnets from the Cross kimberlite (southeastern British Columbia) compared to kimberlites in the Wyoming Province argue for post-Archean replacement and (or) modification of mantle beneath the Archean Hearne Province. Convective removal of mantle lithosphere beneath the Archean Hearne Province in a "tEctonic vise" during the Proterozoic terminal collisions that formed Laurentia either did not occur, or was followed by replacement of thick mantle lithosphere that was sampled by kimberlite in the Triassic, and is still observed there seismically today.

  2. A genetic and molecular characterization of the garnet gene of Drosophila melanogaster.

    PubMed

    Lloyd, V K; Sinclair, D A; Wennberg, R; Warner, T S; Honda, B M; Grigliatti, T A

    1999-12-01

    The garnet gene was one of the first genes to be identified in Drosophila melanogaster. Mutations in the garnet gene affect both of the biochemically distinct types of pigments in the eye and disrupt pigmentation of other organs. As an initial step in the analysis of this gene, we have analyzed the pigmentation defects in several of the garnet alleles. We have also cloned the gene and examined its expression in various tissues and at different stages of development. The garnet gene is expressed throughout development and in all tissues examined. Structurally related sequences can be detected in a variety of other eukaryotes. The predicted protein sequence of the garnet product resembles clathrin and nonclathrin adaptin proteins and is highly similar to the delta subunit of the newly isolated mammalian AP-3 adaptin complex, which is associated with the trans-Golgi network and endosomes. This suggests that garnet encodes a protein that acts in the intracellular sorting and trafficking of vesicles from the trans-Golgi network to endosomes, and related specialized organelles such as the pigment granule. This finding provides an explanation for the phenotype of garnet mutations and predicts that other Drosophila eye-colour genes will be a rich resource for the genetic dissection of intracellular vesicle transport. PMID:10659786

  3. Garnet Polycrystals in a Barrovian Sequence in Dutchess County, New York

    NASA Astrophysics Data System (ADS)

    Alpert, A.; Whitney, D.; Seaton, N.

    2008-12-01

    An understanding of porphyroblast growth mechanisms is crucial to the study of fluid and element transport during metamorphism. Garnet porphyroblasts are particularly interesting because they preserve a record of metamorphic reaction history and past metamorphic pressure and temperature conditions. Although garnet has long been thought to occur most typically as single crystals, electron backscatter diffraction (EBSD) analysis of garnet has revealed the existence of polycrystalline porphyroblasts that consist of several domains, each with a different lattice orientation separated by high-angle boundaries. New results from an EBSD investigation of metapelitic schists from a complete Barrovian sequence in Dutchess County, New York, document the presence of garnet polycrystals in several different Barrovian zones. The Barrovian sequence allows us to observe garnet growth history during progressive metamorphism because a range of P-T conditions are represented, from 430° C and 3 kbar in the garnet zone to 600° C and 6 kbar in the sillimanite zone. Lutetium-hafnium dating results suggest that garnet grew entirely during Taconic metamorphism at ~430 Ma. Polycrystals were found in the garnet, staurolite and kyanite zones and therefore were either able to grow or survive over a range of P-T conditions. Of 220 garnets analyzed, 10 were polycrystals (4.5%), including both cryptic (no morphological expression) and morphologically distinct polycrystals. Some lattice misorientations (18%) across domain boundaries correspond to coincidence site lattices in cubic minerals, but this incidence is not significantly greater than the 15% predicted for a random distribution in a cubic mineral. Zoning of Fe, Mg, Ca and Mn within polycrystals cuts across domain boundaries and is concentric within the polycrystal as a whole. The formation of polycrystals suggests that closely spaced nuclei may form in a chemically or mechanically heterogeneous matrix, e.g. within a chemically and

  4. Garnetization as a ground preparation process for copper mineralization: evidence from the Mazraeh skarn deposit, Iran

    NASA Astrophysics Data System (ADS)

    Karimzadeh Somarin, Alireza

    2010-03-01

    The Mazraeh Cu-Fe skarn deposit, NW Iran is the result of the intrusion of an Oligocene-Miocene granitic pluton into Cretaceous calcareous rocks. The pluton ranges in composition from monzonite to quartz monzonite, monzogranite, tonalite and granodiorite with I-type, calc-alkaline, and weakly peraluminous characteristics. The Mazraeh pluton was emplaced in a volcanic arc setting in an active continental margin at a depth of ~8 km. Pyroxene skarn, garnet skarn, and epidote skarn zones were formed during the intrusive phase. The garnet skarn developed as exoskarn and endoskarn from the calcareous wall rocks and the pluton, respectively, prior to mineralization. Garnet skarn from the exoskarn zone is identified by relict layering inherited from the precursor calcareous lithologies. Mass balance calculation of garnet skarn in the endoskarn zone indicates that hydrothermal fluids originating from the cooling magma introduced Si, Fe, Mn, Ca, Mg, P, Ag, Cu, Zn, La, Pb, Cd, Mo, and Y. The main mass loss in the garnet skarn was due to destruction of feldspars in the Mazraeh plutonic rocks and leaching of K2O and Na2O. Released Ca has been fixed in the andraditic garnet. Garnetization of the Mazraeh pluton was accompanied by mass and volume increase. The magnitude of these changes depends mainly on the degree of alteration and composition of the precursor. The brittle behavior of the endoskarn zone was increased due to formation of massive garnet which subsequently fractured. These fractures not only facilitated movement of hydrothermal fluids but also provided new locations for Cu mineralization. Therefore locating strongly garnetized zones may be a vector to ore in skarn deposits.

  5. Radiative Performance of Rare Earth Garnet Thin Film Selective Emitters

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Good, Brian S.

    1994-01-01

    In this paper we present the first emitter efficiency results for the thin film 40 percent Er-1.5 percent Ho YAG (Yttrium Aluminum Garnet, Y3Al5O12) and 25 percent Ho YAG selective emitter at 1500 K with a platinum substrate. Spectral emittance and emissive power measurements were made (1.2 less than lambda less than 3.2 microns). Emitter efficiency and power density are significantly improved with the addition of multiple rare earth dopants. Predicted efficiency results are presented for an optimized (equal power density in the Er, (4)I(sub 15/2)-(4)I(sub 13/2) at 1.5 microns, and Ho, (5)I(sub 7)-(5)I(sub 8) at 2.0 micron emission bands) Er-Ho YAG thin film selective emitter.

  6. Interplay of disorder and geometrical frustration in Gadolinium Gallium Garnet

    NASA Astrophysics Data System (ADS)

    Woo, Nayoon; Silevitch, D. M.; Rosenbaum, T. F.

    2015-03-01

    We study the effects of disorder on the geometrically frustrated Heisenberg antiferromagnet Gadolinium Gallium Garnet (GGG) using neodymium doping (0.1 to 1%) in combination with linear and nonlinear ac magnetic susceptibility. The Nd doping actually alleviates the effects of disorder due to excess Gd ions occupying Ga sites. The linear, frequency-dependent susceptibility reveals that 1% Nd doping suppresses the appearance of any long-range order from approximately 80mK to below 30mK. The dynamics of isolated, correlated spin clusters were studied as a function of doping level using nonlinear susceptometry. In this regime, both the aggregate moment of the clustered spins and the activation field required to excite a nonlinear response were inversely correlated with the dopant density.

  7. Magnetic properties of Bi3Fe5O12 garnet

    NASA Astrophysics Data System (ADS)

    Okuda, T.; Katayama, T.; Kobayashi, H.; Kobayashi, N.; Satoh, K.; Yamamoto, H.

    1990-05-01

    Nonthermodynamical garnet Bi3Fe5O12 was synthesized by direct epitaxial growth via vapor phase using a reactive ion beam sputtering technique. The lattice constant was 12.631 Å. The saturation magnetization of the film grown onto a substrate (a=12.495 Å) was 1500 G at room temperature. The uniaxial anisotropy energy was +7.2×104 erg/cm3. The conversion electron Mössbauer spectroscopy measurement indicates that the internal fields of 24d and 16a sites in the nearly lattice-matched film were 420 and 490 kOe, respectively. The internal field of the 24d site was larger by 30 kOe than that in YIG. The angle between the direction of the internal field and the film normal was 34.8°.

  8. Spodumene and garnet luminescence excited by subnanosecond electron beams

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Burachenko, A. G.; Solomonov, V. I.; Tarasenko, V. F.

    2011-11-01

    Pulsed cathodoluminescence of spodumene and yttrium-aluminum garnet crystals activated by Mn2+ and Nd3+ ions, respectively, is investigated. The luminescence was excited upon crystal irradiation by electron beams with current densities of 35 and 100 A/cm2 and average electron energy of ˜ 50 keV for 0.1, 0.25, and 0.65 ns. It is demonstrated that the electron beam duration decreased to several tenth of a nanosecond does not lead to essential changes of the mechanisms of pulsed cathodoluminescence excitation and character of its spectrum, but in this case, the intensity of luminescence of the hole centers increases compared with the intracenter luminescence.

  9. Transparent garnet ceramic scintillators for gamma-ray detection

    NASA Astrophysics Data System (ADS)

    Wang, Yimin; Baldoni, Gary; Rhodes, William H.; Brecher, Charles; Shah, Ananya; Shirwadkar, Urmila; Glodo, Jarek; Cherepy, Nerine; Payne, Stephen

    2012-10-01

    Lanthanide gallium/aluminum-based garnets have a great potential as host structures for scintillation materials for medical imaging. Particularly attractive features are their high density, chemical radiation stability and more importantly, their cubic structure and isotropic optical properties, which allow them to be fabricated into fully transparent, highperformance polycrystalline optical ceramics. Lutetium/gadolinium aluminum/gallium garnets (described by formulas ((Gd,Lu)3(Al,Ga)5O12:Ce, Gd3(Al,Ga)5O12:Ce and Lu3Al5O12:Pr)) feature high effective atomic number and good scintillation properties, which make them particularly attractive for Positron Emission Tomography (PET) and other γ- ray detection applications. The ceramic processing route offers an attractive alternative to single crystal growth for obtaining scintillator materials at relatively low temperatures and at a reasonable cost, with flexibility in dimension control as well as activator concentration adjustment. In this study, optically transparent polycrystalline ceramics mentioned above were prepared by the sintering-HIP approach, employing nano-sized starting powders. The properties and microstructures of the ceramics were controlled by varying the processing parameters during consolidation. Single-phase, high-density, transparent specimens were obtained after sintering followed by a pressure-assisted densification process, i.e. hot-isostatic-pressing. The transparent ceramics displayed high contact and distance transparency as well as high light yield as high as 60,000-65,000 ph/MeV under gamma-ray excitation, which is about 2 times that of a LSO:Ce single crystal. The excellent scintillation and optical properties make these materials promising candidates for medical imaging and γ-ray detection applications.

  10. Iron Meteorite

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A meteorite composed mainly of nickel-iron, with traces of other metals; also referred to simply as an iron, and formerly known as a siderite. Irons account for over 6% of all known meteorite specimens. They are the easiest type to identify, being heavy, magnetic and rust-colored; their metallic sheen tarnishes quickly on the Earth's surface, but otherwise irons show better resistance to weatheri...

  11. Phosphorus contents in garnet from an ultrahigh pressure, high-temperature eclogite of the Saxonian Erzgebirge

    NASA Astrophysics Data System (ADS)

    Žigovečki Gobac, Željka; Massonne, Hans-Joachim; Theye, Thomas

    2015-04-01

    In the central Saxonian Erzgebirge, ultrahigh pressure rocks occur close to the Saidenbach reservoir. Among these rocks there are eclogites which have experienced metamorphic temperatures in excess of 1000°C (e.g., Massonne, 2013, Elements 9, 267-272). As a result of these high temperatures, the garnet was chemically homogenized with respect to a former growth zonation. Such kind of zonation can be deduced from inclusion minerals such as kyanite, phengite, and (clino)zoisite in garnet cores which point to metamorphic temperatures somewhat below 700°C. In order to test this view of a former prograde zonation in garnet, the content of phosphorus, a presumably much less mobile element at high temperatures compared to the common divalent cations, was determined in this mineral. Concentrations of P in mm-sized garnet in thin sections of eclogite were analyzed by a CAMECA SX100 electron microprobe (EMP). Different instrumental conditions, ranging from beam currents of 50 to 100 nA and counting times of 100 to 600 s on both peak and background at an acceleration voltage of 15 kV, were used in order to find the optimal way to determine this concentration in addition to the concentrations of the common elements at significantly shorter counting times. The interference of the CaKβ 2nd order and PKα 1st order peaks was considered by test measurements on standard material. The calculated detection limit for our P measurements was found to be around 13 ppm at the highest beam current and counting time. Several chemical profiles through a more or less concentrically zoned garnet grain were determined by spot analyses. These measurements on a high temperature eclogite from the Saidenbach reservoir yielded relatively low P contents in the core region of garnet of approximately 150 ppm and a significant increase towards the garnet rim. Maximum P contents were found to be around 350 ppm. In the core of garnet small apatite crystals were included whereas in the matrix no

  12. Limit on the Electron Electric Dipole Moment in Gadolinium-Iron Garnet

    SciTech Connect

    Heidenreich, B.J.; Elliott, O.T.; Charney, N.D.; Virgien, K.A.; Bridges, A.W.; McKeon, M.A.; Peck, S.K.; Krause, D. Jr.; Gordon, J.E.; Hunter, L.R.; Lamoreaux, S.K.

    2005-12-16

    A new method for the detection of the electron electric dipole moment (EDM) using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the sample's magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron EDM of 5x10{sup -24}e cm, which is a factor of 40 below the limit obtained from the only previous solid-state EDM experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.

  13. Effect of Sn doping on the room temperature magnetodielectric properties of yttrium iron garnet

    SciTech Connect

    Zhang, Zhizhi; Chen, Fu; Li, Junnan; Feng, Zekun; Nie, Yan

    2015-10-21

    The structures, magnetic properties, permittivity spectra, and magnetodielectric (MD) effects of polycrystalline Y{sub 3}Fe{sub 5−x}Sn{sub x}O{sub 12} compounds prepared by solid state reactions were systematically investigated. The substitution of Sn{sup 4+} leads to lattice expansion and the donation of excess electrons in ceramics, which affects the concentration of Fe{sup 2+}, space charge, and electric dipole. As a result, as the amount of Sn dopant increases, so does saturation magnetization and permittivity in the low frequency band. The MD coefficient ([ε{sub r}(H) − ε{sub r}(0)]/ε{sub r}(0)) of lightly doped samples (x ≤ 0.05) is negative in the entire frequency band, reaching −2.3% at 350 MHz and 0.6 T for Y{sub 3}Fe{sub 4.95}Sn{sub 0.05}O{sub 12} ceramics. The MD coefficient of heavily doped samples (x > 0.05) is positive in the low frequency band, reaching 0.83% at 10 MHz and 0.6 T for Y{sub 3}Fe{sub 4.925}Sn{sub 0.075}O{sub 12} ceramics, and then decreasing with the increasing frequency, gradually becoming negative in the high frequency band. A detailed explanation is provided based on the origin of permittivity. This study provides a new methodology according to which the MD materials may be designed in order to satisfy the requirements of engineering applications.

  14. Study of yttrium iron garnet rods reveals new magnetostatic echo mode

    NASA Technical Reports Server (NTRS)

    Kedzie, R. W.

    1967-01-01

    Echo mode in YIG rods has different behavior in magnetic fields. This mode, discovered at 8.5 gigahertz, experiences a linear variation. The time delay exhibited is a linear function of the applied magnetic field and the input pulse frequency.

  15. Metal thickness dependence on spin wave propagation in magnonic crystal using yttrium iron garnet

    SciTech Connect

    Kanazawa, Naoki; Goto, Taichi Hoong, Jet Wei; Buyandalai, Altansargai; Takagi, Hiroyuki; Inoue, Mitsuteru

    2015-05-07

    Magnonic crystals (MCs) are key components for spin wave manipulation. MCs realized with periodically metallized surfaces have an advantage in ease of the fabrication, but the effect of the metal thickness has not been studied well. In this work, the metal thickness dependence on the transmission spectra of localized mode spin waves was investigated. The metal thickness over half of the skin depth was necessary to prevent strong attenuation of spin waves.

  16. First-Principles Study of Spin-Orbit Interactions in Bismuth Iron Garnet

    NASA Astrophysics Data System (ADS)

    Oikawa, Tohru; Suzuki, Shugo; Nakao, Kenji

    2005-01-01

    We study the electronic structure of Bi3Fe5O12 (BIG) calculated by the fully relativistic first-principles method based on the density functional theory. It is found that the enhancement of the spin-orbit coupling due to the hybridization of Bi 6p is considerably larger in the Fe 3d conduction bands than in the O 2p and Fe 3d valence bands. The origin of this enhancement is that the Fe 3d conduction bands energetically overlap with Bi 6p bands. The results indicate the significance of spin-orbit coupling in Fe 3d conduction bands in relation to the large magneto-optical effect observed in BIG.

  17. Correlation by Rb-Sr geochronology of garnet growth histories from different structural levels within the Tauern Window, Eastern Alps

    SciTech Connect

    Christensen, John N.; Selverstone, Jane; Rosenfeld, John L.; Depaolo, Donald J.

    1993-06-01

    In order to evaluate rates of tectonometamorphic processes, growth rates of garnets from metamorphic rocks of the Tauern Window, Eastern Alps were measured using Rb-Sr isotopes. The garnet growth rates were determined from Rb-Sr isotopic zonation of single garnet crystals and the Rb-Sr isotopic compositions of their associated rock matrices. Garnets were analyzed from the Upper Schieferhulle (USH) and Lower Schieferhulle (LSH) within the Tauern Window. Two garnets from the USH grew at rates of 0.67(-0.13)+0.19 mm/million years and 0.88(-0.19)+0.34 mm/million years, respectively, indicating an average growth duration of 5.4 +- 1.7 million years. The duration of growth coupled with the amount of rotation recorded by inclusion trails in the USH garnets yields an average shear-strain rate during garnet growth of 2.7(-0.7)+1.2 x 10(-14) s-1 . Garnet growth in the sample from the USH occurred between 35.4 +- 0.6 and 30 +- 0.8 Ma. The garnet from the LSH grew at a rate of 0.23 +- 0.015 mm/mil lion years, between 62 +- 1.5 Ma and 30.2 +- 1.5 Ma. Contemporaneous cessation of garnet growth in both units at approximately 30 Ma is in accord with previous dating of the thermal peak of metamorphism in the Tauern Window. Correlation with previously published pressure-temperature paths for garnets from the USH and LSH yields approximate rates of burial, exhumation and heating during garnet growth. Assuming that these P - T paths are applicable to the garnets in this study, the contemporaneous exhumation rates recorded by garnet in the USH and LSH were approximately 4(-2)+3 mm/year and 2 +- 1 mm/year, respectively. [References: 34

  18. High temperature garnet growth in New England: regional temperature-time trends revealed

    NASA Astrophysics Data System (ADS)

    Sullivan, N.; Ostwald, C.; Chu, X.; Baxter, E. F.; Ague, J. J.; Eckert, J. O.

    2013-12-01

    A series of localized ultrahigh-temperature (UHT)/high-temperature (HT) granulite facies regions have been identified within the regional amphibolite facies metamorphic zone of the Central Maine Terrane stretching from north-central New Hampshire, through central Massachusetts, and into northeastern Connecticut. Here, we aim to constrain the age and peak temperature of metamorphism at three localities within this region: Bristol, NH, Phillipston, MA and Willington, CT. Garnet-forming reactions are linked directly to peak metamorphic temperatures through thermodynamic modeling and/or Zr-in-rutile thermometry. Precise garnet geochronology allows us to identify the timing of these peak temperatures, as well as the duration of garnet growth. Geochronologic and thermodynamic work was done on 12 samples collected throughout a ~5 km2 metamorphic 'hotspot' previously identified in Bristol, NH (Chamberlain and Rumble, 1988; Journal of Petrology). The highest temperature assemblage within this hotspot is characterized by the presence of garnet + sillimanite + K-feldspar + cordierite and reached temperatures >820οC. The lowest temperature periphery of the hotspot is characterized by sillimanite + muscovite + K-feldspar + minor garnet and reached a maximum temperature of 650οC. Bulk garnet ages from samples within the hotspot range significantly from at least 400.0 × 2.5 Ma to 352.7 × 1.8 Ma with the youngest ages associated with the lower temperature samples. This collection of ages indicates a prolonged period (~50 Ma) of >650οC temperatures interspersed by period(s) of garnet growth. Zoned garnet geochronology will help reveal whether garnet growth and related heating was continuous or episodic. Further south, in Phillipston, MA, zoned garnet geochronology performed on a 2.5 cm diameter garnet porphyroblast indicates garnet growth spanning 389 - 363 Ma, reaching peak temperatures at the end of that time span of 920-940οC, followed by a younger event recorded in

  19. Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition

    USGS Publications Warehouse

    Manning, C.E.; Bird, D.K.

    1990-01-01

    Zoned, silica-deficient, calcic garnets containing up to 5 mol% F substitution for O formed during contact metamorphism of basalts by the Skaergaard intrusion in East Greenland. Fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30-70 m from the intrusion. The F content of garnet is extremely sensitive to minor changes in fluid composition. The calculations show that a decrease in pH or an increase in log aF- of 0.3 at constant pressure and temperature will decrease the F concentration in garnet from 5 to 0 mol%. The results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities of F species in coexisting metamorphic and hydrothermal fluids. -from Authors

  20. Evidence of mantle metasomatism in garnet peridotites from V. Grib kimberlite pipe (Arkhangelsk region, Russia)

    NASA Astrophysics Data System (ADS)

    Shchukina, Elena; Agashev, Alexey; Golovin, Nikolai; Pokhilenko, Nikolai

    2013-04-01

    We have studied 26 samples of garnet peridotite xenoliths from V.Grib pipe and 17 of them are phlogopite bearing. Studied peridotites have features of two types of modal metasomatism: low-temperature (˜ 1100 C°) and high-temperature (˜ 1100 C°). Low-temperature modal metasomatism: 17 samples contain modal phlogopite, which is present in the form of tabular grains (to 3 mm in size) and rims around pyrope grains. Chemical composition of minerals from phlogopite-garnet peridotites and phlogopite free peridotites is distinctly different. Olivine, garnet, orthopyroxene and clinopyroxene have higher concentration of FeO relative to these minerals in phlogopite free peridotites. Occurrence of phlogopite in peridotites indicates the influence of melt enriched in K2O, H2O, FeO and other incompatible elements. Two types of phlogopite have difference in chemical composition that indicates two different sources. High-temperature modal metasomatism: Reconstructed V.Grib pipe peridotite whole-rocks composition and high Mg# of peridotite olivines indicates that these samples are residues after 30-40 % partial melting of primitive mantle. At those high degree of partial melting all clinopyroxene and probably all garnet should be exhausted from residue. Character of REE patterns in garnets and clinopyroxenes indicates that the most garnets and all clinopyroxene in studied peridotites are of metasomatic origin. We used the method of geochemical modeling of fractional crystallization to establish the source's composition for garnets and clinopyroxenes. For geochemical modeling we used the composition of tholeitic basalts, picrites and carbonatites which occurred in Arkhangelsk diamondiferous province (ADP) and have emplacement ages similar to that of kimberlites. Modeling result indicates that garnets could be crystallized from alkali picrite and tholeite basalts compositions. Peridotites containing garnets equilibrated with picritic melt have a different position in lithospheric

  1. Partitioning REE between minerals and coexisting melts during partial melting of a garnet lherzolite

    NASA Technical Reports Server (NTRS)

    Harrison, W. J.

    1981-01-01

    Partition coefficients for Ce, Sm, and Tm between garnet, clinopyroxene, orthopyroxene, olivine, and melt are determined at 35 kbar for 2.3, 8, 20, and 37.7% melting of a garnet lherzolite nodule with chondritic REE abundances. Partition coefficients are found to increase as the degree of partial melting increases. From 2.3 to 8% melting, this increase is for the most part a consequence of non-Henry's law behavior of REE in minerals.

  2. Optical absorption of Ni2+ and Ni3+ ions in gadolinium gallium garnet epitaxial films

    NASA Astrophysics Data System (ADS)

    Vasileva, N. V.; Gerus, P. A.; Sokolov, V. O.; Plotnichenko, V. G.

    2012-12-01

    Single-crystal Ni-doped gadolinium gallium garnet films were grown for the first time from supercooled Bi2O3-B2O3-based melt solutions by liquid-phase epitaxy. Optical absorption bands due to Ni2+, Ni3+ and Bi3+ ions were observed in those films. Interpretation and tabulation of all absorption bands of nickel ions occupying octahedral and tetrahedral sites in the garnet lattice are presented.

  3. Evidence for polymetamorphic garnet growth in the Çine (southern Menderes) Massif, Western Turkey

    NASA Astrophysics Data System (ADS)

    Baker, C. B.; Catlos, E. J.; Sorensen, S. S.; Çemen, I.; Hancer, M.

    2008-07-01

    Garnet-based thermobarometry is often used to develop models for the evolution of the Menderes Massif, a key Aegean metamorphic core complex. Here we present X-ray element maps and high-contrast backscattered electron (BSE) and cathodoluminescence (CL) images from a garnet-bearing rock from the Çine (southern Menderes) Massif. The images document a polymetamorphic history as plagioclase and garnet grains show distinct cores and rims. The sample contains matrix monazite in reaction with allanite. The garnet in the sample is likely not in equilibrium with its matrix minerals. This is evidenced by BSE images that document compositional variability in both core and rim zoning and tracks of bright streaks extending from rim to core. We propose that some garnet that is now present in the Menderes Massif formed due to collision during Cambro-Ordovician and may have recrystallized during subsequent collisional and extensional events. These processes led to non-equilibrium compositions and can result in spurious pressure-temperature (P-T) calculations. To establish the feasibility of the P-T estimates of rocks from the Çine Massif for input into tectonic models for the region, more than one sample from single outcrops should be analyzed. Rocks within the Çine Massif have been suggested to display inverted metamorphism, an increase in T towards structurally higher levels. Based on the garnet documented here, we propose that the inverted metamorphism may be a consequence of apparent P-T rather than a real phenomenon.

  4. Metastable garnet in oceanic crust at the top of the lower mantle.

    PubMed

    Kubo, Tomoaki; Ohtani, Eiji; Kondo, Tadashi; Kato, Takumi; Toma, Motomasa; Hosoya, Tomofumi; Sano, Asami; Kikegawa, Takumi; Nagase, Toshiro

    As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account. PMID:12490946

  5. Raman imaging of fluid inclusions in garnet from UHPM rocks (Kokchetav massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Dieing, Thomas; Golovin, Aleksandr V; Toporski, Jan

    2011-10-01

    Confocal Raman imaging of fluid inclusions in garnet porphyroblasts from diamond-grade metamorphic calc-silicate rocks from the Kumdy-Kol microdiamond deposit (Kokchetav Massif, Northern Kazakhstan) reveals that these fluid inclusions consist of almost pure water with different step-daughter phases (e.g., calcite, mica and rare quartz). These fluid inclusions are characterized by negative crystal shape of the host-garnet and they exclusively occur within the core of garnet porphyroblasts. These observations are consistent with their primary origin, most likely at ultrahigh-pressure (UHP) metamorphic conditions. The euhedral newly formed garnet, different in color and composition, was found to be associated with these fluid inclusions. It is proposed that newly formed garnet and water fluid inclusions appear by reaction between the hydrous fluid and the garnet-host. These fluid inclusions provide an unequivocal record of almost pure H(2)O fluids, indicating water-saturated conditions within subducted continental crust during prograde stage and/or ultrahigh-P metamorphism.

  6. Amorphization of rare earth aluminate garnets by ionic irradiation and decay of 244Cm admixture

    SciTech Connect

    Livshits, T. S.; Lizin, A. A.; Zhang, J. M.; Ewing, R. C.

    2010-08-29

    The stability of synthetic REE-aluminate garnets irradiated by accelerated Kr2+ ions and affected by alpha decay of ²⁴⁴Cm (T1/2 = 18.1 yr) has been studied. The dose of irradiation sufficient for the complete disordering of the aluminate garnet structure is 0.40–0.55 displacements per atom. This value increases with rising temperature due to the increasing intensity of recovery from radiation damage to the lattice by heating. The critical temperature above which the structure of REE-aluminate is not damaged by radiation is 550°C. The amorphization dose for aluminates with garnet structure is two to three times higher than of that previously studied ferrites; the critical temperature of both is similar. In resistance to radiation, aluminate garnets do not yield to zirconolite and exceed titanate pyrochlore. Heating to 250°C does not lead to substantial recovery from radiation defects in the garnet structure. The radiation impact on matrices of real actinide (An) wastes is lower than that related to ion irradiation and ²⁴⁴Cm doping, and this facilitates a higher radiation resistance of garnets containing HLW.

  7. Raman imaging of fluid inclusions in garnet from UHPM rocks (Kokchetav massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Dieing, Thomas; Golovin, Aleksandr V; Toporski, Jan

    2011-10-01

    Confocal Raman imaging of fluid inclusions in garnet porphyroblasts from diamond-grade metamorphic calc-silicate rocks from the Kumdy-Kol microdiamond deposit (Kokchetav Massif, Northern Kazakhstan) reveals that these fluid inclusions consist of almost pure water with different step-daughter phases (e.g., calcite, mica and rare quartz). These fluid inclusions are characterized by negative crystal shape of the host-garnet and they exclusively occur within the core of garnet porphyroblasts. These observations are consistent with their primary origin, most likely at ultrahigh-pressure (UHP) metamorphic conditions. The euhedral newly formed garnet, different in color and composition, was found to be associated with these fluid inclusions. It is proposed that newly formed garnet and water fluid inclusions appear by reaction between the hydrous fluid and the garnet-host. These fluid inclusions provide an unequivocal record of almost pure H(2)O fluids, indicating water-saturated conditions within subducted continental crust during prograde stage and/or ultrahigh-P metamorphism. PMID:21377920

  8. Metastable garnet in oceanic crust at the top of the lower mantle.

    PubMed

    Kubo, Tomoaki; Ohtani, Eiji; Kondo, Tadashi; Kato, Takumi; Toma, Motomasa; Hosoya, Tomofumi; Sano, Asami; Kikegawa, Takumi; Nagase, Toshiro

    As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account.

  9. Crystal chemistry of Ti-bearing garnets with volcanic origin

    NASA Astrophysics Data System (ADS)

    Scordari, F.; Schingaro, E.; Malitesta, C.; Pedrazzi, G.

    2003-04-01

    The crystal chemistry of Ti-bearing andradites ("melanites") belonging to different pyroclastic units of Albani Hills (Lazio, Italy) has been investigated electron probe microanalysis (EPMA), single crystal X-ray diffraction (SCXRD), Mössbauer spectroscopy (MS) and X-ray Photoelectron Spectroscopy (XPS). The aim is to determine the correct cations distribution over the X(8-fold), Y(6-fold) and Z(4-fold) sites and accurate values of cations site populations. The analysed samples are characterized by a low Ti-content ( TiO_2 in the range 1.76-3.59 wt%) and cell edges in the range 11.996(3)-12.014(1). MS investigation reveald Fe to be present predominantly as Fe3+(Y) and subordinately as Fe2+(X). XPS analysis was accomplished according to the procedure developed by Malitesta et al.(1989). The fitting of Ti2p signals seem to indicate that two (octahedral Ti3+ and Ti4+) or three (octahedral Ti3+ and Ti4+, tetrahedral Ti4+) Ti species may occur in these specimen. From the combination of the results from different techniques the distribution of Al over the Y and Z sites has been deduced. By comparing the Albani Hills samples crystal chemistry with that of melanites from Mt. Vulture (Scordari et al., 1999), it has been found that in the latter samples the Z sites is occupied by Si, Fe3+ and Ti4+, whereas in the former by Si,Ti4+ and Al3+. Substitution mechanisms through which Fe and Ti enter the garnet structure are expected to be related to the geologic environment in which they occurr. It has been recently proposed that in samples from volcanic rocks schorlomite substitution, Ti4+(Y) + Fe3+(Z) leftrightarrow Si4+(Z) + Fe3+(Y) is predominant, associated to a low degree of hydrogarnet component, (SiO_4)4- leftrightarrow (O_4H_4)4-; on the contrary Ti-garnets from metamorphic rocks should be affected by morimotoite substitution Ti4+(Y) + Fe2+(Y) leftrightarrow 2Fe3+(Y) and a high degree of hydrogarnet component (Armbruster et al., 1998). The result obtained in the present

  10. Graphical representations of the chemistry of garnets in a three-dimensional MATLAB based provenance plot

    NASA Astrophysics Data System (ADS)

    Knierzinger, Wolfgang; Palzer, Markus; Wagreich, Michael; Meszar, Maria; Gier, Susanne

    2016-04-01

    A newly developed, MATLAB based garnet provenance plot allows a three-dimensional tetrahedral representation of the chemistry of garnets for the endmembers almandine, pyrope, spessartine and grossular. Based on a freely accessible database of Suggate & Hall (2013) and additional EPMA-data on the internet, the chemistry of more than 2500 garnets was evaluated and used to create various subfields that correspond to different facies conditions of metapelitic, metasomatic and metaigneous rocks as well as granitic rocks. These triangulated subfields act as reference structures within the tetrahedron, facilitating assignments of garnet chemistries to different lithologies. In comparison with conventional tenary garnet discrimination diagrams by Mange & Morton (2007), Wright/Preston et al. (1938/2002) and Aubrecht et al. (2009), this tetrahedral provenance plot enables a better assessment of the conditions of formation of garnets by reducing the overlapping of certain subfields. In particular, a clearer distinction between greenschist facies rocks, amphibolite facies rocks and granitic rocks can be achieved. First applications of the tetrahedral garnet plot provided new insights on sedimentary processes during the Lower Miocene in the pre-Alpine Molasse basin. Bibliography Aubrecht, R., Meres, S., Sykora, M., Mikus, T. (2009). Provenance of the detrital garnets and spinels from the Albian sediments of the Czorsztyn Unit (Pieniny Klippen Belt , Western Carpathians, Slovakia). In: Geologica Carpathica, Dec. 2009, 60, 6, pp. 463-483. Mange, M.A., Morton, A.C. (2007). Geochemistry of Heavy Minerals. In: Mange, M.A. & Wright, D.T.(2007).Heavy Minerals in Use, Amsterdam, pp. 345-391. Preston, J., Hartley, A., Mange-Rajetzky, M., Hole, M., May, G., Buck, S., Vaughan, L. (2002). The provenance of Triassic continental sandstones from the Beryl Field, northern North Sea: Mineralogical, geochemical and sedimentological constraints. In: Journal of Sedimentary Research, 72, pp. 18

  11. Low-temperature thermal conductivity of terbium-gallium garnet

    SciTech Connect

    Inyushkin, A. V. Taldenkov, A. N.

    2010-11-15

    Thermal conductivity of paramagnetic Tb{sub 3}Ga{sub 5}O{sub 12} (TbGG) terbium-gallium garnet single crystals is investigated at temperatures from 0.4 to 300 K in magnetic fields up to 3.25 T. A minimum is observed in the temperature dependence {kappa}(T) of thermal conductivity at T{sub min} = 0.52 K. This and other singularities on the {kappa}(T) dependence are associated with scattering of phonons from terbium ions. The thermal conductivity at T = 5.1 K strongly depends on the magnetic field direction relative to the crystallographic axes of the crystal. Experimental data are considered using the Debye theory of thermal conductivity taking into account resonance scattering of phonons from Tb{sup 3+} ions. Analysis of the temperature and field dependences of the thermal conductivity indicates the existence of a strong spin-phonon interaction in TbGG. The low-temperature behavior of the thermal conductivity (field and angular dependences) is mainly determined by resonance scattering of phonons at the first quasi-doublet of the electron spectrum of Tb{sup 3+} ion.

