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1

Optical properties of gadolinium gallium garnet.  

PubMed

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. PMID:20567472

Wood, D L; Nassau, K

1990-09-01

2

Research in Gadolinium Scandium Gallium Garnet (GSGG) crystal development  

NASA Astrophysics Data System (ADS)

The Czochralski growth technique was utilized for the development of a large diameter, laser quality gadolinium, scandium gallium garnet co-doped with neodymium and chromium (Nd:Cr:GSGG). Vary aspects of the development were determinations of raw material purity, foule growth runs, boule composition and lattice parameters, and losses.

1985-07-01

3

Gadolinium Gallium Garnet at Multi-Megabar Pressures  

NASA Astrophysics Data System (ADS)

Gadolinium gallium oxide Gd3Ga5O12, which crystallizes in the garnet structure, has recently attracted strong interest due to shock-wave experiments revealing a highly incompressible high-pressure phase above 1 Mbar [1]. In addition, recent diamond-cell x-ray diffraction experiments provide evidence for a phase transition from garnet to double-perovskite structures around 1 Mbar [2]. We present the results of laser-driven shock experiments on gadolinium gallium garnet (GGG) at pressures of 3 to more than 20 Mbar, obtained at the Omega-LLE and Jupiter-LLNL facilities, and compare these with the results of ab-initio molecular dynamic simulations. Velocimetry (VISAR) and pyrometry (SOP) diagnostics, and an impedance match analysis with quartz standards, provide data on the equation of state, temperature and optical reflectivity at 532 nm. No obvious phase transition is detected in the explored pressure range, but the data indicate that GGG remains surprisingly stiff up to more than 20 Mbar. We observe metallic-like reflectivity in the ultra-high pressure (possibly liquid) regime. This study could be relevant for planetary interior modeling, as many Earth and super-Earth minerals adopt the garnet and perovskite structures, and may exhibit transition to metallic and highly incompressible behavior.

Millot, M.; Ali, S. J.; Militzer, B.; Barrios, M. A.; Boehly, T.; Eggert, J. H.; Collins, G.; Jeanloz, R.

2011-12-01

4

Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet.  

National Technical Information Service (NTIS)

Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorpor...

R. W. Murphy

1992-01-01

5

Integrated magnetooptic Bragg cell modulator in yttrium iron garnet-gadolinium gallium garnet taper waveguide and applications  

Microsoft Academic Search

An integrated magnetooptic (MO) device which consists of an ion-milled collimation-focusing lens pair and a guided-wave MO Bragg cell modulator in a yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) taper waveguide substrate with dimensions of 6.0×16.0 mm 2 has been realized for the first time. Performance characteristics of the waveguide lenses including the focal spot size, sidelobe level and throughput, and

C. L. Wang; Chen S. Tsai

1997-01-01

6

Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet.  

National Technical Information Service (NTIS)

Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd(sub 3)Ga(sub 5)O(sub 12)) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the ...

R. W. Murphy

1994-01-01

7

Study of the low temperature thermal properties of the geometrically frustrated magnet: Gadolinium gallium garnet  

Microsoft Academic Search

Gadolinium gallium garnet, Gd3Ga5O12 (GGG) has an extraordinary low temperature phase diagram. Although the Curie-Weiss temperature of GGG is about -2 K, GGG shows no long-range order down to T~0.4 K. At low temperatures GGG has a spin glass phase at low fields (<=0.1 T) and a field-induced long-range order antiferromagnetic state at fields of between 0.7 and 1.3 T

Y. K. Tsui; N. Kalechofsky; C. A. Burns; P. Schiffer

1999-01-01

8

Study of the low temperature thermal properties of the geometrically frustrated magnet: Gadolinium gallium garnet  

Microsoft Academic Search

Gadolinium gallium garnet, Gd3Ga5O12 (GGG) has an extraordinary low temperature phase diagram. Although the Curie–Weiss temperature of GGG is about ?2 K, GGG shows no long-range order down to T?0.4 K. At low temperatures GGG has a spin glass phase at low fields (?0.1 T) and a field-induced long-range order antiferromagnetic state at fields of between 0.7 and 1.3 T

Y. K. Tsui; N. Kalechofsky; C. A. Burns; P. Schiffer

1999-01-01

9

A study of a strongly geometrically frustrated magnet: Gadolinium gallium garnet  

Microsoft Academic Search

Geometrically frustrated antiferromagnets are materials in which the geometry of the lattice results in frustration of the antiferromagnetic (AFM) exchange interactions. They are characterized by the absence of long-range order at temperatures well below the Curie-Weiss temperature (theta cw). One such material is Gd3Ga5O12 (gadolinium gallium garnet or GGG), in which the magnetic Gd ions are on three-dimensional (3D) corner-sharing

Yee-Kin Tsui

2000-01-01

10

Light-induced phase and amplitude gratings in centrosymmetric Gadolinium Gallium garnet doped with calcium.  

PubMed

The photosensitive properties of a centrosymmetric gadolinium gallium garnet crystal doped with calcium are investigated at room temperature. Elementary holograms can be recorded over a wide range of wavelengths in the visible spectral range. The photosensitive properties are studied experimentally using beam coupling and angular response experiments. Mixed absorption and refractive-index gratings are observed and their amplitudes and relative phases determined. Moreover, the candidate centers that are responsible for the photorefractive effect are discussed. PMID:19503376

Ellabban, Mostafa A; Fally, Martin; Rupp, Romano A; Kovács, László

2006-01-23

11

Luminescence of gadolinium gallium garnet epitaxial films under excitation by synchrotron radiation  

NASA Astrophysics Data System (ADS)

The luminescence excited by synchrotron radiation in gadolinium gallium garnet single-crystal films grown by liquid-phase epitaxy from lead-and bismuth-containing solution melts on Gd3Ga5O12 substrates is investigated. It is shown that the luminescence intensity in the visible range of the spectrum depends on the type and concentration of impurity ions passing from the solvent into the film.

Randoshkin, V. V.; Alparov, R. M.; Vasil'Eva, N. V.; Kolobanov, V. N.; Mikha?lin, V. V.; Petrovnin, N. N.; Spasski?, D. A.; Sysoev, N. N.

2006-11-01

12

Light-induced phase and amplitude gratings in centrosymmetric Gadolinium Gallium garnet doped with calcium  

NASA Astrophysics Data System (ADS)

The photosensitive properties of a centrosymmetric gadolinium gallium garnet crystal doped with calcium are investigated at room temperature. Elementary holograms can be recorded over a wide range of wavelengths in the visible spectral range. The photosensitive properties are studied experimentally using beam coupling and angular response experiments. Mixed absorption and refractive-index gratings are observed and their amplitudes and relative phases determined. Moreover, the candidate centers that are responsible for the photorefractive effect are discussed.

Ellabban, Mostafa A.; Fally, Martin; Rupp, Romano A.; Kovács, László

2006-01-01

13

Spectroscopy of gadolinium gallium garnet crystals doped with Y b3 + revisited  

NASA Astrophysics Data System (ADS)

The optical spectroscopy measurements of gadolinium gallium garnet (GGG) crystals doped with Yb show evidence of the presence of non-equivalent optical centers with very similar radiative decay rates. The energy level schemes of those centers have been determined on the basis of optical absorption, luminescence and Raman experiments. Crystal field fitting resulted in two sets of slightly different crystal field parameters for two non-equivalent Yb centers. Both sets of parameters describe perfectly the experimentally detected Y b3 + energy levels. Correlation between systematic trends in the experimental energy level schemes and crystal field parameters is discussed.

Kami?ska, A.; Brik, M. G.; Boulon, G.; Karbowiak, M.; Suchocki, A.

2010-06-01

14

Effects of doping on the geometrically frustrated Heisenberg antiferromagnet Gadolinium Gallium Garnet  

NASA Astrophysics Data System (ADS)

Geometric frustration in the Heisenberg antiferromagnet Gadolinium Gallium Garnet (GGG) gives rise to a set of quantum protectorates where clusters of spins decouple from the overall spin liquid state. At 110 mK, there is a partial transition to an ordered AF state. Here, we examine the effect of lightly doping GGG with Nd ions, which partially alleviates the underlying frustration. We examine the size and binding energy of the spin clusters as a function of doping and temperature, and also characterize the suppression of the Neel temperature as the dopant concentration is increased.

Silevitch, D. M.; Schmidt, M. A.; Ghosh, S.; Aeppli, G.; Rosenbaum, T. F.

2011-03-01

15

Spectroscopy of gadolinium gallium garnet crystals doped with Yb(3+) revisited.  

PubMed

The optical spectroscopy measurements of gadolinium gallium garnet (GGG) crystals doped with Yb show evidence of the presence of non-equivalent optical centers with very similar radiative decay rates. The energy level schemes of those centers have been determined on the basis of optical absorption, luminescence and Raman experiments. Crystal field fitting resulted in two sets of slightly different crystal field parameters for two non-equivalent Yb centers. Both sets of parameters describe perfectly the experimentally detected Yb(3+) energy levels. Correlation between systematic trends in the experimental energy level schemes and crystal field parameters is discussed. PMID:21393800

Kami?ska, A; Brik, M G; Boulon, G; Karbowiak, M; Suchocki, A

2010-06-04

16

Structural and luminescence investigation on gadolinium gallium garnet nanocrystalline powders prepared by solution combustion synthesis  

NASA Astrophysics Data System (ADS)

Nanocrystalline powders of undoped and lanthanide (Pr3+, Tm3+)-doped gadolinium gallium garnet, Gd3Ga5O12 (GGG), were prepared by propellant synthesis and studied by x-ray powder diffraction (XRD), electron diffraction (ED), high-resolution electron microscopy (HREM) and luminescence spectroscopy. The x-ray diffraction patterns of the GGG samples were analysed using the Rietveld method. The Rietveld refinement reveals the existence of two garnet-type phases: both are cubic (space group Ia\\bar {3}d ) with a slightly different lattice parameter and probably a slightly different composition. Electron diffraction and electron microscopy measurements confirm the x-ray diffraction results. EDX measurements for lanthanide-doped samples show that stable solid solutions with composition Gd3-xLnxGa5O12, xap0.3 (Ln = Pr; Tm) have been obtained. The luminescence properties of the Tm3+-doped nanocrystalline GGG samples were measured and analysed.

Krsmanovi?, R.; Morozov, V. A.; Lebedev, O. I.; Polizzi, S.; Speghini, A.; Bettinelli, M.; Van Tendeloo, G.

2007-08-01

17

ACTIVE MEDIA. RESONATORS: Short-lived absorption in excited gadolinium scandium gallium garnet crystals activated with Cr and Nd  

Microsoft Academic Search

An analysis is made of the possibility of reducing short-lived losses in a gadolinium scandium gallium garnet crystal activated with Cr and Nd when these losses are due to the short-wavelength component of the spectrum of the exciting radiation.

Evgeny V. Zharikov; S. P. Nasel'skii; A. I. Ryabov; Ivan A. Shcherbakov

1987-01-01

18

Noncollinear coplanar magneto-optic interaction of guided optical wave and magnetostatic surface waves in yttrium iron garnet-gadolinium gallium garnet waveguides  

Microsoft Academic Search

Wideband noncollinear coplanar guided-wave magneto-optic diffraction and mode conversion by magnetostatic surface waves at multigigahertz (3-7 GHz) carrier frequencies in yttrium iron garnet-gadolinium gallium garnet waveguides have been observed and measured in detail for the first time. Interaction configuration, physical mechanisms, summary of a theoretical treatment, and some experimental results obtained at 1.152 micron optical wavelength are presented. This noncollinear

C. S. Tsai; D. Young; W. Chen; L. Adkins; C. C. Lee; H. Glass

1985-01-01

19

Site selectivity in praseodymium- and bismuth-substituted gadolinium gallium garnet epilayers  

SciTech Connect

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.

Klages, C.P.

1984-05-01

20

Equation of state for gadolinium gallium garnet crystals: Experimental and computational study  

NASA Astrophysics Data System (ADS)

Experimentally and theoretically determined elastic properties of gadolinium gallium garnet, Gd3Ga5O12, under high-pressure are reported. The x-ray diffraction part of the study was performed using a diamond-anvil cell at pressures up to 25 GPa, at conditions ascertaining hydrostatic compression up to about 10 GPa. The experimental bulk modulus, K0=169(15) GPa, and its first derivative, K0'=3.6(2.9), were derived from the diffraction data collected in pressure range limited to 10.2 GPa, assuming the Birch-Murnaghan equation of state. Ab initio calculations yielded K0=161(8) GPa and K0'=5.4(0.6) being in excellent agreement with the experiment.

Durygin, A.; Drozd, V.; Paszkowicz, W.; Werner-Malento, E.; Buczko, R.; Kaminska, A.; Saxena, S.; Suchocki, A.

2009-10-01

21

Influence of high pressure on the luminescence transitions of Mn4+-doped gadolinium gallium garnet  

NASA Astrophysics Data System (ADS)

We present results of a high-pressure photoluminescence study of Mn- and Ca-doped gadolinium gallium garnet (GGG) crystals. Since the Mn4+ ion has the same electronic structure of the open 3d3 shell as Cr3+, its spectroscopic properties are expected to be similar to those of the Cr-doped GGG. We observed the luminescence R-lines of various Mn4+ centres in GGG. In the 0-118 kbar pressure range those R-lines shift linearly to lower energies. The pressure coefficients are of the order of 2 cm-1 kbar-1, about three times larger than that for Cr3+ ions. This fact can be explained by different strength of coupling of isoelectronic Cr3+ and Mn4+ ions with GGG host. The changes of the radiative decay times of the Mn4+ centres as a function of pressure are fitted with a theoretical model.

Galanciak, D.; Grinberg, M.; Gryk, W.; Kobyakov, S.; Suchocki, A.; Boulon, G.; Brenier, A.

2005-11-01

22

Low temperature properties of the gadolinium gallium garnet: Monte Carlo versus experiments  

NASA Astrophysics Data System (ADS)

Due to an arrangement of magnetic ions on triangular lattices and a negligible single-ion anisotropy, the gadolinium gallium garnet Gd_3Ga_5O_12 (GGG) is an example of a magnet with a very high geometrical frustration. The frustration is believed to be responsible for its unique magnetic properties at low temperatures by amplifying the competition between different microscopic mechanisms. These properties include extended short-range order in GGG, unusual features in its magnetic and thermal characteristics, as well as spin dynamics down to the lowest temperature. We use classical Monte Carlo simulations to investigate the low temperature properties of the system and make comparison with experiments. In particular, we study the nature of the spin-spin correlations developing at low temperatures and compare our results with the data from elastic neutron scattering experiments on isotopically enriched GGG samples.

Gingras, Michel; Yavors'kii, Taras

2004-03-01

23

Spectral Signature of Neodymium Dopants in Frustrated Gadolinium Gallium Garnet Lattice  

NASA Astrophysics Data System (ADS)

We investigate the spectral emission of Nd3+ dopant ions (1% at. wt) in the frustrated magnet Gadolinium gallium Garnet (GGG) as a function of temperature and magnetic field. We concentrate on the low energy excitations centered at 1064 nm and 935 nm, which show a multiplet structure at room temperature. As temperature decreases the emission spectra demonstrate changes in relative intensities that undergo a cross-over at 122 K under zero field cooled conditions. This cross-over is magnetic field dependent and changes as we field-cool the sample. Typically, with decreasing temperature the line widths of the spectral peaks decrease, as is expected. However, when cooled below 10 K selective peaks start exhibiting broadening, even when zero-field cooled. We follow this line broadening as a function of magnetic field and dopant concentration and speculate it is a result of the dopant ions coupling to the internal magnetic fields of the host lattice.

Ferri, Christopher; Tennenbaum, Michael; Ghosh, Sayantani

2012-02-01

24

An experimental search for the electron Electric Dipole Moment in Gadolinium Gallium Garnet  

NASA Astrophysics Data System (ADS)

A discovery of a permanent electric dipole moment of the electron (eEDM) would provide crucial information about the nature of T-violation and imply new sources of CP-violation beyond the Standard Model. While the leading experimental technique used to measure EDM is based on the nuclear magnetic resonance, we are pursuing research that would improve the present experimental limit of the eEDM using a new technique in solid-state systems at low temperatures. The experiment uses a paramagnetic insulator Gadolinium Gallium Garnet with a large magnetic response. The presence of the eEDM leads to a finite magnetization when the garnet sample is subjected to a strong electric field. The resulting magnetization can be measured using the Superconducting Quantum Interference Device (SQUID) as a sensitive magnetometer. In this talk, we will discuss the progress to control the systematic effects and improve the sensitivity. The major efforts include the design and implementation of a 24-bit data acquisition system with ultra-low level of channel crosstalk, and the control of the high voltage drift from the supply. With these considerable progresses, we report our first background-free experimental limit of the eEDM on the order of 10-24 e.cm .

Kim, Young Jin; Liu, Chen-Yu

2011-04-01

25

Spectral and luminescence properties of gadolinium gallium garnet epitaxial films doped with terbium  

NASA Astrophysics Data System (ADS)

Gadolinium gallium garnet single-crystal films containing terbium are grown through liquid-phase epitaxy from a supercooled solution melt in the PbO-B2O3 system. The optical absorption spectra in the wavelength range 0.2 10.0 ?m and the luminescence spectra excited by synchrotron radiation with energies in the range 3.5 30.0 eV are investigated at temperatures of 10 and 300 K. It is revealed that the optical absorption spectra contain an absorption band with the maximum at a wavelength ? ?0.260 ?m, which corresponds to the spin-allowed electric dipole transition between the electronic configurations 4f 8(7 F 6) ? 4f 7(8 S)5d of the Tb3+ ions. The narrow low-intensity absorption bands attributed to the 4f ? 4f transitions from the 7 F 6 ground level to the 7 F 0 5 multiplet levels of the Tb3+ ions are observed in the wavelength range 1.7 10.0 ?m. In the luminescence spectra measured at a temperature of 10 K, the highest intensity is observed for a band with the maximum at a wavelength ? ? 0.544 ?m, which is associated with the 5 D 4 ? 7 F 5 radiative transition in the Tb3+ ion.

Vasil'Eva, N. V.; Randoshkin, V. V.; Kolobanov, V. N.; Kryukova, E. B.; Mikha?lin, V. V.; Petrovnin, N. N.; Plotnichenko, V. G.; Pyrkov, Yu. N.; Spasski?, D. A.; Sysoev, N. N.

2007-03-01

26

Visible upconversion emission of Pr3+ doped gadolinium gallium garnet nanocrystals.  

PubMed

The luminescence properties of a Pr3+-doped gadolinium gallium garnet (GGG, Gd3Ga5O12) nanocrystalline host were investigated. Dominant blue/green emission was observed emanating from the 3P0 --> 3H4 transition after excitation using a wavelength of 457.9 nm. Continuous wave excitation into the 1D2 level of the Pr3+ ion at 606.9 nm transition produced blue upconversion luminescence spectra, ascribed to emission from the 3P1 --> 3H4 and 3P0 --> 3H4 transitions. The increase in the decay times of the observed transitions following excitation with 606.9 nm is indicative of the dominance of an energy transfer upconversion (ETU) mechanism relative to excited state absorption (ESA). Furthermore, blue, green and red upconversion emission was observed from the 3P0, 3P1 and 1D2 states following excitation into the 1G4 energy level with 980 nm. No change in the decay times of the emitting states was observed following excitation with a wavelength of 980 or 457.9 nm; hence, upconversion was determined to primarily occur through ESA. The luminescence properties of the nanocrystals are compared to a single crystal of GGG:Pr3+ (bulk) with an identical Pr3+ concentration (1%). PMID:15656197

Naccache, R; Vetrone, F; Boyer, J C; Capobianco, J A; Speghini, A; Bettinelli, M

2004-11-01

27

Enhancement of the electron electric dipole moment in gadolinium garnets  

NASA Astrophysics Data System (ADS)

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.

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

2003-10-01

28

Evidence of multicenter structure of cerium ions in gadolinium gallium garnet crystals studied by infrared absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Low temperature, infrared absorption spectra of gadolinium gallium garnet crystals doped with Ce are presented. In the region of intraconfigurational 4f-4f transitions the spectra exhibit existence of at least two different, major Ce3+ related centers in the GGG crystals and also some other centers at lower concentration. The spectrum of 4f-4f intrashell transitions of Ce3+ ions extends up to about 3700 cm-1 due to the large splitting of the 2F7/2 excited state. In the visible region the absorption spectrum shows influence of symmetry-related selection rules. The absorption coefficient changes in the region of 4f1-5d1 transitions due to thermal population of the second level, belonging to the 2F5/2 ground state. This suggests that the symmetry of the site occupied by Ce3+ ions, which substitute Gd3+, is higher than D2 expected for garnet hosts.

Przybyli?ska, H.; Ma, Chong-Geng; Brik, M. G.; Kami?ska, A.; Szczepkowski, J.; Sybilski, P.; Wittlin, A.; Berkowski, M.; Jastrz?bski, W.; Suchocki, A.

2013-01-01

29

Probability of Yb3+ 4f-4f transitions in gadolinium gallium garnet crystals at high hydrostatic pressures  

NASA Astrophysics Data System (ADS)

We show that the probability of f-f radiative transitions (F7/22?F5/22) of Yb3+ ions in gadolinium gallium garnet (GGG) crystals is sensitive to hydrostatic pressure application. The changes of the transition energy with pressure are very small, almost negligible. However, we observed much more pronounced variations of the transition probability, which are ascribed to a coupling between the 4f13 with the 4f125d1 electronic configurations and variations of the coupling coefficient with pressure. The theoretical model, explaining this behavior, assumes nonmonotonic changes of the odd-parity crystal-field terms associated with lattice distortions induced by pressure. The magnitude of these distortions correlates well with the magnitude of the distortion from the noncubic symmetry of the dodecahedral crystallographic sites in GGG host, monitored by the pressure dependence of the splitting of the F3/24 level of Nd3+ ions.

Kami?ska, A.; Biernacki, S.; Kobyakov, S.; Suchocki, A.; Boulon, G.; Ramirez, M. O.; Bausa, L.

2007-05-01

30

Merging of the 4F3/2 level states of Nd3+ ions in the photoluminescence spectra of gadolinium-gallium garnets under high pressure  

NASA Astrophysics Data System (ADS)

The 4F3/2 state of Nd3+ dopant ions is split due to the crystal field at orthorhombic D2 symmetry sites in several members of the garnet family of crystals. In the gadolinium-gallium garnet crystal this splitting is found to almost disappear under hydrostatic pressures between 8 and 11 GPa created in the diamond-anvil cell. This pressure is much lower than that required for the phase transition to the so called high-pressure phase. This effect is explained with help of x-ray diffraction, optical spectroscopy, and ab initio calculations as an effect of accidental near-degeneracy arising from a particular lattice structure of garnets.

Kaminska, A.; Buczko, R.; Paszkowicz, W.; Przybyli?ska, H.; Werner-Malento, E.; Suchocki, A.; Brik, M.; Durygin, A.; Drozd, V.; Saxena, S.

2011-08-01

31

Molecular Beam Epitaxial Growth of GaAs on Gadolinium-Gallium Garnet.  

National Technical Information Service (NTIS)

Over the past decade there has been considerable interest in devices using ferrimagnetic garnets. Of particular interest are microwave non-reciprocal devices such as circulators and isolators, and devices based on the propagation of a magnetostatic wave (...

A. R. Calawa M. J. Manfra

1990-01-01

32

Static contribution to thermal shifts of spectral lines in gadolinium gallium garnet Gd3Ga5O12:Nd3+ laser crystal  

NASA Astrophysics Data System (ADS)

The static contribution due to lattice thermal expansion and the vibrational contribution due to electron-phonon interaction to the thermal shifts of the spectral lines E1(R1 --> Z5) and E2 (R2 --> Z5) in the high-power laser crystal gadolinium gallium garnet Gd3Ga5O12 (GGG):Nd3+ are studied by analyzing the observed pressure- and temperature-dependence of these spectral lines. It is found that the static contribution due to thermal expansion in magnitude is greater than, and it in sign is opposite to the vibrational contribution due to electron-phonon interaction. So for the theoretical study of thermal shifts of the spectral lines in GGG:Nd3+ and other similar ``hard'' crystals, the neglect of the contribution due to the lattice thermal expansion suggested in the previous papers is unsuitable.

Zheng, W. C.; Su, P.; Liu, H. G.

2011-03-01

33

Magnetothermodynamics of gadolinium gallium garnet. I. Heat capacity, entropy, magnetic moment from 0.5 to 4.2 °K, with fields to 90 kG along the [100] axis  

Microsoft Academic Search

The magnetic moment of a 2.44 cm diam spherical single crystal of gadolinium gallium garnet has been measured with stabilized fields of 500, 1000, 2500, 5000, 10 000, 15 000, 25 000, 40 000, 65 000, and 90 000 G along the [100] axis, over the range 0.35 to 4.2 °K. The heat capacity was measured over similar ranges, except

R. A. Fisher; G. E. Brodale; E. W. Hornung; W. F. Giauque

1973-01-01

34

Specific features of Eu 3+ and Tb 3+ magnetooptics in gadolinium-gallium garnet (Gd 3Ga 5O 12)  

Microsoft Academic Search

We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG

Uygun V. Valiev; John B. Gruber; Dejun FU; Vasiliy O. Pelenovich; Gary W. Burdick; Mariya E. Malysheva

2011-01-01

35

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

NASA Astrophysics Data System (ADS)

Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd3Ga5O12 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 ?m showing good crystalline quality and epitaxial growth.

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

2006-04-01

36

PAPERS DEVOTED TO THE 90TH ANNIVERSARY OF A.M.PROKHOROV: Study of energy transfer in gadolinium—gallium garnet crystals doped with Yb3+ and Ho3+ ions  

NASA Astrophysics Data System (ADS)

The luminescence kinetics of Yb3+ donors and Ho3+ acceptors is quantitatively studied in gallium—gadolinium garnet (GGG) crystals doped with Yb3+ and Ho3+ ions. It is shown that the sensitisation of transitions in Ho3+ ions occurs due to migration-accelerated (hopping) energy transfer. The microparameters of donor—donor energy transfer are determined at 300 and 77 K. The microparameters of donor—acceptor energy transfer are found at the same temperatures at the first stage of successive sensitisation (resulting in the population of the 5I6 state of Ho3+ ions) and at the second stage of successive sensitisation of the 5S2, 5F4?5I8 transition in Ho3+ ions. At the second stage of sensitisation, the values of the microparameter of reverse energy transfer are also determined. The possibility of obtaining lasing at sensitised transitions in Ho3+ ions in Yb3+:Ho3+:GGG crystals pumped into the absorption band of Yb3+ ions is discussed.

Belovolov, A. M.; Belovolov, M. I.; Dianov, Evgenii M.; Ivanov, M. A.; Kochurikhin, V. V.; Randoshkin, V. V.

2006-08-01

37

Nanocrystalline gadolinium iron garnet for circulator applications  

NASA Astrophysics Data System (ADS)

Due to high resistivity and low microwave losses, gadolinium iron garnets (GdIG) are useful materials for non-reciprocal devices such as circulators or isolators. Keeping the miniaturization and cost reduction in mind, the trend is to modify the conventional methods of preparation of samples. In this connection we have synthesized nanocystalline GdIG by using the Microwave Hydrothermal method at 160 °C/45 min. As synthesized powders were characterized by using X-ray diffraction (XRD), transmission electron microscopy and Fourier Transform Infrared Spectroscopy. XRD patterns show the formation of a garnet phase with crystallite size varying between 19 nm and 40 nm. Differential Thermal Analysis studies were also carried out on the nanopowders. The powders were densified at a lower sintering temperature of 1100 °C/45 min using a microwave sintering method. The sintered samples were characterized by XRD and atomic force microscopy. The frequency dependence of complex permittivity and ferromagnetic resonance were measured in the Ka band frequency (27-40 GHz). Magnetic properties were also measured at room temperature.

Ramesh, T.; Shinde, R. S.; Murthy, S. R.

2012-11-01

38

Origin of color centers in the flux-grown europium gallium garnet  

NASA Astrophysics Data System (ADS)

Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Mössbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Mössbauer isotope shifts and quadrupole splitting for EuGG are determined.

Aleksandrovsky, A. S.; Arkhipkin, V. G.; Bezmaternykh, L. N.; Gudim, I. A.; Krylov, A. S.; Vagizov, F.

2008-04-01

39

Thermo-optic properties of gadolinium garnet laser crystals  

SciTech Connect

The indices of refraction, thermal variations of refractive indices, and thermal expansion coefficients were measured for the gadolinium garnets Gd/sub 3/Sc/sub 2/Ga/sub 3/O/sub 12/ (GSGG) and Gd/sub 3/Sc/sub 2/Al/sub 3/O/sub 12/. The variation of these properties with trivalent chromium doping was investigated for GSGG. The refractive indices were determined by the minimum-deviation technique, with indices fitted to a five-parameter Sellmeier formula. The thermal coefficients were measured by an interferometric technique using simultaneous Twyman--Green and Fizeau interferometry.

Hoefer, C.S.; Kirby, K.W.; DeShazer, L.G.

1988-11-01

40

Sol-gel synthesis and characterization of yttrium gallium garnets  

Microsoft Academic Search

Precursor powders for yttrium gallium garnet (Y3Ga5O12, YGG) were prepared by a simple sol-gel method based on the formation of metal chelates in aqueous solvents. A systematic study of sol-gel technique synthesized YGG samples is presented using different complexing agents. Six high-purity organic substances were used as complexing agents, namely, tartaric acid, 1,2-ethanediol, citric acid, ethylene diamine tetra-acetic acid (EDTA),

Asta Leleckaite; Sigita Urbonaite; Kaia Tõnsuaadu; Aivaras Kareiva

2005-01-01

41

Faraday rotation in single-crystal ytterbium gallium garnet  

Microsoft Academic Search

Faraday rotation (FR) measurements performed on single-crystal ytterbium gallium garnet (YbGG) at 0.6328- and 1.15-?m wavelengths are presented in a magnetic field up to 20 kOe applied along the three main crystallographic directions and in the 6–300 K temperature range. At 0.6328 ?m, the FR is proportional to the magnetic field and a strong anisotropy of the Verdet constant (V)

M. Guillot; H. Le Gall; J. Ostorero; M. Artinian; A. Marchand

1987-01-01

42

Sol-gel synthesis and characterization of yttrium gallium garnets  

NASA Astrophysics Data System (ADS)

Precursor powders for yttrium gallium garnet (Y3Ga5O12, YGG) were prepared by a simple sol-gel method based on the formation of metal chelates in aqueous solvents. A systematic study of sol-gel technique synthesized YGG samples is presented using different complexing agents. Six high-purity organic substances were used as complexing agents, namely, tartaric acid, 1,2-ethanediol, citric acid, ethylene diamine tetra-acetic acid (EDTA), malonic acid, and oxalic acid. These agents were found to influence the characteristics of the end products, in particular their homogeneity. The phase purity, composition, and microstructure of the polycrystalline samples were studied by thermoanalytical methods (TGADTA), x-ray diffraction (XRD) analysis, IR spectroscopy, and scanning electron microscopy (SEM). From the typical XRD patterns of different synthesis products it is concluded that only the use tartaric acid, 1,2-ethanediol, citric acid, and EDTA yields a single YGG phase.

Leleckaite, Asta; Urbonaite, Sigita; Tõnsuaadu, Kaia; Kareiva, Aivaras

2005-08-01

43

Magnetization and coercivity of nanocrystalline gadolinium iron garnet  

NASA Astrophysics Data System (ADS)

Gadolinium iron garnet (GdIG) nanoparticles with mean particle size of about 37 nm have been synthesized by citrate precursor gel formation followed by annealing at 800 °C for 2 hours. Magnetic behavior of clustered GdIG nanoparticles was studied in temperature range from 5 K to above Curie temperature. The sample shows a magnetization compensation temperature Tcomp˜286.5 K and a Curie temperature TC˜560 K. In comparison with the bulk saturation magnetization, the sample exhibits lower spontaneous magnetization in the temperature region from 5 K to Tcomp whereas higher spontaneous magnetization is observed at higher temperatures up to near the Curie point. The magnetization curves show a differential susceptibility in high fields which increases sharply below 50 K. At very low temperatures, irreversibility was observed in the magnetization loops, enduring in the fields up to ˜12.5 kOe. The spontaneous magnetization, high-field susceptibility and low-temperature irreversible effect were discussed based on a model for the interacting particles consisting of ferrimagnetically aligned core spins and disordered spins in surface layer which become frozen at low temperatures. We proposed a mechanism for the enhancement of the spontaneous magnetization above Tcomp in which the Gd and Fe spins in the surface layer are largely decoupled at high temperatures and the surface Fe spins realign to the magnetic moment of the core. The magnetic coercivity Hc at low temperatures is governed by the effective anisotropy whereas in the vicinity of the compensation point a peak in the coercive force shows up as a result of the so-called paraprocess with the maximum value of 1.2 kOe at Tcomp and by further increasing temperature the coercivity decreases and eventually vanishes at about 500 K. The interparticle interactions were found to play an important role in the hysteresis behavior of the sample.

Nguyet, Dao Thi Thuy; Duong, Nguyen Phuc; Satoh, Takuya; Anh, Luong Ngoc; Hien, Than Duc

2013-04-01

44

Epitaxial cubic gadolinium oxide as a dielectric for gallium arsenide passivation  

PubMed

Epitaxial growth of single-crystal gadolinium oxide dielectric thin films on gallium arsenide is reported. The gadolinium oxide film has a cubic structure isomorphic to manganese oxide and is (110)-oriented in single domain on the (100) gallium arsenide surface. The gadolinium oxide film has a dielectric constant of approximately 10, with low leakage current densities of about 10(-9) to 10(-10) amperes per square centimeter at zero bias. Typical breakdown field is 4 megavolts per centimeter for an oxide film 185 angstroms thick and 10 megavolts per centimeter for an oxide 45 angstroms thick. Both accumulation and inversion layers were observed in the gadolinium oxide-gallium arsenide metal oxide semiconductor diodes, using capacitance-voltage measurements. The ability to grow thin single-crystal oxide films on gallium arsenide with a low interfacial density of states has great potential impact on the electronic industry of compound semiconductors. PMID:10082459

Hong; Kwo; Kortan; Mannaerts; Sergent

1999-03-19

45

Gallium-67/stable gadolinium antagonism: MRI contrast agent markedly alters the normal biodistribution of gallium-67  

SciTech Connect

An 11-yr-old patient was scanned 96 hr after the administration of gallium-67 ({sup 67}Ga). The scan emulated the biodistribution of a typical bone-seeking radipharmaceutical-rather than that of {sup 67}Ga. None of the factors previously identified with alteration of the biodistribution of {sup 67}Ga were found. However, the patient had been injected with gadopentetate in conjunction with magnetic resonance imaging 4 hr before receiving the {sup 67}Ga. Gadolinium appears to cause a strong carrier-like effect in {sup 67}Ga scans.

Hattner, R.S.; White, D.L. (Univ. of California, San Francisco (USA))

1990-11-01

46

Low-temperature thermal conductivity of terbium-gallium garnet  

SciTech Connect

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.

Inyushkin, A. V., E-mail: inyushkin@imp.kiae.ru; Taldenkov, A. N. [Kurchatov Institute, Russian Research Centre (Russian Federation)

2010-11-15

47

Laser-related properties of chromium- and neodymium-doped gadolinium scandium aluminum garnet (Cr:Nd:GSAG)  

SciTech Connect

The spectroscopic, lasing, and thermal properties of chromium- and neodymium-doped gadolinium scandium aluminum garnet (Cr:Nd:GSAG) are reported. The Judd--Ofelt parameters, radiative lifetime, and branching ratios were determined, and an effective emission cross-section value of 0.92 [times] 10[sup [minus]19][ital cm][sup 2] was derived at 1.06 [mu]m from our spectroscopic measurements. The temporal behavior of the Cr[sup 3+] fluorescence intensity agreed with the Inokuti--Hirayama model for the chromium--neodymium energy-transfer mechanism, which invokes a static dipole--dipole interaction and no migrational energy transfer. Under identical flash-lamp-pumping conditions the measured pumping efficiency of Cr:Nd:GSAG for threshold lasing is nearly equal to the pumping efficiency of codoped gadolinium scandium gallium garnet (Cr:Nd:GSGG). From the threshold-lasing data, an effective emission cross section of 0.7 [times] 10[sup [minus]19] cm[sup 2] for Cr:Nd:GSAG was independently determined, as well as a value of 1.3 [times] 10[sup [minus]19] cm[sup 2] for Cr:Nd:GSGG. The normalized heating parameter [chi], defined as the heat deposited per unit stored energy, experimentally ranges from 2.1 to 2.7, depending on the effective emission cross-section value. Our calculated value of [chi] is 1.9 [plus minus] 0.3. Based on our heating-efficiency measurements, calculated Cr:Nd:GSAG thermal lensing values are [similar to] 2.1--2.6 D/kW, which indicates a thermally induced focal length that is weaker than that of Nd:YAG by approximately a factor of 2 at the same output power. Finally, the benefits and trade-offs of laser-diode pumping are discussed.