  12. Optical spectroscopy of the Ce-doped multicomponent garnets.

    PubMed

    Canimoglu, A; Karabulut, Y; Ayvacikli, M; Muresan, L E; Perhaita, I; Barbu-Tudoran, L; Garcia Guinea, J; Karali, T; Can, N

    2016-08-01

    Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530nm assigned to 5d-4f transitions of the dopant Ce(3+) ions with a broad emission band in 400-700nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312nm and 624nm corresponding to transition of (6)P7/2 →(8)S7/2 and (6)GJ→(6)PJ (Gd(3+)), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation. PMID:27235885

  13. Diffusion kinetics of samarium and neodymium in garnet, and a method for determining cooling rates of rocks

    PubMed

    Ganguly; Tirone; Hervig

    1998-08-01

    Experimental determinations of the diffusion coefficients of samarium and neodymium in almandine garnet and theoretical considerations show that one cannot assign a sufficiently restricted range of closure temperature, TC, to the samarium-neodymium decay system in garnet for the purpose of constraining the cooling rate. However, it is shown that the samarium-neodymium cooling age of garnet can be used to calculate both cooling rate and TC if the temperature and age at the peak metamorphic conditions are known.

  14. Exsolution halos surrounding ruptured inclusions in garnets from UHT and UHP rocks

    NASA Astrophysics Data System (ADS)

    Axler, Jennifer; Ague, Jay

    2015-04-01

    Distinctive halos of rutile ± apatite needles and/or plates centered on quartz or multiphase inclusions with radial cracks in garnet are investigated. The quartz is likely former coesite and the multiphase inclusions are interpreted to be decrepitated fluid inclusions. We study samples from two localities: (1) ultrahigh-temperature (UHT) metapelitic gneisses from the Central Maine Terrane in Connecticut, USA (Ague et al., 2013) (rutile halos only) and (2) ultrahigh-pressure (UHP) diamondiferous saidenbachite from the Saxonian Erzgebirge (Massonne, 2003) (rutile and apatite halos). The rutile and apatite needles in the halos are typically oriented in three directions. Within the halos, garnet is depleted in Ti (and P if apatite is present). The halos extend about three inclusion radii away from the central quartz or multiphase inclusions. We propose that the inclusion halos of rutile ± apatite formed by exsolution out of garnet due to rupturing of the central inclusions. The internal pressure of an inclusion in garnet can be larger than the surrounding lithostatic pressure if the entrapment pressure is maintained or if a large positive volume phase change occurs. A large pressure difference between an inclusion and host strains the host and causes deformation, which in turn produces dislocations and other defects. During exhumation the pressure difference between inclusions and the surrounding rock matrix can become so great that rupturing of the garnet occurs. The rupturing creates more dislocations and defects in the garnet with the dislocation density highest around the inclusion. The defects in the crystal structure are ideal nucleation sites for exsolved precipitates. Another factor assisting exsolution is the drop in pressure in the surrounding garnet caused by the rupturing which should in turn decrease the solubility of Ti and P in garnet. To test the exsolution hypothesis, chemical reintegration of the Ti or P contents of the garnet in the halos plus the

  15. Iron refractory iron deficiency anemia

    PubMed Central

    De Falco, Luigia; Sanchez, Mayka; Silvestri, Laura; Kannengiesser, Caroline; Muckenthaler, Martina U.; Iolascon, Achille; Gouya, Laurent; Camaschella, Clara; Beaumont, Carole

    2013-01-01

    Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in adulthood. The disease is refractory to oral iron treatment but shows a slow response to intravenous iron injections and partial correction of the anemia. To date, 40 different Matriptase-2 mutations have been reported, affecting all the functional domains of the large ectodomain of the protein. In vitro experiments on transfected cells suggest that Matriptase-2 cleaves Hemojuvelin, a major regulator of hepcidin expression and that this function is altered in this genetic form of anemia. In contrast to the low/undetectable hepcidin levels observed in acquired iron deficiency, in patients with Matriptase-2 deficiency, serum hepcidin is inappropriately high for the low iron status and accounts for the absent/delayed response to oral iron treatment. A challenge for the clinicians and pediatricians is the recognition of the disorder among iron deficiency and other microcytic anemias commonly found in pediatric patients. The current treatment of iron refractory iron deficiency anemia is based on parenteral iron administration; in the future, manipulation of the hepcidin pathway with the aim of suppressing it might become an alternative therapeutic approach. PMID:23729726

  16. The effect of fluid and deformation on zoning and inclusion patterns in poly-metamorphic garnets

    NASA Astrophysics Data System (ADS)

    Erambert, Muriel; Austrheim, Håkon

    1993-11-01

    Within the Bergen Arcs of W Norway, Caledonian eclogite facies assemblages ( T≥650°C, P≥15 kbar) have formed from Grenvillian granulites ( T= 800 900°C, P≥10 kbar) along shear zones and fluid pathways. Garnets in the granulites (grtI: Pyr56 40 Alm45 25Gro19 14) are unzoned or display a weak (ca. 1 wt% FeO over 1000μm) zoning. The eclogite facies rocks contain garnets inherited from their granulite facies protoliths. These relict garnets have certain areas with compositions identical to the garnets in their nearby granulite, but can be crosscut by bands of a more Almrich composition (grtII: Pyr31 41Alm40 47Gro17 21) formed during the eclogite facies event. These bands, orientated preferentially parallel or perpendicular to the eclogite foliation, may contain mineral filled veins or trails of eclogite-facies minerals (omphacite, amphibole, white mica, kyanite, quartz and dolomite). Steep compositional gradients (up to 9 wt% FeO over 40 μm) separate the two generations of garnets, indicating limited volume diffusion. The bands are interpreted as fluid rich channels where element mobility must have been infinitely greater than it was for the temperature controlled volume diffusion at mineral interfaces in the granulites. The re-equilibration of granulite facies garnets during the eclogite facies event must, therefore, be a function of fracture density (deformation) and fluid availability. The results cast doubts on modern petrological and geochronological methods that assume pure temperature controlled chemical re-equilibration of garnets.

  17. Mantle refertilization by garnet pyroxenite melts: Evidence from the Ronda peridotite massif, southern Spain

    NASA Astrophysics Data System (ADS)

    Marchesi, C.; Garrido, C.; Bosch, D.; Bodinier, J.; Gervilla, F.

    2011-12-01

    Lherzolite at the recrystallization front of the Ronda peridotite massif, a mantle region that experienced pervasive melt migration and melt/rock reaction, hosts pyroxenite composite layers that show an inner transition from Al- to Cr-rich compositions. These particular pyroxenite-peridotite associations record intense processes of pyroxenite melting/replacement and related peridotite refertilization. Al-rich spinel websterite in a composite layer close to the front was generated by melting of former garnet pyroxenite with an evident imprint of primary plagioclase and reaction of this protolith with incoming peridotite melt. These events produced more refractory major element compositions of whole-rock and higher REE contents in clinopyroxene but preserved the characteristic MREE/HREE fractionation and positive Eu anomaly of the garnet pyroxenite protolith. In the waning stages of melt porous flow at the recrystallization front, the parental melts of Cr-rich pyroxenite progressively replaced residual Al-rich spinel websterite partially conserving their original subduction-related affinity. Lherzolite hosting the composite layer was intensely refertilized by melt resulted from garnet pyroxenite replacement. The presence in the refertilizing agent of an important component extracted from garnet pyroxenite induced Eu and Sr positive anomalies, higher FeO* at similar SiO2 and higher Sm/Yb in these mantle rocks compared to common peridotite from the Ronda massif. Some peculiar geochemical signatures of garnet pyroxenite were thus imparted to highly fertile lherzolite hosting the pyroxenite composite layer by partial melting, melt migration and melt/rock reaction in the Ronda massif. These mechanisms may explain the presence of a garnet pyroxenite component in the source of different types of melt generated in the mantle. However, the efficiency of these processes in transferring the geochemical imprint of garnet pyroxenite to extruded lavas depends on the reactivity of

  18. Melts of garnet lherzolite: experiments, models and comparison to melts of pyroxenite and carbonated lherzolite

    USGS Publications Warehouse

    Grove, Timothy L.; Holbig, Eva S.; Barr, Jay A.; Till, Christy B.; Krawczynski, Michael J.

    2013-01-01

    Phase equilibrium experiments on a compositionally modified olivine leucitite from the Tibetan plateau have been carried out from 2.2 to 2.8 GPa and 1,380–1,480 °C. The experiments-produced liquids multiply saturated with spinel and garnet lherzolite phase assemblages (olivine, orthopyroxene, clinopyroxene and spinel ± garnet) under nominally anhydrous conditions. These SiO2-undersaturated liquids and published experimental data are utilized to develop a predictive model for garnet lherzolite melting of compositionally variable mantle under anhydrous conditions over the pressure range of 1.9–6 GPa. The model estimates the major element compositions of garnet-saturated melts for a range of mantle lherzolite compositions and predicts the conditions of the spinel to garnet lherzolite phase transition for natural peridotite compositions at above-solidus temperatures and pressures. We compare our predicted garnet lherzolite melts to those of pyroxenite and carbonated lherzolite and develop criteria for distinguishing among melts of these different source types. We also use the model in conjunction with a published predictive model for plagioclase and spinel lherzolite to characterize the differences in major element composition for melts in the plagioclase, spinel and garnet facies and develop tests to distinguish between melts of these three lherzolite facies based on major elements. The model is applied to understand the source materials and conditions of melting for high-K lavas erupted in the Tibetan plateau, basanite–nephelinite lavas erupted early in the evolution of Kilauea volcano, Hawaii, as well as younger tholeiitic to alkali lavas from Kilauea.

  19. Vapor-Phase Garnet at Yucca Mountain, Nevada: Geochemistry and Oxygen-Isotope Thermometry

    SciTech Connect

    R. J. Moscati; C.A. Johnson; J.F. Whelan

    2001-07-03

    About 20 vapor-phase garnets were studied in two samples of the Topopah Spring Tuff from Yucca Mountain, in southern Nevada. The Miocene-age Topopah Spring Tuff is a 350-m-thick, devitrified, moderately to densely welded ash flow that is compositionally zoned from high-silica rhyolite to quartz latite. During cooling of the tuff, escaping vapor produced lithophysae (former gas cavities) lined with an assemblage of tridymite, cristobalite, alkali feldspar, and locally, hematite and/or garnet. Vapor-phase topaz and economic deposits (such as porphyry molybdenum-tungsten) commonly associated with topaz-bearing rhyolites (characteristically enriched in fluorine) were not found in the Topopah Spring Tuff at Yucca Mountain. The garnets are not primary igneous phenocrysts, but rather crystals that grew from a fluorine-poor magma-derived vapor trapped during emplacement of the tuff. The garnets are euhedral, vitreous, reddish brown, trapezohedral, as large as 2 mm in diameter, and fractured. The garnets also contain inclusions of tridymite. Electron-microprobe analyses of the garnets reveal that they are almandine-spessartine (48.0 and 47.9 mol percent, respectively), have an average chemical formula of (Fe{sub 1.46}, Mn{sub 1.45}, Mg{sub 0.03}, Ca{sub 0.10}) (Al{sub 1.93}, TiO{sub 0.02}) Si{sub 3.01}O{sub 12}, and are homogeneous in Fe and Mn concentrations from core to rim. Composited garnets from each sample site have {delta}{sup 18}O values of 7.2 and 7.4{per_thousand}. The coexisting tridymite, however, has {delta}{sup 18}O values of 17.4 and 17.6{per_thousand} values indicative of reaction with later, low-temperature water. Unaltered tridymite from higher in the stratigraphic section has a {delta}{sup 18}O of 11.1{per_thousand} which, when coupled with the garnet {delta}{sup 18}O values in a quartz-garnet fractionation equation, indicates vapor-phase crystallization at temperatures of almost 600 C. This high-temperature mineralization, formed during cooling of the

  20. Mechanisms and Kinetics of the Post-Garnet Transformation in Pyrope

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Ohtani, E.; Kondo, T.; Kato, T.; Kikegawa, T.; Nagase, T.

    2001-12-01

    Garnet, which is one of the major constituent minerals of the subducting oceanic crust, transforms to perovskite (post-garnet transformation) at the depth of ~600-800 km. Metastability of garnet and changes of microstructures in the post-garnet transformation under subduction zone conditions possibly affect on dynamics of the subducting oceanic crust in the deep mantle. In order to clarify them, we performed high-pressure and high-temperature in-situ X-ray diffraction experiments on the post-garnet transformation kinetics of pyrope. Here we report preliminary results on mechanisms and kinetics of the decomposition reaction of pyrope garnet into aluminous perovskite and corundum. In-situ X-ray diffraction experiments were carried out using sintered-diamond multi-anvil apparatus MAX-III installed at KEK-PF. White X-ray from synchrotron radiation was used as the incident X-ray beam and the diffracted beam was measured by the energy dispersive method. Pressure was evaluated from the equation of state of gold (Anderson, 1989). The starting material is a sintered mixture of Mg3Al2Si3O12 pyrope (grain size is 2-5 μm ) and gold. It was compressed to the desired pressure at room temperature, and then heated to the desired temperature at constant oil pressure. When the temperature reached to the desired value, it was kept constant and time-resolved X-ray diffraction profiles were taken every 10-200 seconds. The transformation proceeded by about 50%\\ in 4 and 130 minutes at 31.0 GPa and 1473K, and 30.3 GPa and 1273K, respectively. When the transformed fraction reached about 50% the transformation rate drastically slowed down. At 26.0 GPa and 1673K, the transformation completed in 10 seconds. These preliminary kinetic data qualitatively suggest that kinetics of the post-garnet transformation in pyrope is significantly slower than those of the post-spinel transformation. SEM and TEM observations of the sample recovered from 30.3 GPa and 1273K revealed the grain

  1. Garnet geochronology: improvements and application in studying India-Asia collision

    NASA Astrophysics Data System (ADS)

    Smit, Matthijs; Scherer, Erik; Mezger, Klaus; Lee, Jeffrey; Ratschbacher, Lothar; Kooijman, Ellen; Stearns, Michael

    2016-04-01

    Garnet enables constraints on all parameters relevant to lithosphere studies: pressure, temperature, strain, and time. This aspect, in combination with its widespread occurrence in metamorphic rocks, make the mineral a prime target in research into the dynamics of mountain belts. Our ability to obtain and interpret precise age constraints from garnet Lu-Hf and Sm-Nd data has greatly improved over the years. This contribution highlights recent enhancements in garnet geochronology and demonstrates the versatility of this method in two case studies set in the India-Asia collision zone. To enable a more effective use of garnet geochronology, we investigated the retentiveness of Lu-Hf and Sm-Nd isotope signatures in naturally metamorphosed garnet. A grain-size dependent Lu-Hf and Sm-Nd analysis of garnet was done on a sample of a slowly cooled Archean granulite from the Pikwitonei Granulite Domain, Canada. Comparison of the apparent ages to the known thermal history of this rock allowed constraints on chronometer systematics at high temperature. Diffusive re-equilibration is shown to occur to a small (Sm-Nd) to minor, if not insignificant (Lu-Hf), extent during high temperature metamorphism, thus firmly establishing the Lu-Hf and Sm-Nd chronometers as reliable, well-characterized dating tools. Garnet Lu-Hf chronology was done to show that mid-crustal flow and 'Barrovian-type' metamorphism of rocks now exposed in the North Himalayan Gneiss Domes in Central Tibet commenced in the early Eocene. This result is the first to confirm that crustal thickening and contraction in the Tibetan Himalaya was broadly synchronous with the collision between Greater India and Eurasia. Garnet dating and thermometry, and rutile U-Pb thermochronology on granulites from the Pamir (an exposed segment of deep Asia) revealed a history of heating to 750-830 °C, commencing at 37 Ma in the South Pamir and occurring progressively later northward. The data advocate a causal link between Indian slab

  2. Slow Si-Al interdiffusion in garnet and stagnation of subducting slabs

    NASA Astrophysics Data System (ADS)

    Nishi, Masayuki; Kubo, Tomoaki; Ohfuji, Hiroaki; Kato, Takumi; Nishihara, Yu; Irifune, Tetsuo

    2013-01-01

    Si4++M2+↔2Al3+ (M=Mg+Fe+Ca) interdiffusion rates in majoritic garnet have been determined at pressure of 17 GPa and temperatures of 1550-1700 °C using a Kawai-type high-pressure apparatus. The diffusion profiles were measured across the interface between pyropic garnet and majoritic garnet samples by an analytical transmission electron microscope, and the rate of the Si4++M2+↔2Al3+ interdiffusion was determined to be a DSi-Al (m2 s-1)=2×10-10 exp [-364 (kJ mol-1)/RT]. We found that the diffusion rate is low compared to the Si diffusion rate in other silicate minerals relevant to the deep mantle. Slow kinetics of the pyroxene-garnet transformation due to the low diffusion rate indicates that large low-density metastable regions may exist in the slab, greatly contributing to the slab stagnation around the transition region. Stagnant slabs possibly stay in this region over 108 yr because of the sluggish pyroxene-garnet transformation, but may eventually fall into the lower mantle after the completion of the transformation.

  3. Thermodynamics of aluminosilicate garnet solid solution: new experimental data, an optimized model, and thermometric applications

    NASA Astrophysics Data System (ADS)

    Ganguly, J.; Cheng, Weiji; Tirone, Massimiliano

    1996-12-01

    We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇆ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clino-pyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints.

  4. Transition from Superlithiophobicity to Superlithiophilicity of Garnet Solid-State Electrolyte.

    PubMed

    Luo, Wei; Gong, Yunhui; Zhu, Yizhou; Fu, Kun Kelvin; Dai, Jiaqi; Lacey, Steven D; Wang, Chengwei; Liu, Boyang; Han, Xiaogang; Mo, Yifei; Wachsman, Eric D; Hu, Liangbing

    2016-09-21

    All-solid-state Li-batteries using solid-state electrolytes (SSEs) offer enhanced safety over conventional Li-ion batteries with organic liquid electrolytes due to the nonflammable nature of SSEs. The superior mechanical strength of SSEs can also protect against Li dendrite penetration, which enables the use of the highest specific capacity (3861 mAh/g) and lowest redox potential (-3.04 V vs standard hydrogen electrode) anode: Li metal. However, contact between the Li metal and SSEs presents a major challenge, where a large polarization occurs at the Li metal/SSE interface. Here, the chemical properties of a promising oxide-based SSE (garnet) changed from "super-lithiophobicity" to "super-lithiophilicity" through an ultrathin coating of amorphous Si deposited by plasma-enhanced chemical vapor deposition (PECVD). The wettability transition is due to the reaction between Li and Si and the in situ formation of lithiated Si. As a result, symmetric cells composed of a Si-coated garnet-structured SSE and Li metal electrodes exhibited much smaller impedance and excellent stability upon plating/stripping cycles compared to cells using bare garnet SSE. Specifically, the interfacial resistance between Li and garnet dramatically decreased from 925 to 127 Ω cm(2) when lithiated Si was formed on the garnet. Our discovery of switchable lithiophobic-lithiophilic surfaces to improve the Li metal/SSE interface opens opportunities for improving many other SSEs. PMID:27570205

  5. Thermodynamic Calibration of Cr-Al Exchange Equilibria for Garnet and Spinel

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2009-12-01

    xMELTS is a new thermodynamic model of igneous phase equilibria (Ghiorso et al., 2007, Eos 88, V31C-0608) that extends MELTS (Ghiorso and Sack, 1995, CMP 119, 197-212) and pMELTS (Ghiorso et al., 2002, G3, 10.1029/2001GC000217) to a broader range of bulk compositions and to pressure and temperature conditions spanning from the shallow crust to the top of Earth’s lower mantle. To complete xMELTS, comprehensive garnet and pyroxene solid solution models that include Cr and other minor components must be developed. Garnet is an important phase involved in partial melting of the upper mantle because it controls partitioning of major and minor elements at pressures greater than 3 GPa. Chromium is a minor but significant component of mantle rocks as its presence increases the stability of spinel relative to plagioclase at low pressure and to garnet at high pressure. Thermodynamic models incorporating Cr into garnet solid solutions have been absent from the MELTS packages, motivating simulations for Cr-free bulk compositions and preventing accurate modeling of the spinel-garnet phase transition. The extension of the garnet model to include energetics of mixing on the Y-site is the first step in a planned calibration that will also include the majorite component needed for transition zone garnets. Initially, standard state properties and phase equilibria experiments for a Cr-bearing garnet endmember were compiled. Internally consistent thermodynamic properties of the endmember species were found by examination of reversal experiments on pure systems. We used the reversal experiments of Klemme (2004, Lithos 77, 639-646) to fix the enthalpy and entropy of knorringite (Mg3Cr2Si3O12), but were unable to fit the reversals using the standard state values given by Klemme and instead re-optimized these parameters. Although a Cr-bearing garnet model is included in the PERPLEX package (Connolly, 1990, AJS 290, 666-718; Connolly and Petrini, 2002, J.Met.Pet. 20, 697-708), the Y

  6. Solidus and liquidus temperatures and mineralogies for anhydrous garnet-lherzolite to 15 GPa

    NASA Technical Reports Server (NTRS)

    Herzberg, C. T.

    1983-01-01

    Strong convergence is noted, in experimental data for systems pertaining to anhydrous fertile garnet-lherzolite in the 6.5-15 GPa range, either to a common temperature or to temperatures differing by only about 100 C. The major element composition of magmas generated by even minor degrees of partial melting may be similar to the composition of the primordial, bulk silicate earth in an upper mantle stratigraphic column more than 160 km deep. Whether or not the solidus and liquidus intersect, the liquidus mineralogy for undepleted garnet-lherzolite compositions is found to change from olivine, at low pressures, to pyroxene, garnet, or a solid solution of both, at pressures greater than 10-15 GPa.

  7. A predictive thermodynamic model of garnet-melt trace element partitioning

    NASA Astrophysics Data System (ADS)

    Westrenen, Wim; Wood, Bernard; Blundy, Jonathan

    2001-08-01

    We have developed a predictive model for the partitioning of magnesium and a range of trivalent trace elements (rare earth elements, Y, In and Sc) between garnet and anhydrous silicate melt as a function of pressure, temperature and bulk composition. The model for the magnesium partition coefficient, DMg, is based on a thermodynamic description of the pyrope (Mg3Al2Si3O12) melting reaction between garnet and melt. Simple activity-composition relations, which take explicit account of garnet non-ideality, link DMg to the free energy of fusion (ΔGf) of pure pyrope without the need to invoke non-ideality in the liquid phase. The resulting predictive equation, based on the compositions of a large set (n=160) of published garnet-melt pairs, produces values of DMg that are within 20% of measured values at temperatures between 1,450 and 1,930 °C, and pressures between 2.5 and 7.5 GPa. The model for trivalent (3+) trace elements is based on the lattice strain approach to partitioning, which describes mineral-melt partition coefficients in terms of three parameters: the effective radius, r0(3+), of the site on which partitioning takes place (in this case, the garnet X-site); the apparent site Young's modulus EX(3+); and the partition coefficient D0(3+) for a fictive trivalent element J3+, with radius r0(3+), that does not strain the crystal lattice when entering the garnet X-site. Analogous to the model for DMg, simple activity-composition relations link D0(3+) to ΔGf of a hypothetical garnet component incorporating a hypothetical rare earth element J3+ through a YAG-type charge-balancing mechanism (J3+Mg2Al3Si2O12). Through analysis of existing garnet-melt rare earth element partitioning data (n=18 garnet-melt pairs), an expression is derived relating D0(3+) to pressure, temperature and DMg. Predicted DREE/Y/Sc values agree to within 5-50% of experimental measurements for all elements except La and Ce, which are liable to large experimental errors, spanning pressures

  8. Growth of garnet crystals for laser applications. Final report, 1 February-31 July 1984

    SciTech Connect

    Khattak, C.P.

    1984-08-01

    The objective of the Phase I effort was to establish feasibility of growth of Gd3Ga5O12(GGG) crystals as a precursor to growth of other garnet crystals, e.g. Gd35c2Ga3O12 (GSGG), for laser applications. Experimental work showed that Ga/sub 2/O/sub 3/ has a high vapor pressure and, therefore, it results in decomposition of GGG prior to meltdown. Introduction of oxygen into the furnace chamber to prevent decomposition was not feasible with existing graphite resistance-heated HEM furnaces. An alternative material in the Al-garnet family, Gd3Sc2Al3O12 (GSAG), was chosen. The higher stability of the melt suggests that low intrinsic defects containing larger crystals of GSAG can be grown as compared to GSGG. This new class of garnet-structured crystals offers potential for high-power, tunable, solid-state laser materials.

  9. Monomeric Garnet, a far-red fluorescent protein for live-cell STED imaging.

    PubMed

    Hense, Anika; Prunsche, Benedikt; Gao, Peng; Ishitsuka, Yuji; Nienhaus, Karin; Nienhaus, G Ulrich

    2015-12-09

    The advancement of far-red emitting variants of the green fluorescent protein (GFP) is crucially important for imaging live cells, tissues and organisms. Despite notable efforts, far-red marker proteins still need further optimization to match the performance of their green counterparts. Here we present mGarnet, a robust monomeric marker protein with far-red fluorescence peaking at 670 nm. Thanks to its large extinction coefficient of 95,000 M(-1)cm(-1), mGarnet can be efficiently excited with 640-nm light on the red edge of its 598-nm excitation band. A large Stokes shift allows essentially the entire fluorescence emission to be collected even with 640-nm excitation, counterbalancing the lower fluorescence quantum yield of mGarnet, 9.1%, that is typical of far-red FPs. We demonstrate an excellent performance as a live-cell fusion marker in STED microscopy, using 640 nm excitation and 780 nm depletion wavelengths.

  10. Fluorine-bearing grossular-rich garnet - an indicator for UHP - LT metamorphism of metagranitoids.

    NASA Astrophysics Data System (ADS)

    Burchard, M.

    2002-12-01

    Melting experiments on biotite-phengite-gneiss at pressures of 1.5 to 4.5 GPa and temperatures of 675°C to 1000°C were performed to clarify the phase assemblages of S-type metagranitoids at high pressures. The starting material used was S-type granitic biotite-phengite-gneiss, which represents the country rock for the pyrope-quarztites from the Dora-Maira-Massif, Western Italy. These pyrope-quarztites contain the silicate ellenbergerite, which, together with the growth of pyrope, indicates P and T of more than 3 GPa and 700°C. Experimental evidence confirms that the presence of ellenbergerite indicates high water activities. For this reason all experiments were performed with a water fraction of 1.9 to 9.9 wt.%. The most important phases in the run products are melt, K-feldspar / K-felspar-hydrate, coesite / quartz, phengite, jadeite-rich clinopyroxene, almandine-grossular garnet, epidote, rutile and sphene. At pressures between 3.5 and 4.5 GPa and T of less than 675°C or 775°C, respectively, small, rare crystals of grossular garnets were observed. These grs-rich garnets form corona structures around the alm-grs garnets of the starting material. EMP-analysis shows that these garnets contain up to 1.2 wt.% F at 700°C, decreasing with temperature to 0.4 wt.% at 750°C. A garnet analysis from a run at 4 GPa and 700°C yields 69% grossular, 8% hydrogrossular, 6% fluorgrossular, 6% almandine, 2% spessartine and 3% andradite. The coexistence of such garnets with sphene and epidote in HP experiments shows that the high-pressure reaction sph + zoi -> grs + coe + H2O suggested by Chopin et al (1991) is not relevant at these conditions. From Chopin et al (1991) and Schertl at al (1991) it is known that there are extremely rare inclusions of grs-rich garnet in plagioclase and alm-grs garnet in the original rock, but these authors unfortunately did not analyze the F content. During a reinvestigation of the biotite-phengite gneiss grs inclusions in sph were found that

  11. Garnet/high-silica rhyolite trace element partition coefficients measured by ion microprobe

    USGS Publications Warehouse

    Sisson, T.W.; Bacon, C.R.

    1992-01-01

    Garnet/liquid trace element partition coefficients have been measured in situ by ion microprobe in a rhyolite from Monache Mountain, California. Partition coefficients are reported for La, Ce, Nd, Sm, Dy, Er, Yb, Sc, Ti, V, Cr, Sr, Y, and Zr. The in situ analyses avoid the problem of contamination of the garnet phase by trace element-rich accessory minerals encountered in traditional bulk phenocryst/matrix partitioning studies. The partitioning pattern for the rare earth elements (REEs, excluding Eu) is smooth and rises steeply from the light to the heavy REEs with no sharp kinks or changes in slope, unlike patterns for garnet /silicic liquid REE partitioning determined by bulk methods. This difference suggests that the previous determinations by bulk methods are in error, having suffered from contamination of the phenocryst separates. ?? 1992.

  12. Characteristics of Polycrystalline Garnets in Micaschists From the Southern Menderes Massif (Turkey) and the Solitude Range (BC, Canada)

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Whitney, D. L.; Seaton, N.

    2008-12-01

    Electron backscatter diffraction (EBSD) analysis of garnets in metamorphic rocks has revealed the presence of grain boundaries within what appear, based on morphology, to be single crystals. There have only been a few previous studies that have described these types of polycrystals in nature. In this study we analyzed garnets from two suites of metamorphic rocks: kyanite-staurolite schist from the Solitude Range, SW Rocky Mountains (BC, Canada), and mica schist from the southern Menderes Massif (western Turkey). Garnets from both sites are growth zoned and formed during a single metamorphic event, although the Solitude Range garnets record in their zoning and inclusion textures a change from chloritoid-present to staurolite- present (chloritoid-out) reaction history. The garnet-bearing rocks from these sites formed at P-T conditions of 430-550 C, 7-8 kbar (Menderes) and 550-600 C, 6-7 kbar (BC). Less than 10% of the garnets analyzed are polycrystals, but all polycrystals detected have similar characteristics: high-angle misorientation boundaries that crosscut inclusions and inclusion trails. Most polycrystals have 2-3 domains (crystals), but one complex polycrystal was comprised of 16 distinct lattice domains. In most cases, misorientation boundaries crosscut growth zoning, but one Menderes polycrystal exhibited distinct zoning in each domain. Most polycrystals likely formed early in the garnet growth history as closely-spaced nuclei coalesced, but clustering (coalescence) continued throughout the history of garnet crystallization in these rocks.

  13. U-Pb dating of garnets in Paleozoic leucogranites, southwestern New England Appalachians

    SciTech Connect

    Sevigny, J.H.; Hanson, G.N. . Dept. of Earth and Space Sciences)

    1992-01-01

    U-Pb dating of zircon and monazite is generally the most effective method of precisely dating crystallization in granitic rocks. It is, however, often difficult to precisely date leucogranites using these minerals because of persistent inheritance in zircon and complicated U-Pb systematics in some monazites. Garnet, a common igneous mineral in leucogranites, has a closure temperature greater than 800 C and has been shown to yield precise U-Pb ages in metamorphic rocks. The utility of U-Pb dating of garnet in leucogranites was evaluated in two samples of Acadian leucogranites with euhedral garnet phenocrysts. These leucogranites are exposed in the Bridgeport synform in southwestern Connecticut. Zircons from both samples have significant inheritance making precise age determinations difficult. A garnet separate from the Shelton muscovite granite yields a concordant age of 380 [+-] 3 Ma, in agreement with U-Pb monazite ages for the sample. A garnet separate from a transported dike of muscovite granite yields a concordant age of 390 [+-] 4 Ma. This dike lacks monazite. These results in combination with U-Pb ages for other leucogranites and metapelitic units in the area show that leucogranites were generated during and toward the end of Acadian metamorphism in southwestern Connecticut. The authors developed procedures to purify Pb and U and to eliminate discordance during sample preparation. The garnets contain 2.35--2.64 ppm U and 0.146--0.157 ppm radiogenic Pb of which 5.1--10.9% is radiogenic Pb-208. Measured Pb-206/Pb-204 ratios vary from 101--113. Thus, initial Pb correction using leached K-feldspars is advised. Blank corrected U-238/P-204 ratios are 1560--2076.

  14. High-pressure and high-temperature studies on oxide garnets

    SciTech Connect

    Hua, H.; Mirov, S.; Vohra, Y.K.

    1996-09-01

    We report high-pressure and high-temperature studies on a series of oxide garnets of chemical composition {ital A}{sub 3}{ital B}{sub 2}{ital C}{sub 3}O{sub 12}. The members of this family investigated are gadolinium scandium gallium garnet (GSGG), gadolinium gallium garnet (GGG), and yttrium aluminum garnet (YAG). The GSGG and GGG are doped with both neodymium and chromium while the YAG is doped only with neodymium. Photoluminescence, synchrotron x-ray-diffraction, and laser heating studies were carried out in a diamond-anvil cell. Variety of optical sensors (ruby, Sm-doped YAG) and x-ray pressure marker (copper) were employed for pressure measurement. Pressure-induced amorphization was observed in GSGG at 58{plus_minus}3 GPa and GGG at 84{plus_minus}4 GPa by x-ray-diffraction studies. The photoluminescence studies show only gradual broadening of emission bands through the amorphization transition. On increasing pressure beyond amorphization, very broad and featureless emission bands were observed in the fluorescence spectra at 77{plus_minus}2 GPa for GSGG and at 88{plus_minus}2 GPa for GGG. Laser heating of the pressure-induced amorphous phase in GSGG caused recrystallization to the stable cubic phase. High-pressure x-ray study on YAG shows that it retains cubic phase up to 101{plus_minus}4 GPa. A pressure-volume relation for each member of the oxide garnet at ambient temperatures is presented, structural transformation mechanisms, and application of oxide garnets as pressure sensors are also discussed. {copyright} {ital 1996 The American Physical Society.}

  15. Thermo-compression of pyrope-grossular garnet solid solutions: non-linear compositional dependence

    NASA Astrophysics Data System (ADS)

    Clark, S. M.; Du, W.; Walker, D.

    2014-12-01

    Unit cell parameters of a series of synthetic garnets with the pyrope, grossular, and four intermediate compositions were measured up to about 900K and to 10 GPa using synchrotron X-ray powder diffraction. Coefficients of thermal expansion of pyrope-grossular garnets are in the range 2.10~ 2.74 x 10-5 K-1 and uniformly increase with temperature. Values for the two end members pyrope and grossular are identical within experimental error 2.74±0.05 x 10-5 K-1 and 2.73±0.01 x 10-5 K-1 respectively. Coefficients of thermal expansion for intermediate compositions are smaller than those of end members, and are not linearly dependent on composition. Bulk modulus of grossular is Κ0=164.3(1) GPa (with Κ0' the pressure derivative of the bulk modulus fixed to 5.92) and bulk modulus of pyrope is Κ0=169.2(2) GPa (with Κ0' fixed to 4.4) using a third order Birch-Murnaghan equation of state, which are consistent with previously reported values. The bulk moduli of garnets of intermediate composition are between ~155 and ~160 GPa, smaller than those of the end-members no matter which Κ0' is chosen. The compositional dependence of bulk modulus resembles the compositional dependence of thermal expansion. Intermediate garnets on this binary have large positive excess volume, which makes them more compressible. We find that excess volumes in the pyrope-grossular series remain relatively large even at high pressure (~6GPa) and temperature (~800K), supporting the observation of crystal exsolution on this garnet join. (Ref: Wei Du, Simon Martin Clark, and David Walker (2014) Thermo-compression of pyrope-grossular garnet solid solutions:non-linear compositional dependence. American Mineralogist, In Press).

  16. The Behaviour of Garnet and Accessory-Phase Paragenesis in Metapelites From the Black Hills, South Dakota

    NASA Astrophysics Data System (ADS)

    Yang, P.; Pattison, D.

    2004-05-01

    We have examined petrographic textures, occurrence, chemical zoning of garnet, monazite and apatite, and electron microprobe ages of monazite in pelitic schists from Black Hills, South Dakota. Early Proterozoic metasedimentary rocks, deformed and regionally metamorphosed at 1.76 Ga, were uplifted for several kilometers (Holm et al., Tectonics, 1997) prior to the post-tectonic intrusion of the 1.71 Ga Harney Peak Granite. Contact metamorphism reached the second sillimanite isograd, at a pressure between 3.5 and 4.5 kbar. In staurolite zone garnet porphyroblasts included in staurolite and those in matrix have euhedral crystal outlines and display continuous Mn zoning profiles, suggesting that garnet was not consumed during the growth of staurolite. Some garnet porphyroblasts in the staurolite and sillimanite zones show euhedral Y-annuli which are not correlated with major elements and are thought to reflect growth rather than resorption processes. YAG-xenotime temperature estimates for xenotime-bearing garnet cores ranges from 450 to 490" C. Zoning patterns of monazite from garnet to sillimanite zones are similar. The monazite contains two compositionally distinct zones: Th-rich (up to 13 wt%) cores and Y-rich (up to 1.7 wt%) rims. Monazite-xenotime solvus thermometry yields temperature estimates of 504-530" C for the monazite rims from garnet to sillimanite zone, suggesting that the monazite in all the metamorphic zones grew during early garnet growth and did not continue to grow thereafter. Electron microprobe ages of Y-rich monazite rims are similar to that of the granite intrusion and are interpreted to date the growth of garnet cores equilibrated with xenotime. Apatite is present in all rocks and contains high-Y cores with Y-depleted rims which thicken as metamorphic grade increases. Oscillatory high-Y cores in apatite appear to be detrital but homogeneous euhedral ones are interpreted to be in equilibrium with xenotime. Y and Mn zoning patterns in Y

  17. Far-infrared spectra of dysprosium doped yttrium aluminum garnet nanopowder

    NASA Astrophysics Data System (ADS)

    Trajić, J.; Rabasović, M. S.; Savić-Šević, S.; Ševic, D.; Babić, B.; Romčević, M.; Ristić-Djurović, J. L.; Paunović, N.; Križan, J.; Romčević, N.

    2016-07-01

    The solution combustion synthesis was used to prepare nanopowders of yttrium aluminum garnet (YAG) and YAG doped with dysprosium ions, Dy3+, (YAG:Dy). The morphology, specific surface area, texture, and optical properties of the prepared materials were studied by the means of scanning electron microscopy (SEM), nitrogen adsorption method, and far-infrared spectroscopy at room temperature in the spectral region between 80 and 600 cm-1. It was established that all the examined samples were microporous. The Maxwell-Garnet formula was used to model dielectric function of YAG and YAG:Dy nanopowders as mixtures of homogenous spherical inclusions in air.

  18. High P-T Elastic Properties of OH-Bearing Majoritic Garnet

    NASA Astrophysics Data System (ADS)

    Lazarz, J. D.; Thomas, S. M.; Tkachev, S. N.; Townsend, J. P.; Bina, C. R.; Jacobsen, S. D.

    2014-12-01

    The mantle transition zone (TZ) is believed to be primarily composed of three constituents: wadsleyite, ringwoodite, and majorite garnet (Ringwood, 1975). Laboratory sound velocity measurements for wadsleyite and ringwoodite alone are too high to match TZ seismological models (Li et al., Science, 1998; Sinogeikin et al., JGR, 1998), while majorite yields significantly lower sound velocities (Sinogeikin et al., GRL, 2002; Gwanmesia et al., PEPI, 2009). Taken together, a compositional model such as pyrolite yields a good fit to seismology within uncertainties, with the major discrepancies being that pyrolite yields slightly larger velocity jumps and shallower velocity gradients than seismology (Li and Liebermann, Science, 2007; Irifune et al., Nature, 2008). Hydration of ringwoodite in the transition zone is expected to reduce seismic velocities. If the lower part of the TZ is hydrated, as some recent studies suggest (Pearson et al., Nature, 2014; Schmandt et al., Science, 2014), the proportions of ringwoodite and majoritic garnet in the TZ should be re-evaluated. Velocity gradients in the TZ are likely related to the gradual eclogite-garnetite transition. Over the TZ pressure range (~13-24 GPa), the dissolution of pyroxene into garnet gradually increases, resulting in a complex depth-varying garnet-majorite solid solution, ranging from M4Si4O12 majorite (Mj) to M3Al2Si3O12 garnet (Gt), where M is Mg, Fe, Ca0.5Mg0.5, etc. (Akaogi and Akimoto, PEPI, 1977; Bina and Wood, GRL, 1984; Gasparik, CMP, 1989). Several studies have considered the compositional dependence of majoritic garnet elastic moduli (Liu et al., PEPI, 2000; Sinogeikin et al., EPSL, 2002; Sinogeikin and Bass, GRL, 2002; Murakami et al., EPSL, 2008), but few have considered both composition and hydration state under the high-pressure and high-temperature conditions of the TZ. Here we combine in situ X-ray and Brillouin measurements to determine the elastic constants of various majoritic garnet compositions

  19. Garnet shapes within Kimberlite xenoliths record the tectonic evolution of a cratonic root

    NASA Astrophysics Data System (ADS)

    Michibayashi, K.; Kino, M.; Okamoto, A.; Katayama, I.; Komiya, T.

    2013-12-01

    Interfacial tension and differential stress affect the shape of a mineral grain included within a crystalline host. On this basis, we present a simple numerical model that successfully predicts the progressive change in aspect ratio (L) of garnet inclusions with respect to grain size (R) within peridotite xenoliths, Kimberley, South Africa, over a period of more than 1 billion years. We focused on coarse (>5 mm) granular type peridotite. Five large samples of garnet harzburgite xenoliths were selected for analysis from 35 samples because of the large grain size, and several thin sections were prepared from each sample in each of three orthogonal planes (e.g., parallel to the foliation and lineation, etc.) The calculated equilibrium temperature and pressure are similar among all five samples (~1000 degree C and ~40 kbar). Olivine fabrics are characterized by a point maximum of [010] and girdle distributions of [100] and [001]. Orthopyroxene fabrics are characterized by a point maximum of [001] and girdle distributions of [100] and [001]. Garnet within the five samples varies in both size and shape. Coarser garnet grains (R>=2mm) tend to be more spherical, whereas smaller grains (R<2mm) tend to be spherical and ellipsoidal. Three deformation mechanisms are considered to explain the shape of garnet in the numerical model following to Okamoto and Michibayashi (2005): dislocation creep, interface diffusion creep, and rounding by interface diffusion. The model reveals that the dominant deformation mechanism changes from diffusion creep to dislocation creep with increasing grain size and a two-stage deformation, with a period of high differential stress followed by low differential stress, best explains the observed shapes and grain sizes of garnet. The duration of stage 1 is calculated to have been 10 million years, assuming a temperature of 1000 degree C and a differential stress of 0.1 MPa which was related to the size independency of dislocation creep. The garnet data

  20. Potential for diamond in kimberlites from Michigan and Montana as indicated by garnet xenocryst compositions

    USGS Publications Warehouse

    McGee, E.S.

    1988-01-01

    The Williams kimberlite in north-central Montana and the Lake Ellen kimberlite in northern Michigan contain diagnostic xenoliths and xenocrysts which indicate that diamonds may be present. To date, however, no diamonds have been reported from either locality. In this study, particular compositions of garnet xenocrysts which are associated with diamond elsewhere were sought as an indication of the potential for diamond in the Williams and Lake Ellen kimberlites. For this study, garnets were carefully selected for purple color in order to increase the chance of finding the subcalcic chrome-rich compositions that are associated with the presence of diamond. -Author

  1. Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

    PubMed

    Maeda, Y

    1994-01-10

    Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

  2. Effect of Titanium on REE and HFSE Partitioning Between Garnet and Melt

    NASA Astrophysics Data System (ADS)

    Dwarzski, R. E.; Draper, D. S.

    2004-12-01

    Garnet is a strong fractionator of trace elements and plays an important role in the petrogenetic history of planetary interiors at high pressure. In order to model petrogenetic processes that operate within terrestrial planets accurately, it is important to understand how garnet partitions rare earth and high field strength elements. Here we assess the influence of Ti on garnet-melt trace element partitioning with a view both to constrain important crystal-chemical effects and to evaluate possible roles for garnet in lunar petrogenesis. Experiments were performed at ˜5 GPa and 1650-1675° C in a Walker-style multi-anvil high pressure apparatus using an Apollo 14 black picritic glass composition ( ˜17 wt% TiO2) to assess the effect of Ti on garnet partitioning. These experiments were also designed to examine the possible presence of garnet in mare source regions. Experimental charges were analyzed for major and trace elements by EPMA and SIMS, respectively. D-values measured in this study using the Apollo 14 black Ti-rich composition are consistently higher than those measured by Draper et al. (2004, LPSC XXXV:1297), who used Apollo 15 green C glass (<0.5 wt% TiO2). D vs. ionic radii are well-described for the trivalent cations by the lattice-strain partitioning model of Blundy and Wood (1994, Nature 372:452), with D0 = 2.27 ± 0.40, E = 159 ± 58 GPa, and r0 = 0.879 ± 0.044 Å (r2 = 0.957). For comparison, this model applied to the low-Ti experiments of Draper et al. (2004) yields D0 = 2.93 ± 0.25, E = 572 ± 40 GPa, and r0 = 0.926 ± 0.005 Å (r2 = 0.996) at ˜3.5 GPa. Both these fits show significant mismatch to the partitioning predicted by the formulations of van Westrenen et al. (2001, CMP 142:219), as previously shown for Fe-rich systems by Draper et al. (2003, PEPI 139:149). Use of our D-values (for rare earth and high field strength elements in batch-melting models) provisionally supports the hypotheses of Neal (2001, JGR 106:27865) and Neal and

  3. Preparation of polycrystalline Bi3Fe5O12 garnet films

    NASA Astrophysics Data System (ADS)

    Okuda, T.; Katayama, T.; Satoh, K.; Yamamoto, H.

    1991-04-01

    Polycrystalline films of nonthermodynamical garnet Bi3Fe5O12 were synthesized by direct epitaxial growth from the vapor phase. Polycrystalline thin layers of various kinds of thermodynamical garnets prepared on fused quartz substrates were employed as the substrate materials. The saturation magnetization of the film grown onto the polycrystalline GGG layer was 140 mT at 5 K. The films showed quite large magneto-optical effects. In the film on the GGG layer, the Faraday rotation angle at a wavelength of 633 nm was -5.5 deg/μm and the magneto-optical Kerr rotation angle at 455 nm was -0.9°.

  4. Rare-Earth Garnets and Perovskites for Space-Based ADR Cooling at High T and Low H

    NASA Technical Reports Server (NTRS)

    King, T. T.; Rowlett, B. A.; Ramirez, R. A.; Shirron, P. J.; Canavan, E. R.; DiPirro, M. J.; Panek, J. S.; Tuttle, J. G.; Shull, R. D.; Fry, R. A.; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    Future NASA satellite detector systems must be cooled to the 0.1 K temperature range to meet the stringent energy resolution and sensitivity requirements demanded by mid-term astronomy missions. The development of adiabatic demagnetization refrigeration (ADR) materials that can efficiently cool from the passive radiative cooling limit of approx. 30 K down to sub-Kelvin under low magnetic fields (H less than or equal to 3 T) would represent a significant improvement in space-based cooling technology. Governed by these engineering goals, our efforts have focused on quantifying the change in magnetic entropy of rare-earth garnets and perovskites. Various compositions within the gadolinium gallium iron garnet solid solution series (GGIG, Gd3Ga(5-x)Fe(x)O12, 0.00 less than or equal to X less than or equal to 5.00) and gadolinium aluminum perovskite (GAP, GdAlO3) have been synthesized via an organometallic complex approach and confirmed with powder x-ray diffraction. The magnetization of the GGIG and GAP materials has been measured as a function of composition (0.00 less than or equal to X less than or equal to 5.00), temperature (2 K less than or equal to T less than or equal to 30 K) and applied magnetic field (0 T less than or equal to H less than or equal to 3 T). The magnetic entropy change (DeltaS(sub mag)) between 0 T and 3 T was determined from the magnetization data. In the GGIG system, DeltaS(sub mag) was compositionally dependent; Fe(sup 3+) additions up to X less than or equal to 2.44 increased DeltaS(sub mag) at T > 5 K. For GAP, DeltaS(sub mag) was similar to that of GGIG, X = 0.00, both in terms of magnitude and temperature dependence at T > 10 K. However, the DeltaS(sub mag) of GAP at T < 10 K was less than the endmember GGIG composition, X = 0.00, and exhibited maximum approx. 5 K.

  5. Excited state dynamics of thulium ions in yttrium aluminum garnets

    NASA Technical Reports Server (NTRS)

    Armagan, G.; Buoncristiani, A. M.; Dibartolo, B.

    1991-01-01

    The processes that take place in the excited states of a trivalent Thulium (Tm) ion in an Yttrium Aluminum Garnet (YAG) crystal, being relevant to the use of this system for laser applications, have been the object of several studies. We have reexamined this system focusing our attention on the dynamics of Tm following its excitation in the H-3(sub 4) level. Under these conditions the system relaxes through a cross-relaxation process. H-3(sub 4) yields F-3(sub 4), H-3(sub 6) yields F-3(sub 4), whose rate depends upon both the concentration of the Tm ion and the temperature of the crystal. The excitation spectrum obtained by monitoring the 1.8 micron emission of Tm (due to the F-3(sub 4) yields H-3(sub 6) transition) indicates an increase in the contribution to this emission from the H-3(sub 4) level relative to the H-3(sub 5) level as the Tm concentration increases; this shows the increased role played by the H-3(sub 4) level in pumping the infrared emission. Correspondingly, the duration of the luminescence originating in the H-3(sub 4) level is shortened as the concentration of Tm increases. The concentration quenching of this lifetime can be fit to a model which assumes that the cross-relaxation is due to a dipole-dipole interaction; from this fit, the intrinsic Tm lifetime in the absence of cross relaxation can be derived. We have used this lifetime to calculate the rate of the cross-relaxation process. We have evaluated this rate as a function of the temperature and found it to be fastest at 77 K. We have also calculated the microscopic interaction parameters for the cross-relaxation process by using two independent experimental features: (1) the time evolution of the emission from the H-3(sub 4) level; and (2) the spectral overlap between the H-3(sub 4) yields F-3(sub 4) emission and the H-3(sub 6) yields F-3(sub 4) absorption. We have also considered the migration of excitation among the Tm ions in the F-3(sub 4) level and calculated the relevant

  6. Garnet cannibalism provides clues to extensive hydration of lower crustal fragments in a subduction channel (Sesia Zone, Northwestern Alps)

    NASA Astrophysics Data System (ADS)

    Giuntoli, Francesco; Lanari, Pierre; Engi, Martin

    2015-04-01

    The extent to which granulites are transformed to eclogites is thought to impose critical limits on the subduction of continental lower crust. Although it is seldom possible to document such densification processes in detail, the transformation is believed to depend on fluid access and deformation. Remarkably complex garnet porphyroblasts are widespread in eclogite facies micaschists in central parts of the Sesia Zone (Western Italian Alps). They occur in polydeformed samples in assemblages involving phengite+quartz+rutile ±paragonite, Na-amphibole, Na-pyroxene, chloritoid. Detailed study of textural and compositional types reveals a rich inventory of growth and partial resorption zones in garnet. These reflect several stages of the polycyclic metamorphic evolution. A most critical observation is that the relict garnet cores indicate growth at 900 °C and 0.9 GPa. This part of the Eclogitic Micaschist Complex thus derived from granulite facies metapelites of Permian age. These dry rocks must have been extensively hydrated during Cretaceous subduction, and garnet records the conditions of these processes. Garnet from micaschist containing rutile, epidote, paragonite and phengite were investigated in detail. Two types of garnet crystals are found in many thin sections: mm-size porphyroclasts and smaller atoll garnets, some 100 µm in diameter. X-ray maps of the porphyroclasts show complex zoning in garnet: a late Paleozoic HT-LP porphyroclastic core is overgrown by several layers of HP-LT Alpine garnet, these show evidence of growth at the expense of earlier garnet generations. Textures indicate 1-2 stages of resorption, with garnet cores that were fractured and then sealed by garnet veins, rimmed by multiple Alpine overgrowth rims with lobate edges. Garnet rim 1 forms peninsula and embayment structures at the expense of the core. Rim 2 surrounds rim 1, both internally and externally, and seems to have grown mainly at the expense of the core. Rim 3 grew mainly at

  7. METABOLISM OF IRON STORES

    PubMed Central

    SAITO, HIROSHI

    2014-01-01

    ABSTRACT Remarkable progress was recently achieved in the studies on molecular regulators of iron metabolism. Among the main regulators, storage iron, iron absorption, erythropoiesis and hepcidin interact in keeping iron homeostasis. Diseases with gene-mutations resulting in iron overload, iron deficiency, and local iron deposition have been introduced in relation to the regulators of storage iron metabolism. On the other hand, the research on storage iron metabolism has not advanced since the pioneering research by Shoden in 1953. However, we recently developed a new method for determining ferritin iron and hemosiderin iron by computer-assisted serum ferritin kinetics. Serum ferritin increase or decrease curves were measured in patients with normal storage iron levels (chronic hepatitis C and iron deficiency anemia treated by intravenous iron injection), and iron overload (hereditary hemochromatosis and transfusion dependent anemia). We thereby confirmed the existence of two iron pathways where iron flows followed the numbered order (1) labile iron, (2) ferritin and (3) hemosiderin in iron deposition and mobilization among many previously proposed but mostly unproven routes. We also demonstrated the increasing and decreasing phases of ferritin iron and hemosiderin iron in iron deposition and mobilization. The author first demonstrated here the change in proportion between pre-existing ferritin iron and new ferritin iron synthesized by removing iron from hemosiderin in the course of iron removal. In addition, the author disclosed the cause of underestimation of storage iron turnover rate which had been reported by previous investigators in estimating storage iron turnover rate of normal subjects. PMID:25741033

  8. Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia

    USGS Publications Warehouse

    Nesheim, T.O.; Vervoort, J.D.; McClelland, W.C.; Gilotti, J.A.; Lang, H.M.

    2012-01-01

    Northern Idaho contains Belt-Purcell Supergroup equivalent metamorphic tectonites that underwent two regional deformational and metamorphic events during the Mesoproterozoic. Garnet-bearing pelitic schists from the Snow Peak area of northern Idaho yield Lu-Hf garnet-whole rock ages of 1085??2. Ma, 1198??79. Ma, 1207??8. Ma, 1255??28. Ma, and 1314??2. Ma. Garnet from one sample, collected from the Clarkia area, was micro-drilled to obtain separate core and rim material that produced ages of 1347??10. Ma and 1102??47. Ma. The core versus rim ages from the micro-drilled sample along with the textural and spatial evidence of the other Lu-Hf garnet ages indicate two metamorphic garnet growth events at ~. 1330. Ma (M1) and ~. 1080. Ma (M2) with the intermediate ages representing mixed ages. Some garnet likely nucleated and grew M1 garnet cores that were later overgrown by younger M2 garnet rims. Most garnet throughout the Clarkia and Snow Peak areas are syntectonic with a regional penetrative deformational fabric, preserved as a strong preferred orientation of metamorphic matrix minerals (e.g., muscovite and biotite). The syntectonic garnets are interpreted to represent one regional, coeval metamorphic and deformation event at ~. 1080. Ma, which overlaps in time with the Grenville Orogeny. The older ~. 1330. Ma ages may represent an extension of the East Kootenay Orogeny described in western Canada. These deformational and metamorphic events indicate that western Laurentia (North America) was tectonically active in the Mesoproterozoic and during the assembly of the supercontinent Rodinia. ?? 2011 Elsevier B.V.

  9. Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia

    NASA Astrophysics Data System (ADS)

    Nesheim, Timothy O.; Vervoort, Jeffrey D.; McClelland, William C.; Gilotti, Jane A.; Lang, Helen M.

    2012-03-01

    Northern Idaho contains Belt-Purcell Supergroup equivalent metamorphic tectonites that underwent two regional deformational and metamorphic events during the Mesoproterozoic. Garnet-bearing pelitic schists from the Snow Peak area of northern Idaho yield Lu-Hf garnet-whole rock ages of 1085 ± 2 Ma, 1198 ± 79 Ma, 1207 ± 8 Ma, 1255 ± 28 Ma, and 1314 ± 2 Ma. Garnet from one sample, collected from the Clarkia area, was micro-drilled to obtain separate core and rim material that produced ages of 1347 ± 10 Ma and 1102 ± 47 Ma. The core versus rim ages from the micro-drilled sample along with the textural and spatial evidence of the other Lu-Hf garnet ages indicate two metamorphic garnet growth events at ~ 1330 Ma (M1) and ~ 1080 Ma (M2) with the intermediate ages representing mixed ages. Some garnet likely nucleated and grew M1 garnet cores that were later overgrown by younger M2 garnet rims. Most garnet throughout the Clarkia and Snow Peak areas are syntectonic with a regional penetrative deformational fabric, preserved as a strong preferred orientation of metamorphic matrix minerals (e.g., muscovite and biotite). The syntectonic garnets are interpreted to represent one regional, coeval metamorphic and deformation event at ~ 1080 Ma, which overlaps in time with the Grenville Orogeny. The older ~ 1330 Ma ages may represent an extension of the East Kootenay Orogeny described in western Canada. These deformational and metamorphic events indicate that western Laurentia (North America) was tectonically active in the Mesoproterozoic and during the assembly of the supercontinent Rodinia.

  10. Multistage metasomatism in lithospheric mantle beneath V. Grib pipe (Arkhangelsk diamondiferous province, Russia): evidence from REE patterns in garnet xenocrysts.

    NASA Astrophysics Data System (ADS)

    Shchukina, Elena; Alexei, Agashev; Nikolai, Pokhilenko

    2015-04-01

    150 garnet xenocrysts from V. Grib kimberlite pipe were analyzed for major and trace elements compositions. 70 % of garnet belong to lherzolite field; 14 % - megacrysts and pyroxenites; 11 % - eclogites; 4 % - harzburgite; 1 % (1- wehrlite defined by Sobolev (1973). Harzburgite garnets: sinusoidal REE patterns Smn/Ern > 5 (5.2 - 19.8). low Y (0.5 - 3.9 ppm), Zr (1.1 - 44.6 ppm), Ti (54 - 1322 ppm). Wehrlite garnetd: close to sinusoidal REE patterns, Smn/Ern - 1.8. Megacrysts and pyroxenites garnets: normal REE patterns Smn/Ern < 1 (0.2 - 0.6), high TiO2 (0.9 - 1.3 wt %). Lherzolite garnets 70 % show four groups of REE patterns similar to peridotite xenoliths (Shchukina et al., 2013, 2015). 1-st contains MREE at С1 level, Sm/Ern - 0.03, La/Ybn - 0.002. increasing La -Yb range, low Y, Zr, Ti indicating residual nature. 2-nd: MREE at 2 - 13 chondrite units, Smn/Ern (0.16 - 0.98), La/Ybn - 0.001 - 0.040 and flat pattern from MREE to HREE. 3-rd -MREE at 5 - 14 chondrite units, Sm/Ern > 1 (1.05 - 4.81) La/Ybn - 0.010-0.051 increasing an hump at MREE decreasing to HREE. 4-th: sinusoidal REE, Sm/Ern 4.2 - 27.2. and harzburgite Y, Zr, Ti . Average Cr2O3 content increases from 2-nd to the 3-rd group (3.3 to 5.7 wt%) and 4th (7.9 wt %). Average Y/Zr decreases from 2-nd (0.6) to 3rd (0.2) and 4th group (0.08). REE and Y, Zr, Ti indicate the metasomatic origin of garnets of 2, 3. 4 groups. Modeling of TREfor equilibrated melts and fractional crystallization 2nd group close to Turyino field basalts and 3-rd - to Izmozero field picrites of Arkhangelsk diamondiferous province (ADP). Basing on geochemical data of garnet xenocrysts and garnets and clinopyroxenes in peridotites (Shchukina et al., 2013, 2015) we suppose at least 3 stage of high-temperature metasomatic enrichment. 1st stage - is enrichment of residual garnets (found only in peridotite garnets) in LREE by the influence of carbonatite melt close to the Mela field carbonatites of ADP. REE patterns in clinopyroxenes from

  11. Garnet-bearing ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high pressure oceanic complex?

    NASA Astrophysics Data System (ADS)

    Gazel, Esteban; Abbott, Richard N.; Draper, Grenville

    2011-07-01

    Ultra high pressure (UHP) garnet-bearing ultramafic rocks from the Dominican Republic may represent the only known example where such rocks were exhumed at an ocean-ocean convergent plate boundary, and where the protolith crystallized from a UHP magma (> 3.2 GPa, > 1500 °C). This study focuses on the petrology and geochemistry of one of the ultramafic lithologies, the pegmatitic garnet-clinopyroxenite (garnet + clinopyroxene + spinel + corundum + hornblende). Three distinct types of garnet were recognized: Type-1 garnet (low Ca, high Mg) is interpreted as near magmatic (P > 3.2 GPa, > 1500 °C). Type-1‧ garnet (high Ca, low Mg) is interpreted as having formed approximately isochemically from magmatic high-Al clinopyroxene. Type-2 garnet (intermediate Ca, high Mg, and low Fe + Mn) formed together with hornblende as a result of late, low-pressure retrograde hydration. Clinopyroxene is close to diopside-hedenbergite (Mg# ~ 88) and metasomatized by arc-related fluids. Spinel and corundum occur as microinclusions in type-1 and type-1‧ garnets in the only reported natural occurrence of coexisting garnet + spinel + corundum, indicative of very high pressure. Chondrite-normalized REEs (rare earth elements) of the garnets show humped or weakly sinusoidal patterns, typically associated with garnet inclusions in diamond and garnet in kimberlite that crystallized at UHP conditions. These humped to weakly sinusoidal REE patterns developed as the result of interaction with a light REE-enriched metasomatic fluid. Partitioning of REEs between type-1‧ and type-1 garnets is consistent with the former having inherited its REEs from a high-Al clinopyroxene predecessor. The partitioning preserves a record of near-solidus temperatures (~ 1475 °C). Petrology and phase relationships independently suggest near-solidus conditions > 1500 °C (the highest temperature conditions reported in a UHP orogenic setting), providing evidence for an origin in a mantle plume. Therefore, the

  12. Exsolution kinetics of majoritic garnet from clinopyroxene in subducting oceanic crust

    NASA Astrophysics Data System (ADS)

    Nishi, Masayuki; Kubo, Tomoaki; Kato, Takumi; Tominaga, Aiko; Funakoshi, Ken-ichi; Higo, Yuji

    2011-11-01

    Mechanisms and kinetics of exsolution of majoritic garnet from Ca-Tschermak-rich clinopyroxene were examined at 14.0-15.6 GPa, 1250-1590 °C, and H 2O-undersaturated conditions (800-1170 wt. ppm H 2O) by time-resolved in situ synchrotron X-ray diffraction measurements. Textural observations of recovered samples revealed that majoritic garnet had exsolved along the grain boundaries of parent clinopyroxene. Analyses of the kinetic data obtained indicate that exsolved majoritic garnet grew by diffusion-controlled growth, and the growth kinetics can be described by k2 (m 2/s) = 7.4 × 10 -5 exp[-389(kJ mol -1)/ RT]. The exsolution of majoritic garnet from clinopyroxene would be kinetically inhibited at temperatures below ˜800 °C in geological time scales (10 5-10 6 years) when the parent grain size is larger than 1 mm. We constructed possible phase relations of subducting mid-ocean ridge basalt (MORB) taking the exsolution kinetics into consideration. When the effect of reaction kinetics is considered, the density contrast between the MORB component of a subducting slab and surrounding mantle becomes significantly reduced relative to that calculated for the equilibrium MORB assemblage.

  13. Late Cretaceous UHP metamorphism recorded in kyanite-garnet schists from the Central Rhodope Mountains, Bulgaria

    NASA Astrophysics Data System (ADS)

    Collings, David; Savov, Ivan; Maneiro, Kathryn; Baxter, Ethan; Harvey, Jason; Dimitrov, Iliya

    2016-03-01

    In this study, we report the first discovery of microdiamond inclusions in kyanite-garnet schists from the Central Rhodope Mountains in Bulgaria. These inclusions occur in garnets from metapelites that are part of a meta-igneous and meta-sedimentary mélange hosted by Variscan (Hercynian) orthogneiss. Ultra-high-pressure (UHP) conditions are further supported by the presence of exsolved needles of quartz and rutile in the garnet and by geothermobarometry estimates that suggest peak metamorphic temperatures of 750-800 °C and pressures in excess of 4 GPa. The discovery of UHP conditions in the Central Rhodopes of Bulgaria compliments the well-documented evidence for such conditions in the southernmost (Greek) part of the Rhodope Massif. Dating of garnets from these UHP metapelites (Chepelare Shear Zone) using Sm-Nd geochronology indicates a Late Cretaceous age (70.5-92.7 Ma) for the UHP metamorphic event. This is significantly younger than previously reported ages and suggests that the UHP conditions are associated with the Late Mesozoic subduction of the Vardar Ocean northward beneath the Moesian platform (Europe). The present-day structure of the RM is the result of a series of subduction-exhumation events that span the Cenozoic, alongside subsequent post-orogenic extension and metamorphic core complex formation.

  14. COMPARATIVE EVALUATION OF R3f GARNET BEAD FILTRATION AND MULTIMEDIA FILTRATION SYSTEMS; FINAL REPORT

    EPA Science Inventory

    This report summarizes the results of tests conducted to date at the EPA T&E Facility on the R3f filtration system utilizing fine beads (such as garnet beads or glass beads) and a conventional multimedia filtration system. Both systems have been designed and built by Enprotec, a...

  15. Single and multiphase inclusions in metapelitic garnets of the Rhodope Metamorphic Province, NE Greece.

    PubMed

    Mposkos, Evripidis; Perraki, Maria; Palikari, Sarra

    2009-08-01

    Single and multiphase inclusions in garnet porphyroblasts from the diamond-bearing pelitic gneisses were studied by means of combined Raman Spectroscopy and Electron Scanning Microscopy (SEM/EDX). They are either randomly distributed or with preferred orientation within the garnet host and their dimensions vary from less than 5 up to 60 microm. In the single-phase inclusions quartz, rutile, kyanite and graphite dominate. Biotite, zircon, apatite, monazite and allanite are also common. Two types of multiphase inclusions were recognized, hydrous silicate (Type I) and silicate-carbonate (Type II) ones. The carbon-bearing multiphase inclusions predominantly consist of Mg-siderite+graphite+CO(2)+muscovite+quartz formed by a high density carboniferous fluid rich in Fe, Mg, Si and less Ca, Mn, Al and K trapped in the growing garnet in a prograde stage of metamorphism at high-pressure (HP) conditions. The carbon-free multiphase inclusions predominantly consist of biotite+quartz+rutile+/-kyanite+muscovite formed through decompression-dehydration/melting reactions of pre-existing phengite. Single and multiphase inclusions are characterized by polygonal to negative crystal shape formed by dissolution-reprecipitation mechanism between the garnet host and the inclusions during the long lasting cooling period (>100 Ma) of the Kimi Complex.

  16. Multielemental analyses of isomorphous Indian garnet gemstones by XRD and external pixe techniques.

    PubMed

    Venkateswarulu, P; Srinivasa Rao, K; Kasipathi, C; Ramakrishna, Y

    2012-12-01

    Garnet gemstones were collected from parts of Eastern Ghats geological formations of Andhra Pradesh, India and their gemological studies were carried out. Their study of chemistry is not possible as they represent mixtures of isomorphism nature, and none of the individual specimens indicate independent chemistry. Hence, non-destructive instrumental methodology of external PIXE technique was employed to understand their chemistry and identity. A 3 MeV proton beam was employed to excite the samples. In the present study geochemical characteristics of garnet gemstones were studied by proton induced X-ray emission. Almandine variety of garnet is found to be abundant in the present study by means of their chemical contents. The crystal structure and the lattice parameters were estimated using X-Ray Diffraction studies. The trace and minor elements are estimated using PIXE technique and major compositional elements are confirmed by XRD studies. The technique is found very useful in characterizing the garnet gemstones. The present work, thus establishes usefulness and versatility of the PIXE technique with external beam for research in Geo-scientific methodology.

  17. Raman calibration of the HT-7 yttrium aluminum garnet Thomson scattering for electron density measurements

    SciTech Connect

    Zang Qing; Zhao Junyu; Gao Xiang; Shi Lingwei; Zhang Tao; Xi Xiaoqi; Yang Li; Hu Qingsheng; Sajjad, S.

    2007-11-15

    A multipulse neodym doped yttrium aluminum garnet laser Thomson scattering system calibrated by the anti-Stokes rotational Raman scattering from nitrogen gas had been developed in the HT-7 superconducting Tokmak. By virtue of this system, measured electron density results of the plasma were obtained. The results showed good repeatability and its total uncertainty was estimated to be {+-}18%.

  18. Multielemental analyses of isomorphous Indian garnet gemstones by XRD and external pixe techniques.

    PubMed

    Venkateswarulu, P; Srinivasa Rao, K; Kasipathi, C; Ramakrishna, Y

    2012-12-01

    Garnet gemstones were collected from parts of Eastern Ghats geological formations of Andhra Pradesh, India and their gemological studies were carried out. Their study of chemistry is not possible as they represent mixtures of isomorphism nature, and none of the individual specimens indicate independent chemistry. Hence, non-destructive instrumental methodology of external PIXE technique was employed to understand their chemistry and identity. A 3 MeV proton beam was employed to excite the samples. In the present study geochemical characteristics of garnet gemstones were studied by proton induced X-ray emission. Almandine variety of garnet is found to be abundant in the present study by means of their chemical contents. The crystal structure and the lattice parameters were estimated using X-Ray Diffraction studies. The trace and minor elements are estimated using PIXE technique and major compositional elements are confirmed by XRD studies. The technique is found very useful in characterizing the garnet gemstones. The present work, thus establishes usefulness and versatility of the PIXE technique with external beam for research in Geo-scientific methodology. PMID:23041780

  19. Single and multiphase inclusions in metapelitic garnets of the Rhodope Metamorphic Province, NE Greece.

    PubMed

    Mposkos, Evripidis; Perraki, Maria; Palikari, Sarra

    2009-08-01

    Single and multiphase inclusions in garnet porphyroblasts from the diamond-bearing pelitic gneisses were studied by means of combined Raman Spectroscopy and Electron Scanning Microscopy (SEM/EDX). They are either randomly distributed or with preferred orientation within the garnet host and their dimensions vary from less than 5 up to 60 microm. In the single-phase inclusions quartz, rutile, kyanite and graphite dominate. Biotite, zircon, apatite, monazite and allanite are also common. Two types of multiphase inclusions were recognized, hydrous silicate (Type I) and silicate-carbonate (Type II) ones. The carbon-bearing multiphase inclusions predominantly consist of Mg-siderite+graphite+CO(2)+muscovite+quartz formed by a high density carboniferous fluid rich in Fe, Mg, Si and less Ca, Mn, Al and K trapped in the growing garnet in a prograde stage of metamorphism at high-pressure (HP) conditions. The carbon-free multiphase inclusions predominantly consist of biotite+quartz+rutile+/-kyanite+muscovite formed through decompression-dehydration/melting reactions of pre-existing phengite. Single and multiphase inclusions are characterized by polygonal to negative crystal shape formed by dissolution-reprecipitation mechanism between the garnet host and the inclusions during the long lasting cooling period (>100 Ma) of the Kimi Complex. PMID:19181569

  20. Experimental determination of the spinel-garnet boundary in a Martian mantle composition

    NASA Technical Reports Server (NTRS)

    Patera, E. S.; Holloway, J. R.