Sumida, D.S.; Mangir, M.S.; Rockwell, D.A. (Hughes Research Laboratories, 3011 Malibu Canyon Road, M/S RL 65, Malibu, California 90265-4799 (United States)); Shinn, M.D. (Bryn Mawr College, Department of Physics, Bryn Mawr, Pennsylvania 19010-2899 (United States))

1994-10-01

48

Luminescence Properties of Praseodymium Doped Gadolinium Gallium Garnet (GGG) Nanocrystals  

Microsoft Academic Search

Significant strides have been achieved in recent years in the field of luminescence especially in the nanocrystalline domain. Nanocrystalline particles are of great interest as their optical properties can be varied greatly by tailoring the particle size. Rare-earths represent highly interesting dopant ions due to their intensely luminescent f-f electronic transitions. Praseodymium, in particular, can be employed as a probe

Rafik Naccache; Fiorenzo Vetrone; John-Christopher Boyer; John A. Capobianco; Adolfo Speghini; Marco Bettinelli

2004-01-01

49

Luminescence Properties of Praseodymium Doped Gadolinium Gallium Garnet (GGG) Nanocrystals  

NASA Astrophysics Data System (ADS)

Significant strides have been achieved in recent years in the field of luminescence especially in the nanocrystalline domain. Nanocrystalline particles are of great interest as their optical properties can be varied greatly by tailoring the particle size. Rare-earths represent highly interesting dopant ions due to their intensely luminescent f-f electronic transitions. Praseodymium, in particular, can be employed as a probe for the study of radiative and non-radiative processes which are essential in the understanding of upconversion mechanisms. Much of the recent literature has targeted near infrared to visible upconversion in lanthanide-doped hosts. Relatively little work has been carried out on upconversion processes in nanoparticles. Cubic GGG nanocrystals doped with varying concentrations of Pr^3+ (0.1%, 1%, 5% and 10%) and Yb^3+ ions were prepared using a solution combustion (propellant) synthesis. The aqueous precursor solution consisted of carbohydrazide, Ga(NO_3)_3-H_2O, Gd(NO_3)_3-6H_2O and Pr(NO_3)_3-6H_2O. The average particle size of the resultant powder was approximately 20 nm. Blue anti-Stokes emission centered at 443 nm and 486 nm and emanating from the ^3P_2?^3H4 and ^3P_0?^3H4 transitions, respectively, was observed after continuous wave excitation (606.9 nm) into the ^1D_2?^3H4 transition of the Pr^3+ ion. Blue, green and red anti-Stokes emission was observed from the ^3P_0, ^3P1 and 1D2 states following excitation into the ^1G_4?^3H4 (980 nm) energy level. Transition lifetime measurements were used to try to elucidate the mechanisms that lead to different upconversion luminescence spectra in the nanocrystals including excited state absorption (ESA) and energy transfer upconversion (ETU).

Naccache, Rafik; Vetrone, Fiorenzo; Boyer, John-Christopher; Capobianco, John A.; Speghini, Adolfo; Bettinelli, Marco

2004-03-01

50

Structural and thermal investigation of gadolinium gallium mixed oxides obtained by coprecipitation: Observation of a new metastable phase  

SciTech Connect

Polycrystalline gadolinium gallium mixed oxides were prepared by coprecipitation and annealing at various temperatures below 1000 deg. C. The oxide materials appear to be X-ray amorphous after a heat treatment at 500 deg. C for 30 h, but after 30 h at 800 and 900 deg. C a major, unreported, hexagonal phase, isostructural with TAlO{sub 3} compounds (where T=Y, Eu, Gd, Tb, Dy, Ho, Er) appears to crystallize. On the other hand, a highly energetic mechanical treatment of the amorphous powder previously annealed at 500 deg. C changes considerably the shape and position of exothermal events occurring in the range from 700 up to 900 deg. C. Subsequent annealing at 900 deg. C of the mechanically treated powder gives rise to the complete formation of the Gd{sub 3}Ga{sub 5}O{sub 12} garnet structure at the expense of the hexagonal phase and of the minor Gd{sub 4}Ga{sub 2}O{sub 9} oxide phase. However, a 7.0 wt% contamination is found to be due to tetragonal zirconia coming from vials and balls colliding media. The garnet phase may have strong deviations from the nominal stoichiometry of the garnet, as suggested by the refined lattice parameter obtained from the powder diffraction patterns and by the remarkable absence of intensity relative to the (220) Bragg peak position.

Bazzoni, Marco [Dipartimento di Chimica, Universita di Sassari, via Vienna n. 2, I-07100 Sassari (Italy); Bettinelli, Marco [Dipartimento Scientifico e Tecnologico, Universita di Verona, Ca' Vignal 1, strada le Grazie 15, I-37134 Verona (Italy); Daldosso, Matteo [Dipartimento Scientifico e Tecnologico, Universita di Verona, Ca' Vignal 1, strada le Grazie 15, I-37134 Verona (Italy); Enzo, Stefano [Dipartimento di Chimica, Universita di Sassari, via Vienna n. 2, I-07100 Sassari (Italy)]. E-mail: enzo@uniss.it; Serra, Filomena [Dipartimento di Chimica, Universita di Sassari, via Vienna n. 2, I-07100 Sassari (Italy); Speghini, Adolfo [Dipartimento Scientifico e Tecnologico, Universita di Verona, Ca' Vignal 1, strada le Grazie 15, I-37134 Verona (Italy)

2005-07-15

51

Reflectivity and thermally modulated reflectivity of yttrium, gadolinium, erbium and ytterbium iron garnets  

NASA Astrophysics Data System (ADS)

Optical reflectivity and thermoreflectivity measurements in the 2.5-4.7 eV region for gadolinium iron garnet, erbium iron garnet and ytterbium iron garnet are reported and discussed in relation to previous measurements performed on yttrium iron garnet. Near normal incidence reflectivity spectra of YbIG, ErIG, GdIG and YIG single crystals measured at room temperature and YIG measured at 80 K are shown to consist of two peaks centered around 3.3 and 4.4 eV and a number of structural features, demonstrating that the absolute reflectivity is not appreciably altered by the substitution of yttrium with heavier rare earth ions. Thermoreflectivity spectra of the same compounds taken at a temperature of 300 K are shown to contain the same number of positive and negative derivative peaks, which are strongly correlated with the reflectivity structures, and a gradual shift of the baseline with respect to YIG with increasing atomic weight. The experimental data for YbIG and YIG are analyzed in terms of a model describing the dielectric response of a system of localized excitations associated with a classical damped Lorentz operator. On the basis of the similarity of the rare earth spectra, assignments of YIG transitions are concluded to apply to the rare earth iron garnets, with the shift of the baseline with increasing atomic number attributed to the tailing of high-energy oscillators.

Balzarotti, A.; Picozzi, P.; Ricchiuto, A.; Santucci, S.

1980-12-01

52

Plasmon resonance enhancement of Faraday rotation in thin garnet films  

NASA Astrophysics Data System (ADS)

Garnet films have been grown over (100)-oriented substituted gadolinium gallium garnet substrates partially populated with gold nanoparticles in order to study plasmon resonance enhancement of magneto-optic effects. The results of measurements of light transmission through these films as well as Faraday rotation are reported.

Tkachuk, S.; Lang, G.; Krafft, C.; Rabin, O.; Mayergoyz, I.

2011-04-01

53

Molecular field theory analysis of magneto-optic sensitivity of gallium-substituted yttrium iron garnets  

Microsoft Academic Search

The temperature dependence of the magneto-optic sensitivity of gallium-substituted yttrium iron garnets was measured at 1.3 ?m and compared with a model based on molecular field theory. The model incorporates results of measurements of both the saturation magnetization and saturation Faraday rotation versus temperature. These measurements were analyzed in the context of molecular field theory to extract the fundamental molecular

Merritt N. Deeter; Silvia Milia´n Bon

1996-01-01

54

Paramagnetic Resonance of Fe3+ in Octahedral and Tetrahedral Sites in Yttrium Gallium Garnet (YGaG) and Anisotropy of Yttrium Iron Garnet (YIG)  

Microsoft Academic Search

The electron paramagnetic resonance spectrum of a small Fe3+ impurity which enters substitutionally for the gallium in single crystals of yttrium gallium garnet (chemical formula Y3Ga5O12) has been examined at 24 kMc\\/sec at 295°K and 1.6°K. Fe3+ is studied for the first time in tetrahedral coordination. The results for the crystal field parameters that appear in the usual spin Hamiltonian

S. Geschwind

1961-01-01

55

Processing of gadolinium-iron garnet under non-equilibrium conditions  

NASA Astrophysics Data System (ADS)

We have investigated the mechanosynthesis of gadolinium iron garnet (GdIG) by high-energy ball-milling of 3.(Gd2O3) + 10.(?-Fe) followed by thermal annealing conducted at moderate temperatures (1100 °C). The samples were characterized by X-ray diffraction and Mössbauer spectroscopy in order to determine the influence of the milling time on the final products. For as-milled samples the results revealed the enlargement of the magnetic component belonging to iron and a discrete paramagnetic component. The formation of a garnet phase was observed in all as-annealed samples treated at 1100 °C for 6 h in quantities proportional to the time of grinding the precursors. Evidently, high-energy ball milling of Gd2O3 + ?-Fe powders is an important step in GdIG synthesis by a ceramic method. Single-phase garnet is observed for the samples milled for 12 and 24 h treated at 1100 °C for 6 h.

Zanatta, S. C.; Ivashita, F. F.; da Silva, K. L.; Machado, C. F. C.; Paesano, A.

2013-02-01

56

Sputter Deposition of Cerium Yttrium Iron Garnet Films on Substrates with Ion-Beam Bombarded Patterns  

Microsoft Academic Search

We report the experimental results of magnetooptic rare-earth iron-garnet sputtered film deposition on substrates with a modified surface. The magnetooptic garnet considered here is cerium-substituted yttrium iron garnet which is one of the promising materials for nonreciprocal optical devices and magnetooptic recording media. The surface of the substrate, gadolinium gallium garnet, is etched by ion-beam bombardment, whose energy was controllable

Yasuyuki Okamura; Sadahiko Yamamoto

1999-01-01

57

Microstrip lines using yttrium iron garnet film  

Microsoft Academic Search

The spectral-domain technique is used to compute the dispersion characteristics and the transverse field distributions of microstrip lines using a yttrium-iron-garnet (YIG) film on a gadolinium-gallium-garnet (GGG) substrate. Numerical results are presented to show a sharp cutoff characteristic for a large thickness of GGG (which is caused by the reduction in the negative permeability range), and to show the effect

M. Tsutsumi; T. Asahara

1990-01-01

58

Effects of Lead Incorporation on the Ferromagnetic Resonance Linewidths of Liquid Phase Epitaxial Grown Yttrium Iron Garnet.  

National Technical Information Service (NTIS)

Single crystal thin films of yttrium iron garnet (YIG) were grown on gadolinium gallium garnet (GGG) substrates by the isothermal dipping method of liquid phase epitaxy. The concentration of Pb in the films was adjustable through selection of the growth t...

M. T. Elliott

1975-01-01

59

A wideband electronically tunable microwave notch filter in yttrium iron garnet-gallium arsenide material structure  

NASA Astrophysics Data System (ADS)

A wideband electronically tunable microwave notch (band-stop) filter has been constructed in an yttrium iron garnet (YIG)/gallium arsenide (GaAs) material structure. An incident microwave propagating along the microstrip transmission line in the GaAs substrate is coupled into and to excite the magnetostatic surface waves in the YIG layer, which is laid upon the microstrip transmission line. Maximum coupling and thus the peak absorption of the output microwave power occur at the ferromagnetic resonance frequency in the YIG film as determined by a bias magnetic field. A tuning range as large as 2.5-23.0 GHz in the peak absorption frequency with the corresponding magnetic field tuning range of 290-7300 Oe has been accomplished. Peak absorption of 15-38 dB in the microwave output power has also been measured.

Tsai, Chen S.; Su, Jun

1999-04-01

60

Low-temperature synthesis and characterization of yttrium–gallium garnet Y 3Ga 5O 12 (YGG)  

Microsoft Academic Search

To obtain yttrium–gallium garnet (Y3Ga5O12, YGG) a simple “chimie douce” method has been developed. This sol–gel method yielded excellent starting gel precursor for the fabrication of YGG phase, which could be used as host material for optical applications. The pattern of X-ray diffraction analysis of the ceramic sample sintered for 10h at 1000°C showed the formation of monophasic Y3Ga5O12 phase.

Sanjay Mathur; Hao Shen; Asta Leleckaite; Aldona Beganskiene; Aivaras. Kareiva

2005-01-01

61

Crystal fields in Pr3+ doped rare earth gallium garnets, RE3Ga5O12:Pr3+  

Microsoft Academic Search

The optical absorption, site selective excitation and luminescence spectra of the trivalent praseodymium ion in three rare earth gallium garnet matrices, RE3Ga5O12 (REGG; RE=Y, Gd, and Pr) were detected at 4, 77 and 300 K. The 4f2 energy level schemes comprising 56 to 68 crystal field (CF) sublevels were simulated according to a phenomenological model taking into account both the

E. Antic-Fidancev; J. Holsa; J.-C. Krupa; M. Lemaitre-Blaise; P. Porcher

1992-01-01

62

Absorption Spectra and Energy Levels of Gd(3+), Nd(3+), and Cr(3+) in the Garnet Gd3Sc2Ga3O12.  

National Technical Information Service (NTIS)

Absorption spectra recorded between 0.3 and 6.7 micro are reported for trivalent gadolinium, trivalent neodymium, and trivalent chromium in single-crystal gadolinium scandium gallium garnet, Gd3Sc2Ga3O12, at liquid nitrogen, and room temperatures. Crystal...

J. B. Gruber M. E. Hills C. A. Morrison G. A. Turner M. R. Kokta

1988-01-01

63

ACTIVE MEDIA: Interaction of Er3+ ions in Er-doped calcium — niobium — gallium garnet crystals  

NASA Astrophysics Data System (ADS)

The processes of nonradiative energy transfer in calcium — niobium — gallium garnet (CNGG) crystals doped with Er3+ ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations CEr=6% and 11% is transferred via the nonradiative co-operative processes 4I11/2? 4I15/2, 4I11/2? 4F7/2, 4I11/2? 4I15/2, 4I13/2? 4F9/2; and 4I13/2? 4I15/2, 4I13/2? 4I9/2, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes 4S3/2?4I9/2, 4I15/2?4I13/2, whose intensity depends on the concentration of Er3+ ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%.

Malov, A. V.; Ryabochkina, P. A.; Popov, A. V.; Bol'shakov, E. V.

2010-08-01

64

Decontamination of deep dentin by means of erbium, chromium:yttrium-scandium-gallium-garnet laser irradiation.  

PubMed

The aim of this in vitro study was to evaluate the depth of effectiveness of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation on microorganism reduction. From human roots, dentin slices of 100 microm to 1,000 microm thickness were prepared. These specimens were sterilized and then inoculated with 1 microl of Enterococcus faecalis suspension. The backs of the specimens were then irradiated with Er,Cr:YSGG radiation at a pulse energy of 3.13 mJ, delivered at an incidence angle of 5 degrees to the dentin slice surface. A control group was left without irradiation. The remaining bacteria were collected in 1 ml sterilized NaCl solution, serially diluted and seeded in Columbia-Agar plates. Despite the low pulse energy of 3.13 mJ, the Er,Cr:YSGG laser irradiation resulted in significant bacterial reduction up to a dentin thickness of 500 microm (P < 0.05). Scanning electron microscopy (SEM) micrographs of the contaminated and irradiated surfaces showed the absence of a smear layer and opened dentinal tubules. PMID:18027063

Franzen, René; Esteves-Oliveira, Marcella; Meister, Jörg; Wallerang, Anja; Vanweersch, Leon; Lampert, Friedrich; Gutknecht, Norbert

2007-11-20

65

Interaction of Er{sup 3+} ions in Er-doped calcium - niobium - gallium garnet crystals  

SciTech Connect

The processes of nonradiative energy transfer in calcium - niobium - gallium garnet (CNGG) crystals doped with Er{sup 3+} ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations C{sub Er}=6% and 11% is transferred via the nonradiative co-operative processes {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 11/2{yields}} {sup 4}F{sub 7/2}, {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}F{sub 9/2}; and {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 9/2}, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes {sup 4}S{sub 3/2{yields}}{sup 4}I{sub 9/2}, {sup 4}I{sub 15/2{yields}}{sup 4}I{sub 13/2}, whose intensity depends on the concentration of Er{sup 3+} ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%. (active media)

Malov, A V [N.P. Ogarev Mordovian State University, Saransk (Russian Federation); Popov, A V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Ryabochkina, P A; Bol'shakov, E V

2010-08-03

66

Enhanced microwave ferromagnetic resonance absorption and bandwidth using a microstrip meander line with step-impedance low-pass filter in a yttrium iron garnet-gallium arsenide layer structure  

NASA Astrophysics Data System (ADS)

Simulations of the step-impedance low-pass filter (LPF) in gallium arsenide (GaAs) substrate show that, in contrast to a 50 ? microstrip, the magnetic fields of the propagating microwaves are heavily concentrated in its inductive elements. The concentrated local magnetic fields facilitate enhanced coupling into an yttrium iron garnet/gadolinium gallium garnet layer over the GaAs substrate and, thus, significantly increase the microwave power absorptions at the ferromagnetic resonance (FMR) frequencies. The large tunable range of FMR frequency and the corresponding S21 and S11 parameters measured have verified the simulation results. Simultaneous enhancement of FMR absorption level and widening of absorption bandwidth has been accomplished in a band-stop filter that utilizes a microstrip meander line with four identical step-impedance LPFs, each of 5.70 mm long, inserted in a nonuniform bias magnetic field. A tunable FMR absorption frequency range of 5-21 GHz, an absorption level of -35.5 dB, and a corresponding 3 dB absorption bandwidth as large as 1.70 GHz, centered at 20.3 GHz, have been demonstrated.

Qiu, Gang; Tsai, Chen S.; Kobayashi, Masatoshi M.; Wang, Bert S. T.

2008-04-01

67

A monolithic single-crystal yttrium iron garnet\\/silicon X-band circulator  

Microsoft Academic Search

Production of truly monolithic microwave integrated circuits that incorporate ferrite passive control elements has been hindered by the material property mismatches between ferrites and semiconductors. In this work, monolithic Y-junction circulators were fabricated by bonding 100-?m-thick single-crystal yttrium iron garnet films to silicon at 195°C, and then removing the gadolinium gallium garnet substrate. S-parameter measurements on the circulator and matching

S. A. Oliver; P. M. Zavracky; N. E. McGruer; R. Schmidt

1997-01-01

68

Magnetic and magneto-optical properties of bismuth-substituted gadolinium iron garnet films  

Microsoft Academic Search

The saturation magnetization Ms, the uniaxial anisotropy Ku, the optical absorption alpha, the Faraday rotation thetaF, and the Faraday ellipticity psiF of epitaxial garnet films of composition Gd3-xBixFe5O12 have been investigated for x<=1.43. The temperature dependence of Ms and thetaF have been measured in the range 4.2 K<=T<=TC. The compensation temperature decreases and the Curie temperature increases linearly with the

P. Hansen; K. Witter; W. Tolksdorf

1983-01-01

69

Interaction of optical waveguide modes with magnetostatic transverse surface eigenmodes in a channel yttrium iron garnet waveguide  

Microsoft Academic Search

The objective of this study was to experimentally investigate the peculiarities of the interaction of optical waveguide modes with surface magnetostatic wave (MSW) in a narrow channel waveguide. A 3-mm-wide yttrium iron garnet-gadolinium gallium garnet (YGG-GGG) layered structure was employed as a waveguide for MSW and optical waves. The ferrimagnetic layer was 3.8- micron thick. Due to isotropic prisms, the

V. V. Matyushev; A. A. Stashkevich; A. I. Lukyanov

1993-01-01

70

A comparative study of gadolinium gallium garnet growth by femtosecond and nanosecond pulsed laser deposition  

NASA Astrophysics Data System (ADS)

The growth of epitaxial Nd:Gd 3Ga 5O 12 (GGG) on Y 3Al 5O 12 (YAG) by femtosecond pulsed laser deposition is reported. We have used a Ti:sapphire laser at a wavelength of 800 nm and pulse length of 130 fs, operating at a repetition rate of 1 kHz. The film properties have been studied systematically as a function of the deposition parameters of laser fluence, spot-size, oxygen pressure, target-substrate distance and temperature. Scanning electron microscopy, atomic force microscopy and X-ray diffractometry were used to characterise the surface structure and crystallinity of the films. X-ray diffraction analysis shows that epitaxial growth has occurred. A comparison between the ion velocities produced by nanosecond and femtosecond laser ablation of the GGG target material has been investigated by the Langmuir probe technique. The results indicate a large difference in the plasma characteristics between femtosecond and nanosecond ablation, with ion velocities up to eight times faster observed in the femtosecond case.

Darby, M. S. B.; May-Smith, T. C.; Eason, R. W.; Donnelly, T.; Lunney, J. G.; Rogers, K. D.

2008-03-01

71

Pressure-induced luminescence of cerium-doped gadolinium gallium garnet crystal  

NASA Astrophysics Data System (ADS)

Studies of the spectroscopic properties of Ce3+ dopant in bulk Gd3Ga5O12:Ce crystal under pressure are presented. In spite of strong intershell 4f?5d absorption bands at ambient pressure, the cerium luminescence in Gd3Ga5O12 is entirely quenched even at low temperature. It has been shown that applying pressure allows for recovery of the 5d?4f radiative transitions. Further increase of pressure improves the emission efficiency. This effect is analyzed in terms of two possible phenomena: (i) by pressure-induced electronic crossover of the excited 5d energy level of the Ce3+ with the conduction band bottom of the host crystal, and (ii) by decrease of electron-lattice coupling with increasing pressure, resulting in reduction of the Stokes shift and nonradiative transitions between the low vibrational levels of the 5d state and high vibrational levels of the ground 4f state. The results of high-pressure absorption and luminescence measurements point out that the ambient-pressure luminescence quenching is caused by the donor-like charge transfer processes due to the resonant location of the Ce3+ 5d electronic levels with respect to the host conduction band. In such a situation, the ionization of Ce3+ to Ce4+ occurs, accompanied by large lattice relaxation, which enables the nonradiative recombination to the Ce 4f state. The pressure-induced approach of the conduction-band bottom of the host crystal by the excited 5d energy level of the Ce3+ results in mixing between conduction band states and the 5d state, and the broadband luminescence from this mixed state is observed at pressures from 30 up to about 60 kbar. Then, for pressures exceeding 60 kbar, this luminescence is replaced by the classic Ce3+5d?4f transitions. Using a simple anticrossing model and configuration coordinate model in the appropriate pressure range, quantitative description of the system has been carried out, and the pressure-induced decrease of electron-lattice coupling has been shown.

Kaminska, A.; Duzynska, A.; Berkowski, M.; Trushkin, S.; Suchocki, A.

2012-04-01

72

Transmission of gamma rays through the curved single crystals of gadolinium-gallium garnet  

NASA Astrophysics Data System (ADS)

The effect of anomalous transmission of gamma rays (E?=0.662 MeV) through the bent single crystals of Gd3Ga5O12 (GGG) has been experimentally studied. A simple model has been proposed, which explains the observed phenomenon by the gamma ray focusing.

Khairulin, R. A.; Stankus, S. V.; Savchenko, O. Ya.; Baginskii, A. V.; Ulyusov, P. V.

2004-02-01

73

Field induced magnetic order in the frustrated magnet gadolinium gallium garnet  

NASA Astrophysics Data System (ADS)

Gd3Ga5O12, (GGG), has an extraordinary magnetic phase diagram, where no long range order is found down to 25 mK despite ?CW approx2 K. However, long range order is induced by an applied field of around 1 T. Motivated by recent theoretical developments and the experimental results for a closely related hyperkagome system, we have performed neutron diffraction measurements on a single crystal sample of GGG in an applied magnetic field. The measurements reveal that the H - T phase diagram of GGG is much more complicated than previously assumed. The application of an external field at low T results in an intensity change for most of the magnetic peaks which can be divided into three distinct sets: ferromagnetic, commensurate antiferromagnetic, and incommensurate antiferromagnetic. The ferromagnetic peaks (e.g. (112), (440) and (220)) have intensities that increase with the field and saturate at high field. The antiferromagnetic reflections have intensities that grow in low fields, reach a maximum at an intermediate field (apart from the (002) peak which shows two local maxima) and then decrease and disappear above 2 T. These AFM peaks appear, disappear and reach maxima in different fields. We conclude that the competition between magnetic interactions and alternative ground states prevents GGG from ordering in zero field. It is, however, on the verge of ordering and an applied magnetic field can be used to crystallise ordered components. The range of ferromagnetic (FM) and antiferromagnetic (AFM) propagation vectors found reflects the complex frustration in GGG.

Petrenko, O. A.; Balakrishnan, G.; McK Paul, D.; Yethiraj, M.; McIntyre, G. J.; Wills, A. S.

2009-01-01

74

Complete Stokes polarimetry of magneto-optical Faraday effect in a terbium gallium garnet crystal at cryogenic temperatures.  

PubMed

We report the complete determination of the polarization changes caused in linearly polarized incident light due to propagation in a magneto-optically active terbium gallium garnet (TGG) single crystal, at temperatures ranging from 6.3 to 300 K. A 28-fold increase in the Verdet constant of the TGG crystal is seen as its temperature decreases to 6.3 K. In contrast with polarimetry of light emerging from a Faraday material at room temperature, polarimetry at cryogenic temperatures cannot be carried out using the conventional fixed polarizer-analyzer technique because the assumption that ellipticity is negligible becomes increasingly invalid as temperature is lowered. It is shown that complete determination of light polarization in such a case requires the determination of its Stokes parameters, otherwise inaccurate measurements will result with negative implications for practical devices. PMID:24150356

Majeed, Hassaan; Shaheen, Amrozia; Anwar, Muhammad Sabieh

2013-10-21

75

Growth of terbium gallium garnet (TGG) magneto-optic crystals by edge-defined film-fed growth method  

NASA Astrophysics Data System (ADS)

Although terbium gallium garnet (TGG) single crystals suitable for practical applications have been grown by the Czochralski technique due to its congruent melting nature, the interface shape readily deteriorates to spiral growth when grown with a flat interface or facet formation when grown with a convex interface. The Edge-defined Film-fed Growth (EFG) method was used to grow TGG crystals for the first time. The influence of the raw material sintering temperature, growth atmosphere, growth rate and other growth conditions on the crystal quality were investigated. The Verdet constant of as-grown crystal was measured as 39 rad/T.m at 1064 nm by the extinction method, which was close to the literature value. The source of color centers in the crystals is also discussed.

Zhuang, Naifeng; Song, Caigen; Guo, Liwei; Wang, Rongfeng; Hu, Xiaolin; Zhao, Bin; Lin, Shukun; Chen, Jianzhong

2013-10-01

76

Paramagnetic Resonance of Fe3+ in Yttrium Aluminum, Lutetium Aluminum, and Lutetium Gallium Garnets  

Microsoft Academic Search

The spin-Hamiltonian parameters have been determined for the Fe3+ ion when present as substitutional impurity in the series of isomorphous diamagnetic garnets. Most of the parameters vary rather slowly from host to host. It is shown that the dependence of the cubic field splitting in the octahedral sites on lattice parameters as obtained from the present results is consistent with

L. Rimai; T. Kushida

1966-01-01

77

Energy levels and symmetry assignments for Stark components of Ho3+(4f10) in yttrium gallium garnet (Y3Ga5O12)  

Microsoft Academic Search

Absorption and fluorescence spectra observed between 1950 and 320 nm at sample temperatures of 8, 78, and 293 K, representing more than 900 transitions between 24 multiplets 2S+1LJ of Ho3+(4f10) split by the crystal field, have been analyzed in Czochralski-grown single crystals of Ho3+ doped-yttrium gallium garnet (Y3Ga5O12 or YGG). The Ho3+ ions replace Y3+ ions in sites of D2

John B. Gruber; Gary W. Burdick; Uygun V. Valiev; Kelly L. Nash; Sharof A. Rakhimov; Dhiraj K. Sardar

2009-01-01

78

SOLID-STATE AND SEMICONDUCTOR LASERS: Q-switched laser utilizing an yttrium scandium gallium garnet crystal activated with holmium ions  

Microsoft Academic Search

The 5I7 transition in Ho ions in an ytrrium scandium gallium garnet crystal containing Cr, Tm, and Ho (lambda = 2.088 mum) resulted in Q-switched lasing when the crystal was pumped with a flashlamp at room temperature. The output energy of a giant pulse was 280 mJ when a rotating prism was employed and 80 mJ when an electrooptic switch

A. N. Alpat'ev; Evgeny V. Zharikov; S. P. Kalitin; Valerii A. Smirnov; A. F. Umyskov; Ivan A. Shcherbakov

1988-01-01

79

The effect of erbium, chromium:yttrium–scandium–gallium–garnet laser etching on marginal integrity of a resin-based fissure sealant in primary teeth  

Microsoft Academic Search

The aim of this in vitro study was to evaluate the effect of erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG)\\u000a laser pretreatment alone, or associated with acid etching, on the quality of marginal integrity (microleakage and marginal\\u000a gap) of a resin-based fissure sealant in primary teeth. Fifty sound primary molar teeth were randomly assigned to one of five\\u000a study groups, pretreated as follows: (1)

Elif Sungurtekin; Nurhan Özta?

2010-01-01

80

Photon self-induced spin-to-orbital conversion in a terbium-gallium-garnet crystal at high laser power  

SciTech Connect

In this paper, we present experimental evidence of a third-order nonlinear optical process, self-induced spin-to-orbital conversion (SISTOC) of the photon angular momentum. This effect is the physical mechanism at the origin of the depolarization of very intense laser beams propagating in isotropic materials. The SISTOC process, like self-focusing, is triggered by laser heating leading to a radial temperature gradient in the medium. In this work we tested the occurrence of SISTOC in a terbium-gallium-garnet rod for an impinging laser power of about 100 W. To study the SISTOC process we used different techniques: polarization analysis, interferometry, and tomography of the photon orbital angular momentum. Our results confirm, in particular, that the apparent depolarization of the beam is due to the occurrence of maximal entanglement between the spin and orbital angular momentum of the photons undergoing the SISTOC process. This explanation of the true nature of the depolarization mechanism could be of some help in finding novel methods to reduce or to compensate for this usually unwanted depolarization effect in all cases where very high laser power and good beam quality are required.

Mosca, S.; De Rosa, R.; Milano, L. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy); INFN Sezione di Napoli, Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy); Canuel, B.; Genin, E. [EGO, European Gravitational Observatory, Via E. Amaldi, 56021 S. Stefano a Macerata, Cascina (Italy); Karimi, E. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy); Piccirillo, B.; Santamato, E. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy); CNISM-Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Napoli (Italy); Marrucci, L. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy); CNR-INFM Coherentia, Complesso Universitario di Monte S. Angelo, 80126 Napoli (Italy)

2010-10-15

81

Charge-transfer luminescence and spectroscopic properties of Yb3+ in aluminium and gallium garnets  

NASA Astrophysics Data System (ADS)

Luminescence of Yb3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino (?e) real-time spectroscopy, since the ?e capture by 176Yb is followed by a specific emission signature which can accordingly excite the Yb3+ fluorescence. Studies on scintillation and luminescence in aluminium garnets containing Yb3+ have shown that these materials meet some of the required properties for such scintillators. In defining our priorities, the best compromise between host crystal, Yb3+ concentration, production method, post-growth treatment and performance is to be considered based on the studies of charge-transfer luminescence and quenching mechanisms. The experiments have been extended to a large number of compounds: YAG:Yb-YbAG, YGG:Yb-YbGG, YAP:Yb-YbAP, LaYbO3 in the form of single crystals and/or powders. In garnets, the temperature-dependent fluorescence intensity and decay time under X-ray and VUV excitations decrease at low temperatures (T<100K) and demonstrate the important role played by the traps. The thermoluminescence peaks show a strong dependence on the crystal history, composition and impurities introduced intentionally. The fluorescence intensity and decay time are also dependent on Yb3+ concentration and the presence of Yb2+. The results trace the major directions to optimised scintillators in terms of their efficiency and lifetime.

Guerassimova, N.; Dujardin, C.; Garnier, N.; Pédrini, C.; Petrosyan, A. G.; Kamenskikh, I. A.; Mikhailin, V. V.; Shpinkov, I. N.; Spassky, D. A.; Ovanesyan, K. L.; Shirinyan, G. O.; Chipaux, R.; Cribier, M.; Mallet, J.; Meyer, J.-P.

2002-06-01

82

Growth and ferromagnetic resonance properties of nanometer-thick yttrium iron garnet films  

NASA Astrophysics Data System (ADS)

Growth of nm-thick yttrium iron garnet films and ferromagnetic resonance (FMR) linewidth properties in the films are reported. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition (PLD). Films in the 5-35 nm thickness range showed a (111) orientation and a surface roughness between 0.1 and 0.3 nm. The 10 nm films showed a 10 GHz FMR linewidth of about 6 Oe and a damping constant of 3.2 × 10-4. The FMR linewidth increases with both the surface roughness and the surface Fe deficiency. Thicker films exhibit a smaller FMR linewidth and a lower damping constant.

Sun, Yiyan; Song, Young-Yeal; Chang, Houchen; Kabatek, Michael; Jantz, Michael; Schneider, William; Wu, Mingzhong; Schultheiss, Helmut; Hoffmann, Axel

2012-10-01

83

Room temperature magnetoelectric control of micromagnetic structure in iron garnet films  

NASA Astrophysics Data System (ADS)

The effect of magnetic domain wall motion induced by electric field is observed in epitaxial iron garnet films grown on (210) and (110) gadolinium-gallium garnet substrates. The displacement of the domain wall changes to the opposite at the reversal of electric field polarity, and it is independent of the magnetic polarity of the domains. Dynamic observation of the domain wall motion in 400 V electric pulses gives the domain wall velocity of about 50 m/s. The same velocity is achieved in a magnetic field pulse of about 50 Oe. This type of magnetoelectric effect is implemented in single phase material at room temperature.

Logginov, A. S.; Meshkov, G. A.; Nikolaev, A. V.; Nikolaeva, E. P.; Pyatakov, A. P.; Zvezdin, A. K.

2008-11-01

84

Interaction of optical waveguide modes with magnetostatic transverse surface eigenmodes in a channel yttrium iron garnet waveguide  

NASA Astrophysics Data System (ADS)

The objective of this study was to experimentally investigate the peculiarities of the interaction of optical waveguide modes with surface magnetostatic wave (MSW) in a narrow channel waveguide. A 3-mm-wide yttrium iron garnet-gadolinium gallium garnet (YGG-GGG) layered structure was employed as a waveguide for MSW and optical waves. The ferrimagnetic layer was 3.8- micron thick. Due to isotropic prisms, the difference between the wave numbers of a TE and TM mode in a couple of optical waveguide modes were measured with high accuracy. The experiments were performed on four couples of optical waveguide modes: the zeroth, first, second, and third.

Matyushev, V. V.; Stashkevich, A. A.; Lukyanov, A. I.

1993-09-01

85

Low-temperature synthesis and characterization of yttrium-gallium garnet Y{sub 3}Ga{sub 5}O{sub 12} (YGG)  

SciTech Connect

To obtain yttrium-gallium garnet (Y{sub 3}Ga{sub 5}O{sub 12}, YGG) a simple 'chimie douce' method has been developed. This sol-gel method yielded excellent starting gel precursor for the fabrication of YGG phase, which could be used as host material for optical applications. The pattern of X-ray diffraction analysis of the ceramic sample sintered for 10 h at 1000 deg. C showed the formation of monophasic Y{sub 3}Ga{sub 5}O{sub 12} phase. The phase transformations, composition and micro-structural features in the gels and polycrystalline sample were studied by thermoanalytical methods (TGA/DTA), powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The quality of the resulting products (homogeneity, crystallisation temperature, grain size, grain size distribution, etc.) is discussed.

Mathur, Sanjay [Leibniz Institute of New Materials, CVD Division, Im Stadtwald, D-66123 Saarbruecken (Germany); Shen Hao [Leibniz Institute of New Materials, CVD Division, Im Stadtwald, D-66123 Saarbruecken (Germany); Leleckaite, Asta [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03011 Vilnius (Lithuania); Beganskiene, Aldona [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03011 Vilnius (Lithuania); Kareiva, Aivaras [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03011 Vilnius (Lithuania)]. E-mail: aivaras.kareiva@chf.vu.lt

2005-03-08

86

Coupling Single-Mode Fiber to Uniform and Symmetrically Tapered Thin-Film Waveguide Structures Using Gadolinium Gallium Garnet.  

National Technical Information Service (NTIS)

The need for high efficiency components has grown significantly due to the expanding role of fiber optic communications for various applications. Integrated optics is in a state of metamorphosis and there are many problems awaiting solutions. One of the m...

J. Gadi R. Yalamanchili M. Shahid

1995-01-01

87

Preparation of Nd-doped gadolinium-gallium garnet laser ceramic powder by sol-gel method  

NASA Astrophysics Data System (ADS)

Preparation of Nd3+: Gd3 Ga5 O12 polycrystalline material by sol-gel method was preparated in this paper. The structure and the pattern of the sample were analyzed by thermogravimetric analysis and differential thermal analysis (TG-DTA), Infrared spectrum, XRD, TEM and electron spectrum, which indicated that the powder with good characteristics of 70-100 nm can be obtained by sintering at 1 000°C. It was shown that the chemical composition of the sample was agreed with experimental requirements by electron spectrum analysis.

Yao, Yan-Ping; Liu, Jing-He

2006-07-01

88

High-pressure and high-temperature studies on oxide garnets  

SciTech Connect

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.}

Hua, H.; Mirov, S.; Vohra, Y.K. [Department of Physics, University of Alabama at Birmingham (UAB), Birmingham, Alabama 35294-1170 (United States)

1996-09-01

89

Growth and characterization of high purity epitaxial yttrium iron garnet films grown from BaO-B2O3-BaF2 flux  

NASA Astrophysics Data System (ADS)

The growth of yttrium iron garnet (YIG) epitaxial films of excellent purity from a lead-free BaO-B2O3-BaF2 flux and their characterization by the magnetic resonance methods are reported. The films were prepared by the standard dipping liquid-phase epitaxy onto gadolinium gallium garnet substrates of three crystallographic orientations (111), (110), and (100). The objective of utilization of a lead-free flux was to reduce the content of impurities and intrinsic defects in the garnet films and to obtain samples with minimum microwave losses. The samples exhibited very narrow NMR and spin wave linewidths. The diamagnetic and paramagnetic doping of YIG with ions of different valency and segregation of these ions between the garnet layer and the barium melt were also studied and the relevant distribution coefficients for doping into the tetrahedral (Ga, Al, Si Ge), octahedral (In) and dodecahedral (La, Ca) sites were determined.

Kuera, M.; Nitsch, K.; Tpánková, H.; Maryko, M.; Reiche, P.

2003-08-01

90

Erbium, chromium:yttrium scandium gallium garnet laser for caries removal: influence on bonding of a self-etching adhesive system.  

PubMed

This study evaluated the influence of the dental substrates obtained after the use of different caries removal techniques on bonding of a self-etching system. Forty, extracted, carious, human molars were ground to expose flat surfaces containing caries-infected dentine surrounded by sound dentine. The caries lesions of the specimens were removed or not (control--G1) either by round steel burs and water-cooled, low speed, handpiece (G2), or by irradiation with an erbium, chromium:yttrium scandium gallium garnet (Er,Cr:YSGG) laser (2W, 20 Hz, 35.38 J/cm(2), fiber G4 handpiece with 0.2826 mm(2), non-contact mode at a 2 mm distance, 70% air/20% water--G3) or using a chemo-mechanical method (Carisolv--G4). Caries-infected, caries-affected and sound dentines were submitted to a bonding system followed by construction of a resin-based composite crown. Hour-glass shaped samples were obtained and submitted to a micro-tensile bond test. The bond strength data were compared by analysis of variance (ANOVA), complemented by Tukey's test (P

Tachibana, Arlene; Marques, Márcia Martins; Soler, Julia Maria Pavan; Matos, Adriana Bona

2007-10-26

91

Energy levels and symmetry assignments for Stark components of Ho3+(4f10) in yttrium gallium garnet (Y3Ga5O12)  

NASA Astrophysics Data System (ADS)

Absorption and fluorescence spectra observed between 1950 and 320 nm at sample temperatures of 8, 78, and 293 K, representing more than 900 transitions between 24 multiplets 2S+1LJ of Ho3+(4f10) split by the crystal field, have been analyzed in Czochralski-grown single crystals of Ho3+ doped-yttrium gallium garnet (Y3Ga5O12 or YGG). The Ho3+ ions replace Y3+ ions in sites of D2 symmetry during crystal growth. Associated with each multiplet manifold are 2J+1 nondegenerate crystal-field split sublevels (Stark levels) characterized by one of four different irreducible representations (irreps) associated with D2 symmetry. The energy and irrep assignments for individual experimental Stark levels were established by an algorithm that makes use of the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels. Nearly degenerate Stark levels (quasidoublets) in several manifolds have been observed and investigated by magneto-optical methods reported in a separate study. Of the 252 predicted Stark levels associated with the 24 multiplet manifolds, 241 were experimentally determined of which 161 had symmetry irreps unambiguously identified by the algorithm method and confirmed by crystal-field modeling studies. A final least-squares fitting between 241 calculated-to-experimental Stark levels was obtained with a standard deviation of 4.86 cm-1 (rms error of 4.60 cm-1). The algorithm works best for identifying irreps when neighboring excited Stark levels are sufficiently separated so that a pattern of temperature-dependent (``hot band'') transitions can be unambiguously associated with each excited Stark level.

Gruber, John B.; Burdick, Gary W.; Valiev, Uygun V.; Nash, Kelly L.; Rakhimov, Sharof A.; Sardar, Dhiraj K.

2009-12-01

92

Inverse spin Hall effect in nanometer-thick yttrium iron garnet/Pt system  

NASA Astrophysics Data System (ADS)

High quality nanometer-thick (20 nm, 7 nm, and 4 nm) epitaxial Yttrium Iron Garnet (YIG) films have been grown on gadolinium gallium garnet substrates using pulsed laser deposition. The Gilbert damping coefficient for the 20 nm thick films is 2.3 × 10-4 which is the lowest value reported for sub-micrometric thick films. We demonstrate Inverse spin Hall effect (ISHE) detection of propagating spin waves using Pt. The amplitude and the lineshape of the ISHE voltage correlate well to the increase of the Gilbert damping when decreasing thickness of YIG. Spin Hall effect based loss-compensation experiments have been conducted but no change in the magnetization dynamics could be detected.

d'Allivy Kelly, O.; Anane, A.; Bernard, R.; Ben Youssef, J.; Hahn, C.; Molpeceres, A. H.; Carrétéro, C.; Jacquet, E.; Deranlot, C.; Bortolotti, P.; Lebourgeois, R.; Mage, J.-C.; de Loubens, G.; Klein, O.; Cros, V.; Fert, A.

2013-08-01

93

Growth of High-Quality Yttrium Iron Garnet Thin Films on Metallic Thin Layers  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) is one type of ferrite materials that has the lowest loss at microwave frequencies. One typically grows YIG on gadolinium gallium garnet (GGG) substrates, and this is typical mainly because of the perfect matching between the YIG and GGG lattice constants. For applications in monolithic devices, however, one needs to grow YIG films on metallic conductors or electrodes. This presentation reports the deposition of YIG thin films on metallic thin layers and the optimization of the deposition procedures. The metallic and YIG films were deposited by pulsed laser deposition and magnetron sputtering techniques and were characterized by scanning electron microscopy, x-ray diffraction, and ferromagnetic resonance measurements. The work shows rather clearly the critical roles of the selection of metallic materials, the thickness of the metallic layers, the deposition temperature, and the use of buffer layers on the deposition of high-quality YIG films.

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

2009-10-01

94

Crystal field disorder effects in the optical spectra of Nd3+ and Yb3+-doped calcium lithium niobium gallium garnets laser crystals and ceramics  

NASA Astrophysics Data System (ADS)

The optical spectroscopic properties of RE3+ (Nd, 1 at. % or Yb, 1 to 10 at. %)-doped calcium-lithium-niobium-gallium garnet (CLNGG) single crystals and ceramics in the 10 K-300 K range are analyzed. In these compositionally disordered materials, RE3+ substitute Ca2+ in dodecahedral sites and the charge compensation is accomplished by adjusting the proportion of Li+, Nb5+, and Ga3+ to the doping concentration. The crystals and ceramics show similar optical spectra, with broad and structured (especially at low temperatures) bands whose shape depends on temperature and doping concentration. At 10 K, the Nd3+ 4I9/2 --> 4F3/2, 5/2 and Yb3+ 2F7/2 --> 2F5/2 absorption bands, which show prospect for diode laser pumping, can be decomposed in several lines that can be attributed to centers with large differences in the crystal field. The positions of these components are the same, but the relative intensity depends on the doping concentration and two main centers dominate the spectra. Non-selective excitation evidences broad emission bands, of prospect for short-pulse laser emission, whereas the selective excitation reveals the particular emission spectra of the various centers. The modeling reveals that the nonequivalent centers correspond to RE3+ ions with different cationic combinations in the nearest octahedral and tetrahedral coordination spheres, and the most abundant two centers have 4Nb and, respectively, 3Nb1Li in the nearest octahedral sphere. At 300 K, the spectral resolution is lost. It is then inferred that the observed optical bands are envelopes of the spectra of various structural centers, whose resolution is determined by the relative contribution of the temperature-dependent homogeneous broadening and the effects of crystal field disordering (multicenter structure, inhomogeneous broadening). The relevance of spectroscopic properties for selection of pumping conditions and of laser design that would enable utilization of the broad optical bands for efficient laser emission and reduced heat generation is discussed.

Lupei, V.; Lupei, A.; Gheorghe, C.; Gheorghe, L.; Achim, A.; Ikesue, A.

2012-09-01

95

Crystal field disorder effects in the optical spectra of Nd{sup 3+} and Yb{sup 3+}-doped calcium lithium niobium gallium garnets laser crystals and ceramics  

SciTech Connect

The optical spectroscopic properties of RE{sup 3+} (Nd, 1 at. % or Yb, 1 to 10 at. %)-doped calcium-lithium-niobium-gallium garnet (CLNGG) single crystals and ceramics in the 10 K-300 K range are analyzed. In these compositionally disordered materials, RE{sup 3+} substitute Ca{sup 2+} in dodecahedral sites and the charge compensation is accomplished by adjusting the proportion of Li{sup +}, Nb{sup 5+}, and Ga{sup 3+} to the doping concentration. The crystals and ceramics show similar optical spectra, with broad and structured (especially at low temperatures) bands whose shape depends on temperature and doping concentration. At 10 K, the Nd{sup 3+4}I{sub 9/2}{yields}{sup 4}F{sub 3/2,5/2} and Yb{sup 3+2}F{sub 7/2}{yields}{sup 2}F{sub 5/2} absorption bands, which show prospect for diode laser pumping, can be decomposed in several lines that can be attributed to centers with large differences in the crystal field. The positions of these components are the same, but the relative intensity depends on the doping concentration and two main centers dominate the spectra. Non-selective excitation evidences broad emission bands, of prospect for short-pulse laser emission, whereas the selective excitation reveals the particular emission spectra of the various centers. The modeling reveals that the nonequivalent centers correspond to RE{sup 3+} ions with different cationic combinations in the nearest octahedral and tetrahedral coordination spheres, and the most abundant two centers have 4Nb and, respectively, 3Nb1Li in the nearest octahedral sphere. At 300 K, the spectral resolution is lost. It is then inferred that the observed optical bands are envelopes of the spectra of various structural centers, whose resolution is determined by the relative contribution of the temperature-dependent homogeneous broadening and the effects of crystal field disordering (multicenter structure, inhomogeneous broadening). The relevance of spectroscopic properties for selection of pumping conditions and of laser design that would enable utilization of the broad optical bands for efficient laser emission and reduced heat generation is discussed.

Lupei, V.; Lupei, A.; Gheorghe, C.; Gheorghe, L.; Achim, A. [National Institute for Lasers, Plasma and Radiation Physics, Lab. ECS, Bucharest (Romania); Ikesue, A. [World-Lab Co. Ltd., Atsuta-ku, Nagoya 456-8587 (Japan)

2012-09-15

96

Effective lattice stabilization of gadolinium aluminate garnet (GdAG) via Lu3+ doping and development of highly efficient (Gd,Lu)AG:Eu3+ red phosphors  

Microsoft Academic Search

The metastable garnet lattice of Gd3Al5O12 is stabilized by doping with smaller Lu3+, which then allows an effective incorporation of larger Eu3+ activators. The [(Gd1?xLux)1?yEuy]3Al5O12 (x = 0.1–0.5, y = 0.01–0.09) garnet solid solutions, calcined from their precursors synthesized via carbonate coprecipitation, exhibit strong luminescence at 591 nm (the 5D0 ? 7F1 magnetic dipole transition of Eu3+) upon UV excitation

Jinkai Li; Ji-Guang Li; Zhongjie Zhang; Xiaoli Wu; Shaohong Liu; Xiaodong Li; Xudong Sun; Yoshio Sakka

2012-01-01

97

Site-selective couplings in x-ray-detected magnetic resonance spectra of rare-earth-substituted yttrium iron garnets  

NASA Astrophysics Data System (ADS)

Site-selective x-ray detected magnetic resonance (XDMR) spectra were recorded in transverse detection geometry on two iron garnet thin films grown by liquid phase epitaxy (LPE) on oriented gadolinium gallium garnet (GGG) substrates: whereas the stoichiometry of the first film corresponded to pure yttrium iron garnet (1 = YIG) used as reference, yttrium was partly substituted with lanthanum and lutetium in the second film (2 = La-Lu-YIG). Surprisingly, the XDMR spectra of film 2 recorded at either the Fe K-edge or the La L3-edge revealed well-resolved structures that had fairly different relative intensity depending on whether we probed the tetrahedral ( {S}_{4} ) sites of iron or the dodecahedral ( {D}_{2} ) sites of lanthanum. The narrow XDMR lines measured at the Fe K-edge also contrast with the broad, foldover distorted lineshapes of the ferrimagnetic resonance spectra measured in the same scan. Further XDMR experiments were carried out with a thin, disc-shaped, single crystal of gadolinium iron garnet (3 = GdIG). At temperatures slightly above the gadolinium ordering temperature (T > TB = 69 K), the Gd L2-edge XDMR spectra were dominated by two well-resolved lines of nearly equal intensities. Similarly, the Fe K-edge XDMR spectra recorded under identical conditions did also split into several narrow lines but of strongly unequal intensity. These results suggest that, in the exchange-enhanced paramagnetic regime, spins precessing at the dodecahedral ( {D}_{2} ) sites of gadolinium do not couple in the same way with spins precessing at either the tetrahedral ( {S}_{4} ) or octahedral ( {S}_{6} ) sites of iron. On the other hand, destructive interferences between modes of opposite helicities were also observed in Fe K-edge XDMR spectra recorded far above the compensation temperature (T ? Tcp = 290 K). This looks like a typical signature of nonlinear four-magnon scattering processes at a very high pumping power.

Goulon, J.; Rogalev, A.; Wilhelm, F.; Goujon, G.; Yaresko, A.; Brouder, Ch; Ben Youssef, J.

2012-06-01

98

Effect of mechanical milling on the magnetic properties of garnets  

Microsoft Academic Search

Rare earth garnets after milling to nanosizes are found to decompose into rare earth orthoferrite and other rare earth and iron oxide phases. The magnetization for the yttrium iron garnet decreases in the nano state due to the formation of antiferromagnetic phases. But for the gadolinium iron garnet when milled up to 25h, the room temperature magnetization increases despite the

R. J. Joseyphus; A. Narayanasamy; A. K. Nigam; R. Krishnan

2006-01-01

99

Electronic sputtering of Gd3Ga5O12 and Y3Fe5O12 garnets: Yield, stoichiometry and comparison to track formation  

NASA Astrophysics Data System (ADS)

The results of present paper have shown that sputtering of yttrium iron garnet (Y3Fe5O12) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd3Ga5O12) as target. The irradiations were performed with different ions (50Cr (589 MeV), 86Kr (195 MeV) and 181Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd3Ga5O12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of Sth = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y3Fe5O12 and Gd3Ga5O12 using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface.

Meftah, A.; Assmann, W.; Khalfaoui, N.; Stoquert, J. P.; Studer, F.; Toulemonde, M.; Trautmann, C.; Voss, K.-O.

2011-05-01

100

Effective lattice stabilization of gadolinium aluminate garnet (GdAG) via Lu3+ doping and development of highly efficient (Gd,Lu)AG:Eu3+ red phosphors  

NASA Astrophysics Data System (ADS)

The metastable garnet lattice of Gd3Al5O12 is stabilized by doping with smaller Lu3+, which then allows an effective incorporation of larger Eu3+ activators. The [(Gd1-xLux)1-yEuy]3Al5O12?(x = 0.1-0.5, y = 0.01-0.09) garnet solid solutions, calcined from their precursors synthesized via carbonate coprecipitation, exhibit strong luminescence at 591 nm (the 5D0 ? 7F1 magnetic dipole transition of Eu3+) upon UV excitation into the charge transfer band (CTB) at ˜239 nm, with CIE chromaticity coordinates of x = 0.620 and y = 0.380 (orange-red). The quenching concentration of Eu3+ was estimated at ˜5 at.%?(y = 0.05), and the quenching was attributed to exchange interactions. Partial replacement of Gd3+ with Lu3+ up to 50 at.%?(x = 0.5) while keeping Eu3+ at the optimal content of 5 at.% does not significantly alter the peak positions of the CTB and 5D0 ? 7F1 emission bands but slightly weakens both bands owing to the higher electronegativity of Lu3+. The effects of processing temperature (1000-1500 °C) and Lu/Eu contents on the intensity, quantum efficiency, lifetime and asymmetry factor of luminescence were thoroughly investigated. The [(Gd0.7Lu0.3)0.95Eu0.05]3Al5O12 phosphor processed at 1500 °C exhibits a high internal quantum efficiency of ˜83.2% under 239 nm excitation, which, in combination with the high theoretical density, favors its use as a new type of photoluminescent and scintillation material.

Li, Jinkai; Li, Ji-Guang; Zhang, Zhongjie; Wu, Xiaoli; Liu, Shaohong; Li, Xiaodong; Sun, Xudong; Sakka, Yoshio

2012-06-01

101

Growth of high quality Cr, Yb codoped gadolinium gallium garnet (Gd3Ga5O12) crystal and its spectral properties  

NASA Astrophysics Data System (ADS)

The Cr(0.1%),Yb(10%):GGG crystals have been grown by the Czochralski method. The chemical composition is: Yb0.33Gd2.47Cr0.005Ga5.2O12. There are no observed Yb3+ ions substituting Ga3+ ions, just like that of Yb:GGG crystals. The defects in Cr,Yb:GGG crystal were also investigated. The absorption and emission spectra of Cr,Yb:GGG crystal at room temperature have been measured. The O2 and H2 annealing effect of Cr,Yb:GGG crystal have been compared. Cr3+ can greatly weak the visible luminescence of this crystal. The Cr Yb-codoped crystals may be potential materials for compact, efficient, high stability LD pumped solid state lasers.

Jiang, Benxue; Zhao, Zhiwei; Xu, Xiaodong; Song, Pingxin; Wang, Xiaodan; Xu, Jun; Deng, Peizhen

2007-05-01

102

Ce-doped single crystal and ceramic garnets for ?y ray detection  

SciTech Connect

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.

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

2007-07-30

103

Erbium-doped yttrium aluminum garnet as a magnetic refrigerant for low temperature x-ray detectors  

NASA Astrophysics Data System (ADS)

Garnets doped with rare-earth elements can be used in adiabatic demagnetization refrigerators. We have measured the specific heat and magnetization of a single crystal yttrium aluminum garnet (YAG) doped with 30% Er3+ ion at temperatures between 93 mK and 8 K under magnetic fields up to 8.0 T along the <111> crystal axis. From the specific heat and magnetization, we derived consistent temperature and magnetic-field dependence of the magnetic entropy. Under zero magnetic field, the magnetic entropy begins to decrease below 2 K and becomes half of R ln 2 at ~160 mK. This decrease is considered to be due to an antiferromagnetic short-range ordering among Er3+ ions. This behavior of the specific heat in the measured temperature range can be explained by a model in which both the crystalline-electric-field ground state and the first excited state are included. The operating temperature of the Er3+-doped YAG as a magnetic coolant is estimated to extend down to ~100 mK, which is lower than those with nonsubstituted garnets such as gallium-gadolinium-garnet used in the range ~4.2-15 K. With a doping level of 30%, we estimate that ~6 kg of Er3+-doped YAG exhibits the same cooling performance at 60 mK as the 916 g of ferric-ammonium-alum salt used for the x-ray spectrometer (microcalorimeter detectors) on the Astro-E satellite.

Kushino, Akihiro; Aoki, Yuji; Yamasaki, Noriko Y.; Namiki, Takahiro; Ishisaki, Yoshitaka; Matsuda, Tatsuma D.; Ohashi, Takaya; Mitsuda, Kazuhisa; Yazawa, Takashi

2001-12-01

104

Transparent garnet ceramic scintillators for gamma-ray detection  

NASA Astrophysics Data System (ADS)

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 ?- 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 ?-ray detection applications.

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

2012-10-01

105

Magnetic garnet film epitaxy on nonsingular faces (abstract)  

SciTech Connect

The single crystal films of magnetic garnets are widely used in various microelectronics devices. The yttrium{endash}iron and bismuth{endash}gallium-substituted magnetic garnet films were grown by liquid phase epitaxy from supercooled solutions on the basis PbO+B{sub 2}O{sub 3}. As substrates for films the gadolinium{endash}gallium garnet wafers crystallographically oriented in the range from (111)- to (110)-directions are used. In experiments such growth process parameters as supercooling temperature and angular velocity of substrate rotation were varied too. The parameters to be examined were thickness, growth rate, crystallografic, magnetic, and magnetooptical characteristics of the as-grown films. To analyze the growth process kinetics it was developed the model, including the terms (supersaturation {ital C}{sub {ital L}}{minus}{ital C}{sub {ital E}}) of the first and second orders for description of surface crystallization reaction. The following expression was derived for epitaxial growth rate: {ital f}={ital D}/{rho}{delta}[({ital C}{sub {ital L}}{minus}{ital C}{sub {ital E}})+{ital k}{sub 1}{delta}+{ital D}/2{ital k}{sub 2}{delta}{minus}{radical} ({ital k}{sub 1}{delta}+{ital D}){sup 2}+4{ital k}{sub 2}{delta}{ital D}({ital C}{sub {ital L}}{minus}{ital C}{sub {ital E}})/2{ital k}{sub 2}{delta}], where {ital D} is diffusion coefficient, {delta} is diffusion boundary layer thickness on the solid{endash}liquid interface, {rho} is film density, {ital C}{sub {ital L}} is concentration of garnet phase in the melted solution, {ital C}{sub {ital E}} is equilibrium concentration, {ital k}{sub {ital m}} is surface reaction constant (kinetic coefficient) of order {ital m} in {ital D}{partial_derivative}{ital C}/{partial_derivative}{ital x}(0,{ital t})={ital k}{sub {ital m}}[{ital C}(0,{ital t}){minus}{ital C}{sub {ital E}}]{sup {ital m}}. (Abstract Truncated)

Gorelik, S.S.; Letyuk, L.M.; Morchenko, A.T. [Moscow State Institute of Steel and Alloys, Leninsky Prospect 4, Moscow, 117936 (Russia)

1996-04-01

106

Effects of processing on the low-voltage performance of cathodoluminescent garnet phosphors  

SciTech Connect

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.

Phillips, M.L.F.; Shea, L.E.

1995-08-01

107

Magneto-optical study of holmium iron garnet Ho3Fe5O12  

NASA Astrophysics Data System (ADS)

Bulk holmium iron garnet Ho3Fe5O12 is a cubic ferrimagnet with Curie temperature TC = 567 K and magnetization compensation point in the range 130-140 K. The magneto-optical data are presented for a holmium iron garnet Ho3Fe5O12 film, ~10 ?m thick, epitaxially grown on a (111)-type gadolinium-gallium garnet Gd3Ga5O12 substrate. A specific feature of this structure is that the parameters of the bulk material, from which the film was grown, closely match the substrate ones. The temperature and field dependences of Faraday rotation as well as the temperature dependence of the domain structure in zero field were investigated. The compensation point of the structure was found to be Tcomp = 127 K. It was shown that the temperature dependence of the characteristic size of domain structure diverges at this point. Based on the obtained results we established that the magnetic anisotropy of the material is determined by both uniaxial and cubic contributions, each characterized by different temperature dependence. A complex shape of hysteresis loops and sharp changes of the domain pattern with temperature indicate the presence of collinear-noncollinear phase transitions. Study of the optical second harmonic generation was carried out using 100 fs laser pulses with central photon energy E = 1.55 eV. The electric dipole contribution (both crystallographic and magnetic) to the second harmonic generation was observed with high reliability despite a small mismatch of the film and substrate parameters.

Kalashnikova, A. M.; Pavlov, V. V.; Kimel, A. V.; Kirilyuk, A.; Rasing, Th.; Pisarev, R. V.

2012-09-01

108

Fabrication and characterization of Bismuth-Cerium composite iron garnet epitaxial films for magneto optical applications  

SciTech Connect

The Bi{sub x}Ce{sub 3-x}Fe{sub 5}O{sub 12} (x = 0.8) epitaxial films of high quality were grown by means of pulsed laser deposition on paramagnetic substrates of Gadolinium Gallium Garnet. We study the modifications of substitutions in the parent garnet Y{sub 3}Fe{sub 5}O{sub 12} that produces a higher magneto-optical response at communication wavelengths. These films displayed a strong in plane textures which are treated in argon as well as reduced atmosphere conditions. The elemental constituents of these films were confirmed by energy dispersive-X ray analysis, elastic recoil detection system, Rutherford backscattering spectroscopy, and X-ray photoelectron spectroscopy measurements. The transmittance spectra were measured and found these films exhibit good transmittance values. The transmittance-spectra were fitted with the theoretical model and the optical constants such as refractive index and absorption edge were evaluated. The highest (negative) Faraday rotation was found for these films treated in the environment of Ar + H{sub 2}. A density matrix theory has been developed for the Faraday rotation and a good agreement between the theory and experiment is found. These epitaxial garnet films can be used in a wide range of frequencies from visible to infrared spectra making them ideal for many magneto optical applications. Therefore, these films may overcome many issues in fabricating all optical isolators which is the viable solution for integrated photonics.

Chandra Sekhar, M.; Singh, Mahi R. [Department of Physics and Astronomy, 1151, Richmond Street, Western University, London, Ontario N6A 3K7 (Canada)

2012-10-15

109

Fabrication and characterization of Bismuth-Cerium composite iron garnet epitaxial films for magneto optical applications  

NASA Astrophysics Data System (ADS)

The BixCe3-xFe5O12 (x = 0.8) epitaxial films of high quality were grown by means of pulsed laser deposition on paramagnetic substrates of Gadolinium Gallium Garnet. We study the modifications of substitutions in the parent garnet Y3Fe5O12 that produces a higher magneto-optical response at communication wavelengths. These films displayed a strong in plane textures which are treated in argon as well as reduced atmosphere conditions. The elemental constituents of these films were confirmed by energy dispersive-X ray analysis, elastic recoil detection system, Rutherford backscattering spectroscopy, and X-ray photoelectron spectroscopy measurements. The transmittance spectra were measured and found these films exhibit good transmittance values. The transmittance-spectra were fitted with the theoretical model and the optical constants such as refractive index and absorption edge were evaluated. The highest (negative) Faraday rotation was found for these films treated in the environment of Ar + H2. A density matrix theory has been developed for the Faraday rotation and a good agreement between the theory and experiment is found. These epitaxial garnet films can be used in a wide range of frequencies from visible to infrared spectra making them ideal for many magneto optical applications. Therefore, these films may overcome many issues in fabricating all optical isolators which is the viable solution for integrated photonics.

Chandra Sekhar, M.; Singh, Mahi R.

2012-10-01

110

Growth of High-Quality Yttrium Iron Garnet Thin Films on Metallic Electrodes  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) is a magnetic garnet and shows extremely low loss at microwave frequencies. One typically grows YIG on single-crystal gadolinium gallium garnet (GGG) substrates. For some monolithic on-chip device applications, however, one needs to grow YIG films on metallic electrodes. This is challenging due to problems with the oxidation, diffusion, and breakup of metallic electrodes during the deposition of YIG films at high temperatures. This presentation reports on the development of new sandwich-type bottom electrodes and the growth of low-loss YIG thin films on such electrodes. The new electrodes consist of a thick metallic layer sandwiched between two thin cladding layers. The thick layer is a high-conductivity metal. The thin cladding layers are materials with high oxidation resistance and good thermal stability. The electrodes were deposited at room temperature by magnetron sputtering, while the YIG films were deposited at 650 C by pulsed laser deposition. Scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy measurements confirmed the structure of the YIG films Static magnetic measurements indicated a saturation induction of about 1471 G, which was 16% smaller than that for a YIG bulk. Ferromagnetic resonance measurements yielded a peak-to-peak linewidth of about 0.8 Oe at 9.45 GHz.

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

2011-10-01

111

Ferrimagnetism in the rare-earth iron garnets: a Monte Carlo study.  

PubMed

We investigate classical vector spin models of the rare-earth iron garnet ferrimagnets yttrium iron garnet (YIG) and gadolinium iron garnet (GdIG) using Monte Carlo simulations. Critical temperatures agree well with experiment. A compensation point is observed in GdIG, again in good agreement with experiment. PMID:21817454

Oitmaa, J; Falk, Thomas

2009-02-25

112

Growth and characterization of Bi, Pr- and Bi, Sc-substituted lutetium iron garnet films with planar magnetization for magneto-optic visualization  

NASA Astrophysics Data System (ADS)

The series of epitaxial garnet films of general composition Lu3-x-yBixPryFe5- zAlzO12 and Lu3-xBixFe5-y- zScyAlzO12 were grown on (111) oriented GGG (gadolinium gallium garnet) substrates by the liquid phase epitaxy. Their magnetic and magneto-optical properties were studied using both experimental techniques and modelling. All obtained films demonstrated generally a magnetic anisotropy close to the easy-plane type. The Pr-containing films exhibited large negative uniaxial anisotropy and significant cubic anisotropy. The latter causes a distortion of magnetization curves in samples magnetized in a direction normal to the film plane, especially at low temperatures. The large negative uniaxial anisotropy of Pr-substituted iron garnets allows us to increase the saturation field up to 0.5 T at liquid nitrogen temperature. The Sc-doped films displayed small positive uniaxial anisotropy that did not exceed the shape anisotropy. The magnetization curves of these films did not show any distortion due to the cubic anisotropy. The suitability of Pr- and Sc-doped garnets that meet the requirements for indicator layers for magneto-optic visualization at liquid nitrogen temperature is discussed.

Syvorotka, Igor M.; Ubizskii, Sergii B.; Kucera, Miroslav; Kuhn, Marcus; Vértesy, Zofia

2001-04-01

113

FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS): An Artificially Garnet Crystal Materials Using In Terahertz Waveguide  

NASA Astrophysics Data System (ADS)

A hypothesis is brought forward that the materials with low propagation loss in both optical and microwave band may exhibit good performance in terahertz (THz) band because THz wave band interspaces those two wave bands. For the purpose of exploring a kind of low-loss material for THz waveguide, Lu2.1Bi0.9Fe5O12 (LuBilG) garnet films are prepared by liquid phase epitaxy (LPE) method on a gadolinium gallium garnet (GGG) substrate from lead-free flux because of the good properties in both optical and microwave bands. In microwave band, the ferromagnetic resonance (FMR) linewidth of the film 2?H = 2.8-5.1 Oe; in optical band, the optical absorption coefficient is 600 cm-1 at visible range and about 100-170 cm-1 when the wavelength is longer than 800nm. In THz range, our hypothesis is well confirmed by a THz-TDS measurement which shows that the absorbance of the him for THz wave is 0.05-0.3 cm-1 and the minimum value appears at 2.3 THz. This artificial ferromagnetic material holds a great promise for magnetic held tunable THz devices such as waveguide, modulator or switch.

Yang, Qing-Hui; Zhang, Huai-Wu; Liu, Ying-Li; Wen, Qi-Ye; Zha, Jie

2008-11-01

114

Induced Magneto-transport Effects in Non-magnetic Metals on Yttrium Iron Garnet  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) was called ``spin Seebeck insulator,'' for it supports heat-generated pure spin currents. Pt thin film, with strong spin-orbit interaction, is used as a spin current generator or detector based on the spin Hall effect or the inverse spin Hall effect. The combination of these two materials plays a very important role in spintronics. A recent magnetotransport study shows strong evidence of a magnetic proximity effect in thin Pt films deposited on YIG. Here, we present a magneto-transport study of several non-magnetic (NM) metal films (e.g. Pt, Pd) on YIG films grown on gadolinium gallium garnet substrates with laser molecular beam epitaxy. The anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) reveal clear ferromagnetic characteristics in NM films. The magnitude of the AHE angle ? in Pd/YIG structure increases with decreasing temperature, while ? in Pt/YIG structure has a sign reversal at an intermediate temperature. Both AMR and AHE have been investigated as the NM film thickness is varied and an optimal effective thickness is identified. The effect of annealing has also been studied and the results are consistent with the observed thickness dependence. In thin NM films, a ln(T) temperature dependence with a resistivity minimum is observed at low temperatures, suggesting that the Kondo effect may be relevant. Detailed discussions about the origin of these effects will be presented.

Lin, Tao; Tang, Chi; Shi, Jing

2013-03-01

115

Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering  

NASA Astrophysics Data System (ADS)

Thin films of Yttrium Iron Garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system. Thin films are crystallised by heat-treatment to obtain magneto-optical properties. On quartz substrate, the network of cracks observed on the annealed samples can be explained by the difference between the thermal expansion coefficient of substrate and YIG. The Faraday rotation of thin films is measured with a classical ellipsometric system based in transmission which allows us to obtained an accuracy of 0.01°. We studied the variation of Faraday rotation versus the applied magnetic field. The variation of the Faraday rotation is the same that this obtained by VSM (vibrating sample magnetometer) analysis. With a quartz substrate, maximum Faraday rotation is observed to be 1900°/cm at the wavelength of 594 nm for an annealing of 740°C. The variation of the Faraday rotation versus the wavelength is studied. The obtained values are comparable to those of the literature for the bulk material. In order to eliminate the stress due to the heat-treatment, we made some films on Gadolinium Gallium Garnet (GGG) which thermal expansion coefficient is near than the YIG one. The material crystallises with no cracks and the Faraday effect is equivalent.

Boudiar, Toufik; Payet-Gervy, Beatrice; Blanc-Mignon, Marie-Francoise; Rousseau, Jean-Jacques; Le Berre, Martine; Joisten, H.; Canut, Bruno

2004-02-01

116

Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering  

NASA Astrophysics Data System (ADS)

Thin films of yttrium iron garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system. Thin films are crystallised by heat-treatment to obtain magneto-optical properties. On quartz substrate, the network of cracks observed on the annealed samples can be explained by the difference between the thermal expansion coefficient of substrate and YIG. Physico-chemical analysis shown that the obtained material has a correct stoichiometry and is crystallised as FCC. The Faraday rotation of thin films is measured with a classical ellipsometric system based on transmission which allows us to obtained an accuracy of 0.01°. The variation of Faraday rotation is studied on the one hand versus radio frequency power applied to the cathode during the deposition and on the other hand versus the applied magnetic field. The results are compared with those obtained by vibrating sample magnetometer analysis in perpendicular configuration. A maximum Faraday rotation is observed to be 1900°/cm at the wavelength of 594 nm for a YIG thin film formed on quartz substrate and annealed at 740°C. The values of the Faraday rotation coefficients obtained in the study versus the wavelength are comparable to those of the literature for the bulk material. In order to eliminate the stress due to the heat-treatment, we made some films on single crystals of gadolinium gallium garnet (1 1 1) substrates for which thermal expansion coefficient is near than the YIG one. The material crystallises with no crackles and the Faraday effect is equivalent.

Boudiar, T.; Payet-Gervy, B.; Blanc-Mignon, M.-F.; Rousseau, J.-J.; Le Berre, M.; Joisten, H.

2004-12-01

117

Interlayer perpendicular domain coupling between thin Fe films and garnet single-crystal underlayers  

NASA Astrophysics Data System (ADS)

The magnetic behavior and domain structure of Fe films grown on yttrium-iron-garnet (YIG) underlayers were studied to elucidate their interlayer coupling, as a function of the Fe layer thickness, using magnetic force microscopy (MFM) and magneto-optic Kerr effect (MOKE). The YIG layer, grown by liquid phase epitaxy on single crystal gadolinium-gallium-garnet (GGG) substrates, showed a characteristic stripe domain structure in MFM images. Fe layers with thickness values of (5, 10, and 20 nm) were separately deposited on the YIG layer using ion beam sputtering system at room temperature. MOKE measurements of Fe/YIG/GGG with different Fe thickness showed that Fe films preferred to be magnetized perpendicular to the surface when the thickness was less than 20 nm. Stripe domain structure was observed for Fe thickness of 5 and 10 nm, but not for 20 nm film. Micromagnetic simulations of these Fe/YIG bilayers show that the volume exchange stiffness term at the interface plays a dominant role, when compared with the bilinear and biquadratic coupling contributions, in determining the interlayer coupling.

Chun, Y. S.; Krishnan, Kannan M.