    1982-01-01

    The high pressure reaction orthopyroxene + clinopyroxene + spinel to garnet + olivine is applicable to the mantle of Mars. Experimental reversals of this reaction in the system CaO-MgO-FeO-Al2O3-SiO2 have been made in the range 1000-1200 C using the bulk composition proposed by Morgan and Anders (1980). At 1000 C, 1100 C, and 1200 C the garnet-out equilibrium is bracketed at 10.8 + or - 0.5, 12.6 + or - 0.5, and 15.2 + or - 0.5 kbars, respectively. A dP/dT slope of 14.0 bar/K at 1000 C increasing to 26.0 bar/K at 1200 C has been inferred. Depending on bulk composition, the mantle of Mars is inferred to have a phase assemblage of either olivine + clinopyroxene + orthopyroxene + garnet or olivine + clinopyroxene + garnet + spinel. In the second, the partial melts will not be buffered by olivine and orthopyroxene and will have markedly lower silica activities than those of the terrestrial mantle.

  1. A new statistical analysis of rare earth element diffusion data in garnet

    NASA Astrophysics Data System (ADS)

    Chu, X.; Ague, J. J.

    2015-12-01

    The incorporation of rare earth elements (REE) in garnet, Sm and Lu in particular, links garnet chemical zoning to absolute age determinations. The application of REE-based geochronology depends critically on the diffusion behaviors of the parent and daughter isotopes. Previous experimental studies on REE diffusion in garnet, however, exhibit significant discrepancies that impact interpretations of garnet Sm/Nd and Lu/Hf ages.We present a new statistical framework to analyze diffusion data for REE using an Arrhenius relationship that accounts for oxygen fugacity, cation radius and garnet unit-cell dimensions [1]. Our approach is based on Bayesian statistics and is implemented by the Markov chain Monte Carlo method. A similar approach has been recently applied to model diffusion of divalent cations in garnet [2]. The analysis incorporates recent data [3] in addition to the data compilation in ref. [1]. We also include the inter-run bias that helps reconcile the discrepancies among data sets. This additional term estimates the reproducibility and other experimental variabilities not explicitly incorporated in the Arrhenius relationship [2] (e.g., compositional dependence [3] and water content).The fitted Arrhenius relationships are consistent with the models in ref. [3], as well as refs. [1]&[4] at high temperatures. Down-temperature extrapolation leads to >0.5 order of magnitude faster diffusion coefficients than in refs. [1]&[4] at <750 °C. The predicted diffusion coefficients are significantly slower than ref. [5]. The fast diffusion [5] was supported by a field test of the Pikwitonei Granulite—the garnet Sm/Nd age postdates the metamorphic peak (750 °C) by ~30 Myr [6], suggesting considerable resetting of the Sm/Nd system during cooling. However, the Pikwitonei Granulite is a recently recognized UHT terrane with peak temperature exceeding 900 °C [7]. The revised closure temperature (~730 °C) is consistent with our new diffusion model.[1] Carlson (2012) Am

  2. Lu-Hf garnet geochronology of the Salmon River Suture Zone, West-Central Idaho

    NASA Astrophysics Data System (ADS)

    Wilford, D. E.; Vervoort, J. D.; Lewis, R.; Tikoff, B.

    2011-12-01

    The Salmon River Suture Zone (SRSZ) in west-central Idaho records the accretion of island arc terranes to North America. It is modified by the Western Idaho Shear Zone (WISZ), a high strain zone within the SRSZ, which defines the present-day boundary between old continental North America and the accreted oceanic assemblages. Timing of the onset of deformation on the WISZ is not well established, primarily due to a poorly constrained metamorphic history. Existing garnet geochronologic studies of units within the SRSZ, using the Sm-Nd isotope system, have provided a framework towards a progressive accretion of arc-derived rocks to North America [1,2]. In this study, we report on the application of the Lu-Hf isotope system to provide ages of garnet growth within the suture zone. This system has the advantage of being insensitive to light rare earth element (LREE)-rich inclusions in garnet, which can complicate Sm-Nd geochronology. Samples were taken from several locations from both along and perpendicular to the suture zone. We report results on two of these samples, within and east of the WISZ. First, a garnet bearing leucocratic layer in a gneissic meta-sedimentary screen near Cascade, Idaho, yields a garnet age of 98 ± 2.0 Ma (2SD). The screen occurs completely within the orthogneisses of the WISZ, and displays similar fabrics and kinematics. Second, a biotite quartzo-feldspathic garnet gneiss from Elk City, Idaho, yields an age 100 ± 2.9 Ma (2SD). This location is ~35 km east of the WISZ, on a sub-parallel deformation zone that was active at the same time. Both samples were single-stage garnet fractions consisting of inclusion-free to inclusion-bearing fragments and whole rock pairs. These ages provide two important implications for the Mesozoic evolution of the western edge of North America. First, transpressional deformation in the WISZ occurred simultaneously with deformation on parallel structures in central Idaho, indicating that a wide zone of deformation

  3. Garnet - two pyroxene rock from the Gridino complex, Russia: a record of the early metasomatic stage

    NASA Astrophysics Data System (ADS)

    Morgunova, Alena A.; Perchuk, Alexei L.

    2010-05-01

    The Gridino complex is one of the oldest high pressure complexes on the Earth. The most spectacular exposures occur in islands and in a 10-50 m wide belt along the shore of the White Sea in the Gridino area. The exotic blocks show wide range of compositions. In addition to predominating amphibolites and eclogites, there are also peridotites, zoisitites and sapphirine-bearing rocks. The peridotites are represented by garnet - two pyroxene rocks and orthopyroxenites. It this paper we present an intriguing results of the petrological study of the garnet- two pyroxene rock. The garnet- two pyroxene rock considered occurs as elliptical body 4×6 m in size within amphibole-biotite gneiss in the island Visokii. The rock consists of mosaic of coarse-grained primary garnet, clinopyroxene and orthopyroxene. Accessories are represented by magnetite, ilmenite, pyrite and zircon. Garnet contains inclusions of clinopyroxene, Mg-calcite and chlorite. The chlorite inclusions always intergrow with dendritic mineral enriched in REE (mainly Ce) situated on the wall of vacuole which shows the tendency of negative crystal shape. Similar chlorite inclusions are hosted by clino- and orthopyroxenes. The chlorite is of diabantite composition. The inclusions are often surrounded by the two systems of cracks - radial and concentric, which is really exotic phenomenon for crystalline rock. The primary minerals experienced different degree of the retrograde alteration expressed as amphibolization and/or growth of the orthopyroxene-amphibole-garnet symplectites. The retrogression is patchy in the central part of garnet- two pyroxene body, but intensifies towards the rims where primary minerals are absent. Mineral thermobarometry reveals HP rock equilibration at 670-750 оС and 14-20 kbar followed by subisothermal decompression down to 640-740 оС and 6-14 kbar. Specific composition of the chlorite and its association with REE phase in all rock-forming minerals suggests that anhydrous HP

  4. Fluid-induced oxidation at the slab-mantle interface: insights from UHP garnet peridotites

    NASA Astrophysics Data System (ADS)

    Malaspina, Nadia; Langenhorst, Falko; Poli, Stefano

    2013-04-01

    At subduction zones the volatile transfer from slab to mantle is accomplished by fluid phases released by dehydration, partial melting and/or decarbonation reactions in the slab lithologies. The mechanism of slab-to-mantle volatile transfer is strongly related to the fluid speciation, which in turn is a function of oxygen fugacity, in a system buffered by equilibria involving redox-sensitive elements. Although much is known about the oxidation state of the upper mantle, the redox processes taking place in the portion of mantle wedge on top of the subducting slab is poorly investigated and the oxidising power of fluids is still unknown. Information on fluid/melt related processes occurring at sub-arc depth can be gained by the study of orogenic UHP metasomatised ultramafic rocks associated with deeply subducted crust. A relevant case study is represented by garnet orthopyroxenites and peridotites coming from the Dabie-Sulu belt (China). Orthopyroxenites (Maowu Ultramafic Complex) are hosted by garnet-coesite gneisses and locally crop out associated with phlogopite-rich layers. They contain an association of orthopyroxene + garnet ± clinopyroxene ± olivine, which form at the expenses of a previous garnet peridotite. Garnet includes core clusters of primary polyphase inclusions corresponding to a solute-rich aqueous fluid enriched in LILE and LREE. Textural and geochemical data demonstrate that these orthopyroxenites represent metasomatic layers produced after the reaction of mantle peridotites with a Si-saturated fluid phase sourced by the associated crustal rocks at UHP conditions. The trace element pattern of this fluid shows a peculiar LILE signature which is recorded by subduction garnet peridotites from Zhimafang. These samples show two UHP mineral assemblages. The older one is made of porphyroclastic garnet, coarse exsolved clinopyroxene and coarse phlogopite flakes. The younger paragenesis consists of fine-grained olivine + clinopyroxene + orthopyroxene

  5. Defects in laser crystals of rare-earth aluminum and gallium garnets

    SciTech Connect

    Vorob`ev, Yu.P.; Goncharov, O.Yu.

    1994-12-01

    Using thermodynamic and crystallochemical analysis of garnets R{sub 3}Ga{sub 5}O{sub 12}(R=Sm - Lu, Y) and R{sub 3}Al{sub 5}O{sub 12} (R = Gd - Lu, Y) and their solid solutions, we characterized point defects present in their structure and, for the first time, estimated their contents. We showed that the garnets under consideration contain cationic defects and oxygen vacancies: (1) In aluminum garnets R{sub 3}Al{sub 5}O{sub 12}, improper-valence ions form at octahedral sites. (2) In gallium garnets R{sub 3}Ga{sub 5}O{sub 12} and Ga-containing solid solutions, there are Ga vacancies at octahedral sites. (3) In Dy{sub 3}(Ga{sub c}Al{sub 1-c}){sub 5}O{sub 12} solid solutions, in addition to the above-mentioned defects typical of gallium garnets, antistructural, substitutional defects (Ga{sup 3+}{sub IV}) are present. The Ga{sup 3+}ions occupy preferentially octahedra; that is, they exhibit a higher affinity for octahedral coordination than Alk{sup 3+} ions, in agreement with Goldschmidt`s crystallochemical approach. The refined solid-solution ranges for R{sub 3}Ga{sub c}Al{sub 1-c}{sub 5}O{sub 12}(R=Nd,Sm,Eu,Gd) are 0.75 {le}c{le} 1 for Nd, 0.5 {le}c{le} 1 for Sm, 0.4 {le}c{le} 1 for Eu, and 0.25 {le}c{le} 1 for Gd.

  6. Iron and alloys of iron. [lunar resources

    NASA Technical Reports Server (NTRS)

    Sastri, Sankar

    1992-01-01

    All lunar soil contains iron in the metallic form, mostly as an iron-nickel alloy in concentrations of a few tenths of 1 percent. Some of this free iron can be easily separated by magnetic means. It is estimated that the magnetic separation of 100,000 tons of lunar soil would yield 150-200 tons of iron. Agglutinates contain metallic iron which could be extracted by melting and made into powder metallurgy products. The characteristics and potential uses of the pure-iron and iron-alloy lunar products are discussed. Processes for working iron that might be used in a nonterrestrial facility are also addressed.

  7. Diffusion-controlled growth and degree of disequilibrium of garnet porphyroblasts: is diffusion-controlled growth of porphyroblasts common?

    NASA Astrophysics Data System (ADS)

    Miyazaki, Kazuhiro

    2015-12-01

    Rate-limiting processes and the degree of disequilibrium during metamorphic mineral growth are key controls on the rate of dehydration and hydration in the Earth's crust. This paper examines diffusion-controlled growth and the degree of disequilibrium of garnet porphyroblasts in the Tsukuba metamorphic rocks of central Japan. The analyzed porphyroblasts have irregular and branching morphologies with clear diffusional haloes, indicating that they grew in a diffusion-controlled regime. Mathematical analysis shows that the dominant wavelength of the interface of a garnet porphyroblast is dependent on the extent of supersaturation (Δ ζ), which is an index for the degree of disequilibrium. Using the calculated upper and lower limits of the dominant wavelength, the value of Δ ζ is estimated to be 0.05 × 10-1-0.16, which corresponds to a Gibbs free energy (Δ G r ) overstep of 0.9-27 kJ per mole of garnet (12 oxygen atoms) and a temperature overstep (Δ T) of 1.7-50 °C. Using the average value of the dominant wavelength, the following results are obtained: Δ ζ = 0.15 × 10-1, Δ G r = 2.7 kJ per mole of garnet, and Δ T = 5 °C. These values bring into question the importance of diffusion-controlled growth of garnet porphyroblasts, as highly irregular and branching garnet porphyroblasts are rare in most metamorphic belts. After significant overstepping for the nucleation of garnet, the garnet porphyroblasts grow at a high degree of disequilibrium. However, a high degree of disequilibrium under diffusion-controlled growth would be characterized by diffusional instability. The results indicate that garnet porphyroblasts that lack an irregular and branching morphology may grow at a high degree of disequilibrium under interface-controlled growth, provided they are set in a medium where the diffusion and supply of constituent elements are sufficient, such as a sufficient volume of metamorphic fluid.

  8. Lu-Hf Garnet Geochronology Reveals the Tectonic History of Precambrian Rocks in the Southern Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Aronoff, R.; Andronicos, C.; Vervoort, J. D.; Hunter, R. A.

    2014-12-01

    Lu-Hf garnet dating of Proterozoic rocks of the southwestern United States provides constraints on the timing and geographic extent of metamorphism associated with the Yavapai, Mazatzal, and newly recognized Picuris orogenies. Prior work focusing on U-Pb dating of plutons and Ar geochronology has left the timing of prograde metamorphism ambiguous, particularly in northern New Mexico and southern Colorado. Because the Lu-Hf system dates the onset of garnet growth, it can constrain the timing of the prograde P-T path. Garnet schist samples from central and northern New Mexico exhibit garnet growth restricted to the time period between ~1460 and 1400 Ma. In the Picuris and Manzano mountains, the oldest Lu-Hf garnet ages predate the U-Pb ages of ~1.4 Ga plutons located near the dated samples. This implies that garnet growth, and therefore the onset of amphibolite facies metamorphism, cannot be driven by contact metamorphism, as has been previously inferred. Garnet-bearing samples from the Needle and Wet Mountains in southern Colorado display a range of garnet ages between ~1750 and 1470 Ma. A garnet gneiss from the Needle Mountains in southwestern Colorado yields an age of 1748 Ma, which is consistent with the Yavapai orogeny. This Lu-Hf garnet age has not been reset by contact metamorphism associated with the emplacement of the ~1.4 Ga Eolus batholith. Anatectic garnet in an orthogneiss from the northern Wet Mountains yields an age of 1601 Ma and is interpreted to date partial melting at the close of the Mazatzal orogeny. A 1476 Ma garnet age from the aureole of the 1440 Ma Oak Creek pluton is interpreted to date upper amphibolite facies metamorphism. The age distribution of these samples shows that rocks in Colorado underwent a complex, poly-metamorphic history, while rocks in New Mexico underwent a single progressive metamorphic event. This contrast implies that the boundary between rocks deformed and metamorphosed during the ~1800-1600 Ma Yavapai and Mazatzal

  9. Iron and iron derived radicals

    SciTech Connect

    Borg, D.C.; Schaich, K.M.

    1987-04-01

    We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fastexclamation Think smallexclamation In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab.

  10. Native iron in the continental lower crust: petrological and geophysical implications.

    PubMed

    Haggerty, S E; Toft, P B

    1985-08-16

    Lower crustal granulite xenoliths recovered from a kimberlite pipe in western Africa contain native iron (Fe(0)) as a decomposition product of garnet and ilmenite. Magnetic measurements show that less than 0.1 percent (by volume) of iron metal is present. Data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron-wüstite and magnetite-wüstite buffers, which may represent the oxidation state of the continental lower crust, and the depleted lithospheric upper mantle. Ferromagnetic native iron could be stable to a depth of approximately 95 kilometers and should be considered in the interpretation of long-wavelength static magnetic anomalies. PMID:17739375

  11. The success and complementarity of Sm-Nd and Lu-Hf garnet geochronology

    NASA Astrophysics Data System (ADS)

    Baxter, E. F.; Scherer, E. E.

    2013-12-01

    Garnet's potential as a direct chronometer of tectonometamorphic processes and conditions was first realized over 30 years ago. Since then, the Sm-Nd and Lu-Hf systems have emerged as the most effective, with both permitting age precision < ×1 Myr. Both have proven successful not merely in dating garnet growth itself, but rather in constraining the ages, durations, and rates of particular earth processes or conditions that can be directly linked to garnet growth via chemical, thermodynamic, or petrographic, means. Appreciating important differences between Sm-Nd and Lu-Hf in terms of contaminant phases, partitioning, daughter element diffusivity, and isotopic analysis makes these two systems powerfully complementary when used and interpreted in concert. Well established, robust analytical methods mitigate the effects of ubiquitous mineral inclusions (monazite is most significant for Sm-Nd; zircon is most significant for Lu-Hf), improving the precision and accuracy of garnet dates from both systems. Parent-daughter ratios tend to be higher for Lu-Hf leading to the potential for better age precision in general. The Lu-176 decay rate is faster than Sm-147, meaning that Lu-Hf provides better age precision potential for young (Cenozoic) samples. However, Sm-Nd provides better precision potential for older (Precambrian) samples primarily because of the higher precisions on the parent-daughter ratios (i.e., 147Sm/144Nd) that can be achieved by ID-TIMS analysis. For dating microsampled zones or growth rings in single garnet crystals, Sm-Nd has proven most successful owing to more uniform distribution of Sm, and established methods to measure <10 ng quantities of Nd at high precision via TIMS. However, new MC-ICP-MS sample introduction technologies are closing this gap for small samples. For analyses of bulk garnet that grew over a protracted interval, Lu-Hf dates are expected to be older than Sm-Nd dates owing to differences in Lu and Sm zonation (i.e. Lu tends to be

  12. Quantitative Prograde P-T Paths From Inclusion Assemblages in Eclogitic Garnets

    NASA Astrophysics Data System (ADS)

    Essene, E. J.; Page, F. Z.; Mukasa, S. B.

    2003-12-01

    Many workers have used garnet inclusions as qualitative indicators of the early history of tectonically exposed eclogites. Assemblages indicative of crustal facies combined with standard P-T conditions of those facies and thermobarometry on the matrix eclogite constrain the prograde path. However, now that conditions of some blueschist, amphibolite and granulite facies rocks have been extended to much higher pressures, in the range of 10-20 kbar, those assignments are in need of review. While undertaking studies on eclogites from the Blue Ridge of North Carolina and the Franciscan in northern California, the authors have identified key inclusion assemblages of sphene-rutile-epidote-quartz and phengite-omphacite together with garnet that constrain the prograde P-T path based on univariant assemblages corrected for observed solid solutions. Equilibria that have proved most useful are those bounding epidote stability and two key reactions, one involving sphene/rutile: (1) clinozoisite + sphene = grossular + rutile + H2O, and the second being the phengite barometer: garnet + Mg-celadonite = clinopyroxene + muscovite. Reactions (1) and (2) have negative slopes, intersecting with the Mg/Fe KD garnet-clinopyroxene thermometer and providing a reasonable estimate of pre- to syn-eclogite facies P-T. In the case of the Bakersville eclogite samples from North Carolina, the inclusion assemblage yields 10 +/- 2 kbar and 500 +/- 50° C with reaction (1) compared to the peak assemblage at P > 15 +/- 2 kbar and 700 +/- 50° C. These data combined with evidence for a granulite facies overprint indicate a clockwise P-T path for those eclogites. A similar study on the Healdsburg eclogite samples from California yields about 500° C and 12 +/- 1 kbar for the garnet cores, 14 +/- 2 kbar for mantles and 16 +/- 2 kbar for rim-matrix assemblages. The introduction of late glaucophane, epidote and chlorite partially replacing omphacite and garnet implies a retrograde return to the blueschist

  13. Comparison of the erbium-yttrium aluminum garnet and carbon dioxide lasers for in vitro bone and cartilage ablation

    SciTech Connect

    Gonzalez, C.; van de Merwe, W.P.; Smith, M.; Reinisch, L. )

    1990-01-01

    The in vitro bone- and cartilage-ablation characteristics of the solid-state erbium:yttrium aluminum garnet laser were compared to those of the carbon dioxide laser. Ablations of fresh, frozen cadaver septal cartilage and maxillary sinus bone were performed using total energies between 1 and 6 J. Specimens were studied using hematoxylin and eosin stain and digitized, computer-assisted measurements of 35-mm photographs. Erbium-yttrium aluminum garnet-ablated bone averaged 5 microns of adjacent tissue thermal injury, compared with 67 microns with carbon dioxide-ablated bone. Erbium-yttrium aluminum garnet-ablated cartilage averaged 2 microns of adjacent tissue thermal injury, compared with 21 microns with the carbon dioxide-ablated cartilage. The tissue-ablation characteristics of the erbium-yttrium aluminum garnet laser are promising for future otolaryngologic applications.

  14. Precipitation of Oriented Rutile and Ilmenite Needles in Garnet, Northeastern Connecticut, USA: Evidence for Extreme Metamorphic Conditions?

    NASA Astrophysics Data System (ADS)

    Ague, J. J.; Eckert, J. O.

    2011-12-01

    We report the discovery of oriented needles of rutile and, less commonly, ilmenite in the cores of garnets from northeastern CT, USA. The rocks preserve granulite facies mineral assemblages, form part of the Merrimack Synclinorium, and underwent metamorphism and deformation during the Acadian orogeny. The needles appear identical to those reported from a number of extreme P-T environments worldwide, including UHP metamorphic rocks, high-P granulites, and garnet peridotites. The needles are predominantly oriented along <111> directions in garnet. The long axes of the rutile needles commonly do not go extinct parallel to the cross hairs under cross-polarized light (e.g., Griffin et al., 1971). This anomalous extinction indicates that the needles do not preserve a specific crystallographic relationship with their garnet hosts (e.g., Hwang et al., 2007). The needles range from a few hundred nm to a few um in diameter, and can be mm-scale in length. Micrometer-scale plates of rutile, srilankite and crichtonite have also been observed in some garnets together with the Fe-Ti oxide needles. Several origins for the needles have been proposed in the literature; we investigate the hypothesis that they precipitated in situ from originally Ti-rich garnet. Chemical profiles across garnets indicate that some retain Ti zoning, with elevated-Ti concentrations in the cores dropping to low values in the rims. For these zoned garnets, high-resolution, 2-D chemical mapping using the JEOL JXA-8530F field emission gun electron microprobe at Yale University reveals that the needles are surrounded by well-defined Ti-depletion halos. Chemical profiles also document strong depletions of Cr (which is present in both rutile and ilmenite) directly adjacent to needles. The observed Ti-depletions demonstrate that the needles precipitated from Ti-bearing garnet, probably during cooling and/or decompression associated with exhumation. The rutile precipitates must be largely incoherent with respect

  15. Raman spectroscopy of detrital garnet from the (U)HP terrane of eastern Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Andò, Sergio; Baldwin, Suzanne L.; Fitzgerald, Paul G.; Malusà, Marco G.; Aliatis, Irene; Vezzoli, Giovanni; Garzanti, Eduardo

    2013-04-01

    Garnet is one of the most widespread heavy minerals in sediments derived from orogenic systems. Its chemical composition varies systematically with temperature and pressure conditions, and thus provides information on the metamorphic evolution of source areas that is crucial in tectonic and geodynamic reconstructions. Garnet is easily identified in mineral grain mounts and is relatively stable during burial diagenesis. Raman spectroscopy allows rapid determination of garnet compositions in grain mounts or thin sections of sand and sandstone samples, and can be used to assess their density and chemical composition quite accurately ("MIRAGEM" method of Bersani et al., 2009; Andò et al., 2009). In the D'Entrecastreaux Islands of southeastern Papua New Guinea, the world's youngest (U)HP rocks are exposed. There, mafic rocks and their felsic host gneisses were metamorphosed under eclogite facies conditions from late Miocene to Pliocene, before being exhumed from depths of ~90 km (Baldwin et al., 2004, 2008). The eclogite preserves a peak assemblage of garnet, omphacite, rutile, phengite and Si02 (Hill and Baldwin, 1993). A coesite-eclogite has been found in one small island outcrop. In order to sample garnet populations representative of a larger geographical area, we sampled and studied a heavy-mineral-dominated placer sand (HMC 80) from a beach from SE Goodenough Island. Garnet grains in beach sand are associated with blue-green to subordinately green-brown amphibole and minor epidote, omphacitic clinopyroxene, titanite, apatite and rutile. The subordinate low-density fraction is feldspatho-quartzose with high-rank metamorphic rock fragments and biotite (Q62 F35 Lm2; MI 360). Detrital garnets are mostly classified as almandine with relatively high Mg and Ca and lacking Mn, typical of the eclogite facies (Win et al., 2007; type Ci garnets of Mange and Morton 2007; Andò et al., 2013). In well-described stratigraphic sequences within syn-and post-tectonic basins

  16. Ancient mantle metasomatism recorded in subcalcic garnet xenocrysts: Temporal links between mantle metasomatism, diamond growth and crustal tectonomagmatism

    NASA Astrophysics Data System (ADS)

    Shu, Qiao; Brey, Gerhard P.

    2015-05-01

    We have identified carbonatitic melts as the main agent for metasomatism in cpx-free garnet harzburgites from the Kaapvaal craton. Substantial overlap of the Ti/Eu and Zr/Hf ratios of subcalcic garnets from xenoliths and garnet inclusions in diamonds corroborate previous findings that mantle metasomatism and the growth of diamonds are connected processes. The key process involves the interaction of a carbonatitic melt with depleted garnet harzburgite leading to dissolution and regrowth of the constituent minerals and the growth of diamonds by redox reactions. Model calculations show that only small amounts of a carbonatite melt, between 0.3 to 3%, are needed to generate the range of sinusoidal Rare Earth Element patterns in the garnets from harzburgites and the inclusions in diamonds. The εHf values of the xenolith garnets range from extremely positive (∼+1000) to extremely negative values (-65) with accompanying εNd values varying from +38 to -41. It can be shown that the negative εHf and εNd values correspond to the initial ratios of the metasomatizing agent. They can only stem from a very old (early Archean or Hadean) crustal component. Very negative εNd values have been found previously in subcalcic garnets from xenoliths and inclusions in diamonds. They yield early Archean model ages for the growth of diamonds. In these studies, very high, unsupported 87Sr/86Sr ratios were found as well. The combined evidence suggests that the metasomatic agents are derived from an old source with a high Rb/Sr ratio, typical for pelitic crustal rocks. Metasomatism in the mantle, the formation of diamonds and tectonomagmatic events in the crust occurred contemporaneously at least within the time span between the early Archean and the middle Proterozoic as can be seen from the comparison of crustal ages, Lu-Hf isochron ages from subcalcic garnets and Sm-Nd and Re-Os ages of inclusions in diamonds.

  17. Structural limitations for optimizing garnet-type solid electrolytes: a perspective.

    PubMed

    Zeier, Wolfgang G

    2014-11-21

    Lithium ion batteries exhibit the highest energy densities of all battery types and are therefore an important technology for energy storage in every day life. Today's commercially available batteries employ organic polymer lithium conducting electrolytes, leading to multiple challenges and safety issues such as poor chemical stability, leakage and flammability. The next generation lithium ion batteries, namely all solid-state batteries, can overcome these limitations through employing a ceramic Li(+) conducting electrolyte. In the past decade, there has been a major focus on the structural and ionic transport properties of lithium-conducting garnets, and the extensive research efforts have led to a thorough understanding of the structure-property relationships in this class of materials. However, further improvement seems difficult due to structural limitations. The purpose of this Perspective article is to provide a brief structural overview of Li conducting garnets and the structural influence on the optimization of Li-ionic conductivities. PMID:25277079

  18. The Role of Garnet Pyroxenite in High-Fe Mantle Melt Generation: High Pressure Melting Experiments

    NASA Astrophysics Data System (ADS)

    Tuff, J.; Takahashi, E.; Gibson, S.

    2004-12-01

    Evidence for the existence of heterogeneous or 'marble cake' convecting mantle1 is provided recently by rare, high MgO ( ˜ 15 wt.%) primitive magmas with anomalously high abundances of FeO* ( ˜ 13.5 to 16 wt. %2,3; where FeO* = total Fe as FeO). These high-Fe mantle melts show a limited occurrence in the initial stage of magmatism in large igneous provinces (e.g. Deccan, Ethiopia and Paraná-Etendeka) and some have incompatible trace-element and radiogenic-isotopic ratios (Sr, Nd and Pb) that resemble those of ocean-island basalts. This suggests that they are predominantly derived from the convecting mantle2. The ferropicrites are mildly- to sub-alkaline and have low contents of Al2O3 (< 10 wt.%) and heavy rare-earth elements (e.g. Lu < 0.18ppm) that are consistent with the increased stability of garnet, due to the high FeO* content in the ferropicrite mantle source. It has been proposed that the source of the high FeO* may be garnet-pyroxenite streaks derived from subducted mafic oceanic crust2. We have undertaken melting experiments between 1 atmosphere and 7 GPa in order to determine the anhydrous phase relations of an uncontaminated ferropicrite lava from the base of the Early-Cretaceous Paraná-Etendeka continental flood-basalt province. The sample has high contents of MgO ( ˜ 14.9 wt.%), FeO* (14.9 wt.%) and NiO (0.07 wt.%). Olivine phenocrysts have maximum Fo contents of 85 and are in equilibrium with the host rock, assuming a Kd of 0.32 and we believe that the sample is representative of a primary Fe-rich mantle plume derived melt. In total, 75 experimental runs were carried out. Melting phase relations as well as compositions and modal proportions of all coexisting phases were successfully determined in 60 run products. Phase relations indicate that the ferropicrite melt was generated either at ˜ 2.2 GPa from an olivine-pyroxene residue or ˜ 5 GPa from a garnet-pyroxene residue. A low bulk-rock Al2O3 content (9 wt.%) and high [Gd/Yb]n ratio (3.1) are

  19. High magneto-optical characteristics of Holmium-doped terbium gallium garnet crystal.

    PubMed

    Chen, Zhe; Yang, Lei; Wang, Xiangyong; Yin, Hang

    2016-06-01

    Magneto-optical characteristics of a new magneto-active material, (Tb(1-x)Hox)3Ga5O12 crystal, have been grown by the Czochralski (Cz) method. A high value of the Verdet constant was obtained at room temperature-namely, 214.9 and 77.8  rad·m-1 T-1 for 632.8 and 1064 nm, respectively. The Verdet constant of the Ho-doped terbium gallium garnet crystal at 1064 nm is about 2 times higher than that of terbium gallium garnet crystal. High value of magneto-optical figure-of-merit makes it an attractive next-generation magneto-optics material for high-power Faraday isolators.

  20. High magneto-optical characteristics of Holmium-doped terbium gallium garnet crystal.

    PubMed

    Chen, Zhe; Yang, Lei; Wang, Xiangyong; Yin, Hang

    2016-06-01

    Magneto-optical characteristics of a new magneto-active material, (Tb(1-x)Hox)3Ga5O12 crystal, have been grown by the Czochralski (Cz) method. A high value of the Verdet constant was obtained at room temperature-namely, 214.9 and 77.8  rad·m-1 T-1 for 632.8 and 1064 nm, respectively. The Verdet constant of the Ho-doped terbium gallium garnet crystal at 1064 nm is about 2 times higher than that of terbium gallium garnet crystal. High value of magneto-optical figure-of-merit makes it an attractive next-generation magneto-optics material for high-power Faraday isolators. PMID:27244419

  1. Discovery of natural MgSiO3 tetragonal garnet in a shocked chondritic meteorite

    PubMed Central

    Tomioka, Naotaka; Miyahara, Masaaki; Ito, Motoo

    2016-01-01

    MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be deduced from electron diffraction intensities, the cooling rate of the shock-induced melt veins from ~2000°C was estimated to be higher than 103°C/s. This cooling rate sets the upper bound for the shock-temperature increase in the bulk meteorite at ~900°C. PMID:27051873

  2. Radiation tests on erbium-doped garnet crystals for spaceborne CH4-Lidar applications

    NASA Astrophysics Data System (ADS)

    Meissner, Ansgar; Kreitler, Martin; Cubera, Miroslaw; Kucirek, Philipp; Gronloh, Bastian; Esser, Dominik; Höfer, Marco; Hoffmann, Hans-Dieter

    2015-02-01

    A test campaign for assessing the radiation hardness of different Erbium-doped garnet crystals including Er:YAG and a compositionally tuned Er:YAG/Er:LuAG mixed garnet is reported. Tests with proton and gamma radiation have been performed with parameters mimicking a 3-year low-earth-orbit satellite mission like MERLIN or ADM-Aeolus. For each test sample broadband transmission spectra in the wavelength range of 500 nm - 1700 nm and characteristic laser curves from a test laser oscillator have been measured. Radiation-induced losses have been calculated from the obtained data. The results indicate that gamma radiation is the dominant loss source with about 0.5 %/cm radiation-induced losses for the nominal dose of the chosen mission scenario.

  3. Majorite-Garnet Partitioning of the Highly Siderophile Elements: New Results and Application to Mars

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Righter, K.; Waeselmann, N.; Humayun, M.

    2015-01-01

    HSE and Os isotopes are used to constrain processes such as accretion, mantle evolution, crustal recycling, and core-mantle mixing, and to constrain the timing and depth of differentiation of Mars. Although showed that the HSE contents of the martian mantle could have been established by metal-silicate equilibrium in early Mars, the role of a cooling magma ocean and associated crystallization in further fractionating the HSEs is unclear. Garnet is thought to have played an important role in controlling trace element concentrations in the martian mantle reservoirs. However, testing these models, including Os isotopes, has been hindered by a dearth of partitioning data for the HSE in deep mantle phases - majorite, wadsleyite, ringwoodite, akimotoite - that may be present in the martian mantle. We examine the partitioning behavior of HSEs between majorite garnet (gt), olivine (oliv), and silicate liquid (melt).

  4. Discovery of natural MgSiO3 tetragonal garnet in a shocked chondritic meteorite.

    PubMed

    Tomioka, Naotaka; Miyahara, Masaaki; Ito, Motoo

    2016-03-01

    MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be deduced from electron diffraction intensities, the cooling rate of the shock-induced melt veins from ~2000°C was estimated to be higher than 10(3)°C/s. This cooling rate sets the upper bound for the shock-temperature increase in the bulk meteorite at ~900°C.

  5. Scintillation properties of the Ce-doped multicomponent garnet epitaxial films

    NASA Astrophysics Data System (ADS)

    Prusa, P.; Kucera, M.; Mares, J. A.; Hanus, M.; Beitlerova, A.; Onderisinova, Z.; Nikl, M.