2004-06-01

118

Sublattice Magnetizations in Rare-Earth Iron Garnets  

Microsoft Academic Search

The individual iron sublattice magnetizations in yttrium iron garnet and gadolinium iron garnet have been measured by NMR techniques as a function of temperature. The observed resonance frequencies are slightly higher for GdIG in both cases, the differences at low temperatures being about 0.67% for the octahedral sites and 0.70% for the tetrahedral sites. These differences are tentatively interpreted as

E. L. Boyd; V. L. Moruzzi; J. S. Smart

1963-01-01

119

Electrically and magnetically tunable phase shifters based on a barium strontium titanate-yttrium iron garnet layered structure  

NASA Astrophysics Data System (ADS)

We report on the tuning of permittivity and permeability of a ferroelectric/ferromagnetic bilayer structure which can be used as a microwave phase shifter with two degrees of tuning freedom. The structure was prepared by the growth of a yttrium iron garnet (YIG) layer on a gadolinium gallium garnet substrate by liquid phase epitaxy, the growth of a barium strontium titanate (BST) layer on the YIG layer through pulsed laser deposition, and then the fabrication of a coplanar waveguide on the top of BST through e-beam evaporation and trilayer liftoff techniques. The phase shifters exhibit a differential phase shift of 38°/cm at 6 GHz through permittivity tuning under an applied electric field of ~75 kV/cm and a static magnetic field of 1700 Oe. By tuning the permeability through the applied magnetic field we increase the differential phase shift to 52°/cm and simultaneously obtain a better match to the zero applied electric field condition, resulting in an improvement in the return loss from 22.4 to 24.9 dB. Additionally, we demonstrate the use of a lead magnesium niobate-lead titanate (PMN-PT) layer to tune the permeability of the YIG layer. This tuning relies on the piezoelectric and magnetostrictive effects of PMN-PT and YIG, respectively. Tuning of the ferromagnetic response through strain and magnetostriction as opposed to applied magnetic field can potentially pave the way for low power consumption, continuously and rapidly tunable, impedance matched phase shifters.

Leach, J. H.; Liu, H.; Avrutin, V.; Rowe, E.; Özgür, Ü.; Morkoç, H.; Song, Y.-Y.; Wu, M.

2010-09-01

120

Research in garnet crystal (GSGG) development. Final report, 1 May 1984-31 December 1984  

SciTech Connect

This program describes the crystal growth of neodymium and chromium doped simultaneously into the host crystal of gadolinium scandium gallium garnet (Nd/sup 3 +/, Cr/sup 3/+:Gd/sub 3/(Sc,Ga)/sub 2/ Ga/sub 3/O/sub 12/ or Nd,Cr:GSGG). Ten experimental boules were grown by the Czochralski method at a diameter of 1.0-1.2 inch. Special attention was given to congruently melting compositions, the Nd and Cr content, growth rate, atmosphere of growth, control of the solid liquid interface, and boule orientation. For each of our crystals a (0.25 x 3.00) inch cylindrical laser rod was extracted, fabricated, tested passively, and delivered to the Lawrence Livermore National Laboratory for active testing. At the same time, boule samples were examined for optical absorption, loss at 1.06..mu..m, refractive index birefringence, and other physical properties. Results have demonstrated that optical quality can approach that of Nd:YAG in rod form. The increased efficiency of Nd,Cr:GSGG was confirmed to be about 2 times that of Nd:YAG. We also show that 2 inch diameter crystal boules can be grown successfully. It appears that larger boules are feasible for slab laser experiments.

Belt, R.F.; Uhrin, R.; Vemuri, K.

1985-01-01

121

Effect of mechanical milling on the magnetic properties of garnets  

NASA Astrophysics Data System (ADS)

Rare earth garnets after milling to nanosizes are found to decompose into rare earth orthoferrite and other rare earth and iron oxide phases. The magnetization for the yttrium iron garnet decreases in the nano state due to the formation of antiferromagnetic phases. But for the gadolinium iron garnet when milled up to 25 h, the room temperature magnetization increases despite the formation of antiferromagnetic and non-magnetic phases. This is attributed to the uncompensated moments of the sublattices because of the weakening of the superexchange interaction due to change in bond angles and the breaking of some superexchange bonds on account of the defects and oxygen vacancies introduced on milling. For the 10 h milled gadolinium iron garnet at 5 K, after correcting for the non-magnetic phases present, there is an increase in the magnetic moment of about 10% as compared to the value for the as-prepared garnet. The magnetic hyperfine fields corresponding to the various phases were measured using 57Fe Mössbauer spectroscopy at 16 K. The isomer shift values indicate the loss of oxygen for the samples milled for larger duration.

Joseyphus, R. J.; Narayanasamy, A.; Nigam, A. K.; Krishnan, R.

2006-01-01

122

Mechanochemical decomposition of Gd 3Fe 5O 12 garnet phase  

Microsoft Academic Search

Gadolinium iron garnet was milled in a high energy ball mill to study its magnetic properties in the nanocrystalline regime. XRD reveals the decomposition of the garnet phase into Gd-orthoferrite and Gd2O3 on milling. The variation of saturation magnetization and coercivity with milling is attributed to a possible shift in the compensation temperature on grain size reduction and an increase

R. Justin Joseyphus; A. Narayanasamy; N. Sivakumar; M. Guyot; R. Krishnan; N. Ponpandian; K. Chattopadhyay

2004-01-01

123

Continuous wave 1.6 mum laser action in Er doped garnets at room temperature  

Microsoft Academic Search

We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 mum. The laser operates from the metastable4 I 13\\/2 manifold into an upper Stark level of the4 I 15\\/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength

H. Stange; K. Petermann; G. Huber; E. W. Duczynski

1989-01-01

124

Molecular Structure of Garnet  

NSDL National Science Digital Library

Garnet has been used in gemstones for many thousands of years. The Koran states that the fourth heaven is composed of carbuncle, which is another name given to the beautiful gem. Garnet is a very abundant gem and can easily be found in many places around the world. Application: Garnet is a silicate mineral and is the birthstone of January. It is also used for many abrasive purposes, and is the symbolic gemstone for the 18th wedding anniversary.

2002-09-06

125

Garnets as hydrochronometers  

SciTech Connect

This study examines oxygen isotope zoning in garnets from a Barrovian metamorphic terrane in eastern Vermont. Previous Sr isotopic and structural studies of these garnets have shown that they grew over an approximately 10 myr interval during thrusting and nappe emplacement. These studies show that the garnets are strongly zoned in delta O-18. This zoning is the result of equilibration of garnet with water derived from dehydration of subjacent pelites during nappe stage deformation. The magnitude of delta O-18 zoning depends upon the garnet's location in the outcrop studied. The garnets come from an isotopically light delta O-18 felsic schist that is adjacent a relatively heavy delta O-18 schist. Garnets from the felsic schists within 10 meters of the contact with the isotopically heavier schists have nearly homogeneous dealt O-18 values around 9.5[per thousand]. Garnet in the felsic schists 85 meters from the contact are more strongly zoned, with delta O-18 ranging from a low of ca 6.0[per thousand] in the cores to a high of ca 9.0[per thousand] at the rims. These zoning patterns were produced by continuous infiltration of relatively heavy delta O-18 waters, derived from the subjacent schists into the felsic schists during garnet grade metamorphism. It is possible to determine the time integrated fluid fluxes by comparison of observed zoning profiles in garnet with those calculated from the equation describing combined advective-diffusive of a tracer. Using this method, the authors calculate time integrated fluid fluxes of 1.5 [times] 10[sup 4] cm[sup 3]/cm[sup 2]. Fluxes of this magnitude could have been produced by dewatering of 1.5 km of schist during garnet grade metamorphism.

Chamberlain, C.P. (Dartmouth Univ., Hanover, NH (United States). Dept. of Earth Sciences); Conrad, M.E. (Lawrence Berkeley Lab., Berkeley, CA (United States))

1992-01-01

126

Gallium complexes and solvent extraction of gallium  

SciTech Connect

This patent describes a process for recovering gallium from aqueous solutions containing gallium which comprises contacting such a solution with an organic solvent containing at least 2% by weight of a water-insoluble N-organo hydroxamic acid having at least about 8 carbon atoms to extract gallium, and separating the gallium loaded organic solvent phase from the aqueous phase.

Coleman, J.P.; Graham, C.R.; Monzyk, B.F.

1988-05-03

127

Mechanochemical decomposition of Gd3Fe5O12 garnet phase  

NASA Astrophysics Data System (ADS)

Gadolinium iron garnet was milled in a high energy ball mill to study its magnetic properties in the nanocrystalline regime. XRD reveals the decomposition of the garnet phase into Gd-orthoferrite and Gd2O3 on milling. The variation of saturation magnetization and coercivity with milling is attributed to a possible shift in the compensation temperature on grain size reduction and an increase in the orthoferrite content. The Mössbauer spectrum at 16K is characteristic of the magnetically ordered state corresponding to GdIG, GdFeO3 and ?-Fe2O3 whereas at room temperature it is a superparamagnetic doublet.

Justin Joseyphus, R.; Narayanasamy, A.; Sivakumar, N.; Guyot, M.; Krishnan, R.; Ponpandian, N.; Chattopadhyay, K.

2004-05-01

128

Continuous wave 1.6 ?m laser action in Er doped garnets at room temperature?  

Microsoft Academic Search

We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 µm. The laser operates from the metastable4I13\\/2 manifold into an upper Stark level of the4I15\\/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields

H. Stange; K. Petermann; G. Huber; E. W. Duczynski

1989-01-01

129

Observation of period doubling and chaos in spin-wave instabilities in yttrium iron garnet  

Microsoft Academic Search

Ferromagnetic resonance in a polished 0.047-cm-radius sphere of gallium-doped yttrium iron garnet is studied at 1.3 GHz in a magnetic field of 460 G. A second-order Suhl instability is observed, owing to the nonlinear coupling of the precessing uniform magnetization with spin waves. This is detected by the onset of auto-oscillations of the magnetization. One of these modes with frequency

George Gibson; Carson Jeffries

1984-01-01

130

Uncompensated Garnet - A Magnetic Semiconductor.  

National Technical Information Service (NTIS)

Ca-substituted YIG single crystal films (Ca:YIG) show p-type conduction while Si or Ge doped YIG garnets (Si:YIG or Ge:YIG) have n-type conduction. Both garnet films maintain their superior magnetic properties of pure YIG, while their electrical resistanc...

P. E. Wigen

1998-01-01

131

Gadolinium-153 line sources  

PubMed

The technology for Gd-153 line source production has been developed at SSC RIAR. The source active core is made of Al-Gd2O3 composition by means of one of the following ways: either collecting pressed pellets or filling the source body with the composition followed by sintering. The composition is prepared by gadolinium salt thermal destruction on aluminium particles. The method allows setting gadolinium mass fraction (from 0.02 to 6%) with high accuracy and uniformity of distribution in the composition volume of more than 95%. PMID:11003528

Lebedev; Gordeev; Karelin; Gavrilov

2000-10-01

132

Investigations in gallium removal  

SciTech Connect

Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

Philip, C.V.; Pitt, W.W. [Texas A and M Univ., College Station, TX (United States); Beard, C.A. [Amarillo National Resource Center for Plutonium, TX (United States)

1997-11-01

133

Epitaxial Garnets and Hexagonal Ferrites.  

National Technical Information Service (NTIS)

The objective of this research is to develop new and improved epitaxial ferrite materials for use in microwave and millimeter-wave signal processing devices. The major emphasis has been on multiple layer magnetic garnet structures for magnetostatic wave (...

H. L. Glass L. R. Adkins

1982-01-01

134

Pb valence in iron garnets  

Microsoft Academic Search

A model for the incorporation of Pb in garnets is presented in which self-compensation occurs via the formation of Pb2+ and Pb4+ and allows an explanation of the following observations: high levels of Pb substitution achievable, the temperature dependence of Pb incorporation, lattice mismatch behavior of epitaxial films of Pb-doped iron garnets, the Pb-induced uniaxial anisotropy behavior in EuIG :

G. B. Scott; J. L. Page

1977-01-01

135

Magnetic and Crystallographic Properties of Substituted Yttrium-Iron Garnet, 3Y2O3.xM2O3.(5- x)Fe2O3  

Microsoft Academic Search

A solid solution of yttrium-iron garnet with yttrium-gallium or yttrium-aluminum garnet is formed over the entire range of composition; the lattice constant variation is nearly linear. The trivalent ions, Sc3+, In3+, and Cr3+, may be substituted for Fe3+ to a limited extent. Substitution proceeds on a steric basis for nonmagnetic ions: those smaller than Fe3+, namely Al3+ and Ga3+, preferentially

M. A. Gilleo; S. Geller

1958-01-01

136

Effect of alloying by gadolinium on the magnetic properties of irradiation-amorphized oxides of the Y3 - x Gd x Fe5O12 system  

NASA Astrophysics Data System (ADS)

Magnetometry and X-ray diffraction have been used to study the structural state and magnetic properties of the system of oxides with an iron garnet structure, Y3 - x Gd x Fe5O12 ( x = 0, 0.75, 1.5), in the course of amorphization via irradiation by fast neutrons. It has been established that the partial replacement of diamagnetic yttrium ions by paramagnetic gadolinium dramatically changes the behavior of the magnetic moment of the garnets during their gradual amorphization. The magnetic moment of the yttrium iron garnet decreases significantly with increasing fluence, whereas the magnetic moments of gadolinium-alloyed garnets, on the contrary, increase noticeably along with the simultaneous increase in the compensation temperatures of the sublattice magnetizations. The observed differences in the radiation behavior of the garnets are explained by the different behavior of the iron and gadolinium sublattices under irradiation. It is shown that the irradiation to a fluence of 3 × 1020 cm-2 leads to a complete amorphization of all samples investigated. It has been established that the amorphous samples were in a spin-glass state.

Chukalki, Yu. G.

2012-04-01

137

Radiation effects in ferrate garnet  

NASA Astrophysics Data System (ADS)

Radiation effects in four synthetic ferrate garnets (A3B2(XO4)3, Ia3d, Z = 8) were examined by ion beam irradiations with in situ observation (T = 298 873 K) using transmission electron microscopy (TEM) at the IVEM Tandem Facility at Argonne National Laboratory. The garnet compositions include: A = Ca, Gd, Th, and Ce; B = Zr, Fe. The critical amorphization temperatures (Tc), the temperature above which the target material cannot be amorphized due to dynamic annealing, were between 820 and 870 K. The amorphization doses at room temperature are between 0.17 and 0.19 dpa (displacement per atom), which is similar to that of silicate- and aluminate-garnets. The small variations in the amorphization dose and Tc of the different compositions suggest that radiation effects in ferrate garnets are structurally constrained. Qualitative analyses of the valence states of Ce and Fe in garnet before and after irradiation were completed using electron energy-loss spectroscopy (EELS). The Ce and Fe in the unirradiated garnet were dominantly trivalent and divalent, respectively. The characteristic peaks of Ce4+, at ˜5 eV higher energy for the M-edges, were present in unirradiated garnet as a minor peak, and the peaks did not disappear after complete amorphization, suggesting that the valence state did not change significantly. EELS analysis was conducted on a nearly pure andradite, Ca3Fe2Si3O12, which ideally contains only ferric iron. The andradite was amorphized at 0.18 dpa. EELS analysis revealed that some of ferric iron was converted to ferrous iron during the irradiation.

Utsunomiya, S.; Yudintsev, S.; Ewing, R. C.

2005-02-01

138

Rare earth elements in garnets and clinopyroxenes from garnet lherzolite nodules in kimberlites  

Microsoft Academic Search

Six pairs of coexisting garnets and clinopyroxenes were separated from the sheared and granular garnet lherzolite nodules in kimberlites and analyzed for rare earth elements (REE). The sheared and granular nodules can be distinguished in terms of REE pattern of both clinopyroxene and garnet. However, there are no significant differences in REE partitioning between clinopyroxene and garnet, indicating that the

N. Shimizu

1975-01-01

139

Efficient triwavelength laser with a Nd:YGG garnet crystal.  

PubMed

We demonstrate a laser-diode pumped efficient triwavelength laser at about 1.06microm with a Nd-doped yttrium gallium garnet crystal for the first time, to our knowledge. Continuous wave output power of 7.15W was achieved under an absorbed pump power of 14.1W, corresponding to the slope efficiency of 52.7%. With Cr:YAG as the saturable absorber, passive Q-switching performance was obtained. The shortest pulse width, largest pulse energy, and highest peak power were obtained at 3.1ns, 153.8microJ, and 46.6kW, respectively. The laser spectrum was found to be a triwavelength, with respective wavelengths of 1062.1, 1060.3, and 1058.9nm, and three laser transitions were assigned. PMID:20517421

Yu, Haohai; Wu, Kui; Yao, Bin; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Zhang, Xingyu; Jiang, Minhua

2010-06-01

140

Local order and magnetic behavior of amorphous and nanocrystalline yttrium iron garnet produced by swift heavy ion irradiations  

Microsoft Academic Search

Thin epitaxial films of gallium or scandium-doped and undoped yttrium iron garnet (Y3Fe5O12 or YIG) on nonmagnetic Gd3Ga5O12 substrates were irradiated with swift heavy ions (50 MeV 32S,50 MeV 63Cu, and 235 MeV 84Kr) in the electronic slowing down regime. The mean electronic stopping power in the films was always larger than the threshold for amorphous track formation in YIG

J. M. Costantini; J. M. Desvignes; A. Pe´rez; F. Studer

2000-01-01

141

Local order and magnetic behavior of amorphous and nanocrystalline yttrium iron garnet produced by swift heavy ion irradiations  

Microsoft Academic Search

Thin epitaxial films of gallium or scandium-doped and undoped yttrium iron garnet (Y3Fe5O12 or YIG) on nonmagnetic Gd3Ga5O12 substrates were irradiated with swift heavy ions (50 MeV 32S, 50 MeV 63Cu, and 235 MeV 84Kr) in the electronic slowing down regime. The mean electronic stopping power in the films was always larger than the threshold for amorphous track formation in

J. M. Costantini; J. M. Desvignes; A. Pérez; F. Studer

2000-01-01

142

A primer on gadolinium chemistry  

PubMed Central

Gadolinium is widely known by all practitioners of MRI but few appreciate the basic solution chemistry of this trivalent lanthanide ion. Given the recent linkage between gadolinium contrast agents and nephrogenic systemic fibrosis, some basic chemistry of this ion must be more widely understood. This short primer on gadolinium chemistry is intended to provide the reader the background principles necessary to understand the basics of chelation chemistry, water hydration numbers, and the differences between thermodynamic stability and kinetic stability or inertness. We illustrate the fundamental importance of kinetic dissociation rates in determining gadolinium toxicity in vivo by presenting new data for a novel europium DOTA-tetraamide complex that is relatively unstable thermodynamically yet extraordinarily inert kinetically and also quite non-toxic. This, plus other literature evidence forms the basis of the fundamental axiom that it is the kinetic stability of a gadolinium complex, not its thermodynamic stability, that determines its in vivo toxicity.

Sherry, A. Dean; Caravan, Peter; Lenkinski, Robert E.

2010-01-01

143

Properties of gallium arsenide  

SciTech Connect

Properties of Gallium Arsenide' is a handbook of evaluated numeric data and reviewed knowledge distilled by those working at the frontiers of gallium arsenide research. In addition to providing numeric data on basic physical, electronic and optical properties, the book covers many device-related aspects of gallium arsenide. Carrier attributes (ionisation coefficients, concentration, mobility, diffusion etc), deep levels and defects are surveyed and related to the various growth techniques such as MBE, VPE, and MOCVD. Sections on surface structure, oxidation, interfaces and etching are of particular relevance to integrated circuit research. Especially important in the race to achieve commercially usable samples is a state-of-the-art survey on the infra-red imaging of defects in semi-insulating gallium arsenide produced by the liquid-encapsulated Czochralski process.

Not Available

1985-01-01

144

Epitaxial garnets and hexagonal ferrites  

Microsoft Academic Search

Epitaxial ferrite materials were developed for use in microwave and millimeter wave signal processing devices. Multiple layer magnetic garnet structures for magnetostatic wave (MSW) delay lines were emphasized. Theoretical analysis and experiments were performed on propagation of magnetostatic surface waves (MSSW), magnetostatic forward volume waves (MSFVW) and magnetostatic backward volume waves in structures containing up to four layers. In the

H. L. Glass; L. R. Adkins

1982-01-01

145

Continuous wave 1.6 ?m laser action in Er doped garnets at room temperature?  

NASA Astrophysics Data System (ADS)

We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 ?m. The laser operates from the metastable4 I 13/2 manifold into an upper Stark level of the4 I 15/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields lowest thresholds around 30 mW and slope efficiencies up to 12.7% for Er:YAG. Laser operation in Er:YGG is achieved with higher thresholds of about 200 mW and smaller slope efficiencies of 0.9%. The effective emission cross section in YAG is estimated to be ?e?5×10-21 cm2.

Stange, H.; Petermann, K.; Huber, G.; Duczynski, E. W.

1989-09-01

146

Gallium Phosphide and the Gallium Arsenide-Gallium Phosphide System, Data Sheets.  

National Technical Information Service (NTIS)

These data sheets present a compilation of a wide range of electrical, optical and energy values for gallium phosphide and the gallium arsenidegallium phosphide system in bulk and film form. Electrical properties include lifetime and thermoelectric effect...

M. Neuberger

1965-01-01

147

Magneto-optical waveguides of aluminum garnet  

Microsoft Academic Search

Planar waveguides of high refractive index aluminum garnets containing magnetic rare-earth cations have been epitaxially grown on <111?-oriented crystal wafers of yttrium aluminum garnet (Y3Al5O12, YAG). Epitaxy was by the liquid phase solution growth technique from supercooled mixtures of lead oxide and boron oxide, as is common for the epitaxy of the magneto-optical iron garnets. The liquid phase epitaxy technique

D. M. Gualtieri

1993-01-01

148

Gallium Phosphide Photodiode Development.  

National Technical Information Service (NTIS)

The specific objectives of this program were to fabricate, test and deliver five single-element (detector size 0.01 x 0.01 inch) gallium phosphide (GaP) photovoltaic detectors with performance design goals (for each element) of eta > 30% and NEP < or = 2....

A. M. Chiang R. Rotolante

1977-01-01

149

Information on Gadolinium-Based Contrast Agents  

Center for Drug Evaluation (CDER)

... Information on Gadolinium-Based Contrast Agents. ... Regulatory History and Labeling from Drugs@FDA. Gadolinium-Based Contrast Agents: ... More results from www.fda.gov/drugs/drugsafety/postmarketdrugsafetyinformationforpatientsandproviders

150

Annealing behaviour and crystal structure of RF-sputtered Bi-substituted dysprosium iron-garnet films having excess co-sputtered Bi-oxide content  

NASA Astrophysics Data System (ADS)

We investigate the magneto-optic properties, crystal structure and annealing behaviour of nano-composite media with record-high magneto-optic quality exceeding the levels reported so far in sputtered iron-garnet films. Bi-substituted dysprosium-gallium iron-garnet films having excess bismuth oxide content are deposited using RF co-sputtering, and a range of garnet materials are crystallized using conventional oven-annealing processes. We report, for the first time ever, the results of optimization of thermal processing regimes for various high-performance magneto-optic iron-garnet compositions synthesized and describe the evolution of the optical and magneto-optical properties of garnet-Bi-oxide composite-material films occurring during the annealing processes. The crystallization temperature boundaries of the system (BiDy)3(FeGa)5O12 : Bi2O3 are presented. We also report the results of x-ray diffraction and energy-dispersive x-ray spectroscopy studies of this recently developed class of high-performance magneto-optic composites. Our hypothesis of iron oxides being the cause of excess optical absorption in sputtered Bi-iron-garnet films is confirmed experimentally.

Vasiliev, M.; Nur-E-Alam, M.; Alameh, K.; Premchander, P.; Lee, Y. T.; Kotov, V. A.; Lee, Y. P.

2011-02-01

151

Gallium-containing anticancer compounds  

PubMed Central

There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin’s lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks cross resistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed.

Chitambar, Christopher R

2013-01-01

152

Gallium interactions with Zircaloy  

SciTech Connect

This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

Woods, A.L. [ed.; West, M.K. [Texas A and M Univ., College Station, TX (United States). Dept. of Nuclear Engineering

1999-01-01

153

Oxidative dissolution of gallium arsenide and separation of gallium from arsenic  

SciTech Connect

The method of dissociating gallium arsenide into a gallium-containing component and an arsenic-containing component, is described which comprises contacting the gallium arsenide with an oxidizing agent and a liquid comprising hydroxamic acid to convert the gallium to a gallium-hydroxamic acid complex and to oxidize the arsenic to a positive valence state.

Coleman, J.P.; Monzyk, B.F.

1988-07-26

154

Hepatic photopenia in gallium imaging  

Microsoft Academic Search

Although Ga-67 has been used extensively in imaging many different conditions, much is yet unknown about the mechanisms by which gallium concentrates preferentially in tissues such as the liver. This paper reports three patients with markedly diminished hepatic uptake of gallium. The cases are examined in light of published data demonstrating such factors as transferrin levels, radiation, and chemotherapeutic agents

ANNE M. GLASER; DAVID C. P. CHEN; MICHAEL E. SIEGEL

1988-01-01

155

Gallium scintigraphy in Hansen's disease  

Microsoft Academic Search

Gallium 67 imaging was used in 12 patients with documented Hansen's disease undergoing treatment or not, in an attempt to determine the pattern of the disease. Diagnosis was confirmed by histopathology in all patients. The Mitsuda reaction was seen in all patients. Specific nuclear studies were performed when needed to evaluate particular organs better. Gallium 67 images show homogeneous, diffuse

Francisco José H. N. Braga; Elaine B. Araújo; Edwaldo E. Camargo; Leontina C. M. Tedesco-Marchesi; Maria Cecilia M. Rivitti; Hateme Bouladour; Pierre Galle

1991-01-01

156

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

SciTech Connect

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.

Lassri, H. [LPMMAT, Universite Hassan II-Ain Chock, Faculte des Sciences, B.P. 5366, Maarif, Casablanca (Morocco); Hlil, E.K., E-mail: hlil@grenoble.cnrs.fr [Institut Neel, CNRS et Universite Joseph Fourier, BP 166, F-38042, Grenoble cedex 9 (France); Prasad, S. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Krishnan, R. [Groupe d'etude de la Matiere Condensee, CNRS/Universite de Versailles-St-Quentin, 45, avenue des Etats-Unis, 78035 Versailles Cedex (France)

2011-12-15

157

Raman spectroscopy of garnet-group minerals  

USGS Publications Warehouse

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.

Mingsheng, P.; Mao, H. K.; Dien, L.; Chao, E. C. T.

1994-01-01

158

Fundamental Studies of the Metallurgical, Electrical, and Optical Properties of Gallium Phosphide and Gallium Phosphide Alloys.  

National Technical Information Service (NTIS)

Abstracts, bibliographic data, oral presentations, and published papers on (1) Diffusion of Sulfur in Gallium Phosphide and Gallium Arsenide, and (2) Properties of Gallium Phosphide Schottky Barrier Rectifiers for Use at High Temperature are presented.

1972-01-01

159

Tumor growth suppression by gadolinium-neutron capture therapy using gadolinium-entrapped liposome as gadolinium delivery agent.  

PubMed

Neutron capture therapy (NCT) is a promising non-invasive cancer therapy approach and some recent NCT research has focused on using compounds containing gadolinium as an alternative to currently used boron-10 considering several advantages that gadolinium offers compared to those of boron. In this study, we evaluated gadolinium-entrapped liposome compound as neutron capture therapy agent by in vivo experiment on colon-26 tumor-bearing mice. Gadolinium compound were injected intravenously via tail vein and allowed to accumulate into tumor site. Tumor samples were taken for quantitative analysis by ICP-MS at 2, 12, and 24 h after gadolinium compound injection. Highest gadolinium concentration was observed at about 2 h after gadolinium compound injection with an average of 40.3 ?g/g of wet tumor tissue. We performed neutron irradiation at JRR-4 reactor facility of Japan Atomic Energy Research Institute in Tokaimura with average neutron fluence of 2×10¹² n/cm². The experimental results showed that the tumor growth suppression of gadolinium-injected irradiated group was revealed until about four times higher compared to the control group, and no significant weight loss were observed after treatment suggesting low systemic toxicity of this compound. The gadolinium-entrapped liposome will become one of the candidates for Gd delivery system on NCT. PMID:23743325

Dewi, Novriana; Yanagie, Hironobu; Zhu, Haito; Demachi, Kazuyuki; Shinohara, Atsuko; Yokoyama, Kazuhito; Sekino, Masaki; Sakurai, Yuriko; Morishita, Yasuyuki; Iyomoto, Naoko; Nagasaki, Takeshi; Horiguchi, Yukichi; Nagasaki, Yukio; Nakajima, Jun; Ono, Minoru; Kakimi, Kazuhiro; Takahashi, Hiroyuki

2012-12-26

160

Infrared Isolator Using Yttrium Iron Garnet.  

National Technical Information Service (NTIS)

Infrared isolators using the Faraday rotation in a single crystal Yttrium Iron Garnet (YIG) and calcite dichroic polarizers have been built. By using the YIG crystal with thorium fluoride antireflection coating the authors obtained isolation better than 3...

H. Gamo S. S. Chuang

1970-01-01

161

Pyroxene-garnet transformation in coorara meteorite.  

PubMed

Majorite is a new garnet in a veinlet of the Coorara meteorite. Its chemical composition is compatible with derivation mostly from original pyroxene, not from olivine as originally reported. Silicon is partly in sixfold coordination. Ringwoodite, a spinel of olivine composition, occurs as purple grains set in a matrix of fine-grained garnet. The similar mineralogy and texture of the Coorara and Tenham meteorites suggest a common parent body. PMID:17768916

Smith, J V; Mason, B

1970-05-15

162

Electrospun Gallium Nitride Nanofibers  

SciTech Connect

The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH{sub 3} flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

Melendez, Anamaris; Morales, Kristle; Ramos, Idalia [University of Puerto Rico at Humacao, Humacao (Puerto Rico); Campo, Eva [Centre Nacional de Microelectronica, Barcelona (Spain); Santiago, Jorge J. [University of Pennsylvania, Philadelphia (United States)

2009-04-19

163

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

SciTech Connect

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.

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. [Physics Department, Amherst College, Amherst, Massachusetts 01002 (United States); Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2005-12-16

164

Nuclear magnetic resonance of 155Gd and 157Gd nuclei in gadolinium iron garnet  

Microsoft Academic Search

The magnetic resonance of 155Gd and 157Gd nuclei was detected in GdIG at liquid helium temperature by a spin echo method. The resonance frequencies (40.5 and 54Mc\\/sec) correspond to the effective field of 338 kOe. This value is consistent with the known hyperfine coupling constant of Gd3+ in different compounds. The observed splittings were ascribed to quadrupole interaction.

Le Dang Khoï

1969-01-01

165

Gallium Safety in the Laboratory  

SciTech Connect

A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

Cadwallader, L.C.

2003-05-07

166

Gallium Safety in the Laboratory  

SciTech Connect

A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

Lee C. Cadwallader

2003-06-01

167

A gallium arsenide power rectifier  

Microsoft Academic Search

In this paper we will describe the fabrication of a gallium arsenide rectifier with a 10 ampere forward current capability, and reverse breakdowns of 40-100 volts. These units are fabricated by a manganese diffusion into gallium arsenide having a prediffusion carrier concentration of about3 times 10^{16}\\/cm3. The diffusion techniques and evaluation will be described. Problems of conversion toward p-type will

L. D. Armstrong; P. Kuznetzoff

1960-01-01

168

Toxicity of Gadolinium to Some Aquatic Microbes  

Microsoft Academic Search

The toxicity of gadolinium to algae and bacteria was determined as part of an effort to develop a biological process to purify drums containing spent nuclear reactor heavy water moderator (D2O). This water was contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS) near

2001-01-01

169

Synthesis and Crystal Chemistry of Oxysulfides with the Garnet Structure.  

National Technical Information Service (NTIS)

In a search for new ternary materials with potential suitability for 10.6 micrometer window applications, the sulfur analogs of the garnet structure were investigated. Pure sulfur end-member garnets cannot be synthesized under ambient pressures. A series ...

R. R. Neurgaonkar W. B. White

1973-01-01

170

The Gallium Melting-Point Standard.  

National Technical Information Service (NTIS)

This Special Publication contains a series of papers published in Clinical Chemistry concerning the Bureau's temperature measurement system, the gallium melting-point as a thermometric fixed-point, how the gallium melting-point fits into the measurement s...

B. W. Mangum D. D. Thornton

1977-01-01

171

Gallium-67 localization in herpetic skin lesion.  

PubMed

Previous cases of gallium localization in various cutaneous lesions have been reported, including sporotrichosis, acne vulgaris, sarcoid, lymphoma, and exfoliative erythroderma. This is a report of a case of gallium localization in cutaneous lesions of herpes zoster. PMID:3180617

Acio, E R; Balasubramanian, N; Vieras, F; Smith, J J

1988-09-01

172

Effect of gallium on bone mineral properties  

Microsoft Academic Search

Summary  Gallium nitrate is biologically active in blocking bone rsorptionin vitro as well asin vivo. Administration of gallium nitrate to growing rats results in a dose-dependent accumulation of low levels of gallium in bone\\u000a that is associated with specific changes in the mineral properties of bone. To elucidate in greater detail the changes induced\\u000a by gallium, the properties of whole and

Mary A. Repo; Richard S. Bockman; Foster Betts; Adele L. Boskey; Nancy W. Alcock; Raymond P. Warrell

1988-01-01

173

Thermodynamic modelling of diffusion-controlled garnet growth  

Microsoft Academic Search

Numerical thermodynamic modelling of mineral composition and modes for specified pressure-temperature paths reveals the strong influence of fractional garnet crystallisation, as well as water fractionation, on garnet growth histories in high pressure rocks. Disequilibrium element incorporation in garnet due to the development of chemical inhomogeneities around porphyroblasts leads to pronounced episodic growth and may even cause growth interruptions. Discontinuous growth,

Matthias Konrad-Schmolke; Mark R. Handy; Jochen Babist; Patrick J. O’Brien

2005-01-01

174

Modification of Magnetic Anisotropy in Garnets by Ion Implantation  

Microsoft Academic Search

Ion implantation into epitaxial films of certain magnetic garnets grown on nonmagnetic substrates has produced layers with uniaxial anisotropy suitable for magnetic ``bubble'' formation and propagation. Implantation of hydrogen or lithium ions causes the garnet lattice to expand and the constraint of the unimplanted material places the implanted layer in lateral compression. In garnets with positive magnetostriction, this stress results

R. Wolfe; J. C. North; R. L. Barns; M. Robinson; H. J. Levinstein

1971-01-01

175

Direct observation of dissociated dislocations in garnet.  

PubMed

Dislocation core structures in garnet [grossularite (Ca(2.9)Fe(II)(0.1))(Al(1.9)Fe(III)(0.1)Si(3.0)O(12)] have been examined with near atomic resolution transmission electron microscopy. Dissociated dislocations have been observed as parallel a/4<111> partial dislocations that are separated by stacking faults. The partial dislocations have narrow cores ( approximately 3 burgers vectors), and the stacking fault zone between the narrow partial dislocations is apparently a low-energy configuration that results from the occupancy of previously unfilled dodecahedral and tetrahedral sites. Previous studies of garnet dislocations suggested that dissociation involves departures from garnet stoichiometry (that is, trace amounts of impurities), but evidence of detectable amounts of impurities has not been found even in the highest resolution images. These results have implications for mantle mineral rheology and transformations as well as for ceramics of material science interest. PMID:17737669

Allen, F M; Smith, B K; Buseck, P R

1987-12-18

176

One-dimensional bigyrotropic magnetic photonic crystals  

NASA Astrophysics Data System (ADS)

Electromagnetic wave propagation in a one-dimensional magnetic photonic crystal (MPC) made of bigyrotropic magnetic yttrium-iron garnet and nonmagnetic gadolinium-gallium garnet is theoretically investigated using the 4×4 transfer matrix method. Band gaps in the electromagnetic spectrum are numerically obtained and appear to depend on the helicity and direction of light propagation through the MPC.

Lyubchanskii, I. L.; Dadoenkova, N. N.; Lyubchanskii, M. I.; Shapovalov, E. A.; Lakhtakia, A.; Rasing, Th.

2004-12-01

177

A new magnetostatic wave delay line using YIG film  

Microsoft Academic Search

We have proposed a delay line of microstrip type consisting of a microstrip line fabricated on a composite substrate of two yttrium iron garnet films separated by a gadolinium gallium garnet layer. The dispersion relations are derived assuming magnetic walls at the edges of the strip. Experiments are carried out at S band with nonuniform magnetic field. Insertion loss less

Kensuke Okubo; Vishnu Priye; Makoto Tsutsumi

1997-01-01

178

Micro-Raman spectra of ugrandite garnet.  

PubMed

The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported. PMID:19084471

Moroz, T; Ragozin, A; Salikhov, D; Belikova, G; Puchkov, V; Kagi, H

2008-10-31

179

Intensities of hypersensitive transitions in garnet crystals doped with Er3+ ions  

NASA Astrophysics Data System (ADS)

We examine the oscillator strengths and the intensity parameters ? 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 ? 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 ? 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 ?2 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 2?. 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 ?2 tend to decrease, which can be related to an increase in the relative fraction of Er3+ ions with higher symmetry of the local environment.

Bol'Shakova, E. V.; Malov, A. V.; Ryabochkina, P. A.; Ushakov, S. N.; Nishchev, K. N.

2011-06-01

180

Micro-Raman Determination of the Composition of Ugrandite Garnets  

NASA Astrophysics Data System (ADS)

A fast method to obtain the molar composition of garnets starting from their Raman spectra was recently proposed. The method, called MIRAGEM-MIcro-RAman Garnets Evaluation Method is based on the assumption that in a garnet solid-solution the Raman wavenumbers are linear combinations of end-member wavenumbers, weighted by their molar fraction. In this work, the application of the MIRAGEM method to garnets belonging to the ugrandite family is discussed in detail, showing very good correspondence with electron-microscope-microprobe results in the grossular-andradite series. Unexpected two-mode behavior of a Raman peak in garnets with large amount of uvarovite is found.