    2013-10-01

    (Lu,Y,Gd)3(Al,Ga)5O12:Ce garnet scintillator single crystalline films were grown onto LuAG, YAG and GGG substrates by liquid phase epitaxy method. Absorption, radioluminescence spectra and photoluminescence excitation, emission spectra, and decay kinetics were measured. Photoelectron yield, its dependence on amplifier shaping time and energy resolution were determined to evaluate scintillation performance. Most of the samples exhibited strong UV emission caused by trapped excitons and/or Gd3+ 4f-4f transition. However, emission spectrum of the best performing Gd2YAl5O12:Ce is dominated by the Ce3+ fast 5d-4f luminescence. This sample has outperformed photoelectron yield of all the garnet films studied so far.

  6. Strong optical reflection of rare-earth garnets in the terahertz regime by reststrahlen bands

    NASA Astrophysics Data System (ADS)

    Adachi, Masaki; Yamahara, Hiroyasu; Kawabe, Shunsuke; Matsui, Hiroaki; Tabata, Hitoshi

    2014-05-01

    The reststrahlen bands of rare-earth garnets were investigated in the terahertz regime. Through this, it was found that the crystal orientation and light polarization directly influence the reststrahlen-related dielectric absorptions of Gd3Ga5O12 (GGG), which is attributed to restriction in the vibrational motion of Gd ions. A theoretical fit to the dielectric absorption revealed that the phonon-polariton frequency in GGG crystals at around 85.5 cm-1 exhibits a narrow spectral width of 100 GHz at room temperature, as estimated using a Lorentz oscillator model. In addition, it was found that the reststrahlen bands can be readily manipulated within a range of 0.7-3.7 THz by changing the chemical composition of the garnet.

  7. Discovery of natural MgSiO3 tetragonal garnet in a shocked chondritic meteorite.

    PubMed

    Tomioka, Naotaka; Miyahara, Masaaki; Ito, Motoo

    2016-03-01

    MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be deduced from electron diffraction intensities, the cooling rate of the shock-induced melt veins from ~2000°C was estimated to be higher than 10(3)°C/s. This cooling rate sets the upper bound for the shock-temperature increase in the bulk meteorite at ~900°C. PMID:27051873

  8. Structural limitations for optimizing garnet-type solid electrolytes: a perspective.

    PubMed

    Zeier, Wolfgang G

    2014-11-21

    Lithium ion batteries exhibit the highest energy densities of all battery types and are therefore an important technology for energy storage in every day life. Today's commercially available batteries employ organic polymer lithium conducting electrolytes, leading to multiple challenges and safety issues such as poor chemical stability, leakage and flammability. The next generation lithium ion batteries, namely all solid-state batteries, can overcome these limitations through employing a ceramic Li(+) conducting electrolyte. In the past decade, there has been a major focus on the structural and ionic transport properties of lithium-conducting garnets, and the extensive research efforts have led to a thorough understanding of the structure-property relationships in this class of materials. However, further improvement seems difficult due to structural limitations. The purpose of this Perspective article is to provide a brief structural overview of Li conducting garnets and the structural influence on the optimization of Li-ionic conductivities.

  9. Rotated garnets: a mechanism to explain the high frequency of inclusion trail curvature angles around 90° and 180°

    NASA Astrophysics Data System (ADS)

    Trouw, Rudolph A. J.; Tavares, Felipe M.; Robyr, Martin

    2008-08-01

    This paper presents numerical data from garnets with inclusion trail curvature angles of up to 260°. Three hundred and twenty-five garnets were studied from an outcrop of greenschist facies phyllite in southern Minas Gerais State, Brazil. Apart from the inclusion trail curvature angle α, also the aspect ratio R and the angle between the long axis of the garnets and the foliation, β, were measured. The results show a remarkable concentration of α at 180° and a minor one at 90°. R varies between 1 and 2 showing that the garnets deviate from sphericity and β shows that all garnets have their long axis in the "forward rotated" quadrant, supporting the rotational interpretation. A model is proposed to explain the concentrations of α, based on preferential growth of the garnets into the mica rich strain caps, orthogonal to the foliation, causing elongated crystals that, because of their shape and position would experience accelerated rotation until relatively stable positions with their long axes parallel to the foliation would be attained. Renewed growth, again into the mica-rich strain caps, orthogonal to the foliation would first restore the spherical shape and then produce an elongated shape, again perpendicular to the foliation, forcing a repetition of the process. It is concluded that this model is capable of explaining the concentration of α in multiples of 90°, in a rotational model, where this concentration was considered earlier as an argument in favor of the non-rotational model.

  10. Pharmacology of Iron Transport

    PubMed Central

    Byrne, Shaina L.; Krishnamurthy, Divya; Wessling-Resnick, Marianne

    2013-01-01

    Elucidating the molecular basis for the regulation of iron uptake, storage, and distribution is necessary to understand iron homeostasis. Pharmacological tools are emerging to identify and distinguish among different iron transport pathways. Stimulatory or inhibitory small molecules with effects on iron uptake can help characterize the mechanistic elements of iron transport and the roles of the transporters involved in these processes. In particular, iron chelators can serve as potential pharmacological tools to alleviate diseases of iron overload. This review focuses on the pharmacology of iron transport, introducing iron transport membrane proteins and known inhibitors. PMID:23020294

  11. Magneto-optical switch with amorphous silicon waveguides on magneto-optical garnet

    NASA Astrophysics Data System (ADS)

    Ishida, Eiichi; Miura, Kengo; Shoji, Yuya; Mizumoto, Tetsuya; Nishiyama, Nobuhiko; Arai, Shigehisa

    2016-08-01

    We fabricated a magneto-optical (MO) switch with a hydrogenated amorphous silicon waveguide on an MO garnet. The switch is composed of a 2 × 2 Mach-Zehnder interferometer (MZI). The switch state is controlled by an MO phase shift through a magnetic field generated by a current flowing in an electrode located on the MZI. The switching operation was successfully demonstrated with an extinction ratio of 11.7 dB at a wavelength of 1550 nm.

  12. High-spin europium and gadolinium centers in yttrium-aluminum garnet

    NASA Astrophysics Data System (ADS)

    Vazhenin, V. A.; Potapov, A. P.; Asatryan, G. R.; Uspenskaya, Yu. A.; Petrosyan, A. G.; Fokin, A. V.

    2016-08-01

    Electron-spin resonance spectra of Eu2+ and Gd3+ centers substituting Y3+ ions in single-crystal yttrium-aluminum garnet have been studied and the parameters of their rhombic spin Hamiltonian have been determined. The fine-structure parameters of the above ions have been calculated in the superposition model disregarding changes in the angular coordinates of the ligand environment of the impurity defect thus demonstrating the necessity of taking these changes into account.

  13. Long-Pulsed Neodymium-Doped Yttrium Aluminum Garnet Laser for Glomuvenous Malformations in Adolescents.

    PubMed

    Trost, Jaren; Buckley, Colin; Smidt, Aimee C

    2015-01-01

    Currently there exist few reported cases where lasers are used successfully to treat glomuvenous malformations in adolescents. In the two cases described here, we provide evidence that the long-pulsed neodymium-doped yttrium aluminum garnet laser is an effective and safe alternative treatment for these lesions. Our case series is unique because it focuses on adolescents, the population that most often seeks treatment for this dermatologic condition.

  14. Magneto-optical switch with amorphous silicon waveguides on magneto-optical garnet

    NASA Astrophysics Data System (ADS)

    Ishida, Eiichi; Miura, Kengo; Shoji, Yuya; Mizumoto, Tetsuya; Nishiyama, Nobuhiko; Arai, Shigehisa

    2016-08-01

    We fabricated a magneto-optical (MO) switch with a hydrogenated amorphous silicon waveguide on an MO garnet. The switch is composed of a 2 × 2 Mach–Zehnder interferometer (MZI). The switch state is controlled by an MO phase shift through a magnetic field generated by a current flowing in an electrode located on the MZI. The switching operation was successfully demonstrated with an extinction ratio of 11.7 dB at a wavelength of 1550 nm.

  15. Lattice dynamics and Born instability in yttrium aluminum garnet, Y3A15O12

    NASA Astrophysics Data System (ADS)

    Goel, Prabhatasree; Mittal, R.; Choudhury, N.; Chaplot, S. L.

    2010-02-01

    We report lattice dynamics calculations of various microscopic and macroscopic vibrational and thermodynamic properties of yttrium aluminum garnet (YAG), Y3Al5O12, as a function of pressure up to 100 GPa and temperature up to 1500 K. YAG is an important solid-state laser material with several technological applications. Garnet has a complex structure with several interconnected dodecahedra, octahedra and tetrahedra. Unlike other aluminosilicate garnets, there are no distinct features to distinguish between intramolecular and intermolecular vibrations of the crystal. At ambient pressure, low energy phonons involving mainly the vibrations of yttrium atoms play a primary role in the manifestations of elastic and thermodynamic behavior. The aluminum atoms in tetrahedral and octahedral coordination are found to be dynamically distinct. Garnet's stability can be discerned from the response of its phonon frequencies to increasing pressure. The dynamics of both octahedral and tetrahedral aluminum atoms undergo radical changes under compression which have an important bearing on their high pressure and temperature properties. At 100 GPa, YAG develops a large phonon bandgap (90-110 meV) and its microscopic and macroscopic physical properties are found to be profoundly different from that at the ambient pressure phase. There are significant changes in the high pressure thermal expansion and specific heat. The mode Grüneisen parameters show significant changes in the low energy range with pressure. Our studies show that the YAG structure becomes mechanically unstable around P = 108 GPa due to the violation of the Born stability criteria. Although this does not rule out thermodynamic crossover to a lower free energy phase at lower pressure, this places an upper bound of P = 110 GPa for the mechanical stability of YAG.

  16. Skarn formation and trace elements in garnet and associated minerals from Zhibula copper deposit, Gangdese Belt, southern Tibet

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Ciobanu, Cristiana L.; Cook, Nigel J.; Zheng, Youye; Sun, Xiang; Wade, Benjamin P.

    2016-10-01

    Trace element concentrations in garnet and associated minerals from the mid-Miocene Zhibula Cu skarn, Gangdese Belt, Tibet reflect a diversity of local environments, evolving fluid parameters and partitioning with coexisting minerals. Exoskarn occurs as massive but narrow intervals within a Lower Jurassic volcano-sedimentary sequence containing limestone, the main skarn protolith. Endoskarn is present at the contact with mid-Miocene granodiorite dikes. Prograde skarn associations are garnet-dominant but also include diopside-dominant pyroxene in variable amounts. Garnet compositions in exoskarn change from andradite (And)- to grossular (Gr)-dominant from the massive intervals to bands/lenses within marble/tuff, but not in endoskarn. In both cases however, associations at the protolith contact include anorthite and wollastonite, both indicative of skarnoid or distal (relative to fluid source) skarn formation. Exoskarns also contain vesuvianite. Retrograde clinozoisite, actinolite and chlorite replace pre-existing skarn minerals. Garnet displays brecciation and replacement by Al-richer garnet. Depending on partitioning among coexisting minerals, chondrite-normalised REY (REE + Y) fractionation trends for garnet depict endo- to exoskarn diversity, the dominance of And- vs. Gr-rich garnet (in turn related to proximal-to-distal relationship to fluid source), as well as prograde-to-retrograde evolution in the same sample. A strong variation in Eu-anomaly, from positive to negative, in And-dominant garnet can be correlated with variation in salinity of ore-forming fluids, concordant with published fluid inclusion data. Trends depicted by And- and Gr-dominant garnets are consistent with published data from skarns elsewhere, in which the dominant substitution mechanism for REY is YAG-type. Zhibula garnets are enriched in a range of trace elements less commonly reported, including W, Sn, and As, but also Mo (as high as 730 ppm), an element seldom analysed for in silicates

  17. On the nature and origin of garnet in highly-refractory Archean lithosphere: implications for continent stabilisation

    NASA Astrophysics Data System (ADS)

    Gibson, Sally

    2014-05-01

    The nature and timescales of garnet formation in the Earth's subcontinental lithospheric mantle (SCLM) are important to our understanding of how this rigid outer shell has evolved and stabilised since the Archean. Nevertheless, the widespread occurrence of pyrope garnet in the sub-cratonic mantle remains one of the 'holy grails' of mantle petrology. The paradox is that garnet often occurs in mantle lithologies (dunites and harzburgites) which represent residues of major melting events (up to 40 %) whereas experimental studies on fertile peridotite suggest this phase should be exhausted by <20 % melting. Furthermore, garnets commonly found in mantle peridotite suites have diverse compositions that are typically in equilibrium with high-pressure, small-fraction, mantle melts suggesting they formed as a result of enrichment of the lithospheric mantle following cratonisation. This refertilisation -- which typically involves addition of Fe, incompatible trace elements and volatiles -- affects the lower 30 km of the lithosphere and potentially leads to negative buoyancy and destabilisation. Pyrope garnets found in mantle xenoliths from the eastern margin of the Tanzanian Craton (Lashaine) have diverse compositions and provide major constraints on how the underlying deep (120 to 160 km) mantle stabilised and evolved during the last 3 billion years. The garnets display systematic trends from ultra-depleted to enriched compositions that have not been recognised in peridotite suites from elsewhere (Gibson et al., 2013). Certain harzburgite members of the xenolith suite contain the first reported occurrence of pyrope garnets with rare-earth element (REE) patterns similar to hypothetical garnets proposed by Stachel et al. (2004) to have formed in the Earth's SCLM during the Archean, prior to metasomatism. These rare ultra-depleted low-Cr garnets occur in low temperature (~1050 oC) xenoliths derived from depths of ~120 km and coexist in chemical and textural equilibrium with

  18. Fast Solid-State Li Ion Conducting Garnet-Type Structure Metal Oxides for Energy Storage.

    PubMed

    Thangadurai, Venkataraman; Pinzaru, Dana; Narayanan, Sumaletha; Baral, Ashok Kumar

    2015-01-15

    Lithium ion batteries are the most promising energy storage system on the market today; however, safety issues associated with the use of flammable organic polymer-based electrolytes with poor electrochemical and chemical stabilities prevent this technology from reaching maturity. Solid lithium ion electrolytes (SLIEs) are being considered as potential replacements for the organic electrolytes to develop all-solid-state Li ion batteries. Out of the recently discovered SLIEs, the garnet-related structured Li-stuffed metal oxides are the most promising electrolytes due to their high total (bulk + grain boundary) Li ion conductivity, high electrochemical stability window (∼6 V versus Li(+)/Li at room temperature), and chemical stability against reaction with an elemental Li anode and high-voltage metal oxide Li cathodes. This Perspective discusses the structural-chemical composition-ionic conductivity relationship of Li-stuffed garnets, followed by a discussion on the Li ion conduction mechanism, as well as the electrochemical and chemical stability of these materials. The performance of a number of all-solid-state batteries employing garnet-type Li ion electrolytes is also discussed.

  19. Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Hutsebaut, Didier; Theunissen, Karel; Vandenabeele, Peter; Stepanov, Alexander S

    2007-12-15

    Coesite inclusions occur in a wide range of lithologies and coesite is therefore a powerful ultrahigh-pressure (UHP) indicator. The transformation of coesite to quartz is evidenced by three optically well identifiable characteristics (e.g. palisade textures, radial crack patterns, polycrystalline quartz pseudomorphs). Under overpressure monomineralic coesite (on an optical basis), lacking the above transformation characteristics may survive. Raman micro-spectroscopy was applied on monomineralic coesite inclusions in garnet porphyroblasts from diamond-bearing garnet-clinozoisite-biotite gneisses of the Barchi-Kol area (Kokchetav Massif, Northern Kazakhstan). These coesite inclusions are euhedral and display a characteristic anisotropic hallo. However, Raman maps and separate spectra of these inclusions display shifted bands for coesite and quartz. Microscopically undetectable, quartz shows on the Raman map as a thin shell around coesite inclusion. Shift of the main coesite band allows to estimate their overpressure: coesite inclusions record 0-2.4 GPa in garnet and zircon. The quartz shell remains under lower pressure 0-1.6 GPa. The possible application of coesite and quartz Raman geobarometers for UHP metamorphic rocks is discussed. PMID:17553735

  20. Monomeric Garnet, a far-red fluorescent protein for live-cell STED imaging

    PubMed Central

    Hense, Anika; Prunsche, Benedikt; Gao, Peng; Ishitsuka, Yuji; Nienhaus, Karin; Ulrich Nienhaus, G.

    2015-01-01

    The advancement of far-red emitting variants of the green fluorescent protein (GFP) is crucially important for imaging live cells, tissues and organisms. Despite notable efforts, far-red marker proteins still need further optimization to match the performance of their green counterparts. Here we present mGarnet, a robust monomeric marker protein with far-red fluorescence peaking at 670 nm. Thanks to its large extinction coefficient of 95,000 M−1cm−1, mGarnet can be efficiently excited with 640-nm light on the red edge of its 598-nm excitation band. A large Stokes shift allows essentially the entire fluorescence emission to be collected even with 640-nm excitation, counterbalancing the lower fluorescence quantum yield of mGarnet, 9.1%, that is typical of far-red FPs. We demonstrate an excellent performance as a live-cell fusion marker in STED microscopy, using 640 nm excitation and 780 nm depletion wavelengths. PMID:26648024

  1. Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Korsakov, Andrey V.; Hutsebaut, Didier; Theunissen, Karel; Vandenabeele, Peter; Stepanov, Alexander S.

    2007-12-01

    Coesite inclusions occur in a wide range of lithologies and coesite is therefore a powerful ultrahigh-pressure (UHP) indicator. The transformation of coesite to quartz is evidenced by three optically well identifiable characteristics (e.g. palisade textures, radial crack patterns, polycrystalline quartz pseudomorphs). Under overpressure monomineralic coesite (on an optical basis), lacking the above transformation characteristics may survive. Raman micro-spectroscopy was applied on monomineralic coesite inclusions in garnet porphyroblasts from diamond-bearing garnet-clinozoisite-biotite gneisses of the Barchi-Kol area (Kokchetav Massif, Northern Kazakhstan). These coesite inclusions are euhedral and display a characteristic anisotropic hallo. However, Raman maps and separate spectra of these inclusions display shifted bands for coesite and quartz. Microscopically undetectable, quartz shows on the Raman map as a thin shell around coesite inclusion. Shift of the main coesite band allows to estimate their overpressure: coesite inclusions record 0-2.4 GPa in garnet and zircon. The quartz shell remains under lower pressure 0-1.6 GPa. The possible application of coesite and quartz Raman geobarometers for UHP metamorphic rocks is discussed.

  2. Effect of recording condition on the diffraction efficiency of magnetic hologram with magnetic garnet films

    SciTech Connect

    Nakamura, Yuichi Takagi, Hiroyuki; Lim, Pang Boey; Inoue, Mitsuteru

    2014-09-14

    A holographic memory has been attracting attention as recording media with high recording density and high data transfer rate. We have studied the magnetic garnets as a rewritable and long life media for magnetic holography. However, since the signal intensity of reconstructed image was relatively low, the effects of recording conditions on the diffraction efficiency of magnetic hologram were investigated with experiments and the numerical simulation using COMSOL multi-physics. The diffraction efficiency tends to decrease as increasing the spatial frequency, and the use of short pulse laser with the pulse width of 50 ps was found to be effective to achieve high diffraction efficiency. This suggests that the formation of clear magnetic fringe similar to interference pattern can be obtained by the use of short pulse laser since undesirable heat diffusion during radiation does not occur. On the other hand, the diffraction efficiency increased as increasing the film thickness up to 3.1 μm but was saturated in the garnet film thicker than 3.1 μm in the case of spatial frequency of 1500 line pair/mm. The numerical simulation showed that the effective depth of magnetic fringe was limited about 1.8 μm irrespective of the garnet film thickness because the fringes were connected by thermal diffusion near the surface of the film, and the effective depth is limited due to this connection of the magnetic fringe. Avoiding this fringe connection, much higher diffraction efficiency will be achieved.

  3. Effects of processing on the low-voltage performance of cathodoluminescent garnet phosphors

    SciTech Connect

    Phillips, M.L.F.; Shea, L.E.

    1995-08-01

    Field emission flat panel displays place new demands on the performance of cathodoluminescent phosphors. In particular, such phosphors must be efficient at lower voltages (ca. 100-1000 V), and must withstand higher current densities than are present on cathode ray tube screens. ZnO:Zn has been studied extensively as a low-voltage phosphor, but problems such as poor chromatic saturation and temperature sensitivity of emission remain. In this work the use of terbium-doped garnet phases such as yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG) as low voltage green-emitting phosphors is evaluated. Hydrothermal synthesis yields well-faceted YAG grains with particle diameters of less than 1 {mu}m. Cathodoluminescent efficiency at a particular voltage was not affected by synthetic route, though the hydrothermally synthesized material was less susceptible to damage at high power densities. An efficiency of 3.5 lm/W was observed for GGG:Tb at 800 V. Deposition of the phosphors onto conducting screens increased their efficiencies at very low voltages (< 200 V). These materials may be considered alternatives to reduced zinc oxide as green-emitting phosphors.

  4. Structural, elastic and vibrational properties of nanocrystalline lutetium gallium garnet under high pressure.

    PubMed

    Monteseguro, V; Rodríguez-Hernández, P; Ortiz, H M; Venkatramu, V; Manjón, F J; Jayasankar, C K; Lavín, V; Muñoz, A

    2015-04-14

    An ab initio study of the structural, elastic and vibrational properties of the lutetium gallium garnet (Lu3Ga5O12) under pressure has been performed in the framework of the density functional theory, up to 95 GPa. Pressure dependence of the elastic constants and the mechanical stability are analyzed, showing that the garnet structure is mechanically unstable above 87 GPa. Lattice-dynamics calculations in bulk at different pressures have been performed and compared with Raman scattering measurements of the nanocrystalline Tm(3+)-doped Lu3Ga5O12 up to 60 GPa. The theoretical frequencies and pressure coefficients of the Raman active modes for bulk Lu3Ga5O12 are in good agreement with the experimental data measured for the nano-crystals. The contributions of the different atoms to the vibrational modes have been analyzed based on the calculated total and partial phonon density of states. The vibrational modes have been discussed in relation to the internal and external modes of the GaO4 tetrahedron and the GaO6 octahedron. The calculated infrared modes and their pressure dependence are also reported. Our results show that with this nano-garnet size the sample has essentially bulk properties.

  5. Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Hutsebaut, Didier; Theunissen, Karel; Vandenabeele, Peter; Stepanov, Alexander S

    2007-12-15

    Coesite inclusions occur in a wide range of lithologies and coesite is therefore a powerful ultrahigh-pressure (UHP) indicator. The transformation of coesite to quartz is evidenced by three optically well identifiable characteristics (e.g. palisade textures, radial crack patterns, polycrystalline quartz pseudomorphs). Under overpressure monomineralic coesite (on an optical basis), lacking the above transformation characteristics may survive. Raman micro-spectroscopy was applied on monomineralic coesite inclusions in garnet porphyroblasts from diamond-bearing garnet-clinozoisite-biotite gneisses of the Barchi-Kol area (Kokchetav Massif, Northern Kazakhstan). These coesite inclusions are euhedral and display a characteristic anisotropic hallo. However, Raman maps and separate spectra of these inclusions display shifted bands for coesite and quartz. Microscopically undetectable, quartz shows on the Raman map as a thin shell around coesite inclusion. Shift of the main coesite band allows to estimate their overpressure: coesite inclusions record 0-2.4 GPa in garnet and zircon. The quartz shell remains under lower pressure 0-1.6 GPa. The possible application of coesite and quartz Raman geobarometers for UHP metamorphic rocks is discussed.

  6. Magnetooptics of quintet states of Tb3+ ion in terbium-yttrium aluminum garnet

    NASA Astrophysics Data System (ADS)

    Valiev, U. V.; Gruber, J. B.; Zandi, B.; Rustamov, U. R.; Rakhmatov, A. S.; Dzhuraev, D. R.; Narzullaev, N. M.

    2005-03-01

    The luminescence spectra and the degrees of magnetic circular polarization of luminescence (MCPL) have been studied in paramagnetic garnet Tb0.2Y2.8Al5O12 (YAG:Tb3+) for the radiative 4f-4f transition 5D4 ® 7F6. The features of the spectral dependencies of the MCPL degree with allowed (in symmetry) optical transitions between the Stark sublevels of the ground 7F6 and excited 5D4 multiplets of the non-Kramers rare-earth Tb3+ ion have been found in the YAG garnet structure. In the paramagnetic garnet Tb0.2Y2.8Al5O12 within the close ultraviolet spectral range, the non-trivial features of the spectra of magnetic circular dichroism (MCD) have been found; they evidence a significant contribution of the quasi-doublet states in the multiplets 5D3, 5G5 and 5L10 to magnetooptics of the 4f-4f transitions. The results of numerical calculations of the energy and wave functions have been presented for some Stark sublevels of the 5D4 and 7F6 multiplets of the Tb3+ ion in the crystalline field of D2 symmetry.

  7. Oxygen Isotope Zoning in Skarn Garnets: Evidence for Spatial and Temporal Fluid Source Variability in the Sierra Nevada and Mojave

    NASA Astrophysics Data System (ADS)

    Gevedon, M. L.; Ryan-Davis, J.; Lackey, J. S.; Barnes, J.; Kitajima, K.; Valley, J. W.

    2014-12-01

    Skarns provide insight to the depth, longevity, and dominant fluid regime associated with Sierra Nevada plutonism and Mesozoic magmatism in the Mojave National Preserve, which represent different spatial and temporal exposures of the Mesozoic arc. Skarns from these regions may serve as proxies for intricacies in the fluid source, and have the potential to resolve magmatic flare-ups and relative depths of emplacement. Both laser fluorination (LF) and secondary ion mass spectrometry (SIMS) δ18O analyses of garnet from multiple Mojave (Lucerne valley) skarns indicate a strong, early influence of meteoric fluid despite the presence of relatively deep plutonism. LF data from individual whole garnets and garnet chips broken during sample preparation reveal variation from +4.2‰ to -8.8‰ (n = 24), with an average of approximately -4.0‰. The large spread in these LF data suggest that (A) δ18O reflects an average of varying δ18O (fluid) compositions spanning multiple garnet growth oscillations; or (B) multiple generations of garnets exist within individual skarns, the growth of each coinciding with changes in the hydrothermal source and composition. SIMS analysis of two individual Mojave skarn garnets with oscillatory zoning (seen in backscatter electron images) reveal crystal cores with δ18O values of -9.6‰, internal variations of -9.4‰ to -3.3‰, and crystal rims of -2.2‰ and -2.9‰ (precision ±0.3; 2σ). In general, δ18O values negatively correlate with andradite compositions, with high andradite zones having lower δ18O values ([AND + CaTi] compositions range from 100 to 73). Similar analyses (both SIMS and LF) of garnets from Sierra Nevadan skarns (Tungsten Hills region) show variation in δ18O values with LF data ranging from 5.4‰ to 6.2‰ (n = 8), with an average of 5.7‰, and an additional 2.7‰ value obtained from a garnet interior. SIMS data show δ18O compositional variation from 4.0‰ to 5.9‰. Data across the two Tungsten Hills garnets

  8. The Effect of fO2 on Partition Coefficients of U and Th between Garnet and Silicate Melt

    NASA Astrophysics Data System (ADS)

    Huang, F.; He, Z.; Schmidt, M. W.; Li, Q.

    2014-12-01

    Garnet is one of the most important minerals controlling partitioning of U and Th in the upper mantle. U is redox sensitive, while Th is tetra-valent at redox conditions of the silicate Earth. U-series disequilibria have provided a unique tool to constrain the time-scales and processes of magmatism at convergent margins. Variation of garnet/meltDU/Th with fO2 is critical to understand U-series disequilibria in arc lavas. However, there is still no systematic experimental study about the effect of fO2 on partitioning of U and Th between garnet and melt. Here we present experiments on partitioning of U, Th, Zr, Hf, Nb, Ta, and REE between garnet and silicate melts at various fO2. The starting material was hydrous haplo-basalt. The piston cylinder experiments were performed with Pt double capsules with C-CO, MnO-Mn3O4 (MM), and hematite-magnetite (HM) buffers at 3 GPa and 1185-1230 oC. The experiments produced garnets with diameters > 50μm and quenched melt. Major elements were measured by EMPA at ETH Zurich. Trace elements were determined using LA-ICP-MS at Northwestern University (Xi'an, China) and SIMS (Cameca1280 at the Institute of Geology and Geophysics, Beijing, China), producing consistent partition coefficient data for U and Th. With fO2 increasing from CCO to MM and HM, garnet/meltDU decreases from 0.041 to 0.005, while garnet/meltDTh ranges from 0.003 to 0.007 without correlation with fO2. Notably, garnet/meltDTh/U increases from 0.136 at CCO to 0.41 at HM. Our results indicate that U is still more compatible than Th in garnet even at the highest fO2 considered for the subarc mantle wedge (~NNO). Therefore, we predict that if garnet is the dominant phase controlling U-Th partitioning during melting of the mantle wedge, melts would still have 230Th excess over 238U. This explains why most young continental arc lavas have 230Th excess. If clinopyroxene is the dominant residual phase during mantle melting, U could be more incompatible than Th at high fO2

  9. Multicomponent diffusion in garnets I: general theoretical considerations and experimental data for Fe-Mg systems

    NASA Astrophysics Data System (ADS)

    Borinski, Sascha André; Hoppe, Ulrich; Chakraborty, Sumit; Ganguly, Jibamitra; Bhowmik, Santanu Kumar

    2012-10-01

    We have carried out a combined theoretical and experimental study of multicomponent diffusion in garnets to address some unresolved issues and to better constrain the diffusion behavior of Fe and Mg in almandine-pyrope-rich garnets. We have (1) improved the convolution correction of concentration profiles measured using electron microprobes, (2) studied the effect of thermodynamic non-ideality on diffusion and (3) explored the use of a mathematical error minimization routine (the Nelder-Mead downhill simplex method) compared to the visual fitting of concentration profiles used in earlier studies. We conclude that incorporation of thermodynamic non-ideality alters the shapes of calculated profiles, resulting in better fits to measured shapes, but retrieved diffusion coefficients do not differ from those retrieved using ideal models by more than a factor of 1.2 for most natural garnet compositions. Diffusion coefficients retrieved using the two kinds of models differ only significantly for some unusual Mg-Mn-Ca-rich garnets. We found that when one of the diffusion coefficients becomes much faster or slower than the rest, or when the diffusion couple has a composition that is dominated by one component (>75 %), then profile shapes become insensitive to one or more tracer diffusion coefficients. Visual fitting and numerical fitting using the Nelder-Mead algorithm give identical results for idealized profile shapes, but for data with strong analytical noise or asymmetric profile shapes, visual fitting returns values closer to the known inputs. Finally, we have carried out four additional diffusion couple experiments (25-35 kbar, 1,260-1,400 °C) in a piston-cylinder apparatus using natural pyrope- and almandine-rich garnets. We have combined our results with a reanalysis of the profiles from Ganguly et al. (1998) using the tools developed in this work to obtain the following Arrhenius parameters in D = D 0 exp{-[ Q 1bar + ( P-1)Δ V +]/ RT} for D {Mg/*} and D {Fe/*}: Mg

  10. Metasomatic Control of Water in Garnet and Pyroxene from Kaapvaal Craton Mantle Xenoliths

    NASA Technical Reports Server (NTRS)

    Peslier, Anne H.; Woodland, Alan B.; Bell, David R.; Lazarov, Marina; Lapen, Thomas J.

    2012-01-01

    Fourier transform infrared spectrometry (FTIR) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) were used to determine water, rare earth (REE), lithophile (LILE), and high field strength (HFSE) element contents in garnet and pyroxene from mantle xenoliths, Kaapvaal craton, southern Africa. Water enters these nominally anhydrous minerals as protons bonded to structural oxygen in lattice defects. Pyroxene water contents (150-400 ppm in clinopyroxene; 40-250 ppm in orthopyroxene) correlate with their Al, Fe, Ca and Na and are homogeneous within a mineral grains and a xenolith. Garnets from Jagersfontein are chemically zoned for Cr, Ca, Ti and water contents. Garnets contain 0 to 20 ppm H2 Despite the fast diffusion rate of H in mantle m inerals, the observations above indicate that the water contents of mantle xenolith minerals were not disturbed during kimberlite entrainment and that the measured water data represent mantle values. Trace elements in all minerals show various degrees of light REE and LILE enrichments indicative of minimal to strong metasomatism. Water contents of peridotite minerals from the Kaapvaal lithosphere are not related to the degree of depletion of the peridotites. Instead, metasomatism exerts a clear control on the amount of water of mantle minerals. Xenoliths from each location record specific types of metasomatism with different outcomes for the water contents of mantle minerals. At pressures . 5.5 GPa, highly alkaline melts metasomatized Liqhobong and Kimberley peridotites, and increased the water contents of their olivine, pyroxenes and garnet. At higher pressures, the circulation of ultramafic melts reacting with peridotite resulted in co-variation of Ca, Ti and water at the edge of garnets at Jagersfontein, overall decreasing their water content, and lowered the water content of olivines at Finsch Mine. The calculated water content of these melts varies depending on whether the water content of the peridotite

  11. Garnet peridotites from Williams kimberlites, north-central Montana, U.S.A

    USGS Publications Warehouse

    Hearn, B.C.; McGee, E.S.

    1983-01-01

    Two Williams kimberlites, 250x350m and 37x390m, in the eastern part of a swarm of 30 middle Eocene alnoitic diatremes in north-central Montana, USA, contain xenoliths of garnet-bearing lherzolites, harzburgites and dunites, in addition to spinel peridotites and upper and lower crustal amphibolites and granulites. Colluvial purple, red, and pink garnets are dominantly Mg- and Cr-rich, indicating their derivation From peridotites or megacrysts, and have CaO and Cr2O3 contents that fall in the lherzolite trend. Temperatures were calculated by the Lindsley-Dixon 20 kb method for lherzolites and by the O'Neill-Wood method for harzburgites and dunites, and pressures were calculated by the MacGregor method, or were assumed to be 50 kb for dunites. Most peridotites equilibrated at 1220-1350?C and 50-60 kb, well above a 44mW/m2 shield geotherm and on or at higher P than the graphite-diamond boundary. Four lherzolites are low T-P (830-990?C, 23-42 kb) and are close to the shield geotherm. All four low T-P lherzolites have coarse textures whereas the high T-P cluster has both coarse and porphyroclastic textures, indicating a range of conditions of deformation and recrystallization in a restricted high T-P range. The tiny size (0.01-0.2 mm) of granulated and euhedral olivines in several xenoliths shows that deformation was occurring just prior to incorporation in kimberlite and that ascent was rapid enough (40-70 km/hr) to retard Further coarsening of fine-grained olivine. For other high T-P peridotites, cessation of deformation and beginning of recrystallization before or during inclusion in kimberlite is suggested by larger (up to 3mm) euhedral olivines in a matrix of fine granulated olivine or by optical continuity of large and nearby small olivines. Two low T-P lherzolites contain distinctive, phlogopite-rimmed, 5-8mm clots of moderate-Cr garnet + Cr-spinel + Cr-diopside + enstatite that are inferred to have formed by reaction of an initial high-Cr garnet brought into the

  12. Strain-dependent evolution of garnets in a high pressure ductile shear zone using Synchroton x-ray microtomography

    NASA Astrophysics Data System (ADS)

    Macente, Alice; Fusseis, Florian; Menegon, Luca; John, Timm

    2016-04-01

    Synkinematic reaction microfabrics carry important information on the kinetics, timing and rheology of tectonometamorphic processes. Despite being routinely interpreted in metamorphic and structural studies, reaction and deformation microfabrics are usually described in two dimensions. We applied Synchrotron-based x-ray microtomography to document the evolution of a pristine olivine gabbro into a deformed omphacite-garnet eclogite in 3D. In the investigated samples, which cover a strain gradient into a shear zone from the Western Gneiss Region (Norway) previously described by John et al., (2009), we focused on the spatial transformation of garnet coronas into elongated clusters of garnets. Our microtomographic data allowed us to quantify changes to the garnet volume, their shapes and their spatial arrangement. We combined microtomographic observations with light microscope- and backscatter electron images as well as electron microprobe- (EMPA) and electron backscatter diffraction (EBSD) analyses to correlate mineral composition and orientation data with the x-ray absorption signal of the same mineral grains. This allowed us to extrapolate our interpretation of the metamorphic microfabric evolution to the third dimension, effectively yielding a 4-dimensional dataset. We found that: - The x-ray absorption contrast between individual mineral phases in our microtomographic data is sufficient to allow the same petrographic observations than in light- and electron microscopy, but extended to 3D. - Amongst the major constituents of the synkinematic reactions, garnet is the only phase that can be segmented confidently from the microtomographic data. - With increasing deformation, the garnet volume increases from about 9% to 25%. - Garnet coronas in the gabbros never completely encapsulate olivine grains. This may indicate that the reaction progressed preferentially in some directions, but also leaves pathways for element transport to and from the olivines that are

  13. Genetics Home Reference: iron-refractory iron deficiency anemia

    MedlinePlus

    ... refractory iron deficiency anemia iron-refractory iron deficiency anemia Enable Javascript to view the expand/collapse boxes. ... All Close All Description Iron-refractory iron deficiency anemia is one of many types of anemia , which ...