Bersani, D.; Andò, S.; Vignola, P.; Marino, I.-G.; Lottici, P. P.

2009-08-01

181

Radiative lifetimes of neutral gadolinium  

NASA Astrophysics Data System (ADS)

The current work is part of an ongoing study of radiative properties of rare earth neutral atoms motivated by research needs in several disparate fields including astrophysics, laser chemistry and lighting technology. Time-resolved laser-induced fluorescence on a slow atomic beam has been used to measure radiative lifetimes, accurate to ±5%, for 136 levels of neutral gadolinium. Of the 136 levels, 6 are odd parity ranging in energy from 32 929 to 36 654 cm-1, and the remaining 130 are even parity ranging from 17 750 to 34 175 cm-1. This set of Gd i lifetimes represents a significant extension to the available published data, with 93 of the 136 level lifetimes measured for the first time. These lifetimes will provide the absolute normalization for a large set of measured Gd i transition probabilities.

Den Hartog, E. A.; Bilty, K. A.; Lawler, J. E.

2011-03-01

182

Nuclear data for gadolinium production  

SciTech Connect

There has been a marked increase in requests for neutron cross-section data of the rare-earth isotopes, /sup 152/Gd, /sup 153/Gd, /sup 151/Eu, /sup 152/Eu, /sup 153/Eu, /sup 154/Eu, and /sup 155/Eu because of the use of natural europium-oxide in reactor production of /sup 153/Gd. This gadolinium isotope is needed because of its use as the working ingredient in an advanced medical scanning machine that can detect loss of bone minerals such as calcium, a possible cause of the disease osteoporosis. Hanford's Fast Flux Test Facility plans to begin production of several /sup 153/Gd specimens during this autumn's operating cycle. An analysis of various experiments led to recommended values for the cross sections and resonance integrals, which are displayed and compared with the ENDF/B-V values. The detailed data underlying these recommendations are presented.

Holden, N.E.

1986-01-01

183

Synthesis of polycrystalline yttrium iron garnet and yttrium aluminium garnet from organic precursors  

Microsoft Academic Search

Polycrystalline Y3Fe5O12 (YIG) and Y3Al5O12 (YAG) garnets have been prepared by the organic solution technique using a novel organic precursor. The thermal decomposition of the precursor and subsequent formation of the garnet phases was studied by thermal analysis, X-ray diffraction and Fourier transform infra red spectroscopy (FTIR) including diffuse reflectance FTIR (DRIFT). The precursor of YIG decomposes to give the

C. D. Veitch

1991-01-01

184

Magnetic Properties of the Rare Earth Garnets  

Microsoft Academic Search

The magnetic properties, in static fields, of the rare earth garnets are described. The Ne´el molecular field theory of ferrimagnetism is extended to treat three sublattices of magnetic ions and is shown to account quantitatively for the observed properties. At low temperature, the magnetic moments of those rare earth ions which have nonzero orbital angular momentum, are much less than

R. Pauthenet

1959-01-01

185

Growth of Garnet Crystals for Laser Applications.  

National Technical Information Service (NTIS)

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 Ga2O3 has a high vapor...

C. P. Khattak

1984-01-01

186

Diode Pumped, Garnet Channel Waveguide Lasers.  

National Technical Information Service (NTIS)

Ion implantation is a technique which can be used to form waveguides in a wide range of materials - including crystals of the garnet family for which no alternative techniques exist by bombarding the material surface with high energy ions and altering the...

A. C. Large S. J. Field D. C. Hanna D. P. Shepherd A. C. Tropper

1992-01-01

187

Hot-pressed polycrystalline yttrium iron garnet  

Microsoft Academic Search

A simple hot-pressing system is described which enables small volumes of polycrystalline yttrium iron garnet to be routinely produced. The products have high density, very low second phase content and a controlled grain size. Their magnetic properties compare very favourably with similar polycrystalline material produced by conventional sintering. Sample porosity may be varied in a controlled manner by simple changes

G. A. Naziripour; A. O. Tooke; K. J. Standley; B. E. Storey

1985-01-01

188

MAGNETOACOUSTIC RESONANCE IN YTTRIUM IRON GARNET  

Microsoft Academic Search

Polished spheres of single-crystal yttrium iron garnet were observed to ; resonate acoustically in the 5 to 30-Mc\\/sec region by applying a 9300 or a 3000-; Mc\\/sec electromagnetic signal under proper conditions. The ferromagnetic line ; width of the samples used was 0.5 oe. Observations and conclusions are presented. ; (W.D.M.);

E. G. Spencer; R. C. LeCraw

1958-01-01

189

Potential effects of gallium on cladding materials  

SciTech Connect

This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

1997-10-01

190

Gadolinium sheet converter for neutron radiography.  

PubMed

This work describes a methodology developed for the confection of gadolinium sheet converter for neutron radiography using the gadolinium chloride (GdCl3) as material converter. Though manufactured at a relatively low cost, they are as good as the sheet converter on the market. Here, we present neutron radiography of the penetrameter, the edge spread function, the modulation transfer function and characteristic curves for each set sheet-AA400 Kodak film. PMID:17702586

Lima, C T S; Crispim, V R; Santos, W M S

2007-07-17

191

Wideband Microwave Filters Using Ferromagnetic Resonance Tuning in Flip-Chip YIG-GaAs Layer Structures  

Microsoft Academic Search

In this paper the most recent advances on ferromagnetic resonance (FMR)-based wideband microwave band-stop and band-pass filters using flip-chip yttrium iron garnet (YIG)\\/gadolinium gallium garnet (GGG)- gallium arsenide (GaAs) layer structures are reported. Specifically, simultaneous enhancement in tunable bandwidths and peak absorption levels by utilizing the meander microstrip line with step-impedance low-pass filter design together with inhomogeneous magnetic field has

Chen S. Tsai; Gang Qiu

2009-01-01

192

Tunable wideband microwave band-stop and band-pass filters using YIG\\/GGG-GaAs layer structures  

Microsoft Academic Search

Magnetically tunable wideband microwave bandstop and bandpass filters using ferromagnetic resonance absorption in yttrium iron garnet\\/gadolinium gallium garnet-gallium arsenide (YIG\\/GGG-GaAs) layer structures are reported. The measured characteristics of the bandstop filter, with nonuniform bias magnetic field distribution along the YIG\\/GGG film, shows a large absorption bandwidth of 1900 MHz at the stopband center frequency of 11.0 GHz, average peak absorption

C. S. Tsai; G. Qiu; H. Gao; L. W. Yang; G. P. Li; S. A. Nikitov; Y. Gulyaev

2005-01-01

193

Surface Passivation of Gallium Arsenide.  

National Technical Information Service (NTIS)

The surface passivation of Si doped (100) n-type gallium arsenide (GaAs) by chemical treatment with phosphoric acid (H3P04), phosphorus trichloride (PCl3), and sodium sulfide (Na2S.9H2O) was investigated using room temperature photoluminescence (PL) and a...

R. J. Racicot

1988-01-01

194

Gallium scan in intracerebral sarcoidosis  

SciTech Connect

Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

Makhija, M.C.; Anayiotos, C.P.

1981-07-01

195

Charge-transfer luminescence and spectroscopic properties of Yb 3+ in aluminium and gallium garnets  

Microsoft Academic Search

Luminescence of Yb3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino (?e) real-time spectroscopy, since the ?e capture

N. Guerassimova; C. Dujardin; N. Garnier; C. Pédrini; A. G Petrosyan; I. A Kamenskikh; V. V. Mikhailin; I. N Shpinkov; D. A Spassky; K. L Ovanesyan; G. O Shirinyan; R. Chipaux; M. Cribier; J. Mallet; J.-P Meyer

2002-01-01

196

40 CFR 721.10391 - Copper gallium indium selenide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

2013-07-01

197

Scintigraphie au gallium-67 et coeur. (Gallium-67 scintigraphy and the Heart).  

National Technical Information Service (NTIS)

Although gallium-67 was initially used for tumor imaging, clinical studies suggested its potential use as a method of detecting occult inflammatory lesions. The demonstration of diffuse myocardial uptake of gallium-67 during Lyme disease myocarditis is co...

D. Garayt

1987-01-01

198

Radiation Effects on Gallium Arsenide Phosphide and Gallium Phosphide Schottky Barrier Diodes.  

National Technical Information Service (NTIS)

Gallium arsenide phosphide (GaAsP) and gallium phosphide (GaP) Schottky barrier diodes were fabricated and the transient ionizing and stable fast neutron radiation effects on these diodes were determined. (Author)

D. A. Neamen W. W. Grannemann

1971-01-01

199

Preparation of polycrystalline yttrium iron garnet ceramics  

Microsoft Academic Search

The production of polycrystalline ceramics from YIG powders, obtained by reacting Y2O3 and Fe2O3 oxides, is a well understood and controlled industrial process. However, methods of production via chemical pathways, such as coprecipitation, possess the advantage that the garnet powder is more reactive and no longer requires prolonged grinding which can affect its purity. In this paper, we will show

P. Grosseau; A. Bachiorrini; B. Guilhot

1997-01-01

200

Heteroepitaxial growth of gallium phosphide on silicon  

Microsoft Academic Search

A new method of growing gallium phosphide on a silicon substrate is presented. The method includes an extra but simple process\\u000a of depositing a thin phosphorus layer on a silicon substrate prior to the growth of gallium phosphide by a so-called halide\\u000a transport method. Electronic and optical properties of the heterojunctions indicate that the interfaces between the gallium\\u000a phosphide layers

T. Katoda; M. Kishi

1980-01-01

201

Collector for recovering gallium from weapons plutonium  

SciTech Connect

Currently, the separation of gallium from weapons plutonium involves the use of aqueous processing using either solvent extraction of ion exchange. However, this process generates significant quantities of liquid radioactive wastes. A Thermally Induced Gallium Removal process, or TIGR, developed by researchers at Los Alamos National Laboratories, is a simpler alternative to aqueous processing. This research examined this process, and the behavior of gallium suboxide, a vapor that is swept away by passing hydrogen/argon over gallium trioxide/plutonium oxide heated at 1100 C during the TIGR process. Through experimental procedures, efforts were made to prevent the deposition of corrosive gallium onto furnace and vent surfaces. Experimental procedures included three options for gallium removal and collection: (1) collection of gallium suboxide through use of a cold finger; (2) collection by in situ air oxidation; and (3) collection of gallium on copper. Results conclude all three collection mechanisms are feasible. In addition, gallium trioxide exists in three crystalline forms, and each form was encountered during each experiment, and that each form will have a different reactivity.

Philip, C.V.; Anthony, R.G.; Chokkaram, S. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemical Engineering

1998-09-01

202

Tunable magnetic properties in ultrathin Co/garnet heterostructures  

NASA Astrophysics Data System (ADS)

We demonstrate how the magnetic properties of metal/dielectric Co/yttrium iron garnet heterostructures can be engineered by both changing the garnet thickness and adding an ultrathin Co cover layer. The observed magnetization reversal process in the heterostructures is explained by both cubic and perpendicular growth-induced magnetic anisotropy of the garnet films. In particular, the perpendicular magnetic anisotropy can be strongly increased for reduced thickness. A strong influence of a 2 nm Co layer on the domain structure geometry and magnetization processes has been found for 1.8 µm garnet films.

Pashkevich, M.; Stupakiewicz, A.; Kirilyuk, A.; Maziewski, A.; Stognij, A.; Novitskii, N.; Kimel, A.; Rasing, Th.

2012-01-01

203

Rare earth element fractionation in magmatic Ca-rich garnets  

NASA Astrophysics Data System (ADS)

Igneous garnets have the potential to strongly fractionate rare earth elements (REE). Yet informations on partition coefficients are very scant, and criteria for distinguishing between hydrothermal and magmatic garnets are ambiguous. To fill this gap, we present trace element and isotopic data for two types of Ca-rich garnets from phonolites (Mt. Somma-Vesuvius). Both Ca-garnet populations are different in their style and dynamics of fractionation: one population is progressively strongly depleted in HREE from core to rim, reflecting REE fractionation in the host phonolite via earlier-crystallized garnets. Such examples for extreme changes in HREE in garnets are only known for hydrothermal grandites by REE-bearing fluids. The second garnet population is homogeneous and formed in a closed system. Near-flat patterns between Sm and Lu confirm experimental data indicating lower D(Sm)/ D(Lu) for Ca-rich garnets than for e.g. pyrope-rich garnets. It follows: D Grt/PhMelt for La = 0.5, Sm = 48 and Yb = 110.

Scheibner, Birgit; Wörner, Gerhard; Civetta, Lucia; Stosch, Heinz-Günter; Simon, Klaus; Kronz, Andreas

2007-07-01

204

Super-Si garnet exsolution kinetics denotes multistage mantle exhumation  

NASA Astrophysics Data System (ADS)

Previous decompression experiments have shown that super-Si garnet decomposes to normal garnet + pyroxene, which supports that natural analogues (found in mantle xenoliths, diamond inclusions, peridotite massifs) record up to several hundreds of kilometre exhumation, all proposed to apply to contrasting geological scenarios including mantle convection, kimberlite magmatism and plate tectonics. To verify this proposition we used glass powder with a 'pyrolite minus olivine' composition for polycrystalline dry super-Si garnet synthesis (18 GPa, 1600 °C, 2 1/3 h) and subsequent decompression (10 GPa, 1450 °C, 0-12 h). All samples recovered after decompression share a coronitic texture of new grains of garnet + pyroxene that surround relic super-Si garnet. Quantified XRD spectra show transformed volumes are similar, ~40 %, that mark a rapid decrease of the transformation rate within the first minutes of the decompression runs. Fitted kinetic data does not fulfil conditions for steady nucleation and growth. The Tschermak's component of corona clinopyroxene is four times higher than that of equilibrium clinopyroxene synthesised along with each decompression experiment. Element concentration profiles (TEM EDS) and element mapping (FE-SEM EDS) across the corona microstructure show steep but discontinuous Al concentration gradients at both relic and corona garnet grain margins. Transformation rate and mineral chemistry suggest that volume diffusion (1) exceeds decompression induced initial partial breakdown of super-Si garnet and (2) will be rate limiting for exsolution to reach equilibrium. Modelled Si-Al and Si-Al-Mg interdiffusion in garnet at different water contents in combination with geological cooling rates suggests that diffusion distances exceed metamorphic garnet grain sizes of ?1 cm within the amphibolit facies, unless dry conditions apply. In contrast, mantle garnet of 1-2 cm in size may allow for up to two types of pyroxene precipitiation, depending on the garnet origin. Exsolution of diamond inclusions occurred prior to lithosphere transit, but is sensitive to internal pressure and hence kinetically difficult to interpret. We suggest that the breakdown of natural super-Si garnet forms two distinct decomposition microstructures, a corona type and a lamellae type, depending on whether diffusion distances exceed the garnet grain size or not. Diffusion distances and statistics on natural occurrences of the lamellae type decomposition microstructure comply with an origin within the SCLM during secular cooling of the Earth. Given the affinity of super-Si garnet breakdown microstructure occurrence to Archaean areas at global scale, models for craton stabilisation require the inclusion of processes that allow garnet bearing SCLM growth in the garnet peridotite stability field. Preceeding shallower stages would have erased the microstructural record.

Spengler, Dirk; Nishihara, Yu; Fujino, Kiyoshi

2013-04-01

205

Ion Implantation in Gallium Arsenide  

Microsoft Academic Search

Ion implantation is a useful method to incorporate dopants into semiconductors. Understanding implantation processes is essential to the advancement of solid state technology. Because of its technical importance, gallium arsenide (GaAs) was chosen for this study. Hall effect, x-ray diffraction, and electrochemical capacitance-voltage (CV) profiling were used to study activation of silicon implants as functions of dose and annealing temperature

John Hamilton Madok

1993-01-01

206

Hepatocellular carcinoma detection by gallium scan and subsequent treatment by gallium maltolate: rationale and case study.  

PubMed

Gallium is antiproliferative to many types of cancer, due primarily to its ability to act as a non-functional mimic of ferric iron (Fe(3+)). Because Fe(3+) is needed for ribonucleotide reductase activity--and thus DNA synthesis--gallium can inhibit DNA production and cell division. Diagnostic gallium scans have shown that hepatocellular carcinoma (HCC) is commonly avid for gallium. Furthermore, in vitro studies have found that gallium nitrate, and particularly gallium maltolate (GaM), have dose-dependent antiproliferative activity against HCC cell lines. Rationale thus exists to use GaM, an orally active compound that has been well tolerated in Phase I clinical trials, to treat patients whose HCC is gallium-avid in a gallium scan. Because gallium absorbed from orally administered GaM is bound predominately to serum transferrin, which travels to all tissues in the body, GaM has the potential to treat even distant metastases. A patient with advanced HCC (20 × 10 cm primary tumor, ascites around liver and spleen, resistant to Nexavar(®) (sorafenib)), whose cancer was highly gallium-avid in a (67)Ga-scan, was treated with oral gallium maltolate at 1500 mg/day q.d. After four weeks of treatment, the patient had a large reduction in pain, with greatly increased mobility and quality of life, and significantly lowered serum bilirubin and inflammation-related liver enzymes. At eight weeks, CT scans showed apparent necrosis of the tumor. PMID:21554205

Bernstein, Lawrence R; van der Hoeven, Jacobus J M; Boer, Robbert O

2011-07-01

207

Trace Element Zoning in Garnets - Retrospective and Prospective  

NASA Astrophysics Data System (ADS)

Deployment of the Cameca IMS-3f (Joy) at MIT enabled the first SIMS analyses of trace-element zoning in garnets. Moderate energy filtering (-35 to -90 Ev) allowed the determination of rare-earth element (REE) and many other trace elements’ (TE) zoning in natural garnets (and determination of element concentrations with appropriate standards) with sub-ppm detection limits for many elements. TE zoning is complementary to major element (ME) zoning and provides additional insights into geologic processes where ME are ambiguous. Key areas where TE zoning in garnet is potentially useful include: (1) investigating reaction histories (including melting) particularly those involving TE-rich phases; (2) examination of disequilibrium processes during petrogenesis; (3) investigating metasomatic events (both fluid induced and melt induced); (4) tracing pressure-temperature-time (P-T-t) paths; and (5) supporting and guiding radiogenic isotope investigations. Both early (1980s) and recent examples of such applications will be discussed - specific TE are useful to investigate specific processes. For area (1) Y and LREE increases indicate involvement of epidote in garnet forming reactions. For (2) and (4) buffered TE such as Ti are particularly useful, although applications of TE in garnets to (4) have not proved fruitful. For (3) a range of fluid-enriched and melt-enriched elements including LREE & MREE are useful. The relevant data (garnet/fluid and garnet/mineral partition coefficients as a function of P, T, & fluid/mineral composition) needed to quantitatively model TE zoning remain largely unavailable. New ion probe technologies (e.g. large-magnet, high-resolution Cameca IMS 1280) open up a plethora of new opportunities to pursue ultra-TE abundance and stable isotopic (SI) zoning in garnets; however development of appropriate matrix-matched standards remains a formidable challenge. Ion implanted standards may be useful for such applications. SI zoning in garnet (and SI in garnet inclusions) may facilitate direct determination of P-T-t paths from garnet zoning.

Hickmott, D.; Shimizu, N.; Spear, F. S.

2009-12-01

208

Garnet geotherms: Pressure-temperature data from Cr-pyrope garnet xenocrysts in volcanic rocks  

Microsoft Academic Search

The temperatures and pressures of equilibration of single peridotitic garnet xenocrysts are estimated using a combination of major- and trace-element data, determined using electron mi- croprobe (EMP) and proton induced X ray emission (PIXE). This new method enables the use of xenocrysts found in kimberlites and other volcanic rocks to determine the local paleogeotherm at the time of eruption of

Chris G. Ryan; William L. Griffin; Norman J. Pearson

1996-01-01

209

Laser Photochemistry of Gallium-Containing Compounds.  

National Technical Information Service (NTIS)

The production of gas-phase gallium atoms in the photolysis of trimethylgallium has been investigated at 193 nm and at other laser wavelengths. Ground state (4 sup 2 P sup 0 /sub 1/2) and metastable (4 sup 2 P sup 0 /sub 3/2/) gallium atoms are detected u...

S. L. Baughcum R. C. Oldenborg

1986-01-01

210

Optical control of gallium nanoparticle growth  

NASA Astrophysics Data System (ADS)

We report that low-intensity light can dramatically influence and regulate the nanoparticle self-assembly process: Illumination of a substrate exposed to a beam of gallium atoms results in the formation of gallium nanoparticles with a relatively narrow size distribution. Very low light intensities, below the threshold for thermally induced evaporation, exert considerable control over nanoparticle formation.

MacDonald, K. F.; Fedotov, V. A.; Pochon, S.; Ross, K. J.; Stevens, G. C.; Zheludev, N. I.; Brocklesby, W. S.; Emel'Yanov, V. I.

2002-03-01

211

An oxygen barometer with the assemblage garnet-epidote  

NASA Astrophysics Data System (ADS)

An oxygen barometer has been developed using garnet-epidote equilibria and the latest available thermodynamic data via the reaction: 2 Ca 2FeAl 2Si 3O 12(OH)= 2 Ca 2FeAl 2Si 3O 12+ H 2O+1/2 O 2epidote (Ps 33Czo 67) garnet (Alm 33Grs 67) fluidwhere epidote (Ps 33Czo 67) reacts to form (Alm 33Grs 67), water and oxygen. The garnet-epidote oxybarometer has been applied to a wide variety of metamorphic rocks including low to medium-pressure greenschists and amphibolites, as well as high-pressure eclogites. Results indicate that this equation represents a sensitive oxygen monitor with only a minor dependence on pressure. Andradite solid solution of less than 15 mol% has only minor influence in the locus of the curve in fO 2/ T space. Garnet-epidote equilibria may also provide a thermometer when combined with an independent oxygen buffer. The garnet-epidote oxythermobarometer is a reliable oxygen sensor that can be applied to many low through medium-grade metamorphic rocks. The extensive solid solution found in both garnet and epidote allows this equation to be applied to mineral pairs with a wide range of compositions. The garnet-epidote oxythermobarometer is potentially applicable to any rocks that contain the equilibrium assemblage garnet+epidote.

Donohue, Casey L.; Essene, Eric J.

2000-09-01

212

Large grain gallium arsenide thin films  

SciTech Connect

Polycrystalline gallium arsenide films deposited on tungsten/graphite substrates have been used for the fabrication of thin film solar cells. Gallium arsenide films deposited on foreign substrates of 10 ..mu..m or less thickness exhibit, in most cases, pronounced shunting effects due to grain boundaries. MOS solar cells of 9 cm/sup 2/ area with an AMI efficiency of 8.5% and p/sup +//n/n/sup +/ homojunction solar cells of 1 cm/sup 2/ area with an AM1 efficiency of 8.8% have been prepared. However, in order to further improve the conversion efficiency before the development of effective passivation techniques, gallium arsenide films with large and uniform grain structure are necessary. The large grain gallium arsenide films have been prepared by using the arsine treatment of a thin layer of molten gallium on the substrate surface and the recrystallized germanium films on tungsten/graphite as substrates.

Chu, S.S.; Chen, W.J.; Chu, T.L.; Firouzi, H.; Han, Y.X.; Wang, Q.H.

1984-05-01

213

Gadolinium: Central Metal of the Lanthanoids  

ERIC Educational Resources Information Center

|The physical and chemical properties of gadolinium are compared with those of the other lanthanoids. Some properties are intermediate between those of lanthanum and lutetium; some between those of barium and hafnium; and others (unexpectedly) between those of ytterbium and lutetium. Both the remarkably high molar heat capacity of the metal and…

Laing, Michael

2009-01-01

214

Pyroelectric detection properties of gadolinium molybdate (gmo)  

Microsoft Academic Search

The pyroelectric detection properties of gadolinium molybdate (GMO) crystals have been studied near and at its 159°C ferroelectric transition temperature. Responsivity and detectivity figures of merit are calculated from measurements of pyroelectric currents induced by white light irradiation and are compared with room temperature figures of merit for TGS and SBN detectors. Since GMO does not exhibit a dielectric anomaly,

F. G. Ullman; B. N. Ganguly; J. R. Zeidler

1972-01-01

215

Chemistry and mineralogy of garnet pyroxenites from Sabah, Malaysia  

USGS Publications Warehouse

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.

Morgan, B. A.

1974-01-01

216

Very high-pressure orogenic garnet peridotites.  

PubMed

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

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

2007-05-22

217

Subcellular SIMS imaging of gadolinium isotopes in human glioblastoma cells treated with a gadolinium containing MRI agent  

NASA Astrophysics Data System (ADS)

Neutron capture therapy is an experimental binary radiotherapeutic modality for the treatment of brain tumors such as glioblastoma multiforme. Recently, neutron capture therapy with gadolinium-157 has gained attention, and techniques for studying the subcellular distribution of gadolinium-157 are needed. In this preliminary study, we have been able to image the subcellular distribution of gadolinium-157, as well as the other six naturally abundant isotopes of gadolinium, with SIMS ion microscopy. T98G human glioblastoma cells were treated for 24 h with 25 mg/ml of the metal ion complex diethylenetriaminepentaacetic acid Gd(III) dihydrogen salt hydrate (Gd-DTPA). Gd-DTPA is a contrast enhancing agent used for MRI of brain tumors, blood-brain barrier impairment, diseases of the central nervous system, etc. A highly heterogeneous subcellular distribution was observed for gadolinium-157. The nuclei in each cell were distinctly lower in gadolinium-157 than in the cytoplasm. Even within the cytoplasm the gadolinium-157 was heterogeneously distributed. The other six naturally abundant isotopes of gadolinium were imaged from the same cells and exhibited a subcellular distribution consistent with that observed for gadolinium-157. These observations indicate that SIMS ion microscopy may be a viable approach for subcellular studies of gadolinium containing neutron capture therapy drugs and may even play a major role in the development and validation of new gadolinium contrast enhancing agents for diagnostic MRI applications.

Smith, Duane R.; Lorey, Daniel R.; Chandra, Subhash

2004-06-01

218

Triethylborane-induced radical reactions with gallium- and indium hydrides  

Microsoft Academic Search

A gallium hydride reagent, HGaCl2, was found to act as a radical mediator. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radical cyclization of halo acetals was also successful with not only the stoichiometric gallium reagent but also a catalytic amount of gallium

Kazuaki Takami; Satoshi Mikami; Hideki Yorimitsu; Hiroshi Shinokubo; Koichiro Oshima

2003-01-01

219

Ion irradiation effects in natural garnets: Comparison with zircon  

NASA Astrophysics Data System (ADS)

The behavior of garnet (A3B2(XO4)3;Ia3d;Z=8) under ion-beam irradiation was investigated in order to compare its radiation susceptibility to another orthosilicate: zircon, ZrSiO4. Five natural end-member compositions were examined by in situ transmission electron microscopy during irradiation with 1.0 MeV Kr2+ over the temperature range of 50-1070 K. The critical amorphization temperature, above which amorphization does not occur, was 1030 K for andradite, but could not be determined for the other garnet composition because the Tc was higher than the highest temperature of the experiment. Based on topologic criterion, the degree of structural freedom in garnet is /~/-2.25 and for zircon /~/-1.5. Based on topology the critical amorphization dose for garnet should be higher than that of zircon; however, the average amorphization dose of garnet (0.20 dpa) is lower than that of zircon (0.37 dpa) at room temperature. This may be the result of the assumed value for the displacement energies, Ed, used in the calculation of dpa. Garnet did not decompose, while zircon decomposes to SiO2+ZrO2 during the ion irradiation at high temperature. This behavior may be related to the phase relations of garnet which melts congruently and zircon which decomposes to ZrO2+SiO2.

Utsunomiya, S.; Wang, L. M.; Ewing, R. C.

2002-05-01

220

Electrospun Gallium Nitride Nanofibers (abstract)  

NASA Astrophysics Data System (ADS)

The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

2009-04-01

221

The Soviet American Gallium Experiment (SAGE)  

SciTech Connect

A radiochemical experiment using the reaction v/sub e/ = /sup 71/Ga + e/sup e/ to determine the integral flux of low-energy neutrinos from the sun is currently under preparation at the Baksan Neutrino Observatory in the USSR. Measurements are scheduled to commence by late 1988 using /approximately/30 tonnes of metallic gallium. With this amount of gallium it should be possible to obtain a fractional statistical accuracy of 12 to 15% after one year (assuming the standard solar model neutrino flux). While initial measurements are in progress, installation of the remaining 30 tonnes of gallium will proceed in order to perform the full 60 tonne experiment.

Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.P.; Avdeyev, A.V.; Belousko, Yu.I.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Gavrin, V.N.; Grigorjev, A.M.; Kalikhov, A.V.; Kireyev, S.M.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentsevah, S.A.; Mirnov, I.N.; Ejikbosverpdze, Sh.M.; Ostrinsky, A.V.; Petukhov, V.V.; Pikhulya, O.E.; Pshukov, A.M.; Revzin, N.Ye.; Shikhin, A.A.; Shilo, Yu.I.; Slyusareva, Ye.D.; Strepanyuk, M.V.; Tikhonov, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Yants, V.E.; Zakhorov, Yu.I.; Zatsepin, G.T.; Cleveland, B.C.; Bowles, T.J.; Elliott, S.R.; O'Brien, H.A.; Wark, D.L.; Wilkerson, J.F.; Cherry, M.L.; Kouzes, R.T.

1988-01-01

222

Status of gallium-67 in tumor detector  

SciTech Connect

The efficacy of gallium-67 citrate in detecting specific tumors is discussed. Tumors in which gallium-67 imaging is useful as a diagnostic tool include Hodgkin's disease, histiocystic lymphoma, Burkitt's lymphoma, hepatoma melanoma, and leukemia. It has not been found to be effective in diagnosing head and neck tumors, gastrointestinal tumors, genitourinary tract tumors, breast tumors, and pediatric tumors. Gallium may be useful in the evaluation of non-Hodgkin's lymphoma, testicular carcinoma, mesothelioma, and carcinoma of the lung. It may also be useful for determining response to treatment and prognosis in some neoplasms.

Hoffer, P.

1980-04-01

223

Garnet clinopyroxenite inclusions from diatremes in the Gloucester area, New South Wales, Australia  

Microsoft Academic Search

The paper discusses the petrography, mineralogy, petrochemical affinities, P\\/T crystallization regimes and genetic aspects of four garnet clinopyroxenite inclusions from diatremes in the Gloucester area, New South Wales. Inclusion mineral assemblages (which generally display textural evidence of annealing) include garnet-plagioclase-(sulphur-rich scapolite)-clinopyroxene, garnet-hornblende-orthopyroxene-clinopyroxene and garnet-hornblende-clinopyroxene. The garnet-plagioclase clinopyroxenite inclusion possesses an essentially alkali basaltic chemistry. It probably represents a crystallized basaltic

J. F. G. Wilkinson; G. I. Z. Kalocsai

1974-01-01

224

Preparation and characterization of nanodispersions of yttria, yttrium aluminium garnet and lutetium aluminium garnet.  

PubMed

Refractory and chemically inert nanoparticulate solids like yttria, yttrium aluminium garnet or lutetium aluminium garnet are notoriously difficult to disperse in aqueous solution, although such dispersions might prove useful for 2D- and 3D-printing, deposition of films or other shaping procedures for ceramic green bodies. This work reports on experiments to prepare such dispersions from nanopowders, using a range of selected carboxylic acids as ligands for electrostatic charging and stabilization of the various nanomaterials. The assessment of the system properties achieved combines ?-potential and viscosity (flow curve) measurements in the resulting colloidal systems. Calculations of the molecular electrostatic potential of the ligands were used to correlate the molecular structure of the ligands and their capability to dock to the surface of the solid particles. The colloid chemical data received have then been interpreted on this background; citric acid and polyacrylic acid have been identified as the most attractive dispersants. PMID:23643249

Bredol, Michael; Micior, Joanna

2013-04-12

225

A possible role for garnet pyroxenite in the origin of the “garnet signature” in MORB  

Microsoft Academic Search

Geochemical data have been interpreted as requiring that a significant fraction of the melting in MORB source regions takes\\u000a place in the garnet peridotite field, an inference that places the onset of melting at ?80?km. However, if melting begins\\u000a at such great depths, most models for melting of the suboceanic mantle predict substantially more melting than that required\\u000a to produce

Marc M. Hirschmann; Edward M. Stolper

1996-01-01

226

Pyroelectric detection properties of gadolinium molybdate (gmo)  

Microsoft Academic Search

The pyroelectric detection properties of gadolinium molybdate (GMO) crystals have been studied near and at its 159?C ferroelectric\\u000a transition temperature. Responsivity and detectivity figures of merit are calculated from measurements of pyroelectric currents\\u000a induced by white light irradiation and are compared with room temperature figures of merit for TGS and SBN detectors. Since\\u000a GMO does not exhibit a dielectric anomaly,

F. G. Ullman; B. N. Ganguly; J. R. Zeidler

1972-01-01

227

Gadolinium Solubility in Peraluminous Borosilicate Glasses  

SciTech Connect

This paper discussed the results of a study, using 18 peraluminous (Na/Al <1) borosilicate glasses, to understand the effect of glass composition on gadolinium solubility. Above Gd solubility, liquid-liquid phase separation occurs in some of the glasses; in others, sodium gadolinium silicate crystallizes. For the samples in which liquid-liquid phase separation occurs, Gd solubility is determined by the concentration of excess Al (i.e., [AlO1.5]-[NaO0.5]-0.2*[BO1.5]). Increasing excess Al increases Gd solubility. For the samples in which sodium gadolinium silicate crystallizes, Gd solubility is determined by the concentration of Na. Increasing Na decreases Gd solubility. When the Al concentration in the baseline glass is high, a minimum amount of Gd is needed to form a clear glass. Otherwise, mullite crystallizes. The minimum concentration of Gd is determined by the [AlO1.5]-[NaO0.5]-[BO1.5] value in the melt. The higher this value is, the more Gd is needed to form a clear glass. In general, the solution behavior of Gd in peraluminous borosilicate melt is similar to that in peralkaline borosilicate melt, and is mostly determined by the ratio of excess Al to equivalent B in the melt.

Li, Liyu; Li, Hong; Qian, Maoxu; Strachan, Denis M.

2001-03-05

228

Garnet melt viscosity, surface tension and drainage  

NASA Astrophysics Data System (ADS)

Good surface morphology and layer uniformity of LPE-grown Bi YIG films are favored by fast melt removal after growth. Three flux modifying oxides: MoO3, V2O3, and WO3 are compared with respect to their effect on viscosity, surface tension and melt drainage. All three oxides increased the viscosities of Bi-garnet melts, but the viscosities and drainage times of V2O3 and MoO3 modified melts were smaller than those of WO3 modified melts. The liquid-gas surface tension was found to be temperature independent. The drainage process was strongly temperature dependent, 40 to 60 kcal/mol, whereas the viscosities of melts had activation energies of 11 to 16 kcal/mol. Contact angles of 16 + or - 2 deg were measured on frozen melt drops.

Luther, L. C.

1986-06-01

229

Recovery of gallium from aluminum industry residues  

SciTech Connect

A procedure is proposed to recover gallium from flue dust aluminum residues produced in plants by using solid-phase extraction with a commercial polyether-type polyurethane foam (PUF). Gallium can be separated from high concentrations of aluminum, iron, nickel, titanium, vanadium, copper, zinc, sulfate, fluoride, and chloride by extraction with PUF from 3 M sulfuric acid and 3 M sodium chloride concentration medium with at least a 92% efficiency. Gallium backextraction was fast and quantitative with ethanol solution. In all recovery steps commercial-grade reagents could be used, including tap water. The recovered gallium was precipitated with sodium hydroxide solution, purified by dissolution and precipitation, calcinated, and the final oxide was 98.6% pure.

Carvalho, M.S.; Neto, K.C.M.; Nobrega, A.W.; Medeiros, J.A.

2000-01-01

230

Generator for gallium-68 and compositions obtained therefrom  

DOEpatents

A generator for obtaining radioactive gallium-68 from germanium-68 bound in a resin containing unsubstituted phenolic hydroxyl groups. The germanium-68 is loaded into the resin from an aqueous solution of the germanium-68. A physiologically acceptable solution of gallium-68 having an activity of 0.1 to 50 millicuries per milliliter of gallium-68 solution is obtained. The solution is obtained from the bound germanium-68 which forms gallium-68 in situ by eluting the column with a hydrochloric acid solution to form an acidic solution of gallium-68. The acidic solution of gallium-68 can be neutralized.

Neirinckx, Rudi D. (Medfield, MA); Davis, Michael A. (Westwood, MA)

1981-01-01

231

Aluminum arsenide eutectic gallium arsenide solar cell  

Microsoft Academic Search

An improved gallium arsenide solar cell is provided by forming a P+ layer on top of a wafer of vertical PN junction eutectic gallium arsenide crystal by liquid phase epitaxial growth of P doped GaAs followed by liquid phase epitaxial growth at Al(x)AsGa(1-x) on the surface of the vertical PN junction substrate. The deposited GaAs layer with P dopant and

Rahilly

1976-01-01

232

Aluminum arsenide eutectic gallium arsenide solar cell  

Microsoft Academic Search

An improved gallium arsenide solar cell is provided by forming a P + layer on top of a wafer of plural vertical PN junction eutectic gallium arsenide crystal by liquid phase epitaxial growth of P doped GaAs followed by liquid phase epitaxial growth at Al\\/sub x\\/AsGa\\/sub l-x\\/ on the surface of the vertical PN junction substrate. The deposited GaAs layer

Rahilly

1978-01-01

233

Nanoscale photonics of structural transformations in Gallium  

NASA Astrophysics Data System (ADS)

We have found recently that Gallium, confined at an interface with silica, responds dramatically to low power optical excitation when held at temperatures close to its melting point (29.8°C). Intensities of just a few kW/cm2 can reversibly modulate the intensity (by up to 40%) and phase (by as much as several degrees) of reflected light as the result of a light-induced structural transition occurring in a layer of gallium of only a few nm thick. Here, we report that this concept - of achieving a nonlinearity via a light-induced transformation in a confined solid at a temperature close to a phase transition temperature - can also be applied to gallium nanoparticles. We present the transient all-optical switching characteristics of gallium nanoparticle films comprising particles, typically 80 nm in diameter, which were formed directly on the ends of optical fibers using a new light-assisted self-assembly technique. We also report, for the first time, that this light-induced structural transition in gallium confined at an interface with silica underlies a new mechanism for photoconductivity. In our opinion, the exploitation of the light-induced phase transition in gallium may be a means of enabling the development of nanoscale photonic devices.

Zheludev, Nikolay I.; Fedotov, V. A.; MacDonald, K. F.; Stevens, G. C.; Pochon, Sebastien C.; Woodford, M.

2002-09-01

234

Gallium poisoning: a rare case report.  

PubMed

The authors present a case of a college student who suffered acute gallium poisoning as a result of accidental exposure to gallium halide complexes. This is extremely rare and has never been reported in the literature. Acute symptoms after the incident, which initially presented as dermatitis and appeared relatively not life-threatening, rapidly progressed to dangerous episodes of tachycardia, tremors, dyspnea, vertigo, and unexpected black-outs. Had there been effective emergency medical care protocols, diagnostic testing, treatment and antidotes, the latent manifestations of irreversible cardiomyopathy may have been prevented. Given how quickly exposure led to morbidity, this article aims to raise an awareness of the toxic potential of gallium. This has particular relevance for workers involved in the production of semiconductors where there is a potential for accidental exposure to gallium by-products during device processing. It may also have implications for dentists who use gallium alloys to replace mercury containing amalgam. In the absence of threshold limit values and exposure limits for humans, as well as emergency medical guidelines for treatment of poisoning, the case calls on the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration to establish guidelines and medical management protocols specific for gallium. PMID:22024274

Ivanoff, Chris S; Ivanoff, Athena E; Hottel, Timothy L

2011-10-18

235

Thermal Conductivity of Garnets and the Middle Mantle  

NASA Astrophysics Data System (ADS)

The thermal conductivity (k) of garnet phases is calculated from a formula originating with Debye, adapted to treat the vibrations in a solid as a collection of damped harmonic oscillators. Our model utilizes phonon lifetimes obtained from Kramers-Kronig analyses of existing IR reflectivity spectra, as well as new measurements presented here, and calculates k at ambient conditions. Two series of natural garnets were investigated: (1) X3Al2Si3O12, where the X site holds varying amounts of Mg, Fe2+, and Ca (pyrope-almandines with subordinate grossular); and (2) Ca3Y2Si3O12, where the Y site holds Al and/or Fe3+ (grossular-andradites). The model predicts k at ambient conditions for the end-members. The occurrence of a minimum in k near the midpoint of each compositional series correlates with the maximum widths of the IR peaks: the amount of disorder on lattice sites is a key factor controlling the thermal conductivity of mixed crystals. We also utilized available IR spectra for three synthetic yttrium garnets to test the model against literature values for their thermal conductivities. Our calculated k for YAG with 5.5% Sm is between the results for pure YAG and YAG with 5% Yb. Experimental determinations of k for YGG and YIG are higher than calculated values; given the close comparison of calculated and measured k for YAG and natural garnets, these measured data may be in excess of the true value. Disparities this size among values of thermal conductivity from different laboratories are common. Based on the success of the model in predicting k for surface garnets, we go on to analyze the spectra of majorite and estimate its thermal conductivity as well. Since a majorite-rich garnet phase is expected to occur in the mantle transition zone, a region whose properties are critical to mantle convection, the thermal conductivity of majorite is an important value that will assist in resolving the debate between layered and full-mantle convection in the earth. Our observation with surface garnets (as well as other phases) of decreased thermal conductivity with greater degrees of solid solution is expected to carry over to mid-mantle garnets, so that the concentration of "impurity" ions like Al and Ca will play an important role in determining the thermal conductivity of the region. Also, since garnet phases have much lower k than the spinel and spineloid phases that should occur at similar conditions, the role of Al in particular in stabilizing garnet will also affect thermal conductivity by encouraging the formation of low k garnet in the mid-mantle.

Giesting, P. A.; Hofmeister, A. M.

2001-12-01

236

On the origin of pyroxene exsolution topotaxy in majoritic garnets  

NASA Astrophysics Data System (ADS)

The pyroxene exsolution in garnet after majorite from garnet peridotites of Otrøy and Fjørtoft Islands suggests a very deep origin (>350 km) of the rocks. Microstructures and trace element compositions of the exsolved pyroxenes and garnets indicate that these ultra-deep mantle rocks may have experienced a complex multiple stage exhumation process. The interstitial pyroxenes were exsolved during the Archean upwelling from mantle transition zone. The intracrystalline pyroxene lamellae were exsolved during the isobaric cooling after accretion to deep cratonic roots (Spengler et al., 2006; Scambelluri et al., 2008). We provide here electron backscattered diffraction (EBSD), electron microprobe (EMP) and laser ablation (LA-ICPMS) analyses of pyroxenes exsolved from the garnets. The EBSD analyses of more than 200 exsolved pyroxenes and host garnets reveal the following exsolution topotaxial relationship: 1) The interstitial milimeter-size orthopyroxenes have no consistent crystallographic relation with the surrounding garnets; 2) There are three different intracrystalline exsolutions in garnet (orthopyroxene rods (major exsolved phase), clinopyroxene rods and the rods of intergrowth of CPX and OPX). The majority (80-90%) of exsolutions have a tight topotaxial relationships with the host garnet by <001>px // <111>grt and <010>px // <110>grt. 3) Pyroxene rods are elongated parallel to the <111>grt or <110>grt. The elongation directions are the <001>px in the former case. 4) The polycrystalline intergrowths of clinopyroxenes and orthopyroxenes have also a tight topotaxial relationships of {100}cpx//{100}opx, <010>cpx//<010>opx and <001>cpx//<100>opx. The interfaces between clinopyroxenes and orthopyroxenes are the {100}px planes. The <100>cpx, the elongation directions for the intergrowth pyroxene rods, are near parallel to the <111>grt. The volume ratio of Cpx/Opx varies from nearly pure Cpx to pure Opx suggesting that these exsolutions are exsolved two-pyroxene solid solutions. All exsolved clinopyroxenes show essentially no difference in major and trace element compositions as revealed by EMP and LA-ICPMS analyses. So are the exsolved orthopyroxenes and the host garnets. Based on our results and previous experimental results, we hypothesis that clinopyroxene rods were exsolved firstly from the precursor majoritic garnet, followed by solid solutions of pyroxenes and orthopyroxene rods. These results provide signature topotaxial relationships for distinguishing pyroxene exsolutions in majoritic garnets.

Zhang, J.; Xu, H.; Dobrzhinetskaya, L.

2009-12-01

237

Sublattice Magnetization in Yttrium and Lutetium Iron Garnets  

Microsoft Academic Search

The temperature dependence of the a and d sublattice magnetization in yttrium iron garnet (YIG) and lutetium iron garnet (LuIG) has been observed by means of the NMR of Fe57 between 4 and 373°K, with special emphasis on the temperature range where the spin-wave theory is expected to hold. An analysis of these results in terms of the spin reversals

Roland Gonano; Earle Hunt; Horst Meyer

1967-01-01

238

Garnet-peridotite stability and occurrence in crust and mantle  

Microsoft Academic Search

The boundary between the spinel- and garnet-lherzolite mineral facies is strongly curved between 1300° C and 1450° C; below 1200° C it lies almost parallel to the temperature axis of the T-P diagram. Pressure of at least 12 kb is required to stabilise garnet-peridotite on the geothermal gradient and the depth at which the boundary is encountered is not sensitive

M. J. O'Hara; S. W. Richardson; G. Wilson

1971-01-01

239

Geobarometry and geothermometry of plagioclase-biotite-garnet-muscovite assemblages  

Microsoft Academic Search

The assemblage, plagioclase-biotite-garnet-muscovite is widespread in garnet to lower sillimanite zone metasedimentary rocks. The equilibria, (1) pyr+gr+mu=3an+phl and (2) alm+gr+mu=3an+ann, involve a change in Al coordination from 6 to 4 and in Mg-Fe coordination from 8 to 6 and should be strongly pressure dependent. Using an ionic solution model we can define solid activity products for (1) and (2). Using

Edward D. Ghent; Mavis Z. Stout

1981-01-01

240

Method of Fabricating Germanium and Gallium Arsenide Devices.  

National Technical Information Service (NTIS)

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium...

M. Jhabvala

1990-01-01

241

Use of Gadolinium as a Neutron Absorber in Nuclear Reactors: Radiolysis of Gadolinium Nitrate Solutions.  

National Technical Information Service (NTIS)

Radiolysis of gadolinium nitrate solutions was investigated in a GAMMACELL and in the WR-1 reactor. The results from the two were similar although the dose rate in the WR-1 reactor was about 200 times higher than in the GAMMACELL. The initial G(H sub 2 ) ...

A. Singh J. C. Leblanc

1976-01-01

242

Extraction-chromatographic affinage in gadolinium-153 preparation production technology  

SciTech Connect

The gadolinium 153 preparation is used for production of medical gamma-sources which are applicable in bone densimeters for early diagnostics of osteoporosis. This preparation must meet strict requirements with respect to the content of europium radionuclides and specific activity. In The Research Institute of Atomic Reactors (RIAR) the gadolinium 153 is produced by neutron irradiation of Europium 151. This process is described.

Melnik, M.I.; Karelin, E.A.; Kuznetsov, R.A. [and others

1993-12-31

243

Gadolinium loaded plastic scintillators for high efficiency neutron detection  

Microsoft Academic Search

Gadolinium has the highest thermal neutron absorption cross section of any naturally occurring element, and emits conversion electrons as well as atomic X-rays in over 50% of its neutron captures, which makes it a useful dopant in scintillators for detecting thermal neutrons. Gadolinium isopropoxide was studied as a possible dopant for styrene-based plastic scintillators as a convenient and inexpensive method

Lena Ovechkina; Kent Riley; Stuart Miller; Zane Bell; Vivek Nagarkar

2009-01-01

244

The nature of subvalent gallium and indium in aqueous media  

Microsoft Academic Search

Subvalent gallium can exist in aqueous solutions as Ga?Ga bonded gallium(II) species stabilised by halide ligands in the form of the complex anions Ga2X62? (X=Cl, Br or I) whose formation and reactivity are discussed. Gallium(I) compounds and mixed valence compounds of gallium react vigorously with water, converting any Ga+ ions into Ga(III) products. Indium(I) is more tolerant of water, so

Lars Kloo; Jan Rosdahl; Michael J. Taylor

2002-01-01

245

Neutron Detection with Lithium Gadolinium Borate  

SciTech Connect

With the advent of a highly efficient, neutron-sensitive inorganic crystal scintillator, a new class of neutron spectrometers and dosimeters becomes feasible. The new material, lithium gadolinium borate, incorporates the three primary neutron-capturing nuclei utilized in solid-state neutron detectors. Eight isotopic permutations of the three capturing elements permit a wide range of applications throughout the neutron energy range from thermal to several MeV. The transparent inorganic crystals may be incorporated in organic plastic matrices to enhance the detection efficiency for neutrons of all energies. This summary describes a number of applications of the new scintillator in several areas of neutron detection.

J. Bart Czirr

2000-11-12

246

Synthesis of gadolinium silicate by hydrothermal method  

NASA Astrophysics Data System (ADS)

A simple method based on hydrothermal synthesis of materials to prepare gadolinium silicate has been prescribed. It is found that molar ratio of Gd(NO3)3: TEOS plays a crucial role in the formation of Gd2SiO5. The effect of calcinations, concentration of the precipitating agent and dopant atoms on composition and morphology of the synthesized materials has been investigated. The desired phase of Gd2SiO5 can be synthesized from hydrothermally grown powder after annealing at 1400°C.

Shinde, Seema; Ghosh, M.; Sen, Shashwati; Singh, S. G.; Gadkari, S. C.; Gupta, S. K.

2013-02-01

247

Studies of the Vaporization Mechanism of Gallium Arsenide Single Crystals  

Microsoft Academic Search

The kinetics of vaporization of gallium arsenide single crystals into vacuum have been investigated using microbalance and mass spectrometric techniques in the temperature range 700–900° C. Although gallium arsenide vaporized incongruently to yield liquid gallium and arsenic vapor molecules, initial steady state evaporation rates can be obtained in the temperature range of study. The total evaporation rates and the activation

C. Y. Lou; G. A. Somorjai

1971-01-01

248

Proportional counter response calculations for gallium solar neutrino detectors  

Microsoft Academic Search

Gallium-based solar neutrino detectors are sensitive to the primary pp reaction in the sun. Two experiments using gallium, SAGE in the Soviet Union and GALLEX in Europe, are under construction and are scheduled to produce data by 1989. The radioactive 71Ge produced by neutrinos interacting with the gallium detector material is chemically extracted and counted in miniature proportional counters. A

R. T. Kouzes; D. Reynolds

1989-01-01

249

Gallium Concentrations in the Metal Phases of Various Meteorites  

Microsoft Academic Search

The metal phases of seven chondrites and fourteen iron meteorites have been analyzed for gallium by neutron activation. Gallium is quite uniform in the ordinary H- and L-group chondrites and averages 12 ppm. The metal phase of the Abee enstatite chondrite contains 64 ppm Ga. It has previously been established that gallium abundances in iron neteorites are distributed around certain

James C. Cobb; George Moran

1965-01-01

250

Gallium Zeolites for Light Paraffin Aromatization  

SciTech Connect

The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

Price, G.L.; Dooley, K.M.

1999-02-10

251

Production of gallium atoms by excimer laser photolysis of trimethyl gallium  

SciTech Connect

The gas phase kinetics of group III elements such as gallium are important in possible chemically driven energy transfer lasers and in chemical vapor deposition processes in the electronics industry. Excimer laser photodissociation of volatile gallium compounds via multiple photon process provides, in principle, a convenient room temperature source of gallium atoms for study using laser photolysis-laser induced fluorescence techniques. In this paper, we report preliminary results of the multiple photon dissociation of trimethyl gallium at 193 nm. Prompt emission from a number of excited gallium states (5 /sup 2/S, 4 /sup 2/D, 6 /sup 2/S, 6 /sup 2/P/sup 0/, 5 /sup 2/D, and 4 /sup 4/P) has been observed. The time histories of the ground state (4/sup 2/P/sup 0//sub 1/2/) and the metastable (4 /sup 2/P/sup 0//sub 3/2/) have been measured using laser induced fluorescence. The resulting time profiles are complicated even in the absence of a reactant gas by the apparent production of ground state gallium at relatively long times (approx. 10 ..mu..s) after the excimer laser pulse. Possible mechanisms for this (i.e., radical reactions to produce gallium, energy transfer cascading from high lying metastable states, ionic processes, etc.) are being investigated. These results indicate that the photodissociation of trimethyl gallium at 193 nm is complex. Photolysis studies at other wavelengths and with other precursors are in progress to find a cleaner source of gas phase atomic gallium for kinetic studies. 20 refs., 7 figs.

Baughcum, S.L.; Oldenborg, R.C.; Winn, K.R.; Hof, D.E.

1985-03-01

252

Low Temperature Spin Structure of Gadolinium Titanate  

NASA Astrophysics Data System (ADS)

Many rare earth pyrochlore oxides exhibit exotic spin configurations at low temperatures due to frustration. The nearest neighbor coupling between spins on the corner-sharing tetrahedral network generate geometrical magnetic frustration. Among these materials, gadolinium titanate (Gd2Ti2O7) is of particular interest. Its low temperature ordered phases are not yet understood theoretically. Bulk thermal measurements such as specific heat and magnetic susceptibility measurements find two phase transitions in zero external field, in agreement with simple mean field calculations. However, recent neutron scattering experiments suggest a so-called 4-k spin structure for intermediate phase and a so called canted 4-k structure for lower temperature phase that does not agree with either mean-field theory or Monte Carlo simulation which find the 1-k state and Palmer-Chalker state respectively as the lowest free energy configuration for those phases. In our work, we study the 4-k structure in detail and present a new phase diagram for dipolar Heisenberg spins on a pyrochlore lattice, certain portions of which describe gadolinium titanate.

Javanparast, Behnam; McClarty, Paul; Gingras, Michel

2012-02-01

253

Surface passivation of Gallium Arsenide  

NASA Astrophysics Data System (ADS)

The surface passivation of Si doped (100) n-type gallium arsenide (GaAs) by chemical treatment with phosphoric acid (H3P04), phosphorus trichloride (PCl3), and sodium sulfide (Na2S.9H2O) was investigated using room temperature photoluminescence (PL) and a capacitance-voltage (C-V) and current-voltage (I-V) profiler. After passivation, the 300K PL increased for all three treatments. Best results obtained showed improvements of 1.4, 3.5 and 5.3 times greater of PL efficiency for H3PO4, PCl3 and Na2S, respectively, over unpassivated samples that were only cleaned and etched. Samples that were cleaned, etched and washed with de-ionized 18 Mohm, 5 ppm O2 content water showed about the same PL increase as the H3PO4 passivation. Capacitance-voltage and I-V profile curves showed the removal of the surface oxide hysteresis with the PCl3 passivated samples; however, re-oxidation seems to take longer than normal and to be confined to the passivation layer.

Racicot, Robert J.

1988-04-01

254

/sup 67/Gallium lung scans in progressive systemic sclerosis  

SciTech Connect

/sup 67/Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the /sup 67/Gallium Uptake Index. The mean total pulmonary /sup 67/Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the /sup 56/Gallium uptake. Increased pulmonary /sup 67/Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity.

Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

1983-08-01

255

REE Zoning in Garnet as a Record of Pressure Changes During Growth  

NASA Astrophysics Data System (ADS)

Radial variations in the concentrations of rare-earth elements (REE) in garnets from metamorphic rocks of the Llano Uplift of central Texas display systematic patterns that indicate that the REE may be sensitive recorders of changes in pressure during growth. LA-ICP-MS analysis of REE concentrations was performed at interior and rim positions of centered sections through garnets from garnet-clinopyroxenites at Whitt Ranch (WR) and from garnet-clinopyroxenites (PHM) and pelitic gneisses (PHP) at Purdy Hill. REE-abundance curves are flatter for PHM garnets than for WR garnets. Curves for WR garnets flatten towards rims; curves for PHM garnets steepen towards rims; and curves for PHP garnets first steepen in HREE toward rims, and then flatten, with negative slopes in HREE for some rim analyses. WR garnets contain negative Eu anomalies in interiors that disappear towards rims; PHM garnets contain small positive Eu anomalies throughout; and PHP garnets contain small negative Eu anomalies in both interiors and rims. Garnet-inclusion suites document that PH garnets formed at higher pressures than WR garnets, which suggests that flatter REE-abundance curves reflect higher pressures, corroborating the observations of Bea et al. (1997, Geostds Newsltr 21:253). Flattening of curves from interiors to rims suggests that WR garnets grew as pressure increased, which is supported by the distribution of inclusions in garnet: interiors contain plagioclase inclusions but rims do not, accounting for the rimward loss of negative Eu anomalies. Conversely, steepening of curves in PHM garnets may imply that they grew during decompression, although positive Eu anomalies suggest breakdown of plagioclase during garnet growth. Relative depletion of HREE in the rims of PHP garnets may record the growth of xenotime. Application of the Gd/Dy-in-garnet barometer of Bea et al. to PHP samples yielded pressures of 0.4-0.5 GPa, inconsistent with their eclogite-facies origin and with prior grt-opx barometry at PH of 1.5-2.1 GPa. Thus, although the shapes of the REE-abundance curves for the Llano garnets change systematically with pressure in a manner similar to the pattern described by Bea et al., the ratio of Gd/Dy alone fails to capture the complex behavior of the REE over the full range of pressure commonly experienced by crustal metamorphic rocks.

Lane, E. D.; Carlson, W. D.

2003-12-01

256

New SMU Gallium Fixed-Point Cells  

NASA Astrophysics Data System (ADS)

In the framework of the European research project EURAMET 732, the Slovak Institute of Metrology (SMU) built three primary gallium fixed-point cells of different designs. The cells are designed for the calibration of the long-stem SPRT. In regard to the procedure commonly used at SMU when realizing the gallium point, the cells are designed for use in a stirred liquid bath. This article provides information about the cell designs, materials used, method of filling, and results of the performed experiments. The experiments were focused on the study of the cells' metrological characteristics, some effects that could influence the melting-point temperature and the effect of the melted metal fraction on the immersion profile. New cells were compared with the SMU reference gallium cell.

Ranostaj, Juraj; ?uriš, Stanislav; Knorová, Renáta; Kaskötö, Mariana; Vysko?ilová, Irena

2011-08-01

257

Bigyrotropic photonic crystals  

NASA Astrophysics Data System (ADS)

Electromagnetic wave propagation in a one-dimensional magnetic photonic crystal made of bigyrotropic magnetic yttrium-iron garnet and nonmagnetic gadolinium-gallium garnet is theoretically investigated using the 4×4 transfer matrix method for longitudinal magneto-optical configuration. Band gaps in the electromagnetic spectrum are numerically obtained and appear to depend on the helicity and direction of light propagation through the magnetic photonic crystal.

Lyubchanskii, Igor L.; Dadoenkova, N. N.; Lyubchanskii, M. I.; Shapovalov, E. A.; Lakhtakia, Akhlesh; Rasing, Theo

2004-08-01

258

Spectra of bigyrotropic magnetic photonic crystals  

NASA Astrophysics Data System (ADS)

We calculated the photonic band gap spectra of a one-dimensional magnetic photonic crystal made of alternating layers of bigyrotropic magnetic yttrium-iron garnet and nonmagnetic gadolinium gallium garnet. The forbidden regimes or band gaps in the electromagnetic wave spectrum were numerically obtained for the transversal magneto-optical configuration and compared with those for the polar and longitudinal magneto-optical configurations.

Lyubchanskii, I. L.; Dadoenkova, N. N.; Lyubchanskii, M. I.; Shapovalov, E. A.; Lakhtakia, A.; Rasing, Th.

2004-12-01

259

Damping of magnetostatic spin waves in substrates  

Microsoft Academic Search

We study damping of magnetostatic spin waves associated with the dielectric and ohmic losses in substrates. It is shown that I) the magnitude of losses in the gallium- gadolinium garnet substrate for high-quality films is comparable with the damping in the ferrite substrate itself; 2) the necessity of using epitaxial films at low temperatures, as well as at frequencies 15-20

M. G. Balinskii; V. V. Danilov; A. Yu. Nechiporuk; V. M. Talalaevskii

1986-01-01

260

Investigation on growth and laser properties of GGG:(Nd,Cr) single crystals  

SciTech Connect

Investigation on the growth and laser properties of gadolinium gallium garnet crystal doped with neodymium and chromium is reported. As the segregation coefficient of Nd in GGG is less than 1 and that of Cr is greater than 1, a modified Czochralski method for growth is adopted in order to keep the dopants being uniform in the grown crystal.

Zhang; Lin; Liu; Liu; Zhu

1986-04-04

261

Investigation on Growth and Laser Properties of GGG:(Nd,Cr) Single Crystals.  

National Technical Information Service (NTIS)

Investigation on the growth and laser properties of gadolinium gallium garnet crystal doped with neodymium and chromium is reported. As the segregation coefficient of Nd in GGG is less than 1 and that of Cr is greater than 1, a modified Czochralski method...

L. Zhang C. Lin H. Liu L. Liu H. Zhu

1986-01-01

262

Anisotropy study of garnet films grown over substrates populated with gold nanoparticles  

NASA Astrophysics Data System (ADS)

Anisotropy of garnet films grown by liquid phase epitaxy (LPE) over (100)-oriented garnet substrates populated with gold nanoparticles is studied. The results of ferromagnetic resonance (FMR) and optical hysteresis loop measurements as well as optical images of domain structures of LPE-grown garnet films are presented and discussed.

Lang, G.; Bowen, D.; Hung, L.; Krafft, C.; Mayergoyz, I.

2012-04-01

263

Garnet layers prepared by liquid phase epitaxy for microwave and magneto-optical applications – a review  

Microsoft Academic Search

The magnetic iron garnets possess two outstanding properties, an excellently narrow linewidth of the ferromagnetic resonance and a magneto-optical activity that is without competition when the iron garnet is substituted with bismuth. Here the growth of bismuth substituted iron garnet layers with a bismuth content of up to 1.8 formula units is reported. The influence of solution compositions and undercooling

T. Aichele; A. Lorenz; R. Hergt; P. Görnert

2003-01-01

264

Combined in situ X-ray diffraction and Raman spectroscopy on majoritic garnet inclusions in diamonds  

Microsoft Academic Search

Mineral inclusions in Sao Luiz diamonds have been characterized using angle dispersive X-ray diffraction and Raman spectroscopy. We identified two different garnet phases coexisting with an omphacitic pyroxene. They represent disintegration products of a former homogeneous majorite-rich garnet phase. The two garnets have significantly different cell parameters but are tightly intergrown with their unit cells parallel to each other. The

Martin Kunz; Philippe Gillet; Guillaume Fiquet; Violaine Sautter; Heinz Graafsma; Pamela Conrad; Jeff Harris

2002-01-01

265

Garnet from Cr and Ca-saturated mantle: implications for diamond exploration  

Microsoft Academic Search

An exotic trend of positively correlated Cr and Ca occurs in garnet from xenoliths in the Jericho kimberlite, northern Canada. The trend shows significantly less enrichment in Cr with increasing Ca than the common lherzolitic trend characteristic of kimberlite concentrate. The trend is found only in spinel–garnet peridotite xenoliths and is attributed to equilibration of garnet with spinel. The compositional

M. G. Kopylova; J. K. Russell; H. Cookenboo

2000-01-01

266

Iso Observations of Ceres: Evidence For Garnet?  

NASA Astrophysics Data System (ADS)

Thermal IR spectra of Ceres have been obtained by ISO in 1997. These data have been compared with various laboratory spectra by [1], but no close match was found. However, there is one salient spectral feature in the ISO data, which consists in a sharp slope and a maximum located at 9.7aµm. We interpret this signature as a Christiansen feature located at particularly long wavelength. Other asteroids observed by ISO have similar signatures located at much shorter wavelength, ranging from 8.0 to 9.0aµm. Only Fe-rich olivine and garnets are known to exhibit a Christiansen feature at such long wavelength. The best candidate mineral is actually andradite, which appears in rocks such as serpentine, eclogite and peridotite, all formed by general metamorphism under pressure and temperature consistent with the interior of a 1000 km-diameter body. Therefore, this material would have form deep inside Ceres, and would have subsequently been exposed at the surface, perhaps in relation with the Piazzi region recently observed by HST [2]. The Christiansen maximum is located at shorter wave- length in the KAO spectra of Ceres [3], which are actually composited from different observations. This difference may be related to the orientation of Ceres and to the visi- bility of the Piazzi region at the time of observations. The presence of material formed in high pressure and temperature is consistent with observations from [4]. [1]Dotto et al. (2000) A&A358, 697-702 [2]Parker et al. (2002) Astron. J. [3]Cohen et al. (1998) Astron. J. 115, 1671-1679. [4]Witteborn et al. (2000) ASP Conf. Ser. 196, 197-200.

Erard, S.; Le Bras, A.

267

Method for Plutonium-Gallium Separation by Anodic Dissolution of a Solid Plutonium-Gallium Alloy  

DOEpatents

Purified plutonium and gallium are efficiently recovered from a solid plutonium-gallium (Pu-Ga) alloy by using an electrorefining process. The solid Pu-Ga alloy is the cell anode, preferably placed in a moving basket within the electrolyte. As the surface of the Pu-Ga anode is depleted in plutonium by the electrotransport of the plutonium to a cathode, the temperature of the electrolyte is sufficient to liquify the surface, preferably at about 500 C, resulting in a liquid anode layer substantially comprised of gallium. The gallium drips from the liquified surface and is collected below the anode within the electrochemical cell. The transported plutonium is collected on the cathode surface and is recovered.

Miller, William E.; Tomczuk, Zygmunt

1998-12-08

268

Luminescence characterization of cerium doped yttrium gadolinium aluminate phosphors  

NASA Astrophysics Data System (ADS)

Yttrium gadolinium aluminate ((Y1-xGdx)3 Al5O12:Ce) doped cerium phosphors with the different yttrium and gadolinium concentration were prepared by a wet-chemical route via the reagent simultaneous addition technique (WCS-SimAdd). The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL), radioluminescence (RL) of cerium doped yttrium gadolinium aluminate phosphors. With increasing Gd dopant concentration, the PL intensity was shifted to the red region. Preliminary RL measurements were performed to further evaluate these newly prepared materials. Intense RL was observed that is typical of Ce3+ doped structure.

Uysal Satilmis, S.; Ege, A.; Ayvacikli, M.; Khatab, A.; Ekdal, E.; Popovici, E. J.; Henini, M.; Can, N.

2012-09-01

269

Kinetics of the Pyroxene-Garnet Transformation: Preliminary Results  

NASA Astrophysics Data System (ADS)

Previous experimental studies have shown that in a "pyrolite" mantle, Ca-poor pyroxene is completely dissolved into garnet at about 10 GPa, and Ca-rich pyroxene at about 16 GPa. Current mineralogical view of the Earth's upper mantle and the transition zone is mainly based on these results with the assumption that the pyroxene-garnet transformation proceeds with relative ease under the mantle conditions. In order to assess the validity of this critical assumption, knowledge about kinetics of the transformation is required. Here we report the preliminary results from an experimental study designed to investigate kinetics of the pyroxene to garnet transformation. A 2000-ton uniaxial-split-sphere high-pressure apparatus was used to achieve mantle conditions of 6 to 14.5 GPa and 1200-1400 °C. Powdered KLB-1, whose bulk composition is close to "pyrolite", was used as starting material. The powder sample was annealed at 6 GPa and 1300 °C for at least 4 hours before the target pressure and temperature were applied. Run duration ranged from 4 to 21 hours. Run products were analyzed using a micro-diffractometer and an electron microprobe. It was found that substantial amount of Ca-poor pyroxene was still present in all samples, including the sample in which olivine has completely transformed to wadsleyite. Concentrations of oxide indicators for phase transition in garnet, such as SiO2, CaO, and Al2O3, were fairly unchanged from the pre-annealed material, suggesting that the transformation is extremely slow in occurring. We also observed exsolutions of Ca-rich pyroxene or garnet in Ca-poor pyroxene, but they were too small to be analyzed. These results indicate that the pyroxene-garnet phase transformation can take complicate paths, and metastable pyroxene may exist in the Earth's lower upper mantle and the transition zone.

Sojda, S. M.; Wang, L.

2002-12-01

270

Elasticity of majorite, MgSiO 3 tetragonal garnet  

NASA Astrophysics Data System (ADS)

The adiabatic elastic moduli of single-crystal MgSiO 3 in the tetragonal garnet structure have been measured at ambient conditions using Brillouin spectroscopy. The results (in GPa) are: C11 = 286.4 ± 1.3; C33 = 280.1 ± 1.8; C44 = 85.0 ± 0.7; C66 = 93.2 ± 1.1; C12 = 83.0 ± 2.9; C23 = 104.9 ± 2.4; C16 = 1.4 ± 1.3. The isotropic properties of MgSiO 3 majorite are KVRH = 159.8 ± 4.4 GPa and ?VRH = 89.7 ± 0.6 GPa. An empirical relationship describing garnet elasticity along the pyrope-majorite join indicates that the bulk modulus increases by about 8% and the shear modulus by about 2% going from majorite to pyrope. The tetragonal garnet structure is characterized by ordering on the octahedral site; axial elastic moduli differ as a result of differing axial arrangements of MgO 6 and SiO 6 units. The overall softening of the garnet structure with increasing majorite content is attributed to the presence of weak magnesium octahedra and may also reflect the extensive cross-linking that is typical of garnets. Two factors contribute to the observed elasticity of majorite: coupled substitution of aluminum by magnesium + silicon, and structural ordering on the octahedral site. In this case, the compositional effect is probably minor, but until we have elasticity measurements on completely disordered 'cubic' MgSiO 3 garnet, the relative importance of the two components cannot be easily distinguished.

Gerald Pacalo, Rosemary E.; Weidner, Donald J.

1997-01-01

271

Distribution Coefficient of Germanium in Gallium Arsenide Crystals Grown from Gallium Solutions  

Microsoft Academic Search

Gallium arsenide crystals doped with germanium were grown from gallium solutions at 900°–875°C. The Ge concentration in the liquid was varied from 0.004 to 56 at.%, and the Ge concentration in the GaAs crystals determined using radiotracer and other techniques. The Ge concentration in the solid varied linearly with increasing Ge concentration in the liquid up to 5 at.% and

F. E. Rosztoczy; K. B. Wolfstirn

1971-01-01

272

Foundations of ohmic contact formation on aluminum gallium nitride\\/gallium nitride heterostructures  

Microsoft Academic Search

Aluminum gallium nitride (AlGaN)\\/gallium nitride (GaN) high electron mobility transistors (HEMTs) have tremendous potential for application in high frequencies, high temperatures and microwave and mm power amplifications. Fabrication of Ohmic contacts for such devices that meet the stringent low-resistance, high thermal stability and smooth surface morphology requirements has been challenging. In the cases where Ohmic behavior can be achieved, a

Fitih Mustefa Mohammed

2007-01-01

273

Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection.  

PubMed

A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 ?g/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli. PMID:23877680

Ball, Katherine R; Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L; Blyth, Robert I R; Sham, Tsun-Kong; Dowling, Patricia M; Thompson, Julie

2013-07-22

274

Origin of the magneto-optical properties of iron garnets  

Microsoft Academic Search

The analysis of experimental optical and magneto-optical spectra of iron garnets R3Fe5O12 shows that all peculiarities of these spectra in a wide range, 2-6 eV, can be explained by means of oxygen-to-iron charge-transfer (CT) transitions in octahedral FeO9-6 complexes and tetrahedral FeO5-4 complexes, being the main magneto-optical centres in iron garnets. The values of effective orbital Landé factors and spin-orbit

A. S. Moskvin; A. V. Zenkov; E. I. Yuryeva; V. A. Gubanov

1991-01-01

275

Ultraviolet Photoelectron Spectra of Gallium Arsenide Clusters.  

National Technical Information Service (NTIS)

The ultraviolet photoelectron spectra (UPS) of mass-selected negative gallium arsenide cluster ions in the 2-50 atom size range was measured with a photon energy of 7.9 eV. The measured photodetachment thresholds displayed a strong even/odd oscillation th...

C. Jin J. Conceicao K. J. Taylor R. E. Smalley

1990-01-01

276

Interfacing epitaxial oxides to gallium nitride  

Microsoft Academic Search

Molecular beam epitaxy (MBE) is lauded for its ability to control thin film material structures at the atomic level. This precision of control can improve performance of microelectronic devices and cultivate the development of novel device structures. This thesis explores the utility of MBE for designing interfaces between oxide epilayers and the wide band gap semiconductor gallium nitride (GaN). The

Mark Daniel Losego

2008-01-01

277

SPECT gallium imaging in abdominal lymphoma  

SciTech Connect

A case of non-Hodgkin's lymphoma of the abdomen studied by gallium SPECT imaging is reported. The tomographic slices accurately demonstrated the location of residual disease after chemotherapy in the region of the transverse mesocolon. Previous transmission CT had shown considerable persistent retroperitoneal lymphadenopathy, but was not helpful in determining the presence of viable lymphoma.

Adcock, K.A.; Friefeld, G.D.; Waldron, J.A. Jr.

1986-05-01

278

Photoluminescence Study of Germanium Implanted Gallium Arsenide.  

National Technical Information Service (NTIS)

The low temperature photoluminescence properties of Ge implanted Gallium Arsenide has been analyzed. Samples were singly implanted with Ge and As, and with Ge and Ga. The substrate used was semi-insulating Chromium-doped GaAs. All ions were implanted at r...