  14. Origin of garnet in aplite and pegmatite from Khajeh Morad in northeastern Iran: A major, trace element, and oxygen isotope approach

    NASA Astrophysics Data System (ADS)

    Samadi, Ramin; Miller, Nathan R.; Mirnejad, Hassan; Harris, Chris; Kawabata, Hiroshi; Shirdashtzadeh, Nargess

    2014-11-01

    Triassic monzogranites and granodiorites of the Khajeh Morad region in northeastern Iran are cut by two types of garnet-bearing intrusive veins: (1) aplite and (2) granitic pegmatite. The former is composed of quartz, feldspar, muscovite, with minor garnet, biotite, and ilmenite. The latter contains quartz, plagioclase (± quartz and muscovite inclusions), alkali feldspar, and muscovite, with minor amounts of garnet, tourmaline, beryl, columbite, and ilmenite. Garnet in both rock types has MnO > 12 wt.% and CaO < ~ 2 wt.% with spessartine-rich cores, and a core-to-rim increase in Fe, Mg, and Ca. Garnet cores are enriched in Y, REE, Zr, Nb, Ta, Hf, and U. The Y, HREE, and Mn concentrations show strong positive correlations in both types of garnet associations and decrease from core-to-rim. These core-to-rim elemental variations can be explained by increasing fluid content and H2O activity in magma, together with decreasing Mn contents of an evolved host melt. Aplite and pegmatite garnet δ18O values are nearly identical (~ 10.3‰, n = 7, SD = 0.09) and are similar to magmatic garnets in granitoids elsewhere. On the basis of calculated δ18O values for magma (~ 12.5 and 12.6‰) and quartz (~ 13.6‰, n = 7, SD = 0.08) as well as the major and trace element characteristics, we suggest that the Khajeh Morad garnets crystallized from a variably fractionated S-type monzogranitic magma.

  15. Cretaceous exhumation history of Cordillera Darwin, southern Patagonia, from patchily recrystallized garnet and U-Th-Pb monazite dating

    NASA Astrophysics Data System (ADS)

    Maloney, K. T.; Clarke, G. L.; Klepeis, K. A.; Fanning, C. M.; Wang, W.

    2010-12-01

    Garnet in amphibolite facies pelitic schists from Bahía Pia of Cordillera Darwin displays patchy textures whereby a single grain may have regions of turbid garnet with comparatively large inclusions of biotite, muscovite, plagioclase and quartz, juxtaposed against a region of clear, “ordinary” garnet. Clear areas with S1 inclusion trails are grossular rich, whereas post-S1 turbid areas are comparatively spessartine-pyrope rich. Raman spectroscopy identified the presence of an aqueous solution in turbid regions of garnet, lacking from clear areas. Turbid patches are associated with the growth of S2 kyanite and staurolite. Pseudosection modelling in Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3 (NCKFMASHTO) is consistent with garnet mode decreasing from c. 5% to less than 1% during exhumation of Cordillera Darwin, coinciding with the growth of S2 kyanite and staurolite at P≈9 kbar and T≈625°C. Turbid garnet in patchy and atoll-style textures is inferred to reflect recrystallization facilitated by fluid ingress whereby garnet cores, formed at higher P-T conditions than the rims, were preferentially recrystallised along grain cracks and boundaries. P-T paths inferred from the modelling indicate higher metamorphic conditions than previously documented, P conditions declining from 12 to 9 kbar over T= 610 to 630°C. U-Th-Pb dating of S2 monazite indicates that rapid exhumation was underway before 72.61±1.13 Ma, reflecting a tectonic shift from burial to uplift of Cordillera Darwin between c. 86 and c. 73 Ma. Sillimanite-bearing assemblages are restricted to contact aureoles associated with the intrusion of the Late Cretaceous Beagle Suite at shallower crustal conditions.

  16. Garnets in porphyry-skarn systems: A LA-ICP-MS, fluid inclusion, and stable isotope study of garnets from the Hongniu-Hongshan copper deposit, Zhongdian area, NW Yunnan Province, China

    NASA Astrophysics Data System (ADS)

    Peng, Hui-juan; Zhang, Chang-qing; Mao, Jing-wen; Santosh, M.; Zhou, Yun-man; Hou, Lin

    2015-05-01

    The Late Cretaceous Hongniu-Hongshan porphyry-skarn copper deposit is located in the Zhongdian area of northwestern Yunnan Province, China. Garnets from the deposit have compositions that range from Adr14Grs86 to almost pure andradite (Adr98Grs2) and display two different styles of zoning. The garnets are predominantly of magmatic-hydrothermal origin, as is evidenced by their 18Ofluid (5.4-6.9‰) and low Dfluid (-142‰ to -100‰) values, both of which likely result from late-stage magmatic open-system degassing. Three generations of garnet have been identified in this deposit: (1) Al-rich garnets (Grt I; Adr22-57Grs78-43) are anisotropic, have sector dodecahedral twinning, are slightly enriched in light rare earth elements (LREEs) compared with the heavy rare earth elements (HREEs), have negative or negligible Eu anomalies, and contain high concentrations of F. Fluid inclusions within these Al-rich garnets generally have salinities of 12-39 wt.% NaCl eq. and have liquid-vapor homogenization temperatures (Th) of 272-331 °C. The Grt I are most likely associated with low- to medium-salinity fluids that were generated by the contraction of an ascending vapor phase and that formed during diffusive metasomatism caused by pore fluids equilibrating with the host rocks at low W/R (water/rock) ratios. These garnets formed as a result of the high F activity of the system, which increased the solubility of Al within the magmato-hydrothermal fluids in the system. (2) Fe-rich garnets (Adr75-98Grs25-2) have trapezohedral faces, and are both anisotropic with oscillatory zoning and isotropic. These second-generation Fe-rich garnets (Grt II) have high ΣREE concentrations, are LREE-enriched and HREE-depleted, and generally have positive but variable Eu anomalies. All of the Fe-rich garnets contain high-salinity fluid inclusions with multiple daughter minerals with salinities of 33-80 wt.% NaCl eq. Some of them show higher temperatures of halite dissolution (465-591 °C) than

  17. HEPCIDIN AND IRON HOMEOSTASIS

    PubMed Central

    Ganz, Tomas; Nemeth, Elizabeta

    2014-01-01

    Despite fluctuations in dietary iron intake and intermittent losses through bleeding, the plasma iron concentrations in humans remain stable at 10–30 μM. While most of the iron entering blood plasma comes from recycling, appropriate amount of iron is absorbed from the diet to compensate for losses and maintain nontoxic amounts in stores. Plasma iron concentration and iron distribution are similarly regulated in laboratory rodents. The hepatic peptide hepcidin was identified as the systemic iron-regulatory hormone. In the efferent arc, hepcidin regulates intestinal iron absorption, plasma iron concentrations, and tissue iron distribution by inducing degradation of its receptor, the cellular iron exporter ferroportin. Ferroportin exports iron into plasma from absorptive enterocytes, from macrophages that recycle the iron of senescent erythrocytes, and from hepatocytes that store iron. In the more complex and less well understood afferent arc, hepatic hepcidin synthesis is transcriptionally regulated by extracellular and intracellular iron concentrations through a molecular complex of bone morphogenetic protein receptors and their iron-specific ligands, modulators and iron sensors. Through as yet undefined pathways, hepcidin is also homeostatically regulated by the iron requirements of erythroid precursors for hemoglobin synthesis. In accordance with the role of hepcidin-mediated iron redistribution in host defense, hepcidin production is regulated by inflammation as well. Increased hepcidin concentrations in plasma are pathogenic in iron-restrictive anemias including anemias associated with inflammation, chronic kidney disease and some cancers. Hepcidin deficiency causes iron overload in hereditary hemochromatosis and ineffective erythropoiesis. Hepcidin, ferroportin and their regulators represent potential targets for the diagnosis and treatment of iron disorders and anemias. PMID:22306005

  18. Oxygen isotope zoning in garnets from Franciscan eclogite blocks: evidence for rock-buffered fluid interaction in the mantle wedge

    NASA Astrophysics Data System (ADS)

    Errico, J. C.; Barnes, J.; Strickland, A.; Valley, J. W.

    2012-12-01

    The oxygen isotope composition of Franciscan Complex eclogite garnets and actinolite rind encasing the high-grade blocks have been analyzed to place constraints on the fluid history of these blocks. In situ SIMS oxygen isotope analysis of single garnet crystals from three eclogite blocks (Ring Mountain, Jenner Beach, Mt. Hamilton) shows an abrupt decrease in the δ18O value by ~1-3‰ from core to rim at ~120 ± 50 μm from the rim at all locations. The δ18O values of two Ring Mountain eclogite garnets decrease from 6.0 ± 0.3‰ to 3.8 ± 0.6‰ from core to rim. Four Mt. Hamilton eclogite garnets decrease from 8.6 ± 0.5‰ to 5.9 ± 0.6‰ from core to rim and two decrease from 7.1 ± 0.2‰ in the core to 5.7 ± 0.5‰ at the rim. Two Jenner Beach eclogite garnets decrease from ~11.0 to ~10‰, whereas two others show little to no variation at 9.9 ± 0.3‰ and 11.4 ± 0.2‰. δ18O values of eclogite garnet cores likely inherit the original oxygen isotope composition of the altered MORB protolith, whereas the abrupt and >1‰ change in the δ18O values of the garnet rims suggest interaction with a lower δ18O value fluid during the final stages of growth. Equilibrium calculations indicate that the temperature change associated with Franciscan eclogite metamorphism (400-600°C) is not likely to account for >~1‰ change in the δ18O value of the growing garnet. Previous work suggests sediments as a potential source of metasomatic fluid during blueschist facies metamorphism (300-350°C); however, these temperatures are too low for garnet growth and sedimentary derived fluids would have high δ18O values. Instead, mantle wedge peridotite is a significant source of lower δ18O material. We suggest that the oxygen composition of infiltrating slab derived fluids is buffered by surrounding ultramafic rock since the volume of ultramafic rock is much greater than that of the fluids. The oxygen isotope composition is recorded in the garnet during final stages of

  19. Mantle refertilization by melts of crustal-derived garnet pyroxenite: Evidence from the Ronda peridotite massif, southern Spain

    NASA Astrophysics Data System (ADS)

    Marchesi, Claudio; Garrido, Carlos J.; Bosch, Delphine; Bodinier, Jean-Louis; Gervilla, Fernando; Hidas, Károly

    2013-01-01

    Geochemical studies of primitive basalts have documented the presence of crustal-derived garnet pyroxenite in their mantle sources. The processes whereby melts with the signature of garnet pyroxenite are produced in the mantle are, however, poorly understood and somewhat controversial. Here we investigate a natural example of the interaction between melts of garnet pyroxenite derived from recycled plagioclase-rich crust and surrounding mantle in the Ronda peridotite massif. Melting of garnet pyroxenite at ˜1.5 GPa generated spinel websterite residues with MREE/HREE fractionation and preserved the positive Eu anomaly of their garnet pyroxenite precursor in whole-rock and clinopyroxene. Reaction of melts from garnet pyroxenite with depleted surrounding peridotite generated secondary fertile spinel lherzolite. These secondary lherzolites differ from common spinel lherzolite from Ronda and elsewhere by their lower-Mg# in clinopyroxene, orthopyroxene and olivine, lower-Cr# in spinel and higher whole-rock Al2O3, CaO, Sm/Yb and FeO* at a given SiO2. Remarkably, secondary spinel lherzolite shows the geochemical signature of ghost plagioclase in the form of positive Eu and Sr anomalies in whole-rock and clinopyroxene, reflecting the transfer of a low-pressure crustal imprint from recycled pyroxenite to hybridized peridotite. Garnet pyroxenite melting and melt-peridotite interaction, as shown in the Ronda massif, may explain how the signature of subducted or delaminated crust is transferred to the mantle and how a garnet pyroxenite component is introduced into the source region of basalts. The efficiency of these processes in conveying the geochemical imprint of crustal-derived garnet pyroxenite to extruded lavas depends on the reactivity of pyroxenite melt with peridotite and the mantle permeability, which may be controlled by prior refertilization reactions similar to those documented in the Ronda massif. Highly fertile heterogeneities produced by pyroxenite

  20. Petrogenesis of Garnet-bearing Rocks in the Grandfather Mountain Window, Blue Ridge Province, Western North Carolina

    NASA Astrophysics Data System (ADS)

    Frushour, A. M.; Abbott, R. N.

    2014-12-01

    The Grandfather Mountain Window in western North Carolina exposes the lowest structural level in the Blue Ridge Province. Rocks in the window constitute a Late Proterozoic basement-cover sequence. The basement consists mainly of Blowing Rock Gneiss (sic, porphyroblastic schist) and Wilson Creek Gneiss, both overlain unconformably by the Grandfather Mountain Formation. All of these rocks have been pervasively overprinted by greenschist facies metamorphism. The typical greenschist mineral assemblage involves combinations of chlorite, muscovite, biotite, actinolite, epidote, calcite, quartz, albite and K-feldspar. Garnet discovered in basement rock calls into question the metamorphic grade. The average garnet (core-rim) is (Fe1.63-1.71Mn0.64-0.77Ca0.52-0.37Mg0.10-0.12)Al1.98-1.96Si3.06-3.04O12; the average biotite is (K0.96Na0.06Ca0.02)(Fe1.73Mg0.87Mn0.02Ti0.04Al0.23)(Si2.83Al1.17)O10(OH)2; the average muscovite is (K1.03Na0.02Ca0.02)(Al1.57Fe0.26Mg0.16Ti0.01)(Si3.31Al0.69)O10(OH)2. Thermometry involving Fe-Mn-Mg components in these minerals gives 766°C (+/- 91°C) at 13.6 kbars (+/- 1.4 kbar), respectively. There are at least four explanations for garnet in these rocks: (1) Garnet may have been stabilized in the greenschist facies by non-AFM components (esp. Mn), but the compositions are not unusual for metamorphic garnet, biotite and muscovite, and the calculated temperatures are too high for greenschist facies. (2) The garnet may be relict from earlier contact metamorphism, but the garnet is not spatially related to otherwise common metamorphosed (greenschist facies) mafic dikes. (3) The garnet is a product of heating during mylonitization. Finally, and most likely, (4) the garnet may be relict from an earlier episode of regional metamorphism. Samples of porphyroblastic schist and greenstone from the same outcrop give low temperature, greenschist facies conditions.

  1. Compositional controls on spinel clouding and garnet formation in plagioclase of olivine metagabbros, Adirondack Mountains, New York

    USGS Publications Warehouse

    McLelland, J.M.; Whitney, P.R.

    1980-01-01

    Olivine metagabbros from the Adirondacks usually contain both clear and spinel-clouded plagioclase, as well as garnet. The latter occurs primarily as the outer rim of coronas surrounding olivine and pyroxene, and less commonly as lamellae or isolated grains within plagioclase. The formation of garnet and metamorphic spinel is dependent upon the anorthite content of the plagioclase. Plagioclase more sodic than An38??2 does not exhibit spinel clouding, and garnet rarely occurs in contact with plagioclase more albitic than An36??4. As a result of these compositional controls, the distribution of spinel and garnet mimics and visually enhances original igneous zoning in plagioclase. Most features of the arrangement of clear (unclouded) plagioclase, including the shells or moats of clear plagioclase which frequently occur inside the garnet rims of coronas, can be explained on the basis of igneous zoning. The form and distribution of the clear zones may also be affected by the metamorphic reactions which have produced the coronas, and by redistribution of plagioclase in response to local volume changes during metamorphism. ?? 1980 Springer-Verlag.

  2. Origin of biotite-hornblende-garnet coronas between oxides and plagioclase in olivine metagabbros, Adirondack region, New York

    USGS Publications Warehouse

    Whitney, P.R.; McLelland, J.M.

    1982-01-01

    Complex multivariant reactions involving Fe-Ti oxide minerals, plagioclase and olivine have produced coronas of biotite, hornblende and garnet between ilmenite and plagioclase in Adirondack olivine metagabbros. Both the biotite (6-10% TiO2) and the hornblende (3-6% TiO2) are exceptionally Titanium-rich. The garnet is nearly identical in composition to the garnet in coronas around olivine in the same rocks. The coronas form in two stages: (a) Plagioclase+Fe-Ti Oxides+Olivine+water =Hornblende+Spinel+Orthopyroxene??Biotite +more-sodic Plagioclase (b) Hornblende+Orthopyroxene??Spinel+Plagioclase =Garnet+Clinopyroxene+more-sodic Plagioclase The Orthopyroxene and part of the clinopyroxene form adjacent to olivine. Both reactions are linked by exchange of Mg2+ and Fe2+ with the reactions forming pyroxene and garnet coronas around olivine in the same rocks. The reactions occur under granulite fades metamorphic conditions, either during isobaric cooling or with increasing pressure at high temperature. ?? 1983 Springer-Verlag.

  3. [Iron-refractory iron deficiency anemia].

    PubMed

    Kawabata, Hiroshi

    2016-02-01

    The major causes of iron deficiency anemia (IDA) include iron loss due to bleeding, increased iron requirements, and decreased iron absorption by the intestine. The most common cause of IDA in Japanese women is iron loss during menstruation. Autoimmune atrophic gastritis and Helicobacter pylori infection can also cause IDA by reducing intestinal iron absorption. In addition to these common etiologies, germline mutations of TMPRSS6 can cause iron-refractory IDA (IRIDA). TMPRSS6 encodes matriptase-2, a membrane-bound serine protease primarily expressed in the liver. Functional loss of matriptase-2 due to homozygous mutations results in an increase in the expression of hepcidin, which is the key regulator of systemic iron homeostasis. The serum hepcidin increase in turn leads to a decrease in iron supply from the intestine and macrophages to erythropoietic cells. IRIDA is microcytic and hypochromic, but decreased serum ferritin is not observed as in IDA. IRIDA is refractory to oral iron supplementation, but does respond to intravenous iron supplementation to some extent. Because genetic testing is required for the diagnoses of IRIDA, a considerable number of cases may go undiagnosed and may thus be overlooked.

  4. First in-situ single-crystal structure refinement of a garnet included in diamond

    NASA Astrophysics Data System (ADS)

    Nestola, Fabrizio; Nimis, Paolo; Longo, Micaela; Kopylova, Maya; de Stefano, Andrea; Marzoli, Andrea; Fedortchouk, Yana; Manghnani, Murli; Harris, Jeff W.

    2010-05-01

    The study of mineral inclusions in diamond is providing invaluable insight into the geodynamics of the Earth's mantle. A complete characterization of inclusions in diamond is fundamental in order to evaluate the P-T-ƒO2 conditions and thus they represent a real "Earth's ultra-deep microprobe". The in-situ investigation of the inclusions using non-destructive techniques remains challenging. One of the potentially most powerful non-destructive methods is single-crystal X-ray diffraction. The application of such technique on inclusions in diamond is hampered by the complicated centering of the X-ray beam on the inclusion single-crystal (Kunz et al. 2002). Because of this experimental problem, in-situ single-crystal structure refinements of inclusions in diamond have never been carried out. In this work we investigated by X-ray diffraction a diamond-hosted garnet single-crystal from the Jericho kimberlite (Slave Craton, Canada). The garnet, not clearly visible under the microscope due to the irregular shape of the diamond host, had the largest size not greater than 100 microns. We used two STADI-IV STOE single-crystal diffractometers: the first instrument, equipped with a CCD detector, allowed us to collect a large number of diffraction reflections and to obtain an approximate orientation matrix for the garnet. Using this matrix, we mounted the diamond on the second instrument, equipped with a point detector and the software SINGLE (Angel et al. 2000), capable of obtaining an accurate X-ray beam centering through the 8-position centering method (this method is often used in high-pressure, in-situ X-ray studies). Such a procedure allowed us to measure with very high accuracy and precision the unit-cell edge (a = 11.5826(2)Å). Then we mounted back the diamond with the perfectly centered garnet on the first diffractometer and collected a complete X-ray intensity dataset in order to obtain complete structural information. We collected 410 unique reflections up to 2theta

  5. Iron deficiency anemia

    MedlinePlus

    Anemia - iron deficiency ... iron from old red blood cells. Iron deficiency anemia develops when your body's iron stores run low. ... You may have no symptoms if the anemia is mild. Most of the time, ... slowly. Symptoms may include: Feeling weak or tired more often ...

  6. Iron status of vegetarians.

    PubMed

    Craig, W J

    1994-05-01

    An appropriately planned well-balanced vegetarian diet is compatible with an adequate iron status. Although the iron stores of vegetarians may be reduced, the incidence of iron-deficiency anemia in vegetarians is not significantly different from that in omnivores. Restrictive vegetarian diets (eg, macrobiotic) are associated with more widespread iron-deficiency anemia. Western vegetarians who consume a variety of foods have a better iron status than do those in developing countries who consume a limited diet based on unleavened, unrefined cereals. Whereas phytates, polyphenolics, and other plant constituents found in vegetarian diets inhibit nonheme-iron absorption, vitamin C, citric acid, and other organic acids facilitate nonheme-iron absorption.

  7. Intensities of hypersensitive transitions in garnet crystals doped with Er3+ ions

    NASA Astrophysics Data System (ADS)

    Bol'Shakova, E. V.; Malov, A. V.; Ryabochkina, P. A.; Ushakov, S. N.; Nishchev, K. N.

    2011-06-01

    We examine the oscillator strengths and the intensity parameters Ω t ( t = 2, 4, 6) of yttrium-aluminum, scandium-containing, and gallium garnet crystals doped with Er3+ ions. A comparative analysis of the oscillator strengths and the intensity parameters Ω t ( t = 2, 4, 6) of garnets with different contents of Al3+ and Sc3+ ions (Gd2.4Er0.5Sc1.8Al3.3O12, Gd2.4Er0.5Sc1.9Al3.2O12, Gd2.4Er0.5Sc2.0Al3.1O12) is performed, as a result of which the oscillator strengths and the intensity parameters Ω t ( t = 2, 4, 6) of these crystals are shown to have close values. We find that Ca3(NbGa)5O12 crystals doped with Er3+ ions are characterized by highest values of the oscillator strengths for hypersensitive transitions and of the intensity parameter Ω2 of Er3+ ions compared to the values of these quantities in the examined garnet crystals, which is determined by the fact that the symmetry of the local environment of Er3+ ions in these crystals is C 1, C 2, or C 2ν. We reveal that, as the concentration of Er3+ ions in these crystals increases from 1 to 39 at %, both the oscillator strength of the hypersensitive transition 4 I 15/2 → 2 H 11/2 of Er3+ ions and their intensity parameter Ω2 tend to decrease, which can be related to an increase in the relative fraction of Er3+ ions with higher symmetry of the local environment.

  8. Comments on Evaluation of thermobarometers for garnet peridotites' by A. A. Finnerty and F. R. Boyd

    SciTech Connect

    Ganguly, J. )

    1992-02-01

    In order to evaluate the accuracy of a given combination of thermo-barometer, Finnerty and Boyd (1984) calculated the P-T conditions of two control samples of garnet lherzolite xenoliths, namely BD 2125 and PHN 1569. The importance of the samples lies in the fact that BD 2125 is diamond bearing, whereas PHN 1569 is graphite bearing. The alumina solubility in orthopyroxene (OPx) coexisting with garnet (Gt) is sensitive to both pressure and temperature changes and has thus been used widely, in combination with various geothermometers, for the thermo-barometry of garnet lherzolite xenoliths. Finnerty and Boyd (1984) concluded that the experimental calibrations of alumina solubility in OPx by Akella (1976) and Lane and Ganguly (1980) are as precise as, but probably less accurate than MC74 barometer,' where MC74 referred to the experimental calibration of alumina solubility in OPx by McGregor (1974) in the system MgSiO{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2} (MAS) based on synthesis experiments from glass of appropriate compositions. This conclusion on the accuracy of the above barometers was based on their observation that the use of only MC74 placed the calculated P-T conditions of the control samples in the right field with respect to the diamond-graphite equilibrium boundary, while those of Akella (1976; AK76) and Lane and Ganguly (1980; LG80) yielded P-T conditions that did not exactly satisfy the latter constraint, but were within 2 kb of the phase boundary. While it is clear from thermodynamic considerations that an unambiguous test of the accuracy of the calibrations cannot be carried out without making corrections for the effects of the additional components which are present in the natural samples but not in the experimental charges, the calculations of Finnerty and Boyd (1984) using LG80 are grossly erroneous.

  9. An occurrence of metastable cristobalite in high-pressure garnet Granulite

    USGS Publications Warehouse

    Darling, R.S.; Chou, I.-Ming; Bodnar, R.J.

    1997-01-01

    High-pressure (0.8 gigapascals) granulite facies garnet from Gore Mountain, New York, hosts multiple solid inclusions containing the low- pressure silica polymorph cristobalite along with albite and minor ilmenite. Identification of cristobalite is based on Raman spectra, electron microprobe analysis, and microthermometric measurements on the ??/?? phase transformation. The cristobalite plus albite inclusions may have originated as small, trapped samples of hydrous sodium-aluminum-siliceous melt. Diffusive loss of water from these inclusions under isothermal, isochoric conditions may have resulted in a large enough internal pressure decrease to promote the metastable crystallization of cristobalite.

  10. Evidence of dilute ferromagnetism in rare-earth doped yttrium aluminium garnet

    SciTech Connect

    Farr, Warrick G.; Goryachev, Maxim; Le Floch, Jean-Michel; Tobar, Michael E.; Bushev, Pavel

    2015-09-21

    This work demonstrates strong coupling regime between an erbium ion spin ensemble and microwave hybrid cavity-whispering gallery modes in a yttrium aluminium garnet dielectric crystal. Coupling strengths of 220 MHz and mode quality factors in excess of 10{sup 6} are demonstrated. Moreover, the magnetic response of high-Q modes demonstrates behaviour which is unusual for paramagnetic systems. This behaviour includes hysteresis and memory effects. Such qualitative change of the system's magnetic field response is interpreted as a phase transition of rare earth ion impurities. This phenomenon is similar to the phenomenon of dilute ferromagnetism in semiconductors. The clear temperature dependence of the phenomenon is demonstrated.

  11. Luminescence of Terbium and Neodymium Ions in Yttrium Aluminum Garnet Xerogels on Porous Anodic Alumina

    NASA Astrophysics Data System (ADS)

    Rudenko, M. V.; Gaponenko, N. V.; Mudryi, A. V.; Orekhovskaya, T. I.

    2016-03-01

    Luminescent structures of yttrium aluminum garnet doped with rare-earth elements Tb and Nd (YAG:Tb3+ and YAG:Nd3+) were formed by the sol-gel route on films of porous anodic alumina. The morphology, phase composition, and luminescence of the fabricated structures were investigated. Photoluminescence spectra of the YAG:Tb3+ and YAG:Nd3+ structures revealed emission bands due to electronic transitions of the relevant rare-earth elements. Fine structure was observed in the luminescence bands of all fabricated samples and was associated with the manifestation of a Stark effect.

  12. Erbium-doped yttrium aluminium garnet ablative laser treatment for endogenous ochronosis.

    PubMed

    Chaptini, Cassandra; Huilgol, Shyamala C

    2015-08-01

    Ochronosis is a rare disease characterised clinically by bluish-grey skin discolouration and histologically by yellow-brown pigment deposits in the dermis. It occurs in endogenous and exogenous forms. Endogenous ochronosis, also known as alkaptonuria, is an autosomal recessive disease of tyrosine metabolism, resulting in the accumulation and deposition of homogentisic acid in connective tissue. We report a case of facial endogenous ochronosis and coexistent photodamage, which was successfully treated with erbium-doped yttrium aluminium garnet laser resurfacing and deep focal point treatment to remove areas of residual deep pigment.

  13. Preliminary study of laryngeal sacculectomy in horses, using a neodymium:yttrium aluminum garnet laser technique.

    PubMed

    Shires, G M; Adair, H S; Patton, C S

    1990-08-01

    In an attempt to ablate the laryngeal saccule as an alternative method of sacculectomy (conventially done through a laryngotomy incision for laryngeal hemiplegia) a neodymium:yttrium aluminum garnet laser was used transendoscopically in noncontact fashion in 6 horses. The procedure was easy, quick, and labor-saving, with few complications. Endoscopically, the lased sacculectomy site appeared healed at postsurgical day 42. On postsurgical day 42, microscopic examination revealed mucosal remnants under the granulation bed. Laser energy caused thermal damage to tissues adjacent to the lased saccule. Additional work must be done to refine the technique before it can be recommended for clinical applications.

  14. Fabrication and characterization of cerium-doped terbium gallium garnet with high magneto-optical properties.

    PubMed

    Chen, Zhe; Hang, Yin; Yang, Lei; Wang, Jun; Wang, Xiangyong; Hong, Jiaqi; Zhang, Peixiong; Shi, Chunjun; Wang, Yaqi

    2015-03-01

    High optical quality (Tb((1-x))Ce(x))₃Ga₅O₁₂ (TCGG) single crystal has been grown by the Czochralski method. The optical and magneto-optical properties of the TCGG are analyzed in detail and the Verdet constant (V) of TCGG is compared with that of undoped terbium gallium garnet (TGG) crystal. TCGG presents a very high transmittance, particularly in the visible-near infrared (VIS-NIR) region, and its V is obviously larger than that of TGG in the VIS-NIR region. The figure of merit and optical features point out the superior characteristics of TCGG with respect to TGG.

  15. Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

    SciTech Connect

    Ostafiychuk, B. K.; Yaremiy, I. P. Yaremiy, S. I.; Fedoriv, V. D.; Tomyn, U. O.; Umantsiv, M. M.; Fodchuk, I. M.; Kladko, V. P.

    2013-12-15

    The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He{sup +} ions has been investigated using high-resolution X-ray diffraction methods and the generalized dynamic theory of X-ray scattering. The main types of growth defects in GGG single crystals and radiation-induced defects in the ion-implanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose.

  16. Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

    NASA Astrophysics Data System (ADS)

    Ostafiychuk, B. K.; Yaremiy, I. P.; Yaremiy, S. I.; Fedoriv, V. D.; Tomyn, U. O.; Umantsiv, M. M.; Fodchuk, I. M.; Kladko, V. P.

    2013-12-01

    The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He+ ions has been investigated using high-resolution X-ray diffraction methods and the generalized dynamic theory of X-ray scattering. The main types of growth defects in GGG single crystals and radiation-induced defects in the ion-implanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose.

  17. Retinal detachment as a complication of neodymium: yttrium aluminum garnet laser cyclophotocoagulation.

    PubMed

    Geyer, O; Neudorfer, M; Lazar, M

    1993-05-01

    We report a traction retinal detachment that developed within one month of transscleral neodymium: yttrium aluminum garnet (Nd:YAG) laser cyclophotocoagulation, a previously unreported complication of the new cyclodestructive procedure. A 17-year-old boy was referred to our department with uncontrolled aphakic glaucoma OD after having undergone cyclocryotherapy twice. Three treatments with transscleral Nd:YAG cyclophotocoagulation were done over nine months to lower his intraocular pressure. Hypotony and traction retinal detachment occurred after the third laser treatment and was managed successfully by vitrectomy with a fluid-gas exchange. Thus, the possibility of this additional complication should be remembered when doing transscleral Nd:YAG cyclophotocoagulation. PMID:8517586

  18. Luminescence of spodumene and garnet crystals excited by subnanosecond and nanosecond electron beams

    NASA Astrophysics Data System (ADS)

    Tarasenko, V. F.; Solomonov, V. I.; Polisadova, E. F.; Burachenko, A. G.; Baksht, E. Kh.

    2012-05-01

    The pulsed cathode luminescence of spodumene and yttrium-aluminum garnet crystals activated by Mn2+ and Nd3+ ions, respectively, is studied. Luminescence is excited by the irradiation of the crystals by electron beams with a duration of 0.1, 0.25, 0.65, and 10 ns and a current density of ˜40 and 100 A/cm2 at an electron energy of ˜200 keV. A decrease in the electron beam duration to several tenths of a nanosecond is shown not to cause substantial changes in the excitation mechanisms of pulsed cathode luminescence and its spectrum.

  19. Preparation of mixed bismuth and iron thin films by pulsed laser deposition using powder targets

    NASA Astrophysics Data System (ADS)

    Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Tanaka, Yuki; Suda, Yoshiaki

    2016-01-01

    Bismuth iron garnet (Bi3Fe5O12) thin films, for use in magnetic optics, were prepared by a pulsed laser deposition method using Bi and Fe mixed powder targets in oxygen gas. The deposition rate of the film strongly depended on the target mixture. The X-ray diffraction and X-ray photoelectron spectroscopy results suggest that the prepared films were not Bi3Fe5O12 but Bi-rich films, because of the lower melting temperature of Bi (544 K) compared with that of Fe (1811 K).

  20. First findings of monocrystalline aragonite inclusions in garnet from diamond-grade UHPM rocks (Kokchetav Massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Vandenabeele, Peter; Perraki, Maria; Moens, Luc

    2011-10-01

    The presence of aragonite inclusions in garnet from diamond-grade metamorphic rocks from the Kokchetav Massif, Northern Kazakhstan was identified for the first time by means of Raman analyses and mapping. Aragonite appears within the inclusions up to 50 μm in size as a single crystal. These inclusions have rounded shape. The grain boundary between the host-garnet is smooth. No cracks occur around the aragonite inclusions. No significant shift in the main aragonite Raman band was measured. These observations indicate that residual pressure within the inclusion is minor. These findings imply either non-UHPM origin of the host garnet or significant plastic deformation of host minerals during retrograde stage. These features should be taken into account for recovery peak metamorphic conditions and modeling of exhumation processes of UHPM complexes. PMID:21247793

  1. First findings of monocrystalline aragonite inclusions in garnet from diamond-grade UHPM rocks (Kokchetav Massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Vandenabeele, Peter; Perraki, Maria; Moens, Luc

    2011-10-01

    The presence of aragonite inclusions in garnet from diamond-grade metamorphic rocks from the Kokchetav Massif, Northern Kazakhstan was identified for the first time by means of Raman analyses and mapping. Aragonite appears within the inclusions up to 50 μm in size as a single crystal. These inclusions have rounded shape. The grain boundary between the host-garnet is smooth. No cracks occur around the aragonite inclusions. No significant shift in the main aragonite Raman band was measured. These observations indicate that residual pressure within the inclusion is minor. These findings imply either non-UHPM origin of the host garnet or significant plastic deformation of host minerals during retrograde stage. These features should be taken into account for recovery peak metamorphic conditions and modeling of exhumation processes of UHPM complexes.