B. P. Thoma

1985-01-01

279

Producing gallium arsenide crystals in space  

Microsoft Academic Search

The production of high quality crystals in space is a promising near-term application of microgravity processing. Gallium arsenide is the selected material for initial commercial production because of its inherent superior electronic properties, wide range of market applications, and broad base of on-going device development effort. Plausible product prices can absorb the high cost of space transportation for the initial

R. L. Randolph

1984-01-01

280

High efficiency monolithic gallium nitride distributed amplifier  

Microsoft Academic Search

The first gallium-nitride monolithic distributed amplifier is demonstrated. A nonuniform design allows the removal of the drain line dummy load with a concomitant increase in efficiency, An optimized nonuniform design shows a 10% increase in efficiency over an optimized uniform design having the dummy termination

Bruce M. Green; Sungjae Lee; Kenneth Chu; Kevin J. Webb; Lester F. Eastman

2000-01-01

281

A classification scheme for mantle-derived garnets in kimberlite: a tool for investigating the mantle and exploring for diamonds  

Microsoft Academic Search

A new empirical method has been devised for classification of mantle-derived garnets in kimberlite. Simple chemical screens have been developed to distinguish between garnets from different parageneses, based on Mg, Fe, Ca, Cr, Ti and Na values of published analyses of garnets from >2000 ultramafic xenoliths in kimberlite. Although crustal garnets are typically uncommon as xenocrysts in kimberlite, the first

Daniel J. Schulze

2003-01-01

282

An Excel spreadsheet to recast analyses of garnet into end-member components, and a synopsis of the crystal chemistry of natural silicate garnets  

Microsoft Academic Search

A Microsoft Excel spreadsheet has been programmed that allows users to calculate with ease the molar proportions of garnet end-members from chemical analyses. Recent advances in the understanding of the crystal chemistry of natural garnets, especially of the Ti-bearing garnets, are used to evaluate 29 end-members (15 species and 14 hypothetical end-members) for each analysis. The amounts of Fe2+ and

Andrew J. Locock

2008-01-01

283

Dose dependent disposition of gallium-67 in rats  

SciTech Connect

Radioactive gallium-67 has been employed as a diagnostic and follow-up agent for cancer therapy. Currently gallium nitrate is undergoing Phase I clinical studies. A million fold increase in the concentration of the carrier gallium citrate over the range of carrier-free gallium-67 (pgm) to 1.0 ..mu..g caused no significant alteration in the disposition of gallium-67 in rats.Gallium-67 was eliminated from blood with a biological t1/2 of 4.1 days. A linear tissue binding profile was observed for gallium-67 over this concentration range. A multi-compartment pharmacokinetic model was developed in which all the tissues studied were treated as separate compartments. At 1.0 mg dose level, significant alteration in the disposition of gallium-67 was observed in rats, > 95% of the initial radioactivity was characteristic reappearance of the radioactivity in the blood approximately 4 hours after dosing leading to a ''hump'' in the blood concentration-time profiles. Following the 1.0 mg dose low tissue levels were observed, except for the kidneys, which contained about 8% of the administered dose per gram of the tissue one-half hour after dosing. A non-linear tissue binding profile was observed to be associated with gallium at high doses. It was hypothesized that the rapid loss of gallium-67 from the vascular system following the high doses of gallium citrate was due to the accumulation of the drug in the kidneys where it was eventually eliminated via urine. The kidneys thus would act as a temporary storage site for gallium. It was concluded that the dose-related renal toxicity associated with gallium therapy may be attributed to the kidney's role as a temporary storage site following high doses.

Gautam, S.R.

1982-01-01

284

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary and secondary germanium and gallium subcategory. 421.180...SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180...Description of the primary and secondary germanium and gallium subcategory. The...

2009-07-01

285

40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary and secondary germanium and gallium subcategory. 421.180...SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180...Description of the primary and secondary germanium and gallium subcategory. The...

2010-07-01

286

Gallium 67 scintigraphy in glomerular disease  

SciTech Connect

To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

1988-12-01

287

Gallium nitride nanowire electromechanical resonators  

NASA Astrophysics Data System (ADS)

Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of energy dissipation not present in the as-grown NWs. By cooling the device to 8 K, Q increases by an order of magnitude to above 104, with a highest value to date of 26,000 under vacuum. We explore additional NW properties through the thermal noise in the NW's mechanical motion and the exponential decay of mechanical motion in the presence of burst drive. Finally, we investigate the low-frequency 1/f parameter noise displayed by f0. We show that the noise in f0 is consistent with noise in the NW's resistance leading to temperature noise from local Joule heating, which in turn generates resonance frequency noise. For sensor applications, there will be optimal drive conditions that balance the f 0 noise with the signal-to-noise ratio of the system. With these insights, along with the simple drive and readout technique, these GaN-NW doubly clamped resonators have significant potential for high-resolution sensing applications.

Gray, Jason Michael

288

Isomorphism of actinides and REE in synthetic ferrite garnets  

NASA Astrophysics Data System (ADS)

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.

Livshits, T. S.

2010-02-01

289

Thermal conductivity of disordered garnets from infrared spectroscopy  

Microsoft Academic Search

The thermal conductivity (k) of garnets is calculated from a formula originating with Debye, adapted to treat the vibrations in a solid as a collection of damped harmonic oscillators. Our model utilizes phonon lifetimes obtained from Kramers-Kronig analyses of existing IR reflectivity spectra, as well as new data presented here, and calculates k at ambient conditions within a nominal uncertainty

P. A. Giesting; A. M. Hofmeister

2002-01-01

290

Domain Lattice Ferromagnetic Resonance in Magnetic Garnet Thin Films  

Microsoft Academic Search

We report on domain lattice ferromagnetic resonance (FMR) data taken on magnetic garnet thin films of the same general variety as those used in currently produced bubble memory devices. Of special interest is our use of optically observed domain lattice geometry and domain dimensions to make possible a more complete qualitative and quantitative correlation of theory and experiment. The background

Edwin Carl Myers

1981-01-01

291

Garnets for short wavelength magneto-optic recording  

Microsoft Academic Search

The bismuth substituted iron garnets have attracted considerable attention as alternative blue wavelength magneto-optic recording media due to their large magneto-optic effects in the short wavelength region of the visible spectrum. However, these materials currently require a high temperature processing step and have not been deposited on inexpensive substrates with adequate carrier to noise ratios. The low CNR is a

Walter R. Eppler; Mark H. Kryder

1995-01-01

292

Systematic ab initio study of the compressibility of silicate garnets.  

PubMed

The structural properties of the silicate garnets andradite, Ca(3)Fe(2)Si(3)O(12), uvarovite, Ca(3)Cr(2)Si(3)O(12), knorringite, Mg(3)Cr(2)Si(3)O(12), goldmanite, Ca(3)V(2)Si(3)O(12), blythite, Mn(2+)(3)Mn(3+)(2)Si(3)O(12), skiagite, Fe(2+)(3)Fe(3+)(2)Si(3)O(12), calderite, Mn(2+)(3)Fe(3+)(2)Si(3)O(12), and khoharite, Mg(3)Fe(3+)(2)Si(3)O(12), have been investigated with a quantum-mechanical model as a function of applied pressure. The study has been performed with the density functional theory code CASTEP, which uses pseudopotentials and a plane-wave basis set. All structural parameters have been optimized. The calculated static geometries (cell parameters, internal coordinates of atoms and bond lengths), bulk moduli and their pressure derivatives are in good agreement with the experimental data available. Predictions are made for those cases where no experimental data have been reported. The data clearly indicate that the elastic properties of all silicate garnets are dominated by the compressibility of the dodecahedral site. The compression mechanism is found to be based on a bending of the angle between the centers of the SiO(4) tetrahedra and the adjacent octahedra, as in the aluminosilicate garnets. An analysis of the relationship between ionic radii of the cations and the compressibility of silicate garnets is presented. PMID:11262431

Milman, V; Akhmatskaya, E V; Nobes, R H; Winkler, B; Pickard, C J; White, J A

2001-04-01

293

Plasmon resonance enhancement of magneto-optic effects in garnets  

NASA Astrophysics Data System (ADS)

Enhancement of magneto-optic effects by strong electric fields induced by plasmon resonances in metallic nanoparticles placed on (or embedded into) garnets is discussed. Theoretical and computational results on excitation of plasmon resonances in such particles are reported and compared to available experimental data.

Mayergoyz, I. D.; Lang, G.; Hung, L.; Tkachuk, S.; Krafft, C.; Rabin, O.

2010-05-01

294

Microwave magnetostatic delay devices based on epitaxial yttrium iron garnet  

Microsoft Academic Search

Low-loss magnetostatic wave (MSW) propagation in epitaxial yttrium iron garnet (YIG) films allows the development of a technology which is complementary to that of surface acoustic waves (SAW's), but capable of operation in the microwave range from 1 to greater than 12 GHz. Experimental low-loss dispersive and nondispersive tapped delay lines are described. Future developments of MSW's involving signal routing

J. D. Adam; J. H. Collins

1976-01-01

295

Synthesis of yttrium iron garnet precursor particles by homogeneous precipitation  

Microsoft Academic Search

Yttrium iron garnet (YIG) precursor particles were obtained by homogeneous precipitation in a nitrate salt solution by a reaction involving the thermal decomposition of urea. Chemical analysis indicated that solid phases were initially precipitated with sequential iron ion content. The precipitate formed was an amorphous mixed iron oxide phase. The complex composition and the thermal decomposition of the precipitate were

Y. S. Ahn; M. H. Han; C. O. Kim

1996-01-01

296

Preparation and characterization of spherical yttrium iron garnet via coprecipitation  

Microsoft Academic Search

The purpose of this work is to obtain spherical particles yttrium iron garnet (YIG) by coprecipitation technique. The spherical particles were obtained from either nitrate or chloride salt solutions by controlling the precipitation medium. Different agents of dispersion such as PVP and ammonium iron sulfate were used to optimize the shape and size of YIG. Samples were characterized by X-ray

M. Jafelicci; R. H. M. Godoi

2001-01-01

297

Synthesis and Characterization of Yttrium Iron Garnet Nanoparticles  

Microsoft Academic Search

Yttrium iron garnet (YIG) was synthesized from a citrate gel containing ethylene glycol. The conditions for obtaining the pure phase depending on the citric acid\\/ethylene glycol ratio were studied. The sizes of the obtained particles ranged from 20 to 500 nm with the annealing temperature. Particles exhibited a rounded surface morphology, without faceted borders.

P. Vaqueiro; M. P. Crosnier-Lopez; M. A. López-Quintela

1996-01-01

298

Thermodynamic properties of aqueous gadolinium perrhenate and gadolinium chloride from high dilution calorimetry at extreme temperatures and pressures.  

PubMed

The heat of solution of solid cubic gadolinium oxide has been measured in noncomplexing perrhenic acid solutions at very high dilutions (10(-4) m) up to 596.30 K, from which the standard state thermodynamic properties of aqueous gadolinium perrhenate were determined up to 623.15 K. From the measured differences between similar properties of aqueous sodium chloride and perrhenate, thermodynamic properties for aqueous gadolinium chloride were obtained by ionic additivity. Data for the hydrolysis of Gd3+(aq) were obtained by separate determinations. The enthalpy of solution of gadolinium chloride at 623.15 K obtained from this research (-2.7 MJ mol(-1)) is apparently larger than any other recorded for a chemical reaction involving aqueous systems. Standard state partial molal heat capacities for ThCl4(aq) were predicted up to 623.15 K. PMID:19191504

Djamali, Essmaiil; Cobble, James W

2009-02-26

299

Raman spectroscopic study of synthesized Na-bearing majoritic garnets  

NASA Astrophysics Data System (ADS)

Majoritic garnets in diamond have been considered as the sample from mantle transition zone (e.g. Moore and Gurney, 1985). For non-destructive, in-situ Raman analysis, Gillet et al. (2002) systematically checked chemistry and Raman peak of various majoritic garnets in diamond. They treated majoritic component as number of excess-silica than 3.0 per formula unit. However, in the basaltic system, majorite garnets also have significant amounts of Na. Na substitution is coupled with Si and Ti as follows; Na +Ti = Ca +Al (Ringwood and Lovering, 1970), Na +Si = Ca + Al (Sobolev and Labrentav, 1971; Ringwood and Major, 1971) or Na + Si = Mg + Al (Gasparik, 1989). Each component in garnet is defined as follows; Mj (majorite) component = ((Si-3)-Na)/2), NaSi (Na2MSi5O12 where M= Ca, Mg, Fe2+) component = (Na-T)/2, and NaTi component = Ti/2. Okamoto and Maruyama (2003) conducted UHP experiments in the MORB + H2O system (KNCFMATSH) at 10-19 GPa. They show that 1) Mj and NaTi component are constant and lower than 0.1 at T = 900 \\deg C, and 2) NaSi component increases drastically above 15 GPa although it is neglibly small at P<15 GPa. Raman spectra was newly analyzed using Okamoto and Maruyama (2003)'s run charges. Above 15 GPa, there is a characteristic sharp peak at 910 cm-1 and broad shoulder between 800 and 900 cm-1 as well as broad band near 960 cm-1. Gillet et at (2002) concluded that the former peak at 910cm-1 is the only reliable signature for the majoritic garnet (Si>3). They also implied that the latter two broad peaks are diagnostic feature for Ti rich garnet (> 1wt% of TiO2) as well as peak at 1030 cm-1. However, in all P range (10-19 GPa) of the present study, TiO2 is higher than 1wt%, and there is a peak at 1030 cm-1. Additional Ti-free experiment at 16 GPa, 1200 \\deg C clearly revealed that Na-bearing majoritic garnet has a significant shoulder at 800-900 cm-1. Ref; Gasparik (1989) CMP, 102,389, Gillet et al. (2002) Am.Min., 87, 312, Moore and Gurney (1985)Nature, 318, 553, Okamoto and Maruyama (2003)PEPI, in press, Ringwood and Lovering (1970) EPSL, 7, 371, Ringwood and Major (1971)EPSL, 12, 411, Sobolev and Labrentav (1971)CMP, 31, 1.

Okamoto, K.

2003-12-01

300

Combined external-beam PIXE and /?-Raman characterisation of garnets used in Merovingian jewellery  

NASA Astrophysics Data System (ADS)

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, /?-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.

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

2002-04-01

301

Preparation and characterization of yttrium gallium garnet nanoparticles by citrate sol–gel method at low temperature  

Microsoft Academic Search

The Y3Ga5O12 (YGG) nanoparticles with pure phase have been successfully prepared with Y(NO3)3 and Ga2O3 at lower sintering temperature and shorter holding time. The process of citrate sol–gel method was simple and the cost was very low. The thermal behavior of the YGG precursor was characterized by thermogravimetry\\/differential thermal analysis (TG\\/DTA). The crystallization temperature was determined by X-ray powder diffraction

Fapeng Yu; Duorong Yuan; Xiufeng Cheng; Xiulan Duan; Xinqiang Wang; Lingmei Kong; Lihua Wang; Zhanfa Li

2007-01-01

302

Gallium arsenide infrared windows for high-speed airborne applications  

NASA Astrophysics Data System (ADS)

Large (7- by 16-inch) plates of semi-insulating gallium arsenide suitable for use as external infrared transmitting windows were grown using a unique compounding process. The plates were grown in an open tube system, the gallium arsenide being solidified from a stoichiometric melt. Detailed growth conditions are discussed. The optical and physical properties of this material are compared with other candidate infrared (IR) optical materials. In addition, some results of captive flight tests comparing gallium arsenide with germanium are given

Brau, M. J.; Stone, L. E.; Boucher, M. W.

1982-10-01

303

Field emission from gallium-doped zinc oxide nanofiber array  

Microsoft Academic Search

Gallium-doped nanostructural zinc oxide fibers have been fabricated by vapor-phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air. The zinc oxide fibers grew along [002] direction, forming a vertically aligned array that is predominantly perpendicular to the substrate surface. With a gallium doping concentration of 0.73 at. %, the corresponding carrier concentration

C. X. Xu; X. W. Sun; B. J. Chen

2004-01-01

304

Gallium scintigraphy in the detection of amiodarone lung toxicity  

SciTech Connect

Fourteen gallium scans were obtained in 11 patients suspected of having amiodarone lung toxicity on the basis of clinical findings, pulmonary function tests, and chest radiographs. All 11 patients had abnormal scans. Gallium accumulates in various inflammatory and neoplastic lesions, but despite this nonspecificity, the findings suggest gallium scintigraphy is a useful procedure to detect amiodarone lung toxicity when used in the appropriate clinical setting.

Moinuddin, M.; Rockett, J.

1986-09-01

305

Interactions of zircaloy cladding with gallium -- 1997 status  

SciTech Connect

A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

1997-11-01

306

Interactions of Zircaloy cladding with gallium: 1998 midyear status  

SciTech Connect

A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

1998-06-01

307

The duration of prograde garnet crystallization in the UHP eclogites at Lago di Cignana, Italy  

NASA Astrophysics Data System (ADS)

The distinct core-to-rim zonation of different REEs in garnet in metamorphic rocks, specifically Sm relative to Lu, suggests that Sm-Nd and Lu-Hf isochron ages will record different times along a prograde garnet growth history. Therefore, REE zonations in garnet must be measured in order to correctly interpret the isochron ages in terms of the garnet growth interval, which could span several m.y. New REE profiles, garnet crystal size distributions, and garnet growth modeling, combined with previously published Sm-Nd and Lu-Hf geochronology on a UHP eclogite of the Zermatt-Saas Fee (ZSF) ophiolite, Lago di Cignana (Italy), demonstrate that prograde garnet growth of this sample occurred over a ~ 30 to 40 m.y. interval. Relative to peak metamorphism at 38 to 40 Ma, garnet growth is estimated to have begun at ~ 11 to 14 kbar pressure at ~ 70 to 80 Ma. Although such a protracted garnet growth interval is surprising, this is supported by plate tectonic reconstructions which suggest that subduction of the Liguro-Piemont ocean occurred through slow and oblique convergence. These results demonstrate that REE zonations in garnet, coupled to crystal size distributions, provide a powerful means for understanding prograde metamorphic paths when combined with Sm-Nd and Lu-Hf geochronology.

Skora, Susanne; Lapen, Thomas J.; Baumgartner, Lukas P.; Johnson, Clark M.; Hellebrand, Eric; Mahlen, Nancy J.

2009-10-01

308

Gadolinium Solubility in Peralkaline Borosilicate Glasses  

SciTech Connect

Lanthanide-containing glasses, commonly used for optical and laser applications, are also important in the vitrification of actinide-bearing radioactive wastes. In order to study the effect of glass composition on the solubility of gadolinium, 25 peralkaline (Na/Al >1) borosilicate glasses were studied. Above Gd solubility, liquid-liquid phase separation was found in the glasses with Na/B less than 0.5; and in the glasses with Na/B more than 0.5, crystallization was found. For the samples from which liquid-liquid phase separation was observed, Gd solubility was mostly decided by the concentration of excess Na (e.g. Na-Al). Increasing excess Na will increase Gd solubility. For the samples from which crystallization was observed, Gd solubility was decided by the concentration of B, Si, and Al. Increasing B and Si will increase Gd solubility, but increasing Al will decrease Gd solubility. The solution mechanism of Gd in peralkaline borosilicate glasses is also discussed.

Li, Liyu; Li, Hong; Qian, Maoxu; Strachan, Denis M.

2001-05-03

309

Ultrathin Iron (Fe) - Gallium Arsenide (GaAs) Layer Structures for Wideband Microwave Devices  

NASA Astrophysics Data System (ADS)

There has been increasing interest and activity in the preparation and device application of ultrathin Iron (Fe) films grown on compound semiconductor substrates such as gallium arsenide (GaAs) and zinc selenide (ZnSe). In this paper a brief review on the preparation and characterization of such Fe-GaAs layer structures using the MBE technique, and realization of wideband microwave band-stop filters is presented. The Fe film-based devices possess an important advantage over their yttrium iron garnet (YIG) film-based counterparts in that for a given operating carrier frequency the former requires a much lower bias magnetic field. This is so because the saturation magnetization of the Fe films is more than one order of magnitude larger than that of YIG films. Accordingly, a much higher device operating carrier frequency with large electronic tunability may be achieved more readily in practice using the Fe-GaAs layer structures. An integrated-type microwave band-stop filter was fabricated in such layer structure through a sequence of chemical etching processes to form a microstrip transmission line. A frequency tuning range as large as 10.0 to 33.0 GHz has been accomplished. The experimental results are shown to be in excellent agreement with the theoretical prediction.

Tsai, Chen S.; Lee, Chin C.; Wu, Wei

2001-04-01

310

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

311

IBIC analysis of gallium arsenide Schottky diodes  

Microsoft Academic Search

Semi-insulating (SI) gallium arsenide (GaAs) devices operating as a reverse biased Schottky diode offer an attractive choice as radiation detector at room temperature both in high energy physics experiments and as X-ray image sensors. However, SI GaAs devices contain a high concentration of traps, which decreases the charge collection efficiency (cce), and affects the energy resolution of such detectors working

E. Vittone; F Fizzotti; K Mirri; E Gargioni; P Polesello; A LoGiudice; C Manfredotti; S Galassini; P Rossi; P Vanni; F Nava

1999-01-01

312

Diffusion of iron in gallium selenide  

SciTech Connect

The temperature dependence of the diffusion coefficient of iron in gallium selenide with a defective sphalerite lattice was studied in the range 98-450 C. Iron 55 and Iron 59, in the form of an iron chloride solution, were used as tracers. The activation energies of fast and slow diffusion in alpha-Ga/sub 2/Se/sub 3/ were determined to be, respectively, 25.1 and 21.2 kJ/mole.

Firsova, L.P.

1987-02-01

313

A Gallium multiphase equation of state  

SciTech Connect

A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

Crockett, Scott D [Los Alamos National Laboratory; Greeff, Carl [Los Alamos National Laboratory

2009-01-01

314

Gallium arsenide - Solar panel assembly technology  

Microsoft Academic Search

Gallium arsenide (GaAs) solar cell devices are maturing at 18 percent AM0 efficiencies for liquid phase epitaxy (LPE) technology, and efforts must be intensified placing necessary focus on the development of panel assembly techniques, and ultimately panel manufacturing methods capable of maintaining these high efficiencies for on-panel operation. Key problems and solutions are described which were experienced during the assembly

D. Zemmrich; N. Mardesich; B. Macfarlane; R. Loo

1984-01-01

315

Strongly Photonic Macroporous Gallium Phosphide Networks  

Microsoft Academic Search

A photo-assisted electrochemical etching technique to fabricate macropores in single-crystalline gallium phosphide (GaP) with variable porosity has been developed. Scanning electron microscopy and x-ray diffraction experiments confirm that the material consists of three-dimensional, interconnected ran- dom networks with pore sizes of about 150 nanometers. Optical transmission measurements demonstrate that the nonabsorbing disordered structures strongly scatter light. The photonic strength is

Frank J. P. Schuurmans; Jao van de Lagemaat

1999-01-01

316

The Baksan gallium solar neutrino experiment  

SciTech Connect

A radiochemical /sup 71/Ga-/sup 71/Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented. 43 refs., 1 fig., 1 tab.

Gavrin, V.N.; Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Girin, S.V.

1989-01-01

317

Foreign atom thermodynamics in liquid gallium arsenide  

Microsoft Academic Search

Thermodynamic equilibrium in gallium arsenide crystal growth systems with the components Ga–As–C–B–N–Si–O has been analysed by using a Gibbs energy minimisation computer package. Emphasis is placed on graphical representations to describe the behaviour of C, B, Si and O in the crystal growth melt at 1513K. The various experimentally observed correlations between solute elements in the liquid and the encapsulant

W. A. Oates; H. Wenzl

1998-01-01

318

Gallium-67 radionuclide imaging in acute pyelonephritis  

SciTech Connect

The symptoms and clinical course of patients with acute pyelonephritis are variable; likewise, urinalysis, blood cultures, and excretory urography may be normal or equivocal. The ability of gallium-67 to accumulate in areas of active inflammation was useful in the diagnosis of acute pyelonephritis in 12 cases. A multiplane tomographic scanner was used for imaging four of these patients. Initial experience with this scanner is also discussed.

Mendez, G.; Morillo, G.; Alonso, M.; Isikoff, M.B.

1980-01-01

319

A YIG\\/GGG\\/GaAs-Based Magnetically Tunable Wideband Microwave BandPass Filter Using Cascaded Band-Stop Filters  

Microsoft Academic Search

A yttrium iron garnet\\/gadolinium gallium garnet-gallium arsenide (YIG\\/GGG-GaAs)-based magnetically-tunable wideband microwave band-pass filter with large tuning ranges for the center frequency (5.90-17.80 GHz) and the bandwidth (1.27-2.08 GHz) in the pass-band using a pair of cascaded band-stop filters is reported. The design and numerical simulation of the band-pass filter that incorporates multisegment microstrip meander-lines and 2-D nonuniform bias magnetic fields

Gang Qiu; Chen S. Tsai; Bert S. T. Wang; Yun Zhu

2008-01-01

320

Gallium arsenide for devices and integrated circuits  

SciTech Connect

Gallium Arsenide has long been hailed as the material of the future and it is only in recent years that the technology associated with its growth and processing has matured to the point where IC production can be contemplated at the industrial level. This point has now been reached and the electronics industries in Europe, the USA and Japan are actively moving from research activities into product development using this and related material. The text is divided into 15 chapters: Gallium Arsenide: Physical and Transport Properties; Liquid phase and Vapour Phase Epitaxy of GaAs and Related Compounds; Expitaxial Growth and GaAs: MBE and MOCVD; Characterization of GaAs I: Electrical Techniques; Characterization of GaAsII: Ion Beam Analysis; Ion Implantation; Wet and Dry Processing GaAs; Microwave and Millimetre - Wave Diodes; GaAs Mesfet's and High Electron Mobility Transistors (HEMT); Optoelectronic Devices and Components; Gallium Arsenide Monolithic Microwave Integrated Circuits; GaAs Digital Integrated Circuits; III-V Semiconductors for Solar Cells.

Morgan, D.V.; Thomas, H.

1986-01-01

321

Atoll Garnets in "Achtarandite" Serpentinites: Morphology, Composition and Mode of Origin  

NASA Astrophysics Data System (ADS)

Atoll garnets in aposkarn serpentinite from the Wiluy River, Republic of Sakha-Yakutia, Russia, have the classic form comprising a garnet core, an intermediate zone filled with chlorite-group minerals and an outer garnet atoll. The core of an illustrated example is complexly zoned from schorlomite to grossular-andradite. Morphologically, the core is a rhombic dodecahedral crystal. The atoll crystallized as a tetragon-trisoctahedron with minor rhombic dodecahedron faces and is composed of hibschite and "hydroandradite". The atoll garnet formed as the result of selective dissolution and substitution by chlorite of an internal hibschite zone with columnar structure that became unstable under new conditions of crystallization. The pattern of dissolution traces defects in the garnet crystal. The growth of the atoll garnets reflects the main stages in the evolution of the Wiluy deposit itself and is associated with the development of the Siberian traps.

Galuskina, Irina; Galuskin, Evgeny; W?odyka, Roman; Dzier?anowski, Piotr; Wrzalik, Roman

2007-01-01

322

Fluid-aided incorporation of Y into almandine-pyrope garnet via coupled dissolution-reprecipitation  

NASA Astrophysics Data System (ADS)

In nature almandine-pyrope garnet is a well-known host for a variety of trace elements including (Y+HREE), Sr, HFSE, as well as LREE such as Sm and Nd; all of which have important roles with regard to various geological processes (Kohn, 2009, GCA, 73, 170). For example, Y exchange between xenotime and garnet has been empirically calibrated as a geothermometer (Pyle and Spear, 2000, CMP, 138, 51). Sm/Nd and Lu/Hf dating, using garnet, is a well-known geochronometer (Thöni et al., 2008, Chem Geol, 254, 216). In general, REE + HFSE + Sr have been used to chart garnet growth and subsequently the evolution of the host rock (Konrad-Schmolke et al., 2008, EPSL, 272, 488). Incorporation of Y into garnet is probably the most widely studied trace element. These studies range from stress-induced redistribution of Y in garnet (Røhr et al, 2007, Am Mineral, 92, 1276) to Y zoning during garnet growth (Zeh, 2005, J Petrol, 47, 2335). While the incorporation of Y into garnet has generally been thought to occur either via diffusion or during garnet growth, more recent workers have suggested that incorporation of Y could also be fluid-aided. Fluid-aided incorporation of Y into garnet has been tested in the piston-cylinder apparatus (CaF2 assemblies, cylindrical graphite ovens) at 1000 MPa and 900 °C (8 days duration). Here, 10 mg of 50-200 µm size, inclusion-free, gem quality, fragments of the Gore Mountain garnet (Alm40-49, Py37-43, Gr13-16, Sp1) plus 5 mg 2N NaOH and 2 mg Y2O3 were loaded into a 3 mm diameter, 1 cm long, Au capsule that was then arc-welded shut and placed vertically in the CaF2 assembly such that the NiCr thermocouple tip came halfway up along the Au capsule length. Examination of the garnet fragments after the experiment indicates both high Y mobility and the partial alteration of the garnet in the form of a remobilized Y3Al5O12 component enriching those areas of the garnet along the grain rim. The enriched areas take the form of a series of intergrowths with sharp compositional boundaries, which appear to be defined by specific lattice planes as determined by the crystallographic axes of the garnet. These textures are the result of coupled dissolution-reprecipitation (Putnis, 2002, Min Mag, 66, 689), which essentially has resulted in the pseudomorphic partial replacement of a portion of the original garnet by a re-precipitated garnet now enriched in Y. The result from this study suggest that Y may be incorporated into garnet by the aid of fluids, which are both reactive with garnet and in which Y is mobile. In general, this result has strong implications with respect to incorporation of REE (and more specifically HREE) into garnet. It provides a mechanism by which garnet and other Y-bearing minerals, such as xenotime, may equilibrate hence enhancing their use as geothermometers. It also indicates that with respect to both Sm/Nd and Lu/Hf dating, the garnet geochronometer can be reset. More importantly, it implies that diffusion after or inclusion during garnet growth is not the only way by which trace elements may be incorporated into garnet.

Harlov, D. E.

2009-12-01

323

Microwave Magnetoelectric Coupling in Ferromagnetic-Piezoelectric Nanostructures  

NASA Astrophysics Data System (ADS)

A theory is presented on the effect of an external electric field on ferromagnetic resonance (FMR) spectra of nanobilayers, nanopillars and nanowires of ferrite and piezoelectrics on MgO or gadolinium gallium garnet substrates. Expressions have been obtained relating the FMR line shift to ME coupling constants. Estimates of ME coupling constants are given. With increasing substrate thickness, the theory predicts a decrease in the ME interaction due to the clamping effect. The strongest ME coupling is expected for ferrite nanopillars in a piezoelectric matrix when the pillar height is large compared to substrate thickness. Numerical estimations are obtained for nanostructures of nickel ferrite and PZT or PMN-PT, yttrium iron garnet and PZT or PMN-PT on MgO or gadolinium gallium garnet substrates. The theory is useful for measurements of ME constants and for the design and analysis of electrically controlled high frequency devices.

Pukinsky, Yu. J.; Bichurin, M. I.; Petrov, V. M.; Filippov, A. V.; Bely, S. V.; Srinivasan, G.

2008-03-01

324

Thermal and magnetic properties of Nd\\/3+\\/ in doped garnets  

Microsoft Academic Search

The Schottky specific heats and magnetic susceptibilities of the Nd3+ in five doped garnets, GGG, LuAG, LuGG, YAG and YGG, have been calculated using effective spin Hamiltonian formalism in connection with the crystal field theory in a temperature interval of 30 to 500 K. Both heat capacities and susceptibilities are determined by two different methods. The first method is dealing

Seyfettin Fakioglu

1979-01-01

325

Mixed garnet laser crystals for water vapour detection  

Microsoft Academic Search

The main objective of this work is the realization of a ground state laser at the required wavelengths of the differential absorption lidar (DIAL)-transmitter, the emission wavelengths of each crystal-type has been analysed. Two possible Nd-doped garnet crystals for different wavelength regions have been identified: GSAG for 942 nm and YGG for 935 nm. In addition to the first grown

B. Ileri; C. Czeranowsky; K. Petermann; G. Huber

2005-01-01

326

Outcome of erbium:yttrium aluminium garnet laser resurfacing treatments  

Microsoft Academic Search

Erbium:yttrium aluminium garnet (erbium:YAG) laser treatment was used to resurface skin abnormalities in patients suffering\\u000a from conditions that included epidermal naevi, tuberous sclerosis, angiofibromata, neurofibromatosis, and scarring caused\\u000a by acne or other means. Patients completed self-report questionnaires before their first laser test patch session, and again\\u000a approximately 4 months after one treatment, so that its success could be evaluated from the

R. P. Cole; D. Widdowson; J. C. Moore

2008-01-01

327

Calibrating the Spinel\\/Garnet transition in CMAS  

Microsoft Academic Search

Previous investigations of the spinel-garnet lherzolite transition (SGT) in the CMAS system have yielded wildly discrepant pressures for the SGT at temperatures between 1400° C and the solidus (~1570° C) depending upon the pressure medium. Melting experiments on compositions in the Di-Wo join have been used to determine the stability of pressure with time in experiments BaCO3 and talc\\/pyrex assemblies.

J. Longhi

2004-01-01

328

Calcium-poor garnet in relation to metamorphism  

Microsoft Academic Search

1. (1) The writer has carried out a systematic study of pyralspites (calcium-poor garnets) in pelitic metamorphic rocks of the Gosaisyo-Takanuki district. With the increase in metamorphic grade of their host-rocks, the MnO content of the pyralspites decreases, while the FeO content increases. Accompanying the variations in composition, the edge length of the unit cell of the minerals shortens and

Akiho Miyashiro

1953-01-01

329

Experimental determination of cation diffusivities in aluminosilicate garnets  

Microsoft Academic Search

Data from experimentally-induced diffusion profiles at approximately 40 Kbar, 1,300 1,500° C in spessartine-almandine couples and a pyrope-almandine couple at ˜ 40 Kbar, 1,440° C, described in Part I, were used to derive tracer diffusion coefficients ( D *) of Fe, Mn and Mg in garnet. The experimental data were fitted by numerical simulations that model multicomponent, compositionally-dependent difussion, including

Timothy P. Loomis; Jibamitra Ganguly; Stephen C. Elphick

1985-01-01

330

Experimental determination of cation diffusivities in aluminosilicate garnets  

Microsoft Academic Search

Data from experimentally-induced diffusion profiles at approximately 40 Kbar, 1,300–1,500° C in spessartine-almandine couples and a pyrope-almandine couple at ~ 40 Kbar, 1,440° C, described in Part I, were used to derive tracer diffusion coefficients (D*) of Fe, Mn and Mg in garnet. The experimental data were fitted by numerical simulations that model multicomponent, compositionally-dependent difussion, including the effects of

Timothy P. Loomis; Jibamitra Ganguly; Stephen C. Elphick

1985-01-01

331

Ferrite phase shifters using stress-insensitive garnet materials  

NASA Astrophysics Data System (ADS)

Stable hysteresis characteristics of ferrimagnetic materials are critical to the RF performance of microwave ferrite toroidal phasers. Particularly troublesome are the magnetostrictive characteristics where the hysteresis properties are altered by stress. This paper presents the results of a study addressing Mn(sup + 3) substitutions in garnets to improve the resultant magnetostrictive characteristics in order to achieve stress-insensitive performance in waveguide toroidal phasers.

Vaughn, J. Todd; Cox, Paul R.; Rodrigue, G. P.; Harrison, Gordon R.

1995-05-01

332

Dielectric properties and electrical conduction in yttrium iron garnet (YIG)  

Microsoft Academic Search

The dielectric properties (dielectric constant and loss) of a single crystal of yttrium iron garnet (Y3Fe5O12) were measured in the temperature range 77–725 K and in the frequency range 100 Hz-1 MHz. AC conductivity was derived from\\u000a dielectric constant and loss. DC conductivity was measured in the temperature range 30–725 K. Thermoelectric power (TEP) was\\u000a measured from 77–800 K. On

Lalitha Sirdeshmukh; K Krishna Kumar; S Bal Laxman; A Rama Krishna; G Sathaiah

1998-01-01

333

Magnetic Aftereffects in Single and Polycrystalline Yttrium Iron Garnet  

Microsoft Academic Search

Magnetic aftereffect (MAE) measurements on single and polycrystalline yttrium iron garnet, Y3Fe5O12, have been carried out from 4.4 to 450 K by means of an LC-oscillator technique. In non-oriented and oriented single crystal samples three processes around 60, 130 and 250 K are observed. Similar peaks appear in polycrystalline samples which had been sintered in air or CO2 atmospheres. Following

L. Torres; F. Walz; J. Iñiguez; H. Kronmüller

1997-01-01

334

Superconducting microstrip resonator with yttrium iron garnet single crystals  

Microsoft Academic Search

A magnetically tunable microstrip superconducting resonator using an yttrium-iron-garnet (YIG) single crystal was demonstrated experimentally. Tunability of 200 MHz at a center frequency of 5.3 GHz was observed, and a quality factor of 965 with minimum insertion loss of 19.5 dB was measured for a half-wavelength microstrip line consisting of a YIG-YBCO-MgO composite structure. The dispersion relation of the resonator

Takeshi Fukusako; Makoto Tsutsumi

1997-01-01

335

Electrical properties of yttrium iron garnet at high temperatures  

Microsoft Academic Search

The dc electrical conductivity (sigma) and the Seebeck coefficient (alpha) have been measured on n- and p-type single crystals of yttrium iron garnet (YIG) in the temperature range 600-1500 K. The temperature dependence of sigma and alpha at an oxygen partial pressure (PO2) of 1 atm shows extrinsic behavior of sigma for both n- and p-type samples with a thermal

P. K. Larsen; R. Metselaar

1976-01-01

336

Nuclear Bragg diffraction of synchrotron radiation in yttrium iron garnet  

Microsoft Academic Search

Monochromatization of synchrotron radiation down to about 10 neV at an energy of 14.4 keV has been achieved by double nuclear Bragg diffraction from (Fe-57)-yttrium iron garnet single-crystal films set for the electronically forbidden 200 plane-type reflection. The monochromatized gamma quanta have been analyzed with respect to time delay and capability of resonance absorption. By setting appropriate energy and time

E. Gerdau; R. Rueffer; H. Winkler; W. Tolksdorf; C. P. Klages; J. P. Hannon

1985-01-01

337

Anisotropy and magnetostriction of cobalt-substituted yttrium iron garnet  

Microsoft Academic Search

The anisotropy, magnetostriction, and ferromagnetic resonance linewidth of cobalt-substituted yttrium iron garnets of composition Y3Fe5-x-yCoxGeyO12 have been investigated by means of ferromagnetic resonance at 9.15 GHz in the temperature range 4.2<=T<=500 K. The impurities, the valence states, and the site distribution of the cobalt ions in the measured crystals have been determined by chemical analysis, optical absorption, and spin-echo measurements.