  2. Neoarchean metamorphism recorded in high-precision Sm-Nd isotope systematics of garnets from the Jack Hills (Western Australia)

    NASA Astrophysics Data System (ADS)

    Eccles, K. A.; Baxter, E. F.; Mojzsis, S. J.; Marschall, H.; Williams, M. L.; Jercinovic, M. J.

    2013-12-01

    Studies of metasedimentary rocks from the Jack Hills, which host Earth's oldest known detrital minerals, have focused on zircon and occasionally monazite or xenotime, but no attention has been directed toward one of the most common mineral markers of metamorphism: garnet. Garnet can provide a record of the post-depositional, prograde metamorphic history of Archean metasedimentary rocks. Additionally, the use of a newly developed detrital garnet dating technique [1,2] may reveal information about pre-depositional metamorphism that could address lingering questions about the nature and timing of Earth's earliest tectonometamorphic events. Here we investigate garnet from the Jack Hills metasedimentary rocks to test whether they record in situ metamorphism or are a detrital relict of even older metamorphic events. We identified garnet in two bulk quartz-pebble conglomerate samples collected from the 'discovery' outcrop at Eranondoo Hill in the Jack Hills of Western Australia. Electron microprobe analyses of polished grains and SEM measurements of unpolished grain surfaces are consistent, revealing garnet composition indicative of a single generation/population of predominantly almandine-spessartine solid solution (~10-35% mole fraction spessartine). Compositional maps of garnet grains reveal little zoning and no discontinuities, most consistent with a single growth event. Dating Jack Hills' garnet via the Sm-Nd system is possible due to continued development of small sample analysis techniques, including running NdO+ TIMS analyses with Ta2O5 activator [3] permitting <50 ppm 2 sigma analytical precision on a 400pg in-house standard and continued improvement in blanks (<15pg full procedural blanks). Additionally, employing a nondestructive chemical prescreening technique (tabletop SEM) allows for grouping of multiple grains based on chemical similarity. Final Nd loads in the 450-750pg range routinely yield dates with precisions <×10Ma for two point isochrons between

  3. Rb-Sr ages from phengite inclusions in garnets from high pressure rocks of the Swiss Western Alps

    NASA Astrophysics Data System (ADS)

    de Meyer, Caroline M. C.; Baumgartner, Lukas P.; Beard, Brian L.; Johnson, Clark M.

    2014-06-01

    The Zermatt-Saas Fee Zone (ZSZ) was subducted to eclogite-facies conditions, reaching peak pressures and temperatures of 20-28 kbar and 500-630 °C. The rocks were partially overprinted under greenschist-facies conditions during exhumation. Previous Rb-Sr isochron ages obtained on matrix phengites in metasediments of the ZSZ have been interpreted to date early exhumation of the ZSZ. Here we present new Rb-Sr geochronology on phengite inclusions in garnets to date prograde growth of garnets. We show that garnet acted as a shield for the included phengites, limiting Rb and Sr isotope exchange with the bulk rock, upon complete enclosure of the mica, during garnet growth, even if peak metamorphism exceeded the Rb-Sr blocking temperature. Similarly, garnet isolated the micas from the matrix during subsequent recrystallization due to fluid infiltration or deformation during exhumation. Phengite inclusion ages for two metapelitic samples from the same locality (Triftji) are 44.86±0.49 Ma and 43.6±1.8 Ma, and are about 4 m.y. older than the corresponding matrix mica ages of 40.01±0.51 Ma and 39.5±1.1 Ma, respectively. The results confirm previous Sm-Nd and Lu-Hf geochronology on the ZSZ that indicated protracted garnet growth during prograde metamorphism, and confirm that at least parts of the ZSZ underwent peak metamorphic HP conditions less than 43 m.y. ago, followed by rapid exhumation to upper greenschist-facies conditions around 40 Ma ago.

  4. Garnet-melt partitioning at 10 GPa in the CMAS-CO2 system: a link between CO2-rich melts and majoritic-garnets in diamonds from the mantle?

    NASA Astrophysics Data System (ADS)

    Keshav, S.; Gudfinnsson, G. H.; Presnall, D. C.; Minarik, W. G.; Fei, Y.

    2005-12-01

    On the basis of mantle xenoliths and silicate inclusions in diamonds brought up by kimberlites, the mantle origin of kimberlite is beyond doubt. The mantle xenoliths and inclusions in diamonds have vastly improved constraints on the petrogenetic processes operating in the silicate portion of the Earth. Especially important among this group of mantle xenoliths is the rare suite of majoritic garnets trapped as inclusions in diamonds that have been interpreted as deeper (greater than 200 km) than usual samples from the mantle. While opinions vary on the ultimate origin of these majoritic garnets, on the basis of trace elements (for example, negative Eu anomalies indicating crystallization of feldspar and thus originally a much shallower origin) and light-element (carbon) isotope geochemistry, a popular view links them to subducted oceanic crust. In this contribution, we present experimentally determined partition coefficients of trace elements for majoritic garnets equilibrated with a kimberlitic melt at 10 GPa and 1800 C, in the CMAS-CO2 system, and test if there is a link between these inclusions and CO2-rich melts in the mantle. The experiments were performed in a MA-6/8 module using 14/8 assemblies with stepped Cr-doped MgO cells, MgO inner parts, Re-furnace, Type-C TC, and ZrO2 insulator. Starting mix was spiked with a suite of trace elements as AAS standard solutions and was contained in a sealed Pt capsule. Concentrations of major and trace elements were determined using EPMA and LA-ICPMS techniques, respectively. On the basis of calculated partition coefficients (D), almost all the trace elements, barring Lu (D greater than 1), are highly-to-moderately incompatible (D moderately-to-greatly less than 1). This behavior is perhaps a response to garnets becoming majoritic with increasing pressure. The data obtained here have been used to invert the trace element composition of melts that may have been in equilibrium with the majoritic garnets found as inclusions

  5. IBA investigations of loose garnets from Pietroasa, Apahida and Cluj-Someşeni treasures (5th century AD)

    NASA Astrophysics Data System (ADS)

    Bugoi, R.; Oanţă-Marghitu, R.; Calligaro, T.

    2016-03-01

    This paper reports the archaeometric investigations of 418 loose garnets from Pietroasa and Cluj-Someşeni treasures and Apahida II and III princely grave inventories (5th century AD). The chemical composition of the gems was determined by external beam micro-PIXE technique at the AGLAE accelerator of C2RMF, Paris, France. Complementary observations made by Optical Microscopy revealed details on the gemstones cutting and polishing and permitted to identify certain mineral inclusions. The compositional results evidenced several types of garnets from the pyralspite series, suggesting distinct provenances for these Early Medieval gems.

  6. Results of 40Ar/39Ar dating of phlogopites from kelyphitic rims around garnet grains (Udachnaya-Vostochnaya kimberlite pipe)

    NASA Astrophysics Data System (ADS)

    Yudin, D. S.; Tomilenko, A. A.; Alifirova, T. A.; Travin, A. V.; Murzintsev, N. G.; Pokhilenko, N. P.

    2016-07-01

    40Ar/39Ar dating of phlogopite from kelyphitic rims around garnet grains from the Udachnaya-Vostochnaya kimberlite pipe in the Sakha (Yakutia) Republic (Russia) revealed that when this mineral has contact with a kimberlite melt its age corresponds (within error limits) to that of the formation of the kimberlite pipe, thus indicating that the method may be used for dating kimberlites and related rocks. In mantle xenoliths, kelyphitic phlogopites rimming garnet grains partially lose radiogenic Ar, which results in a complex age spectrum. Rejuvenation of the K/Ar system in them is determined by the thermal impact of the kimberlite melt on captured rocks.

  7. Neonatal iron nutrition.

    PubMed

    Rao, R; Georgieff, M K

    2001-10-01

    Preterm infants are prone to iron deficiency. Their total body iron content at birth is low and gets further depleted by clinical practices such as uncompensated phlebotomy losses and exogenous erythropoietin administration during the neonatal period. Early iron deficiency appears to adversely affect cognitive development in human infants. To maintain iron sufficiency and meet the iron demands of catch-up postnatal growth, iron supplementation is prudent in preterm infants. A dose of 2-4 mg/kg/day is recommended for preterm infants who are fed exclusively human milk. A dose of 6 mg/kg/day or more is needed with the use of exogenous erythropoietin or to correct preexisting iron deficiency. However, due to the poor antioxidant capabilities of preterm infants and the potential role of iron in several oxidant-related perinatal disorders, indiscriminate iron supplementation should be avoided.

  8. Yttrium aluminium garnet under pressure: Structural, elastic, and vibrational properties from ab initio studies

    SciTech Connect

    Monteseguro, V.; Rodríguez-Hernández, P.; Muñoz, A.

    2015-12-28

    The structural, elastic, and vibrational properties of yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} are studied under high pressure by ab initio calculations in the framework of the density functional theory. The calculated ground state properties are in good agreement with the available experimental data. Pressure dependences of bond length and bulk moduli of the constituent polyhedra are reported. The evolution of the elastic constants and the major elastic properties, Young and shear modulus, Poisson's ratios, and Zener anisotropy ratio, are described. The mechanical stability is analyzed, on the light of “Born generalized stability criteria,” showing that the garnet is mechanically unstable above 116 GPa. Symmetries, frequencies, and pressure coefficients of the Raman-active modes are discussed on the basis of the calculated total and partial phonon density of states, which reflect the dynamical contribution of each atom. The relations between the phonon modes of Y{sub 3}Al{sub 5}O{sub 12} and the internal and external molecular modes of the different polyhedra are discussed. Infrared-active modes, as well as the silent modes, and their pressure dependence are also investigated. No dynamical instabilities were found below 116 GPa.

  9. Origin of high Li⁺ conduction in doped Li₇La₃Zr₂O₁₂ garnets

    SciTech Connect

    Chen, Yan; Rangasamy, Ezhiylmurugan; Liang, Chengdu; An, Ke

    2015-08-06

    Substitution of a native ion in the crystals with a foreign ion that differs in valence (aliovalent doping) has been widely attempted to upgrade solid-state ionic conductors for various charge carriers including O²⁻, H⁺, Li⁺, Na⁺, etc. The doping helps promote the high-conductive framework and dredge the tunnel for fast ion transport. The garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a fast Li⁺ solid conductor, which received much attention as an electrolyte candidate for all-solid-state lithium ion batteries, showing great potential to offer high energy density and minimize battery safety concerns to meet extensive applications in large energy storage systems such as those for electric vehicles and aerospace. In the Li-stuffed garnet framework of LLZO, the 3D pathway formed by the incompletely occupied tetrahedral sites bridged by a single octahedron enables the superior Li⁺ conductivity. For optimal performance, many aliovalent-doping efforts have been made throughout metal elements (Al³⁺, Ta⁵⁺) and metalloid elements (Ga³⁺, Te⁶⁺) in the periodic table with various valences to stabilize the high-conductive phase and increase the Li vacancy concentration.

  10. Origin of high Li⁺ conduction in doped Li₇La₃Zr₂O₁₂ garnets

    DOE PAGESBeta

    Chen, Yan; Rangasamy, Ezhiylmurugan; Liang, Chengdu; An, Ke

    2015-08-06

    Substitution of a native ion in the crystals with a foreign ion that differs in valence (aliovalent doping) has been widely attempted to upgrade solid-state ionic conductors for various charge carriers including O²⁻, H⁺, Li⁺, Na⁺, etc. The doping helps promote the high-conductive framework and dredge the tunnel for fast ion transport. The garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a fast Li⁺ solid conductor, which received much attention as an electrolyte candidate for all-solid-state lithium ion batteries, showing great potential to offer high energy density and minimize battery safety concerns to meet extensive applications in large energy storage systems such as thosemore » for electric vehicles and aerospace. In the Li-stuffed garnet framework of LLZO, the 3D pathway formed by the incompletely occupied tetrahedral sites bridged by a single octahedron enables the superior Li⁺ conductivity. For optimal performance, many aliovalent-doping efforts have been made throughout metal elements (Al³⁺, Ta⁵⁺) and metalloid elements (Ga³⁺, Te⁶⁺) in the periodic table with various valences to stabilize the high-conductive phase and increase the Li vacancy concentration.« less

  11. Multisite optical spectra and energy levels of trivalent thulium ions in yttrium scandium gallium garnet

    NASA Astrophysics Data System (ADS)

    Seltzer, Michael D.; Gruber, John B.; Hills, Marian E.; Quarles, Gregory J.; Morrison, Clyde A.

    1993-08-01

    Intrinsic structural disorder in scandium-substituted garnets, attributed to mixed occupancy of certain sites in the crystal lattice by different cations, has direct consequences for the optical spectra of rare-earth activator ions dispersed over multiple sites. In trivalent thulium-doped yttrium scandium gallium garnet (Tm3+:YSGG), site-selective laser excitation spectra reveal the presence of Tm3+ ions in regular D2 sites, disturbed regular sites, and in octahedral C3i sites. Absorption spectra obtained at 4 K between 0.26 and 1.85 μm are broader than those observed in more-ordered crystal hosts and include structure attributed to Tm3+ ions in sites of other than D2 symmetry. A crystal-field splitting calculation was carried out in which a parametrized Hamiltonian (including Coulombic, spin-orbit, and crystal-field terms for Tm3+ ions in D2 symmetry) was diagonalized for all manifolds of the Tm3+ (4f12) configuration. The rms deviation between 52 experimental and calculated Stark levels of Tm3+ in regular D2 sites was 5 cm-1.

  12. Garnet peridotite xenoliths in a Montana, U.S.A., kimberlite

    USGS Publications Warehouse

    Carter, Hearn B.; Boyd, F.R.

    1975-01-01

    Within a swarm of late middle Eocene subsilicic-alkalic diatremes, one diatreme 270 by 370 m and an associated dike contain common xenoliths of granulite and rare xenoliths of spinel peridotite and garnet peridotite. Six garnet lherzolite xenoliths have been found and these show a range of textures. Four are granular, and two are intensely sheared. Phlogopite is absent from the intensely sheared xenoliths and is thought to be primary in part in the granular xenoliths. Estimated temperatures and depths of equilibration of xenolith pyroxenes range from 920??C, 106 km (32 kbar) to 1315??C, 148 km (47 kbar). The xenoliths show increasing amounts of deformation with greater inferred depths of origin. The temperature-depth points suggest a segment of an Eocene geotherm for Montana which is similar in slope to the steep portion of the pyroxene-determined Lesotho geotherm (Boyd and Nixon, this volume) and is considerably steeper than typical calculated shield and continental geotherms at present. The steep trend could be a result of plate-tectonic shearing and magma ascension within an Eocene low-velocity zone. Preservation of intensely sheared textures requires rapid transport of material from about 150 km depth during active deformation of relatively dry rock. The occurrence of monticellite peridotite in this kimberlite diatreme suggests that magmas which crystallized to monticellite peridotite at relatively shallow depth could be one of the primitive types of kimberlite magma. ?? 1975.

  13. Water-Fluxed Fractional Melting: a new, Efficient Mechanism of Garnet Enrichment During Mid- and Lower-Crustal Anatexis

    NASA Astrophysics Data System (ADS)

    Luffi, P. I.; Saleeby, J. B.; Asimow, P. D.

    2005-12-01

    Garnet porphyroblasts of impressive size and/or abundance spatially associated with trondhjemitic leucosomes are known from a variety of migmatites worldwide [e.g. 1-4], and have frequently been interpreted as peritectic products of dehydration melting due to P-T variations controlled by regional-scale tectonothermal processes. However, to produce the observed abundance of garnet isochemically, such melting mechanisms would require significant overstepping of the solidus. They cannot, therefore, satisfactorily explain why partial melting often is triggered only locally and generates leucosome + abundant garnet in well delimited veins, pods and patches, leaving large volumes of paleosome essentially unaltered and garnet-free. Indeed, textural evidence suggests in many cases that partial melting proceeded in an open system, implying channelized volatile and/or melt influx and, possibly, simultaneous melt removal. To test this alternative mechanism for producing leucosome + garnet assemblages, we used the program Adiabat_1ph [5], a flexible front-end to the MELTS thermodynamic model [6] that facilitates such open-system calculations. We simulated the influx of water into a series of originally vapor-free model tonalites and diorites and tracked the effect of melt fractionation on the abundance of formed garnet. Calculations ran at constant P-T conditions close to the original solidus of the system by progressive addition of small amounts of water and continuous removal of generated melts. Our results show that water-fluxed fractional melting generates mainly trondhjemitic liquids and produces 3-5 times more garnet than melting in closed systems in the presence of similar amounts of water. This reaction may be written in a general form as Plg + Amph + Water ± Qtz ± Bt ± Cpx → Grt + Melt ± Cpx. Simulated water-fluxed fractional melting produces nearly homogeneous garnets in diorites, whereas garnets formed in tonalites are zoned due to larger compositional changes

  14. An oxygen isotope record of prograde and retrograde subduction fluids preserved in garnets from eclogite and related rocks from California and Greece

    NASA Astrophysics Data System (ADS)

    Page, F.; Strickland, A.; Essene, E. J.; Valley, J. W.

    2012-12-01

    In situ analysis of oxygen isotopes in garnet formed during subduction metamorphism offers a powerful new tool to unravel fluid histories of eclogite and related rocks. Slow intracrystalline diffusion rates in garnet allow it to preserve primary oxygen isotope ratios, and its utility in thermobarometry and geochronology allows oxygen isotope ratios to be tied to a P-T-t-fluids path. These paths can be used to identify when, in the history of a rock, fluid infiltration took place. Application of this method to orogenic eclogites has demonstrated external fluid interaction during prograde metamorphism (Russell et al., 2012 CMP in press). Analyses of garnets from metamafic and metasedimentary blocks in mélange-type subduction environments reveal a greater diversity in the timing of fluid infiltration events than those found in continental collision zones. Garnets from two glaucophane eclogites from Syros, Greece were found to be homogeneous within analytical uncertainty (δ18O=3.6±0.5‰ 2SD; 4.6±0.4‰). This result is consistant with existing studies in the region demonstrating limited fluid flow in eclogite blocks during metamorphism. Cation and oxygen isotope zoning in garnet from tectonic blocks of eclogite and garnet hornblendite from the Franciscan Formation reveals separate prograde and retrograde fluid histories. Garnet cores preserve a homogeneous prograde δ18O history with both high (11‰) and low (4‰) values in different samples. Multiple episodes of garnet resorption and regrowth record a dramatically changing bulk oxygen composition resulting in 6-7‰ neoformed garnet rims in both samples. Thermobarometry of inclusions (grt+cpx+phg) in eclogite garnet rims yields lower pressure blueschist-facies PT, requiring that low-δ18O fluid infiltration and garnet rim growth post-dates substantial exhumation. Tectonic blocks of metamafic and metasedimentary rocks are found in mélange on Santa Catalina Island. Samples of garnet hornblendite and garnet

  15. Serum iron test

    MedlinePlus

    ... of iron homeostasis: iron deficiency and overload. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al, ... EJ, Gardner LB. Anemia of chronic diseases. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al, ...

  16. Total iron binding capacity

    MedlinePlus

    ... GM. Disorders of iron homeostasis: iron deficiency and overload. In: Hoffman R, Benz EJ Jr, Silberstein LE, ... to achieve this important distinction for online health information and services. Learn more about A.D.A. ...

  17. Iron and Your Child

    MedlinePlus

    ... 24 months old. Serve iron-rich foods alongside foods containing vitamin C — such as tomatoes, broccoli, oranges, and strawberries — which improves the body's absorption of iron. Avoid serving coffee ...

  18. Ferrous Sulfate (Iron)

    MedlinePlus

    ... cells. It is used to treat or prevent iron-deficiency anemia, a condition that occurs when the body ... than prescribed by your doctor.Although symptoms of iron deficiency usually improve within a few days, you may ...

  19. Iron losses in sweat

    SciTech Connect

    Brune, M.; Magnusson, B.; Persson, H.; Hallberg, L.

    1986-03-01

    The losses of iron in whole body cell-free sweat were determined in eleven healthy men. A new experimental design was used with a very careful cleaning procedure of the skin and repeated consecutive sampling periods of sweat in a sauna. The purpose was to achieve a steady state of sweat iron losses with minimal influence from iron originating from desquamated cells and iron contaminating the skin. A steady state was reached in the third sauna period (second sweat sampling period). Iron loss was directly related to the volume of sweat lost and amounted to 22.5 micrograms iron/l sweat. The findings indicate that iron is a physiological constituent of sweat and derived not only from contamination. Present results imply that variations in the amount of sweat lost will have only a marginal effect on the variation in total body iron losses.

  20. Iron supplements (image)

    MedlinePlus

    The mineral iron is an essential nutrient for humans because it is part of blood cells, which carry oxygen to all body cells. There is no conclusive evidence that iron supplements contribute to heart attacks.

  1. 1064 nm laser emission of highly doped Nd: Yttrium aluminum garnet under 885 nm diode laser pumping

    NASA Astrophysics Data System (ADS)

    Lupei, V.; Pavel, N.; Taira, T.

    2002-06-01

    Highly efficient 1064 nm continuous-wave laser emission under 885 nm diode pumping in concentrated Nd: Yttrium aluminum garnet (YAG) crystals (up to 3.5 at. % Nd) and ceramics (up to 3.8 at. % Nd) is reported. A highly doped (2.4 at. %) Nd:YAG laser, passively Q switched by a Cr4+:YAG saturable absorber, is demonstrated.

  2. An experimental investigation of the stability of majoritic garnet in the Earth's mantle and an improved majorite geobarometer

    NASA Astrophysics Data System (ADS)

    Wijbrans, C. H.; Rohrbach, A.; Klemme, S.

    2016-05-01

    The stability of the majorite component in garnet has been experimentally investigated at high pressure and high temperature, focusing on the effect of bulk composition and temperature. High-pressure experiments were performed in a multi-anvil apparatus, at pressures ranging from 6 to 14.5 GPa, and temperatures between 1400 and 1700 °C. Experiments were performed in a range of bulk compositions in the system SiO2-Al2O3-Cr2O3-CaO-MgO with varying Cr/(Cr + Al) ratios. The majorite content of garnet gradually increases with pressure, and the composition of the garnet, specifically the Cr/(Cr + Al) ratio, exerts a significant effect on the majorite substitution. We found no significant effect of temperature. We use the experimental results in combination with the literature data to derive two empirical geobarometers, which can be used to determine the equilibration pressure of natural majoritic garnets of peridotitic and eclogitic bulk compositions. The barometer for peridotitic compositions is {{P}} = - 77.1 + 27.6 × {{Si}} + 1.67 × {{Cr}} And the barometer for eclogitic compositions is {{P}} = - 29.6 + 11.8 × {{Si}} + 7.81 × {{Na}} + 4.49 × {{Ca}}.

  3. Constituting Antebellum African American Identity: Resistance, Violence, and Masculinity in Henry Highland Garnet's (1843) "Address to the Slaves"

    ERIC Educational Resources Information Center

    Jasinski, James

    2007-01-01

    In August 1843 Presbyterian minister Henry Highland Garnet delivered his "Address to the Slaves of the United States of America" to the National Convention of Colored Citizens in Buffalo, NY. While often read (and almost as often dismissed) as either an unqualified call for a violent slave rebellion or, at the least, a celebration of prior acts of…

  4. Metasomatic mantle origin for Mbuji-Mayi and Kundelungu garnet and clinopyroxene megacrysts (Democratic Republic of Congo)

    NASA Astrophysics Data System (ADS)

    Pivin, M.; Féménias, O.; Demaiffe, D.

    2009-11-01

    Mbuji-Mayi (east Kasai province) and Kundelungu (Shaba province) are the two kimberlite fields known for a long time in the Democratic Republic of Congo (DRC). Mbuji-Mayi intrudes the Archean basement (Congo-Kasai Craton) and is diamond-rich, whereas Kundelungu cuts across Paleoproterozoic basement (Bangweulu block) and is diamond-poor. The megacryst suites (or discrete nodule suites) of both fields include garnet and clinopyroxene megacrysts. The pyrope-rich megacrysts can be subdivided in three groups on the basis of their Cr contents: low-Cr (0.00-1.79 wt.%Cr 2O 3; Mg #: 72.8-84.0); medium-Cr (1.93-5.16 wt.%Cr 2O 3; Mg #: 76.2-86.3) and high-Cr (5.42-7.10 wt.%Cr 2O 3; Mg #: 79.2-84.6). There are no significant geochemical differences between the garnets from Mbuji-Mayi and from Kundelungu. Polymineral inclusions composed of K-rich hydrated phases (phlogopite and amphibole), fresh glass and Cr-spinels are identified in garnets from all three groups, in both localities, which suggest a common origin. Two groups of diopside megacrysts from Mbuji-Mayi are distinguished on the basis of their Ca content: low-Ca (Ca #: 39.5-42.1; 0.61-0.92 wt.%Cr 2O 3) and medium-Ca (Ca #: 44.1-48.5; 0.41-1.09 wt.%Cr 2O 3); they differ from a third group of high-Cr diopsides (Ca #: 47.1-49.4; 1.31-2.77 wt.%Cr 2O 3). The major element compositions of DRC megacrysts are distinct from those of many other megacryst suites worldwide: the clinopyroxenes are lower in Fe and Ti and higher in Mg and the garnets contain more Cr and significantly less Ti, Fe and Al. These DRC megacryst compositions are intermediate between those of peridotite minerals and those of kimberlite megacrysts from other localities. Most garnets have "normal" REE profiles ((La/Yb) N = 0.003-0.027), whereas clinopyroxenes display relative LREE enrichment ((La/Yb) N = 5.1-43.2). The REE patterns of garnet and clinopyroxene megacrysts are similar to those from metasomatized South African mantle lherzolites. The differences

  5. Re-equilibration of primary fluid inclusions in peritectic garnet from metapelitic enclaves, El Hoyazo, Spain

    NASA Astrophysics Data System (ADS)

    Ferrero, Silvio; Bodnar, Robert J.; Cesare, Bernardo; Viti, Cecilia

    2011-05-01

    Primary-appearing fluid (FI) and melt (FI) inclusions occur in peritectic garnet from restitic enclaves from El Hoyazo (Spain). The inclusions were trapped under conditions of immiscibility during partial melting of the enclaves. Trapped fluids in Bt-Grt-Sil and Spl-Crd enclaves have been characterized by microthermometric, Raman spectroscopic, electron microprobe (EMP) and transmission electron microprobe (TEM) analyses to better constrain melt and fluid products and pressure conditions of the partial melting event. In Bt-Grt-Sil enclaves, FI are one phase and contain a CO2-N2 mixture, sometimes with graphite as trapped phase. In Spl-Crd enclaves, FI are two phase and contain an H2O-rich (≤ 90 mol%), with minor amounts of CO2, N2, and traces of H2S and CH4. Graphite often occurs as a trapped phase in the H2O-rich FI, and rare carbonates and other accessory minerals are also observed. Although decrepitation features are not recognized during examination with a petrographic microscope, FI densities based on mass balance constraints are always lower than expected at the inferred PT conditions of entrapment, 5-7 kbar and 800-900 °C. Extremely low densities (≈ 0.1 g cm- 1) of FI in Bt-Grt-Sil enclaves suggest a pressure ≤ 500 bar at 800-900 °C, while densities up to 0.53 g cm- 1 in Spl-Crd enclaves indicate P ≤ 3 kbar at 800-900 °C. Re-equilibration is likely to have occurred via partial decrepitation, as suggested by TEM studies that show rare partially annealed sub-μm cracks, containing small cavities, which may have been the pathways for fluid movement out of the inclusions. MI coexisting with FI have a rhyolitic, peraluminous composition, with higher H2O contents of MI in Spl-Crd enclaves (≈ 9 wt.%) compared to MI in Bt-Grt-Sil enclaves (≈ 3 wt.%). Based on published data, peritectic garnet in Spl-Crd enclaves grew in the presence of a leucogranitic melt saturated in an H2O-rich fluid, in good agreement with the inferred garnet PT growth conditions

  6. Garnet lherzolites from Louwrensia, Namibia: Bulk composition and P/T relations

    USGS Publications Warehouse

    Boyd, F.R.; Pearson, D.G.; Hoal, Karin O.; Hoal, B.G.; Nixon, P.H.; Kingston, M.J.; Mertzman, S.A.

    2004-01-01

    Bulk, mineral and trace element analyses of garnet lherzolite xenoliths from the Louwrensia kimberlite pipe, south-central Namibia, together with previously published Re-Os isotopic data [Chem. Geol. (2004)], form the most extensive set of chemical data for off-craton suites from southern Africa. The Louwrensia suite is similar to those from the Kaapvaal craton in that it includes both predominantly coarse-grained, equant-textured peridotites characterised by equilibration temperatures 1200 ??C. Redepletion ages range back to 2.1 Gy, concordant with the age of the crustal basement and about 1 Gy younger than the older peridotites of the adjacent Kaapvaal craton root. The coarse, low-temperature Louwrensia peridotites have an average Mg number for olivine of 91.6 in comparison to 92.6 for low-temperature peridotites from the craton. Orthopyroxene content averages 24 wt.% with a range of 11-40 wt.% for Louwrensia low-temperature peridotites, in comparison to a mean of 31.5 wt.% and a range of 11-44 wt.% for low-temperature peridotites from the Kaapvaal craton. Other major, minor and trace element concentrations in minerals forming Louwrensia lherzolites are more similar to values in corresponding Kaapvaal peridotite minerals than to those in lithospheric peridotites of Phanerozoic age as represented by off-craton basalt-hosted xenoliths and orogenic peridotites. Proportions of clinopyroxene and garnet in both the Louwrensia and Kaapvaal lherzolites overlap in the range up to 10 wt.% forming a trend extending towards pyrolite composition. Disequilibrium element partitioning between clinopyroxene and garnet for some incompatible trace elements is evidence that some of the trend is caused by enrichment following depletion. The disequilibrium is interpreted to have been caused by relatively recent growth of diopside, as previously suggested for cratonic peridotites. Attempts to constrain the depth of melting required to produce the Louwrensia peridotites suggests

  7. Metasomatic processes in the mantle beneath the Arkhangelsk province, Russia: evidence from garnet in mantle peridotite xenoliths, Grib pipe

    NASA Astrophysics Data System (ADS)

    Kargin, Alexei; Sazonova, Lyudmila; Nosova, Anna; Kovalchuk, Elena; Minevrina, Elena

    2015-04-01

    The Arkhangelsk province is located in the northern East European Craton and includes more than 80 bodies of kimberlite, alkaline picrite and other ultramafic and mafic rocks. They erupted through the Archean-Early Proterozoic basement into the Riphean-Paleozoic sedimentary cover. The Grib kimberlite pipe is located in the central part of the Arkhangelsk province in the Verkhotina (Chernoozerskoe) kimberlite field. The age of the Grib kimberlite is 376+-3 Ma (Rb-Sr by phlogopite). The Grib kimberlite pipe is the moderate-Ti kimberlites (TiO2 1-2 wt %) with strongly fractionated REE pattern , (La/Yb)n = 38-87. The Nd isotopic composition of the Grib pipe ranges epsilon Nd from -0.4 to + 1.0 and 87Sr/86Sr(t) from 0.7042 to 0.7069 (Kononova et al., 2006). Geochemical (Jeol JXA-8200 electron microprobe; SIMS; LA-ICP-MS) composition of clinopyroxene and garnet from mantle-derived xenoliths of the Grib kimberlite pipe was studied to provide new insights into metasomatic processes in the mantle beneath the Arkhangelsk province. Based on both major and trace element data, five geochemical groups of peridotitic garnet were distinguished. The partial melting of metasomatic peridotite with crystallization of a garnet-clinopyroxene association, and orthopyroxene assimilation by protokimberlitic melts was simulated and a model of garnet and clinopyroxene metasomatic origin was proposed. The model includes three stages: 1. Mantle peridotite was fertilized by subduction-derived sediment partial melts/fluids at the lithosphere-asthenosphere boundary to yield a CO2-bearing mantle peridotite (source I). 2. The partial melting of the carbonate-bearing mantle source 1 produced carbonatite-like melts (a degree of partial melting was 1,5 %), which could form the carbonatite-kimberlite rocks of the Mela River (Arkhangelsk province, 50 km North-West of Grib kimberlite) and also produce the metasomatic reworking of (carbonate-bearing) mantle peridotite (mantle source II) and form type-1

  8. Iron Dextran Injection

    MedlinePlus

    ... called iron replacement products. It works by replenishing iron stores so that the body can make more red blood cells. ... and order certain lab tests to check your body's response to iron dextran injection.Before having any laboratory test, tell ...

  9. Iron-Deficiency Anemia

    MedlinePlus

    ... the NHLBI on Twitter. What Is Iron-Deficiency Anemia? Español Iron-deficiency anemia is a common, easily ... Featured Video Living With and Managing Iron-Deficiency Anemia 05/18/2011 This video—presented by the ...

  10. Timing of eclogite-facies metamorphism of mafic and ultramafic rocks from the Pohorje Mountains (Eastern Alps, Slovenia) based on Lu-Hf garnet geochronometry

    NASA Astrophysics Data System (ADS)

    Sandmann, Sascha; Herwartz, Daniel; Kirst, Frederik; Froitzheim, Nikolaus; Nagel, Thorsten J.; Fonseca, Raúl O. C.; Münker, Carsten; Janák, Marian

    2016-10-01

    The metamorphic series of the Pohorje Mountains represents a part of the Eastern Alpine realm that was subjected to ultrahigh-pressure conditions during the Cretaceous Eo-Alpine orogenic cycle. The Slovenska Bistrica Ultramafic Complex located in the south-eastern Pohorje Mountains is an 8 km wide serpentinite body that contains lenses of garnet-bearing ultramafites and eclogites. It is embedded in and part of a mixed continental unit of metapelitic gneisses, orthogneisses, and eclogites. We present Lu-Hf garnet chronometry coupled with geochemical and petrological data from three samples: one garnet lherzolite, one eclogite from within the ultramafic complex, and one eclogite from the surrounding mixed unit. All obtained ages are identical within error, i.e. 96.6 ± 1.2 Ma and 94.8 ± 5.1 Ma, respectively, for the two eclogites and 91.6 ± 4.1 Ma for the garnet lherzolite. Garnet of all samples shows homogeneous concentrations of major bivalent elements due to high temperature re-equilibration. It does, however, preserve growth-related zoning with respect to Lu in all three samples implying that Lu-Hf ages still record garnet growth. The coincidence of ages suggests that the ultramafic complex and the surrounding continental mixed unit share the same subduction history, i.e. the complex was part of the subducting plate during and after the garnet growth stages.

  11. Iron and the liver.

    PubMed

    Pietrangelo, Antonello

    2016-01-01

    Humans have evolved to retain iron in the body and are exposed to a high risk of iron overload and iron-related toxicity. Excess iron in the blood, in the absence of increased erythropoietic needs, can saturate the buffering capacity of serum transferrin and result in non-transferrin-bound highly reactive forms of iron that can cause damage, as well as promote fibrogenesis and carcinogenesis in the parenchymatous organs. A number of hereditary or acquired diseases are associated with systemic or local iron deposition or iron misdistribution in organs or cells. Two of these, the HFE- and non-HFE hemochromatosis syndromes represent the paradigms of genetic iron overload. They share common clinical features and the same pathogenic basis, in particular, a lack of synthesis or activity of hepcidin, the iron hormone. Before hepcidin was discovered, the liver was simply regarded as the main site of iron storage and, as such, the main target of iron toxicity. Now, as the main source of hepcidin, it appears that the loss of the hepcidin-producing liver mass or genetic and acquired factors that repress hepcidin synthesis in the liver may also lead to iron overload. Usually, there is low-grade excess iron which, through oxidative stress, is sufficient to worsen the course of the underlying liver disease or other chronic diseases that are apparently unrelated to iron, such as chronic metabolic and cardiovascular diseases. In the future, modulation of hepcidin synthesis and activity or hepcidin hormone-replacing strategies may become therapeutic options to cure iron-related disorders.

  12. Magneto-optical Q-switching using magnetic garnet film with micromagnetic domains.

    PubMed

    Goto, Taichi; Morimoto, Ryohei; Pritchard, John W; Mina, Mani; Takagi, Hiroyuki; Nakamura, Yuichi; Lim, Pang Boey; Taira, Takunori; Inoue, M

    2016-08-01

    High-power giant pulses can be used applied in various applications with Q-switched micro-lasers. This method can shorten the pulse duration; however, active control is currently impossible in micro-lasers. To achieve precise pulse control while maintaining compactness and simplicity, we exploit the magneto-optical effect in magnetic garnet films with micromagnetic domains that can be actively controlled by a pulsed magnetic field. Our Q-switching technique enhances the output power by a factor of 4 × 103. Moreover, the device itself is smaller than other Q-switching devices. This novel type of active Q-switch can be combined with a micro-laser to obtain megawatt-order pulses. PMID:27505732

  13. Faraday effect improvement by Dy3+-doping of terbium gallium garnet single crystal

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Yang, Lei; Hang, Yin; Wang, Xiangyong

    2016-01-01

    Highly transparent Dy3+-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy3+ in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy3+-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS-NIR) at room temperature. The Verdet constants increase at measured wavelengths and high thermal stability was found in Dy3+-doped TGG, as compared to the properties of pure TGG, indicating that Dy3+-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS-NIR wavelengths.

  14. Pressure effect on elastic anisotropy of crystals from ab initio simulations: The case of silicate garnets

    SciTech Connect

    Mahmoud, A.; Erba, A. Dovesi, R.; Doll, K.

    2014-06-21

    A general methodology has been devised and implemented into the solid-state ab initio quantum-mechanical CRYSTAL program for studying the evolution under geophysical pressure of the elastic anisotropy of crystalline materials. This scheme, which fully exploits both translational and point symmetry of the crystal, is developed within the formal frame of one-electron Hamiltonians and atom-centered basis functions. Six silicate garnet end-members, among the most important rock-forming minerals of the Earth's mantle, are considered, whose elastic anisotropy is fully characterized under high hydrostatic compressions, up to 60 GPa. The pressure dependence of azimuthal anisotropy and shear-wave birefringence of seismic wave velocities for these minerals are accurately simulated and compared with available single-crystal measurements.

  15. Luminescent down shifting effect of Ce-doped yttrium aluminum garnet thin films on solar cells

    SciTech Connect

    Shao, Guojian; Lou, Chaogang; Kang, Jian; Zhang, Hao

    2015-12-21

    Ce-doped yttrium aluminum garnet (YAG:Ce) thin films as luminescent down shifting (LDS) materials are introduced into the module of crystalline silicon solar cells. The films are deposited by RF magnetron sputtering on the lower surface of the quartz glass. They convert ultraviolet and blue light into yellow light. Experiments show that the introduction of YAG:Ce films improves the conversion efficiency from 18.45% of the cells to 19.27% of the module. The increasing efficiency is attributed to LDS effect of YAG:Ce films and the reduced reflection of short wavelength photons. Two intentionally selected samples with similar reflectivities are used to evaluate roughly the effect of LDS alone on the solar cells, which leads to a relative increase by 2.68% in the conversion efficiency.

  16. Uphill diffusion, zero-flux planes and transient chemical solitary waves in garnet

    NASA Astrophysics Data System (ADS)

    Vielzeuf, D.; Saúl, A.

    2011-05-01

    Diffusion profiles in minerals are increasingly used to determine the duration of geological events. For this purpose, the distinction between growth and diffusion zoning is critical; it requires the understanding of complex features associated with multicomponent diffusion. Seed-overgrowth interdiffusion experiments carried out in the range 1,050-1,250°C at 1.3 GPa have been designed to quantify and better understand Fe-Mg-Ca interdiffusion in garnet. Some of the diffusion profiles measured by analytical transmission electron microscope show characteristic features of multicomponent diffusion such as uphill diffusion, chemical solitary waves, zero-flux planes and complex diffusion paths. We implemented three different methods to calculate the interdiffusion coefficients of the D matrix from the experimental penetration curves and determined that with Ca as the dependent component, the crossed coefficients of the D matrix are negative. Experiments and numerical simulations indicate that: (1) uphill diffusion in garnet can be observed indifferently on the three components Fe, Mg and Ca, (2) it takes the form of complementary depletion/repletion waves and (3) chemical waves occur preferentially on initially flat concentration profiles. Derived D matrices are used to simulate the fate of chemical waves in time, in finite crystals. These examples show that the flow of atoms in multicomponent systems is not necessarily unidirectional for all components; it can change both in space along the diffusion profile and in time. Moving zero-flux planes in finite crystals are transitory features that allow flux reversals of atoms in the diffusion zone. Interdiffusion coefficients of the D matrices are also analyzed in terms of eigenvalues and eigenvectors. This analysis and the experimental results show that depending on the composition of the diffusion couple, (1) the shape of chemical waves and diffusion paths changes; (2) the width of the diffusion zone for each component

  17. Nonlinear magneto-optical effects in all-garnet magnetophotonic crystals

    NASA Astrophysics Data System (ADS)

    Murzina, T. V.; Razdolski, I. E.; Aktsipetrov, O. A.; Grishin, A. M.; Khartsev, S. I.

    2009-04-01

    Nonlinear magneto-optical properties of all-garnet magnetophotonic crystals composed of alternating layers of ferromagnetic Bi 3Fe 5O 12 (BIG) and Sm 3Ga 5O 12 quarter-wavelength layers with a half-wavelength BIG microcavity mode are presented. The samples are grown by rf-magnetron sputtering on non-magnetic GGG substrate. Many-fold enhancement of the magnetization-induced effects in second-harmonic generation (SHG) as compared with linear magneto-optical effects are observed: the SHG magnetic contrast up to 50% and magnetization-induced rotation of the polarization plane of about 90° are measured at the resonance microcavity wavelengh of λ=779 nm.

  18. Garnet and chromite- bearing mantle peridotite xenoliths from Komsomolskaya pipe, Alakit field, Yakutia

    NASA Astrophysics Data System (ADS)

    Ashchepkov, Igor; Logvinova, Alla; Valdykin, Nikolai; Makovchuk, Igor; Karpenko, Mikhail; Spetsius, Zdislav; Khmelnikova, Olga; Palessky, Stanislav

    2014-05-01

    Fresh xenoliths in Alakit field in Siberian platform are rare. In the xenoliths from Komsomolskaya pipe there were found 30 xenoliths with fresh Cpx, Gar as well as chromites, phlogopites and ilmenites which allows to construct the Cpx - based geotherm which was before constructed for the Yubileynaya pipe (Ashchepkov et al., 2004). The comparison of the garnets from the breccias and porphyric kimberlites show more depleted and Cr- rich varieties of garnets as it is common for the other pipes. Only relatively fresh material from the dark - grey breccia good relatively fresh xenoliths could be used for the mineral thermobarometry. Large xenolths from the Komsomolskaya pipe belong mainly to the Gar harzburgite or refertilized lherzolite types as also detected on the Cr2O3 - CaO diagram where they belong mainly to the 5-11% Cr2O3 interval. The low Cr varieties are mainly referring to the Fe- enriched pyroxenites or to Phl metasomatites. In SCLM beneath Komsomolskaya pipe is essentially more heated then those beneath Yubileynaya and Sytykanskaya pipes and in lower part they are close to the PTXFO2 are closer in conditrions to the ilmenites which determined the . Peridotites from the lithosphere base (7-6GPa) are enriched in Fe and belong to the porphyroclustic or deformed type by chemistry Fe# =0.14-0.15. the relatively HT conditions were determined also for the peridotites from the 5.0-4. GPa. The most of the Cpx- refertilized varieties give the conditions of the middle part of the mantle section. Their garnest are enriched in CaO probably reflection reactions with the Ca- rich protokimberlites. The Na- richterite bearin xenoliths are from the same PT interval The cold clot in the 60-5.5 GPa (34 mwm-2) are represented by the peridotites of low Fe# 7-9 Fe- low peridotites with the garnets of sub-Ca types. But there are also varieties of reduced Cr and the Fe-enriched which are closer to the pyroxenites or Phl metasomatites which in Pt are from the upper part of mantle

  19. Garnet and clinopyroxene pseudomorphs: example of local mass balance in the Caledonides of western Norway.

    NASA Astrophysics Data System (ADS)

    Centrella, Stephen; Austrheim, Håkon; Putnis, Andrew

    2015-04-01

    The Precambrian granulite facies rocks of Lindås Nappe, Bergen Arcs, Caledonides of W.Norway are partially hydrated at amphibolites and eclogite facies conditions. The Lindås Nappe outcrop over an area of ca 1000 km2 where relict granulite facies lenses make up only ca 10%. At Hillandsvatnet, garnetite displays sharp hydration fronts across which the granulite facies assemblage composed of garnet (70%) and clinopyroxene (30%) is replaced by an amphibolite facies mineralogy defined by chlorite, epidote and amphibole. This setting allows us to assess the mechanism of fluid transport through an initially low permeability rock and how this induces changes of texture and element transport. The replacement of garnet and clinopyroxene is pseudomorphic so that the grain shapes of the garnet and clinopyroxene are preserved even if when they are completely replaced. This requires that the reactive fluids must pass through the solid crystal grains and this can be achieved by an interface coupled dissolution-precipitation mechanism. Porosity generation is a key feature of this mechanism (Putnis and Austrheim 2012). The porosity is not only a consequence of reduction in solid molar volume but depends on the relative solubilities of parent and product phases in the reactive fluid. Putnis et al. 2007 and Xia et al. 2009 have shown that even in pseudomorphic reactions where the molar volume increases, porosity may still be generated by the reaction. This is fundamental in understanding the element mobility and the mass transfer in a low permeability rock even more when the bulk rock composition of these two rocks stay unchanged; except a gain in water during amphibolitisation. The textural evolution during the replacement of garnet by pargasite, epidote and chlorite and pyroxene by hornblende and quartz in our rock sample conforms to that expected by a coupled dissolution-precipitation mechanism. SEM and Microprobe analysis coupled with the software XMapTools V 1.06.1 .(Lanari

  20. Spectroscopic investigation of the Cr to Tm energy transfer in Yttrium Aluminum Garnet (YAG) crystals

    NASA Technical Reports Server (NTRS)

    Dibartolo, B.

    1988-01-01

    New and interesting schemes have recently been considered for the efficient operation of solid-state ionic laser systems. Often the available data on these systems were obtained only because they seemed directly related to the laser performance and provide no insight into the physical processes. A more systematic approach is desirable, where more attention is devoted to the elementary basic processes and to the nature of the mechanisms at work. It is with this aim that we have undertaken the present study. Yttrium Aluminum Garnet (Y4Al5O12), called YAG, has two desirable properties as host for rare earth impurities: (1) trivalent rare earth ions can replace the yttrium without any charge compensation problem, and (2) YAG crystals have high cutoff energies. The results of measurements and calculations indicate that the Cr(3+) ion in YAG can be used to sensitize efficiently the Tm(3+) ion.

  1. Interplay of disorder and geometrical frustration in doped gadolinium gallium garnet.

    PubMed

    Woo, N; Silevitch, D M; Ferri, C; Ghosh, S; Rosenbaum, T F

    2015-07-29

    The geometrically frustrated triangular antiferromagnet Gadolinium Gallium Garnet (Gd3Ga5O12 or GGG) exhibits a rich mix of short-range order and isolated quantum states. We investigate the effects of up to 1% neodymium substitution for gallium on the ac magnetic response at temperatures below 1 K in both the linear and nonlinear regimes. Substitutional disorder actually drives the system toward a more perfectly frustrated state, apparently compensating for the effects of imperfect gadolinium/gallium stoichiometry, while at the same time more closely demarcating the boundaries of isolated, coherent clusters composed of hundreds of spins. Optical measurements of the local Nd environment substantiate the picture of an increased frustration index with doping. PMID:26154501

  2. Site selectivity in praseodymium- and bismuth-substituted gadolinium gallium garnet epilayers

    SciTech Connect

    Klages, C.P.

    1984-05-01

    Praseodymium- and bismuth-substituted gadolinium gallium garnet (GGG) layers have been prepared by liquid-phase epitaxy on (111)- and (110)-oriented GGG substrates. By an investigation of linear dichroism of Pr/sup 3 +/ -transitions, the supercooling dependence of dodecahedral site selectivity in Pr-substituted GGG can be shown to differ considerably for (110)- and (111)-epitaxial layers. An increase insite selectivity with supercooling is found in (111) layers while it is constant in (110) layers. The long-wavelength /sup 1/S /sub 0/ ..-->.. /sup 3/ P/sub 1/-transition of the B/sub 1/ /sup 3 +/ ion has been utilized to detect site selectivity in (110)oriented Bi-substituted GGG layers.

  3. Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

    NASA Astrophysics Data System (ADS)

    Semuk, E. Yu.; Berzhansky, V. N.; Prokopov, A. R.; Shaposhnikov, A. N.; Karavainikov, A. V.; Salyuk, O. Yu.; Golub, V. O.

    2015-11-01

    Magnetic properties of Bi1.5Gd1.5Fe4.5Al0.5O12 (84 nm) and Bi2.8Y0.2Fe5O12 (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi1.5Gd1.5Fe4.5Al0.5O12/Bi2.8Y0.2Fe5O12 bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction.

  4. Interplay of disorder and geometrical frustration in doped gadolinium gallium garnet

    NASA Astrophysics Data System (ADS)

    Woo, N.; Silevitch, D. M.; Ferri, C.; Ghosh, S.; Rosenbaum, T. F.

    2015-07-01

    The geometrically frustrated triangular antiferromagnet Gadolinium Gallium Garnet (Gd3Ga5O12 or GGG) exhibits a rich mix of short-range order and isolated quantum states. We investigate the effects of up to 1% neodymium substitution for gallium on the ac magnetic response at temperatures below 1 K in both the linear and nonlinear regimes. Substitutional disorder actually drives the system toward a more perfectly frustrated state, apparently compensating for the effects of imperfect gadolinium/gallium stoichiometry, while at the same time more closely demarcating the boundaries of isolated, coherent clusters composed of hundreds of spins. Optical measurements of the local Nd environment substantiate the picture of an increased frustration index with doping.

  5. Ytterbium-Doped Yettrium Aluminum Garnet Crystal Fiber Multipass Ring Laser

    NASA Astrophysics Data System (ADS)

    Yi, Jui-Yun; Huang, Kuang-Yao; Lai, Chien-Chih; Peng, Hsin; Chen, Li-Hsuan; Huang, Sheng-Lung

    2010-12-01

    We report the growth of ytterbium-doped yettrium aluminum garnet (Yb:YAG) crystal fibers by the laser-heated pedestal growth (LHPG) method. The characteristics of Yb:YAG crystal fibers were analyzed by electron probe microanalyzer (EPMA) and X-ray diffraction measurements. The small crystal fiber diameter makes it effective for heat removal from a high-Yb3+-concentration and quasi-three-level gain medium. The length of this crystal-fiber-based high absorption can be shorter, which is eminently suitable for a multipass ring cavity to maintain cavity stability and mode symmetry. We successfully demonstrated a two-mirror multipass ring laser with 54.7% slope efficiency, which is higher than the 50.3% for a bulk Yb:YAG laser.

  6. Solid inclusion thermobarometry under fire: Heating experiments on encapsulated quartz inclusions in garnet

    NASA Astrophysics Data System (ADS)

    Ashley, Kyle T.; Steele-MacInnis, Matthew; Bodnar, Robert J.; Darling, Robert S.

    2016-04-01

    Internal pressures of mineral inclusions (Pincl) result from differences in elastic properties of the inclusion mineral and its host mineral. Recent studies utilize pressure-sensitive Raman spectroscopic waveshifts to determine the retained Pincl and apply elastic theory to estimate pressure (or temperature) conditions of entrapment. Quartz inclusions are commonly utilized because quartz is a "soft," compressible mineral that is ubiquitous as an inclusion phase in continental metamorphic rocks. Garnet is a commonly used host because it is rigid and isotropic. Quartz inclusions trapped in garnet at high-P, low-T conditions will retain high Pincl; whereas those trapped at low-P, high-T conditions yield negative waveshifts equating to "negative" pressure, or net tensile stress on the inclusion. While Pincl can be accurately calculated from Raman data, barometry relies also upon the quality of the elastic model, which fundamentally depends on the quality of the P ‑V ‑T equations of state (EOS) applied. For quartz, EOS modeling is challenging due to the spontaneous strain that develops close to the lambda transition. In this study we conduct heating experiments on quartz inclusions in garnet from natural samples to assess the response of inclusion pressure to varying temperature (at ambient external pressure), and to evaluate predictions based on commonly applied EOS. Experiments were conducted on two quartz standards (a Herkimer "diamond" and Brazillian quartz) and four completely encapsulated inclusions of quartz in garnet from three tectonically diverse terranes, including: (i) a dilated quartz inclusion (Pincl = -4.3 kbar) from Port Leyden, Adirondack Mountains, New York, (ii) a Barrovian-sequence quartz inclusion from northern Scotland (Pincl = 3.1 kbar), and (iii) two high-pressure (blueschist) quartz inclusions from Sifnos, Greece (Pincl = 7.7 and 8.9 kbar). Standards were heated in 25 ° C increments with smaller increments near the lambda transition. Quartz

  7. Energy levels of exciton traps in yttrium aluminum garnet single crystals

    NASA Astrophysics Data System (ADS)

    Varney, C. R.; Mackay, D. T.; Pratt, A.; Reda, S. M.; Selim, F. A.

    2012-03-01

    Electronic defects and exciton traps were studied in yttrium aluminum garnet (YAG) single crystals by wavelength and temperature resolved thermoluminescence (TL). Measurements were carried out from room temperature to 400 °C on a number of rare earth (RE) doped and undoped YAG crystals, and the trap parameters were determined. Although the TL emission spectrum is characteristic of the RE ion, the main trap levels are found to be characteristic of the undoped host crystal. Nevertheless, the thermal activation energies of the traps are slightly modified by doping. The trap kinetics are found to be of the first order in both undoped and Ce doped YAG single crystals indicating the absence of retrapping, which suggests that the traps and recombination centers exhibit a close spatial correlation. The effect of annealing on TL response suggests that some of the major traps are associated with oxygen vacancies.

  8. The contact neodymium-yttrium aluminum garnet laser. A new approach to arthroscopic laser surgery.

    PubMed

    O'Brien, S J; Miller, D V

    1990-03-01

    Arthroscopic treatment of meniscal lesions has been modified as technological advances have occurred. However, alternatives to conventional arthroscopic cutting tools, including electrocautery and CO2 lasers, have thus far met with limited success. The recent development of a sapphire tip has enabled the use of the neodymium-yttrium aluminum garnet (Nd-YAG) laser in a contact mode in a saline medium. This study compares the biology of the Nd-YAG laser to that of electrocautery and scalpel techniques with respect to its effects on articular cartilage and the meniscus. The contact Nd-YAG laser has advantages over both scalpel and electrocautery with regard to its effects on articular cartilage. It also has significant biologic advantages over electrocautery for meniscal lesions. Although in its infancy in the clinical setting, the contact Nd-YAG laser represents the possible beginning of a new era for application of laser energy in arthroscopy.

  9. Iron, radiation, and cancer.

    PubMed Central

    Stevens, R G; Kalkwarf, D R

    1990-01-01

    Increased iron content of cells and tissue may increase the risk of cancer. In particular, high available iron status may increase the risk of a radiation-induced cancer. There are two possible mechanisms for this effect: iron can catalyze the production of oxygen radicals, and it may be a limiting nutrient to the growth and development of a transformed cell in vivo. Given the high available iron content of the western diet and the fact that the world is changing to the western model, it is important to determine if high iron increases the risk of cancer. PMID:2269234

  10. Band-gap and band-edge engineering of multicomponent garnet scintillators from first principles

    DOE PAGESBeta

    Yadav, Satyesh K.; Uberuaga, Blas P.; Nikl, Martin; Jiang, Chao; Stanek, Christopher R.

    2015-11-24

    Complex doping schemes in R3Al5O12 (where R is the rare-earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band gap is altered in a manner that facilitates the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density-functional theory and hybrid density-functional theory (HDFT) are used to survey potential admixing candidates that modify either the conduction-band minimum (CBM) or valence-bandmore » maximum (VBM). We consider two sets of compositions based on Lu3B5O12 where B is Al, Ga, In, As, and Sb, and R3Al5O12, where R is Lu, Gd, Dy, and Er. We find that admixing with various R cations does not appreciably affect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sb decrease the band gap by raising the VBM, the relative change in band gap is quantitatively validated by HDFT. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. Furthermore, this approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.« less

  11. CLMSZ, Garnet Mountain area, southern California: A collisionally generated contractional shear zone

    SciTech Connect

    Bracchi, K.A.; Girty, G.H.; Girty, M.S. . Dept. of Geological Sciences)

    1993-04-01

    The Harper Creek gneiss (HCg) and Oriflamme Canyon unit (OCu) underlie the central portion of the Cuyamaca Laguna Mountains shear zone (CLMSZ) in and around Garnet Mountain, Peninsular Ranges, California, and may have been deformed during Cretaceous arc-continent collision. U-Pb zircon work and petrological and geochemical analyses suggest that in the Garnet Mountain area, the 140 Ma HCg is derived from granite and granodiorite, whereas the 122 [+-] 1 Ma OCu is a protomylonite derived from a granite. Both units appear to be per aluminous calc-alkaline magmatic arc granitoids. Mineral assemblages suggest uppermost greenschist to lower amphibolite grade conditions during deformation. In the HCg, S-1hc is a mylonitic gneissosity with a mean attitude of N11W, 60 NE. A mineral streaking lineation lies within the plane of S-1hc and has a mean attitude of 61[degree] N76E. In the OCu, S-1oc strikes about N13W and dips 52 NE and contains a mineral streaking lineation with an attitude of 49 N52E. Dextral and sinistral shear bands, S-2d and S-2s (looking NW), transect S-1hc and S-1oc. S-2d and S-2s strike subparallel to S-1. In the HCg S-2s is weakly developed and dips about 32 NE, whereas S-2d is more dominant and dips about 76 NE. On the OCu these relationships are reversed. S-2d does not cross cut S-2s: hence, the two sets of shear bands are interpreted to be conjugates reflecting NE-SW contraction and subvertical extension during collisional development of the CLMSZ.

  12. Crystal-field splitting of some quintet states of Tb3+ in aluminum garnets

    NASA Astrophysics Data System (ADS)

    Gruber, John B.; Zandi, Bahram; Valiev, Uygun V.; Rakhimov, Sh. A.

    2004-03-01

    A detailed crystal-field splitting analysis is reported for the quintet states 5DJ, 5GJ, and 5LJ of Tb3+(4f8) in the garnets Y3Al5O12(YAG) and Tb3Al5O12(TbAG). In both garnets we assume that Tb3+ ions occupy sites of D2 symmetry in the cubic structure. We have analyzed the optical spectra of Tb3+ between 487 and 349 nm. The absorption spectrum consist of transitions from the ground-state multiplet manifold, 7F6, to individual energy (Stark) levels of the 5D4, 5D3, 5G6, 5L10, 5G5, 5D2, 5G4, and 5L9 multiplet manifolds. An algorithm used successfully by some of us earlier to analyze the spectra of Tm3+(4f12) in YAG is helpful in the present study to establish the crystal quantum labels, Γn(n=1,2,3,4) for individual Stark levels. A lattice-sum model is used to determine an initial set of crystal-field splitting parameters, Bnm. A combined free-ion and crystal-field Hamiltonian is diagonalized for the quintet and septet states. Considerable crystal-field mixing is found among all the quintet states investigated. A least-squares fitting analysis between 130 experimental-to-calculated Stark levels for Tb3+ in YAG gave a rms deviation of 9 cm-1. A least-squares fitting analysis between 136 experimental-to-calculated Stark levels for Tb3+ in TbAG gave a rms deviation of 10 cm-1.

  13. Major and trace elements in pyrope almandine garnets as sediment provenance indicators of the Lower Carboniferous Culm sediments, Drahany Uplands, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Čopjaková, Renata; Sulovský, Petr; Paterson, Bruce A.

    2005-05-01

    The Lower Carboniferous Culm Basin is part of the European Variscan foreland basin. Garnet is an abundant heavy mineral at all stratigraphic levels of the Culm sediments (the Protivanov, Rozstání and Myslejovice Formation from base to top). This paper compares the major element (electron microprobe) and trace element (LA-ICP-MS) compositions of garnet for the purpose of studying the provenance of the Culm sediments. The polymict garnet assemblages ranging from the Protivanov to lower part of the Myslejovice Formation (Goniatite zones Pe γ-Go α) pass into oligomict ones dominated by pyrope-almandine garnets (uppermost part of the Myslejovice Formation; Goniatite zones Go β-Go γ). As the predominant low-grossular pyrope-almandines from oligomict garnet assemblages are very uniform and homogeneous in major element composition, we studied their trace element composition and zoning. Pyrope-almandine garnets are poor in LREE and show enrichment in HREE; the chondrite-normalized patterns are almost flat from Dy to Lu and show a significant negative Eu anomaly, typical for granulite-grade garnets. Major element compositions of detrital low-grossular pyrope-almandines can only be matched with some granulites and garnetiferous felsic gneisses of the Bohemian Massif. Garnets from granulites cropping out at the present-day erosion level of the Bohemian Massif have usually higher Ca and/or lower Mg contents. The major and trace element compositions and zoning patterns of pyrope-almandine garnets from the upper part of the Myslejovice Formation compare well with garnets from the Miroslav granulites and small Moldanubian granulite bodies west of the Třebíč Massif. The Moldanubian granulites are commonly associated with mantle-derived peridotites and eclogites. The presence of detrital Cr-spinels with high Cr# and low Mg# (single grains of Cr-spinels and fine-grained kelyphitic intergrowths of Cr-spinel with chlorite) comparable with spinel types from Moldanubian

  14. Synthesis, magnetic properties, surface modification and cytotoxicity evaluation of Y 3Fe 5- xAl xO 12 (0⩽ x⩽2) garnet submicron particles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Grasset, Fabien; Mornet, Stéphane; Demourgues, Alain; Portier, Josik; Bonnet, Jacques; Vekris, Antoine; Duguet, Etienne

    2001-09-01

    Yttrium aluminum iron garnet Y 3Fe 5- xAl xO 12 compounds were produced by the citrate gel process by varying the aluminum content x from 0 to 2. Particles with an average size of about 100 nm and a specific surface area ranging from 6 to 28 m 2/g were obtained. Curie temperatures ( TC) were determined from the temperature dependence of the field-cooled magnetization (FCM) and the remnant magnetization (REM) and range from -40°C to 280°C. According to the magnetic moment variation, the aluminum cation seems to replace the iron cation in the tetrahedral site for compounds with x<0.7. 3-Aminopropyltrimethoxysilane (γ-APS) was grafted onto the particles surface and its presence confirmed by infra-red spectroscopy. Cytotoxicity assays were carried out during a period of 13 days using human microglia and rat glioblastoma cell lines. The presence of the amine-functionalized particles did not affect the cell viability or the culture growth rate. Finally, amine-functionalized particles were successfully labeled with covalently linked fluorescing molecules.

  15. [Iron function and carcinogenesis].

    PubMed

    Akatsuka, Shinya; Toyokuni, Shinya

    2016-07-01

    Though iron is an essential micronutrient for humans, the excess state is acknowledged to be associated with oncogenesis. For example, iron overload in the liver of the patients with hereditary hemocromatosis highly increases the risk of hepatocellular carcinoma. Also, as to asbestos-related mesothelioma, such kinds of asbestos with a higher iron content are considered to be more carcinogenic. Iron is a useful element, which enables fundamental functions for life such as oxygen carrying and electron transport. However, in the situation where organisms are unable to have good control of it, iron turns into a dangerous element which catalyzes generation of reactive oxygen. In this review, I first outline the relationships between iron and cancer in general, then give an explanation about iron-related animal carcinogenesis models.

  16. Macrophages and Iron Metabolism.

    PubMed

    Soares, Miguel P; Hamza, Iqbal

    2016-03-15

    Iron is a transition metal that due to its inherent ability to exchange electrons with a variety of molecules is essential to support life. In mammals, iron exists mostly in the form of heme, enclosed within an organic protoporphyrin ring and functioning primarily as a prosthetic group in proteins. Paradoxically, free iron also has the potential to become cytotoxic when electron exchange with oxygen is unrestricted and catalyzes the production of reactive oxygen species. These biological properties demand that iron metabolism is tightly regulated such that iron is available for core biological functions while preventing its cytotoxic effects. Macrophages play a central role in establishing this delicate balance. Here, we review the impact of macrophages on heme-iron metabolism and, reciprocally, how heme-iron modulates macrophage function.

  17. [Iron function and carcinogenesis].

    PubMed

    Akatsuka, Shinya; Toyokuni, Shinya

    2016-07-01

    Though iron is an essential micronutrient for humans, the excess state is acknowledged to be associated with oncogenesis. For example, iron overload in the liver of the patients with hereditary hemocromatosis highly increases the risk of hepatocellular carcinoma. Also, as to asbestos-related mesothelioma, such kinds of asbestos with a higher iron content are considered to be more carcinogenic. Iron is a useful element, which enables fundamental functions for life such as oxygen carrying and electron transport. However, in the situation where organisms are unable to have good control of it, iron turns into a dangerous element which catalyzes generation of reactive oxygen. In this review, I first outline the relationships between iron and cancer in general, then give an explanation about iron-related animal carcinogenesis models. PMID:27455808

  18. Cellular iron metabolism.

    PubMed

    Ponka, P

    1999-03-01

    Iron is essential for oxidation-reduction catalysis and bioenergetics, but unless appropriately shielded, iron plays a key role in the formation of toxic oxygen radicals that can attack all biological molecules. Hence, specialized molecules for the acquisition, transport (transferrin), and storage (ferritin) of iron in a soluble nontoxic form have evolved. Delivery of iron to most cells, probably including those of the kidney, occurs following the binding of transferrin to transferrin receptors on the cell membrane. The transferrin-receptor complexes are then internalized by endocytosis, and iron is released from transferrin by a process involving endosomal acidification. Cellular iron storage and uptake are coordinately regulated post-transcriptionally by cytoplasmic factors, iron-regulatory proteins 1 and 2 (IRP-1 and IRP-2). Under conditions of limited iron supply, IRP binding to iron-responsive elements (present in 5' untranslated region of ferritin mRNA and 3' untranslated region of transferrin receptor mRNA) blocks ferritin mRNA translation and stabilizes transferrin receptor mRNA. The opposite scenario develops when iron in the transit pool is plentiful. Moreover, IRP activities/levels can be affected by various forms of "oxidative stress" and nitric oxide. The kidney also requires iron for metabolic processes, and it is likely that iron deficiency or excess can cause disturbed function of kidney cells. Transferrin receptors are not evenly distributed throughout the kidney, and there is a cortical-to-medullary gradient in heme biosynthesis, with greatest activity in the cortex and least in the medulla. This suggests that there are unique iron/heme metabolism features in some kidney cells, but the specific aspects of iron and heme metabolism in the kidney are yet to be explained.

  19. Comparative study of structure and magnetic properties of micro- and nano-sized GdxY3-xFe5O12 garnet

    NASA Astrophysics Data System (ADS)

    Sattar, A. A.; Elsayed, H. M.; Faramawy, A. M.

    2016-08-01

    Gadolinium Yttrium Iron garnet (GdYIG) samples with the chemical formula (GdxY3-xFe5O12) (x=0.0, 0.25, 0.5, 0.75, and 1.0) were prepared via two different methods, the standard ceramic method (SC) and the co-precipitation method (CP). The effect of preparation conditions and Gd3+ ion substitution on the phase formation, crystal structure, morphology and magnetic properties were studied. Moreover, the initial permeability μi and Curie temperature Tc were measured for all investigated samples. It was found that, the lattice parameter increases on addition of Gd3+ ion while the porosity decreases for both systems of samples. The crystallite sizes of the samples prepared by the (CP) method are smaller than those prepared by (SC) method. The magnetization Ms decreases while the coercivity Hc increases by increasing the Gd+3 concentration in both systems of samples. For the samples prepared by the (SC) method the values of Ms are higher than those prepared by (CP) method. Also, it was found that the initial permeability μi and Curie temperature Tc are higher in samples prepared by (SC) method than those prepared by (CP) method. Moreover the magnetic loss (the rate of temperature raise (ΔT/Δt) in an AC magnetic field) was measured for all investigated samples, which increased with increasing Gd concentration. Furthermore, it was found that the samples prepared by (SC) method have magnetic loss higher than those prepared by (CP) method. It was concluded that the preparation method has great effects on the magnetic properties of GdYIG ferrite. The obtained results were explained in the light of Neel's model.

  20. Unraveling the polymetamorphic history of garnet-bearing metabasites: Insights from the North Motagua Mélange (Guatemala Suture Zone)

    NASA Astrophysics Data System (ADS)

    Bonnet, G.; Flores, K. E.; Martin, C.; Harlow, G. E.

    2014-12-01

    The Guatemala Suture Zone is the fault-bound region in central Guatemala that contains the present North American-Caribbean plate boundary. This major composite geotectonic unit contains a variety of ophiolites, serpentinite mélanges, and metavolcano-sedimentary sequences along with high-grade schists, gneisses, low-grade metasediments and metagranites thrusted north and south of the active Motagua fault system (MFS). The North Motagua Mélange (NMM) outcrops north of the MFS and testifies the emplacement of exhumed subduction assemblages along a collisional tectonic setting. The NMM is composed of a serpentinite-matrix mélange that contains blocks of metabasites (subgreenschist facies metabasalt, grt-blueschist, eclogite, grt-amphibolite), vein-related rocks (jadeitite, omphacitite, albitite, mica-rock), and metatrondhjemites. Our new detailed petrographic and thermobarometric study on the garnet-bearing metabasites reveals a complex polymetamorphic history with multiple tectonic events. Eclogites show a classical clockwise PT path composed of (a) prograde blueschist/eclogite facies within garnet cores, (b) eclogite facies metamorphic peak at ~1.7 GPa and 620°C, (c) post-peak blueschist facies, (d) amphibolite facies overprint, and (e) late stage greenschist facies. Two types of garnet amphibolite blocks can be found, the first consist of (a) a relict eclogite facies peak at ~1.3 GPa and 550°C only preserved within anhedral garnet cores, and (b) surrounded by a post-peak amphibolite facies. In contrast, the second type displays a prograde amphibolite facies at 0.6-1.1 GPa and 400-650°C. The eclogites metamorphic peak suggests formation in a normal subduction zone at ~60 km depth, a subsequent exhumation to the middle section of the subduction channel (~35 km), and a later metamorphic reworking at lower P and higher T before its final exhumation. The first type of garnet amphibolite shows a similar trajectory as the eclogites but at warmer conditions. In