P. Hansen; W. Tolksdorf; R. Krishnan

1977-01-01

338

Nonstoichiometry and electronic defects in yttrium iron garnet  

Microsoft Academic Search

Results are presented of a thermogravimetrical analysis of yttrium iron garnet, Y3Fe5O12-delta, in the temperature range 950-1270°C. From these measurements the oxygen vacancy concentration delta is obtained for partial oxygen pressures between 1 and 10-5 atm. The data can be fitted with a relation delta = A exp(-E\\/kT). Values of A and E are given for different values of PO2.

R. Metselaar; M. A. H. Huyberts

1977-01-01

339

Microstrip line filters using yttrium iron garnet film  

Microsoft Academic Search

The yttrium iron garnet (YIG) film microstrip line was fabricated by using 40-?m-thick film with a width of 20 mm and a length of 10 mm along with a 0.7-mm-wide microstrip and was magnetized in a transverse direction to the wave propagation. Sharp notch characteristics of more than 30 dB with few dB insertion loss were observed experimentally with a

Makoto Tsutsumi; Satoshi Tamura

1992-01-01

340

Tunable negative index metamaterial using yttrium iron garnet  

Microsoft Academic Search

A magnetic field tunable, broadband, low-loss, negative refractive index metamaterial is fabricated using yttrium iron garnet (YIG) and a periodic array of copper wires. The tunability is demonstrated from 18 to 23GHz under an applied magnetic field with a figure of merit of 4.2GHz\\/kOe. The tuning bandwidth is measured to be 5GHz compared to 0.9GHz for fixed field. We measure

Yongxue He; Peng He; Soack Dae Yoon; P. V. Parimi; F. J. Rachford; V. G. Harris; C. Vittoria

2007-01-01

341

FERROMAGNETIC RESONANCE LINE WIDTH IN YTTRIUM IRON GARNET SINGLE CRYSTALS  

Microsoft Academic Search

A study of ferromagnetic resonance line width in polished, single-; crystal spheres of yttriunn iron garnet is described. Wave-guide cavity ; perturbation techniques are used with samples 0.013 in. to 0.020 in. in diameter. ; An extremely narrow line width of 520 millioersteds (the full width) is observed ; at 9300 Mc\\/sec along the hard axis STA100!. It is believed

R. C. LeCraw; E. G. Spencer; C. S. Porter

1958-01-01

342

Mossbauer spectroscopy study of substituted yttrium iron garnets  

Microsoft Academic Search

Mossbauer spectroscopy studies of 57Fe in a number of rare earth iron garnets (RxY1?x)3Fe5O12 where R is either Ho3+ or Gd3+ show that the hyperfine field at the iron nucleus in the octahedral and tetrahedral sites increases with rare earth substitution. This increase could be attributed to the increase in the average magnetic moment ? of these compounds with R3+

Abed-Fatah D. Lehlooh

1996-01-01

343

Deposition of gold nanoparticles on liquid phase epitaxy grown garnet films and Faraday rotation enhancement  

NASA Astrophysics Data System (ADS)

Plasmon resonance induced Faraday rotation enhancement in liquid phase epitaxy grown garnet films with gold nanoparticles on their surfaces is discussed. Experimental results are presented, which reveal stronger Faraday rotation enhancement for gold nanoparticles obtained by the annealing of thicker gold films evaporated on garnet film surfaces. This stronger Faraday rotation enhancement can be attributed to larger dimensions and separations of gold nanoparticles, which increase the extent of penetration of plasmon resonance induced electric fields into garnet films.

Lang, G. S.; Bowen, D.; Krafft, C.; Mayergoyz, I. D.

2013-05-01

344

A detailed isotopic and petrological study of a single garnet from the Gassetts Schist, Vermont  

Microsoft Academic Search

Garnets, up to 1.2 cm across, from a metapelite in the Acadian metamorphic terrain of eastern Vermont have been analysed for major elements and segregated into different fractions for isotopic analysis. The garnets preserve abundant inclusions of minerals present during garnet growth which allow a nearly complete reaction history to be established. The Sm-Nd and U-Pb isotopic analyses yield concordant

Derek Vance; Tim Holland

1993-01-01

345

Enhanced Faraday rotation in all-garnet magneto-optical photonic crystal  

Microsoft Academic Search

Research on magneto-optical photonic crystals has so far been focused on theoretical investigations, because suitable multilayers of iron garnet, the most promising material, have not been readily available. We report the preparation and characterization of a one-dimensional magneto-optical photonic crystal composed of 17 heteroepitaxial layers of bismuth iron garnet and yttrium iron garnet. The magneto-optical Faraday rotation was increased by

S. Kahl; A. M. Grishin

2004-01-01

346

Developmental toxicity evaluation of gallium nitrate in mice  

Microsoft Academic Search

Gallium nitrate, a drug with antitumor activity, is presently undergoing clinical trials as a chemotherapeutic agent for the treatment of certain malignancies. Since there are very limited published animal toxicity data available, this study was conducted to investigate the potential adverse developmental effects of this drug. Pregnant Swiss mice were administered intraperitoneally gallium nitrate at 12.5, 25, 50, and 100

Mercedes Gómez; Domingo J. Sánchez; José L. Domingo; Jacinto Corbella

1992-01-01

347

Automated realization of the gallium melting and triple points  

NASA Astrophysics Data System (ADS)

In order to improve the automation and convenience of the process involved in realizing the gallium fixed points, an automated apparatus, based on thermoelectric and heat pipe technologies, was designed and developed. This paper describes the apparatus design and procedures for freezing gallium mantles and realizing gallium melting and triple points. Also, investigations on the melting behavior of a gallium melting point cell and of gallium triple point cells were carried out while controlling the temperature outside the gallium point cells at 30 °C, 30.5 °C, 31 °C, and 31.5 °C. The obtained melting plateau curves show dentate temperature oscillations on the melting plateaus for the gallium point cells when thermal couplings occurred between the outer and inner liquid-solid interfaces. The maximum amplitude of the temperature fluctuations was about 1.5 mK. Therefore, the temperature oscillations can be used to indicate the ending of the equilibrium phase transitions. The duration and amplitude of such temperature oscillations depend on the temperature difference between the setting temperature and the gallium point temperature; the smaller the temperature difference, the longer the duration of both the melting plateaus and the temperature fluctuations.

Yan, X.; Duan, Y.; Zhang, J. T.; Wang, W.

2013-09-01

348

First results from the Soviet-American gallium experiment  

Microsoft Academic Search

The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95%

A. I. Abazov; D. N. Abdurashitov; O. L. Anosov; L. A. Eroshkina; E. L. Faizov; V. N. Gavrin; A. V. Kalikhov; T. V. Knodel; I. I. Knyshenko; V. N. Kornoukhov; S. A. Mezentseva; I. N. Mirmov; A. I. Ostrinsky; V. V. Petukhov; A. M. Pshukov; N. Ye. Revzin; A. A. Shikhin; P. V. Timofeyev; E. P. Veretenkin; V. M. Vermul; Yu. Zakharov; G. T. Zatsepin; V. I. Zhandarov; T. J. Bowles; B. T. Cleveland; S. R. Elliott; H. A. O'Brien; D. L. Wark; J. F. Wilkerson; R. Davis; K. Lande; M. L. Cherry; R. T. Kouzes

1991-01-01

349

Dispersion of submicron Ni particles into liquid gallium  

Microsoft Academic Search

In this paper a liquid gallium with a low melting temperature and good thermal conductivity was used as a carrier to develop a new magnetorheological (MR) fluid that can be employed in energy convection devices. Submicron nickel particles, coated with silica, were chosen to be dispersed in the liquid gallium. The silica coating was used to improve the dispersion and

L. F. Cao; H. S. Park; G. Dodbiba; T. Fujita

2008-01-01

350

ASSESSMENT OF ARSENIC EXPOSURES AND CONTROLS IN GALLIUM ARSENIDE PRODUCTION  

Microsoft Academic Search

The electronics industry is expanding the use of gallium arsenide in the production of optoelectronic devices and integrated circuits. Workers in the electronics industry using gallium arsenide are exposed to hazardous substances such as arsenic, arsine, and various acids. Arsenic requires stringent controls to minimize exposures (the current OSHA PEL for arsenic is 10 ?\\/m3 and the NIOSH REL is

John W. Sheehy; James H. Jones

1993-01-01

351

Crystal Growth of Gallium Arsenide using Carbon Boats  

Microsoft Academic Search

GALLIUM arsenide is a semiconductor of great interest from the purely scientific point of view and as a device material. It is therefore desirable to be able to prepare single crystals of high purity. Because of the reactive nature of gallium liquid and arsenic vapour at high temperature, only a limited number of refractories may be used as boat materials

J. R. Knight

1961-01-01

352

Gallium nitride hybrid microwave circuits for low-noise applications  

Microsoft Academic Search

This paper presents recent work in the area of gallium nitride (GaN) low-noise microwave integrated circuits. Gallium nitride has attracted interest principally due to its power handling ability. However, its noise performance has received relatively little attention. We discuss the noise performance of several discrete devices, and how they perform in hybrid integrated circuits. The predictive and descriptive models used

Tyler Ross; Gabriel Cormier; Khelifa Hettak

2010-01-01

353

Role of gallium-67 in the clinical evaluation of cancer  

Microsoft Academic Search

This review is based primarily on historic data, and it examines the indications for and limitations of gallium-67 scanning in the evaluation of patients with neoplasms. The use of gallium-67 scans is discussed according to tumor type, and data from the most representative and comprehensive studies are included. The results described, some of which were obtained primarily with older imaging

C. Bekerman; P. B. Hoffer; J. D. Bitran

1984-01-01

354

Thermal conductivity of disordered garnets from infrared spectroscopy  

NASA Astrophysics Data System (ADS)

The thermal conductivity (k) of garnets is calculated from a formula originating with Debye, adapted to treat the vibrations in a solid as a collection of damped harmonic oscillators. Our model utilizes phonon lifetimes obtained from Kramers-Kronig analyses of existing IR reflectivity spectra, as well as new data presented here, and calculates k at ambient conditions within a nominal uncertainty of 6% of the experimental values for eight natural samples with well-constrained chemical compositions. Agreement is good for the remaining garnets with uncertain compositions. Two series of natural mixed crystals were studied: (1) X3Al2Si3O12, where the X site has varying amounts of Mg, Fe2+, and Ca and (2) Ca3Y2Si3O12, where the Y site has Al and/or Fe3+. The model predicts k at ambient conditions for the end members. The occurrence of a minimum in k near the midpoint of each compositional series correlates with the maximum widths of the IR peaks. Thus, disorder on crystallographic sites largely controls the thermal conductivity of mixed crystals. We also tested the model using available data on synthetic yttrium garnets. Agreement is good for YAG. Observation of ~30% discrepancy between calculated and experimental k of YGG and YIG suggests that these unconfirmed measurements should be repeated.

Giesting, P. A.; Hofmeister, A. M.

2002-04-01

355

Single-crystal elasticity of andradite garnet to 11 GPa  

NASA Astrophysics Data System (ADS)

The high-pressure elastic properties of single-crystal andradite garnet Ca3Fe23+Si3O12 were determined by Brillouin scattering to 11 GPa. The pressure dependence of the elastic stiffness constants and aggregate bulk and shear moduli were obtained by inversion of the data to finite Eulerian strain equations. The inversion yields C11 = 286.7 ± 0.6 GPa, C12 = 88.6 ± 0.6 GPa, C44 = 83.8 ± 0.3 GPa, K0S = 154.5 ± 0.6 GPa, G0S = 89.7 ± 0.4 GPa, (\\partial K_{0T}/\\partial P)_{T}=4.71\\pm 0.1 , and (\\partial G_{0}/\\partial P)_{T}=1.25\\pm 0.05 . Both individual and aggregate elastic moduli define nearly linear modulus-pressure trends. The elastic anisotropy of andradite garnets increases weakly in magnitude with compression. Previous studies of the high-pressure elasticity of andradite garnet are highly discrepant, with reported pressure derivatives of the bulk modulus varying by 46% and pressure derivatives of the shear modulus varying by 253%. We are able to provide plausible explanations for these discrepancies. In particular, differences between previous x-ray diffraction data and a static compression curve constructed from our Brillouin data can be attributed to the effects of non-hydrostatic stresses on the x-ray data.

Jiang, Fuming; Speziale, Sergio; Shieh, Sean R.; Duffy, Thomas S.

2004-04-01

356

Enrichment behaviour of gallium in heat and surface treatments of Al–Ga foils  

Microsoft Academic Search

The behaviour of gallium is examined after heat and surface treatments of aluminium foils containing either 120 or 1300 ppm gallium, with low enrichments of gallium at the surfaces arising from foil manufacture. Vacuum heat treatment at 823 K for 20 ks caused negligible additional enrichment, probably associated with the high solubility of gallium in aluminium. Subsequent alkaline etching in

Z. Ashitaka; P. Skeldon; G. E. Thompson; K. Shimizu; H. Habazaki

2002-01-01

357

THERIA_G: a software program to numerically model prograde garnet growth  

Microsoft Academic Search

We present the software program THERIA_G, which allows for numerical simulation of garnet growth in a given volume of rock\\u000a along any pressure–temperature–time (P–T–t) path. THERIA_G assumes thermodynamic equilibrium between the garnet rim and the rock matrix during growth and accounts for\\u000a component fractionation associated with garnet formation as well as for intracrystalline diffusion within garnet. In addition,\\u000a THERIA_G keeps

F. Gaidies; C. de Capitani; R. Abart

2008-01-01

358

Nuclear microprobe imaging of gallium nitrate in cancer cells  

NASA Astrophysics Data System (ADS)

Gallium nitrate is used in clinical oncology as treatment for hypercalcemia and for cancer that has spread to the bone. Its mechanism of antitumor action has not been fully elucidated yet. The knowledge of the intracellular distribution of anticancer drugs is of particular interest in oncology to better understand their cellular pharmacology. In addition, most metal-based anticancer compounds interact with endogenous trace elements in cells, altering their metabolism. The purpose of this experiment was to examine, by use of nuclear microprobe analysis, the cellular distribution of gallium and endogenous trace elements within cancer cells exposed to gallium nitrate. In a majority of cellular analyses, gallium was found homogeneously distributed in cells following the distribution of carbon. In a smaller number of cells, however, gallium appeared concentrated together with P, Ca and Fe within round structures of about 2-5 ?m diameter located in the perinuclear region. These intracellular structures are typical of lysosomial material.

Ortega, Richard; Suda, Asami; Devès, Guillaume

2003-09-01

359

Targeting Iron-Dependent DNA Synthesis with Gallium and Transferrin-Gallium  

Microsoft Academic Search

While iron is essential for numerous intracellular processes, its critical role in DNA synthesis relates to the activity of the iron-containing M2 subunit of ribonucleotide reductase, the enzyme responsible for the synthesis of deoxyribonucleotides. Gallium, a metal which resembles iron with respect to transferrin (Tf) binding, cellular uptake by the Tf receptor and incorporation into ferritin, blocks the cellular uptake

Christopher R. Chitambar; Jana Narasimhan

1991-01-01

360

Gallium scintigraphic pattern in lung CMV infections  

SciTech Connect

Due to extensive use of prophylactic therapy for Pneumonitis Carinii Pneumonia (PCP), Cytomegalic Viral (CMV) infection may now be the most common lung infection in AIDS patients. This study was performed to determine Gallium-67 patterns in AIDS patients with CMV. Pathology reports were reviewed in AIDS patients who had a dose of 5 to 10 mCi of Gallium-67 citrate. Analysis of images were obtained 48-72 hours later of the entire body was performed. Gallium-67 scans in 14 AIDS patients with biopsy proven CMV, were evaluated for eye, colon, adrenal, lung and renal uptake. These were compared to 40 AIDS patients without CMV. These controls had infections including PCP, Mycobacterial infections, and lymphocytic interstitial pneumonitis. 100% of CMV patients had bowel uptake greater than or equal to liver. Similar bowel activity was seen in 50% of AIDS patients without CMV. 71% had intense eye uptake which was seen in only 10% of patients without CMV. 50% of CMV patients had renal uptake compared to 5% of non-CMV cases. Adrenal uptake was suggested in 50%, however, SPECT imaging is needed for confirmation. 85% had low grade lung uptake. The low grade lung had perihilar prominence. The remaining 15% had high grade lung uptake (greater than sternum) due to superimposed PCP infection. Colon uptake is very sensitive indicator for CMV infection. However, observing eye, renal, and or adrenal uptake improved the diagnostic specificity. SPECT imaging is needed to confirm renal or adrenal abnormalities due to intense bowel activity present in 100% of cases. When high grade lung uptake is seen superimposed PCP is suggested.

Ganz, W.I.; Cohen, D.; Mallin, W. [Univ. of Miami School of Medicine, FL (United States)] [and others

1994-05-01

361

Gallium-67 imaging in muscular sarcoidosis  

SciTech Connect

A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid muscle disease but is consistent with the rarity of clinical evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

1984-07-01

362

Atomistic computer simulations of yttrium iron garnet as an approach to studying its defect chemistry: Extrinsic defects  

Microsoft Academic Search

We report results of atomistic simulation studies concerning the incorporation of extrinsic defects in yttrium iron garnet crystals. We calculate defect formation energies in order to determine the most favorable impurity incorporation mechanisms in yttrium iron garnet.

H. Donnerberg; C. R. A. Catlow

1994-01-01

363

Neutron Detection Utilizing Gadolinium Doped Hafnium Oxide Films.  

National Technical Information Service (NTIS)

Gadolinium (Gd) doped hafnium oxide (HfO2) was deposited onto a silicon substrate using pulsed laser deposition. Synchrotron radiation was used to perform Gd L3-edge extended X-ray absorption fine structure (EXAFS) measurements on 3%, 10%, and 15% doped H...

B. D. Blasy

2008-01-01

364

Development of gadolinium based nanoparticles having an affinity towards melanin  

NASA Astrophysics Data System (ADS)

Small Rigid Platforms (SRPs) are sub-5 nanometre gadolinium based nanoparticles that have been developed for multimodal imaging and theranostic applications. They are composed of a polysiloxane network surrounded by gadolinium chelates. A covalent coupling with quinoxaline derivatives has been performed. Such derivatives have proven their affinity for melanin frequently expressed in primary melanoma cases. Three different quinoxaline derivatives have been synthesised and coupled to the nanoparticles. The affinity of the grafted nanoparticles for melanin has then been shown in vitro by surface plasmon resonance on a homemade melanin grafted gold chip.Small Rigid Platforms (SRPs) are sub-5 nanometre gadolinium based nanoparticles that have been developed for multimodal imaging and theranostic applications. They are composed of a polysiloxane network surrounded by gadolinium chelates. A covalent coupling with quinoxaline derivatives has been performed. Such derivatives have proven their affinity for melanin frequently expressed in primary melanoma cases. Three different quinoxaline derivatives have been synthesised and coupled to the nanoparticles. The affinity of the grafted nanoparticles for melanin has then been shown in vitro by surface plasmon resonance on a homemade melanin grafted gold chip. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33457g

Morlieras, Jessica; Chezal, Jean-Michel; Miot-Noirault, Elisabeth; Roux, Amandine; Heinrich-Balard, Laurence; Cohen, Richard; Tarrit, Sébastien; Truillet, Charles; Mignot, Anna; Hachani, Roxanne; Kryza, David; Antoine, Rodolphe; Dugourd, Philippe; Perriat, Pascal; Janier, Marc; Sancey, Lucie; Lux, François; Tillement, Olivier

2013-01-01

365

Behavior of Zircaloy Cladding in the Presence of Gallium  

SciTech Connect

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

1998-09-28

366

Compatibility of ITER candidate structural materials with static gallium  

SciTech Connect

Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400{degrees}C, corrosion rates are {approx}4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400{degrees}C are {ge}88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400{degrees}C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized.

Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

1993-12-01

367

Titanian clinohumite–garnet–pyroxene rock from the SuLu UHP metamorphic terrane, China: chemical evolution and tectonic implications  

Microsoft Academic Search

A garnet–pyroxene rock containing abundant Ti-clinohumite (ca. 40 vol.%) occurs along with eclogites as small blocks in quartzo-feldsparthic gneiss in the southern end of the Chinese Su-Lu ultrahigh-pressure (UHP) metamorphic terrane. It consists of three aggregates: (1) Ti-clinohumite-dominated aggregate with interstitial garnet and pyroxene, (2) garnet+pyroxene aggregate with Ti-clinohumite inclusions, and (3) Ti-clinohumite-free aggregate dominated by garnet. Apatite, phlogopite, zircon,

Jian-Jun Yang

2003-01-01

368

Reply to comment on "The applicability of garnet — orthopyroxene geobarometry in mantle xenoliths" by Paolo Nimis and Herman Grütter  

NASA Astrophysics Data System (ADS)

Equilibrium P-T conditions of garnet-facies or garnet-spinel transition facies mantle xenoliths are suggested to be best determined through a combination of the Taylor (1998) two-pyroxene thermometer either with the Taylor (1998) garnet-orthopyroxene barometer for TiO2-rich orthopyroxenes (Al/Ti < 12.0), or with the Nickel and Green (1985) garnet-orthopyroxene barometer for TiO2-poor orthopyroxenes (Al/Ti > 12.0).

Wu, Chun-Ming; Zhao, Guochun

2012-06-01

369

Dating high-grade metamorphism--constraints from rare-earth elements in zircon and garnet  

Microsoft Academic Search

We integrate petrography and SIMS REE analyses of garnet and polyphase zircon from a pelitic granulite adjacent to the Ronda peridotite, Betic Cordillera, southern Spain to constrain the significance of zircon U-Pb geochronology. Sillimanite inclusions in garnet rims suggest that they grew during decompression, and Ca enrichment in their rims records initiation of partial melting. Chondrite-normalised REE profiles of zircon

Martin J. Whitehouse; John P. Platt

2003-01-01

370

Magneto-optic characterization of iron garnet crystals using photoelastic modulation  

Microsoft Academic Search

Depolarization phenomena in demagnetized bulk iron garnet crystals are investigated with the aid of a photoelastic modulator. An experimental configuration which simultaneously measures Faraday rotation and depolarization as a function of applied magnetic field is described. The technique is demonstrated with samples of SF-57 glass, which exhibits no measurable depolarization, and bulk yttrium-iron-garnet, which shows pronounced depolarization in the demagnetized

M. N. Deeter; Paul A. Williams

1992-01-01

371

Combined external-beam PIXE and ?-Raman characterisation of garnets used in Merovingian jewellery  

Microsoft Academic Search

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

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

2002-01-01

372

Garnet peridotite from Colorado Plateau ultramafic diatremes: Hydrates, carbonates, and comparative geothermometry  

Microsoft Academic Search

Crystal fragments of pyrope from diatremes of ultramafic microbreccia in the Navajo Province of the Colorado Plateau contain inclusions of olivine, pyroxene, spinel, chlorite, amphibole, chlorapatite, and dolomite. The included suite supports earlier hypotheses that hydrous phases and carbonates were primary parts of some garnet peridotite assemblages in the Plateau lithosphere. Garnets with spinel and orthopyroxene inclusions likely all were

W. Clay Hunter; Douglas Smith

1981-01-01

373

Investigation of the Growth of Garnet Films by Liquid Phase Epitaxy.  

National Technical Information Service (NTIS)

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 dep...

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

1974-01-01

374

Effects of water and iron content on the rheological contrast between garnet and olivine  

NASA Astrophysics Data System (ADS)

The effects of water and iron content on the relative creep strengths of garnet and olivine were investigated by shear deformation experiments. Garnet and olivine samples were sandwiched together between alumina pistons in a simple shear geometry and were deformed at P = 1-2 GPa, T = 1473 K and strain rates ranging from 10 -5 to 10 -3 s -1 using a Griggs-type solid-medium apparatus. The stress- and strain-rate relation, as well as the deformation microstructures including lattice-preferred orientation and dynamic recrystallization, indicates that the deformation by dislocation creep. The creep tests show that the Fe-rich garnet (Alm 67Prp 29Grs 3) was slightly weaker than olivine (Fo90), whereas the Mg-rich garnet (Alm 19Prp 68Grs 12) was significantly stronger than olivine under dry conditions. The wet experiments show that the creep rate of the Mg-rich garnet is more sensitive to water than olivine; the water fugacity exponent on strain rate was estimated to be ˜2.4 for garnet and ˜1.2 for olivine, and the Mg-rich garnet becomes weaker than olivine in a water-rich environment. The experimental results show that the rheological contrast between garnet and olivine depends strongly on water content and to a lesser degree on Fe content. Consequently, the geodynamic behavior of geochemical reservoirs can be sensitive to their chemical environments in the upper mantle.

Katayama, Ikuo; Karato, Shun-Ichiro

2008-01-01

375

Method for Controlling the Resonance Frequency of Yttrium Iron Garnet Films.  

National Technical Information Service (NTIS)

A method for controlling the resonance frequency of single crystal yttrium iron garnet (YIG) films by incorporating lead as a partial substituent for the yttrium component of the YIG film. This invention relates to yttrium iron garnet films and to a metho...

H. L. Glass

1979-01-01

376

Tectonic history of continental crustal wedge constrained by EBSD measurements of garnet inclusion trails and thermodynamic modeling  

Microsoft Academic Search

Inclusion trails in garnets represent an important but underused tool of structural geology to examine non-coaxial or polyphase coaxial deformation histories of orogens. Garnet growth with respect to deformation during prograde and retrograde orogenic evolution of a continental crustal wedge was constrained by EBSD measurements of internal garnet fabrics and petrological record from mid-crustal rocks of the Snieznik Massif (Western

E. Skrzypek; K. Schulmann; O. Lexa; J. Haloda

2009-01-01

377

Mechanism of gallium-67 accumulation in tumors  

SciTech Connect

Neoplasms are characterized by increased perfusion, increased permeability of their capillary beds to macromolecules, and a delay in new lymphatic vessel growth. These lead to the increased entry and residency time of macromolecules in the interstitial space of tumors. Multiple factors contribute to the localization of /sup 67/Ga in tumors. Adequate blood supply is essential; at areas with no blood supply such as the necrotic center of a large tumor, there is no /sup 67/Ga accumulation. Gallium-67, mainly in the form of transferrin-67Ga complex, is delivered to the tumor through capillaries with increased permeability. In tumors, some /sup 67/Ga is taken up by tumor cells; some may also be taken up by inflammatory cells when they are present. Gallium-67 binding proteins, such as lactoferrin or ferritin, may also contribute to the accumulation and retention of /sup 67/Ga in tumors; however, their roles are less clear. The intensity of these various factors determine their relative contribution and the degree of /sup 67/Ga accumulation in tumors.56 references.

Tsan, M.F.; Scheffel, U.

1986-07-01

378

Gallium scanning in lymphoid interstitial pneumonitis of children with AIDS  

SciTech Connect

Lymphoid interstitial pneumonitis (LIP) is a frequent pulmonary complication in the child with the acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection. We report the gallium scan findings in two children with AIDS and LIP. Gallium scintigraphy in both children demonstrated increased radionuclide concentration throughout the lungs, a pattern indistinguishable scintigraphically from that of Pneumocystis carinii pneumonia (PCP). This should alert nuclear medicine practitioners and referring physicians to another cause of diffusely increased gallium uptake in the lungs of patients with AIDS.

Schiff, R.G.; Kabat, L.; Kamani, N.

1987-12-01

379

Modelling the Formation of Elliptical Garnets during High Strain in a Partially Melted Metapelite  

NASA Astrophysics Data System (ADS)

Some metapelitic xenoliths in the NVP (Neogene Volcanic Province) of SE Spain, display the development of high strain zones during partial melting. These rocks are composed of biotite (XMg= 0.29-0.35, TiO2= 4-7 wt %), sillimanite, plagioclase (An%= 45-55), garnet, hercynite (XMg = 0.15-0.20), cordierite (XMg = 0.45), graphite and melt. Melt of granitic composition occurs as inclusions in minerals and as intergranular pockets. In the high strain zones, the foliation is outlined by layers of oriented fibrolite, biotite, graphite and melt, which wrap around crystals of garnet ranging in shape from elliptical to sigmoidal. Elliptical garnets may have aspect ratio up to 4:1. Both from microstructural and chemical ground, the garnets are characterized by well distinguishable core and mantle. The core typically contains primary inclusions of biotite and melt, trapped during garnet growth. The concentric pattern of inclusions of garnet core is often truncated at strain caps. This part of the garnet is chemically homogeneous, with a composition of Alm76-Pyp08-Sps14-Grs03. The cores are surrounded by a thin (~100 mm) mantle, which is irregular in shape and appears to overgrow the foliated matrix around garnet. Along the strain caps these mantles are rich of oriented fibrolite inclusions, whereas they are intergrown with biotite at strain shadows. In places, the overgrowths form skeletal elongated arms which extend parallel to the foliation. Compared with the cores of garnets, the overgrowths have composition poorer in Mn, but maintain the same XMg= 0.85. These elliptical garnets might be interpreted as a result of: a) crystal plastic deformation b) dissolution (and redeposition) c) constrained growth Investigation by means of orientation contrast imaging and electron backscattered diffraction, leads us to rule out crystal plasticity as a possible mechanism. Based on the observed intracrystalline microstructures and chemical zoning of garnet we can model the formation of elliptical garnets in multistage sequence. After growth of idiomorphic garnet cores, rich of melt inclusions and high in Mn, a process of pressure-solution - redeposition occurred during foliation development, with dissolution at strain caps and growth of garnet poorer in Mn in the strain shadows. In a later episode, after the strain event ceased, a mantle poorer in Mn continued to grow all around garnet. The elliptical shape and the skeletal arms were constrained by the adjacent foliation, and garnet included trails of oriented matrix phases, mainly biotite and fibrolite. Grt-Bt thermometry of the elliptical garnets provides high temperatures, in the range 800-950° C, and in agreement with the Grt-Crd thermometer. There are no systematic differences in T among the different microstructural domains (core, strain shadow, strain cap, skeletal arm) of elliptical garnets. This suggests that high temperature conditions were present throughout the whole garnet development, which is in accordance with the presence of melt both within and outside garnet.

Alvarez-Valero, A.; Cesare, B.

2003-12-01

380

Garnet/silicate Liquid Partitioning in Mafic Lithologies  

NASA Astrophysics Data System (ADS)

It is well-recognized that mafic lithologies such as eclogite in the upper mantle may affect the geochemistry of basalts, but this influence depends in part on the mineral/melt partitioning of the phases in such pyroxenitic domains. Recent studies of garnet (grt) partitioning behavior [Van Westrenen et al., G3, 2000GC000133] indicated that differing grossular content in peridotitic and eclogitic garnets may have a significant influence. Peridotitic grt is Ca-poor (XCa 0.05-0.2), whereas eclogitic grt may have XCa >0.2, which may increase compatibility of tetravalent HFSE (Zr, Hf and Ti) relative to REE, thus potentially making high REE/HFSE ratios a unique indicator of garnet eclogite sources. Our previous work established that at 2-3 GPa typical recycled oceanic crust is ~80% clinopyroxene (cpx) and ~20% garnet (XCa 0.18-0.23). The cpx are Al-rich and have significant M2-site vacancies, lowering overall absolute D-values for 3+ and 4+ cations, thus enhancing the relative role of grt, despite its low modal abundance. Owing to the lack of published partitioning data in this critical grt composition range, we performed experiments at 3.0 GPa and 1360-1390°C, yielding grt (XCa 0.16-0.21) coexisting with Al-rich cpx and andesitic liquid (~57 wt.% SiO2). Experimental run products were analyzed by LAM-ICP-MS, using a 193 nm ArF excimer laser with repetition rates of 10 Hz for glasses (30-60 micron spots) and 5 Hz (4-30 micron spots) for grt and cpx. Ablation was carried out in pure He, mixing Ar to the carrier gas between ablation chamber and the mass spectrometer. Our preliminary results differ little for grt between XCa 0.16 and 0.21. Overall, Ti is little affected by the increase of Ca in grt ({it D}Ti=0.27-0.29) and Ti, Zr and Hf remain moderately incompatible, in contrast to the compatible behavior predicted previously. Melting calculations with our new data show that melts derived from eclogite (80% cpx, 20% grt) and peridotite (60% ol, 22% opx, 10% cpx, 8% grt) differ little in Zr/Hf or Nb/Ta ratios, but eclogite-derived melts show clearly elevated Hf/Sm and Zr/Yb ratios. DTh and DU (0.001-0.002 and 0.008-0.01, respectively) are smaller than previously measured, with large values of DU/DTh. This suggests that partial melts of eclogite may potentially produce large 230Th excesses, but only if melt separation occurs at porosities <1%.

Pertermann, M.; Hirschmann, M. M.; Hametner, K.; Guenther, D.

2002-12-01

381

Ferromagnetic resonance in ion-implanted garnet bubble films  

Microsoft Academic Search

Ferromagnetic resonance spectra in garnet bubble films before and after implantation are reported. These results are in turn used to determine the samples’ anisotropy profile. Two sets of Gd0.9YTm1.1Ga0.44Fe4.56O12 samples of thicknesses 328 nm and 555 nm were used in these experiments. The six 328 nm samples were implanted with 2×1016 H ions\\/cm2 at 50 keV while the six 555

R. F. Soohoo

1978-01-01

382

Ferromagnetic resonance in ion-implanted garnet bubble films  

Microsoft Academic Search

Ferromagnetic resonance spectra in garnet bubble films before and after implantation are reported. These results are in turn used to determine the samples' anisotropy profile. Two sets of Gd0.9YTm1.1Ga0.44Fe4.56O12 samples of thicknesses 328 nm and 555 nm were used in these experiments. The six 328 nm samples were implanted with 2×1016 H ions\\/cm2 at 50 keV while the six 555

R. F. Soohoo

1978-01-01

383

Damping in Yttrium Iron Garnet Nanoscale Films Capped by Platinum  

NASA Astrophysics Data System (ADS)

Strong damping enhancement in nm-thick yttrium iron garnet (YIG) films due to Pt capping layers was observed. This damping is substantially larger than the expected damping due to conventional spin pumping, is accompanied by a shift in the ferromagnetic resonance field, and can be suppressed by the use of a Cu spacer in between the YIG and Pt films. The data indicate that such damping may originate from the ferromagnetic ordering in Pt atomic layers near the YIG/Pt interface and the dynamic exchange coupling between the ordered Pt spins and the spins in the YIG film.

Sun, Yiyan; Chang, Houchen; Kabatek, Michael; Song, Young-Yeal; Wang, Zihui; Jantz, Michael; Schneider, William; Wu, Mingzhong; Montoya, E.; Kardasz, B.; Heinrich, B.; te Velthuis, Suzanne G. E.; Schultheiss, Helmut; Hoffmann, Axel

2013-09-01

384

Enhanced spin pumping at yttrium iron garnet/Au interfaces  

SciTech Connect

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.

Burrowes, C.; Heinrich, B.; Kardasz, B.; Montoya, E. A.; Girt, E. [Physics Department, Simon Fraser University, 8888 University Dr., Burnaby, British Columbia V5A 1S6 (Canada); Sun Yiyan; Song, Young-Yeal; Wu Mingzhong [Physics Department, Colorado State University, Fort Collins, Colorado 80523 (United States)

2012-02-27

385

Anisotropy and Magnetostriction of Iridium-Substituted Yttrium Iron Garnet  

Microsoft Academic Search

The anisotropy, magnetostriction, and linewidth of iridium-substituted yttrium iron garnet single crystals of the composition Y3-xAxFe5-y- zIryBzO12- deltaFdelta (A=Ca+2,Pb2+ and B=Fe2+,Si4+,Zn2+) have been investigated by means of ferromagnetic resonance. Chemical-analysis data of Ir, Zn, Ca and of the impurities Pb, Si, and F are given for all crystals. The anisotropy and magnetostriction measurements were carried out at 9.15 GHz in

P. Hansen; J. Schuldt; W. Tolksdorf

1973-01-01

386

Interactions of Zircaloy Cladding with Gallium: Final Report  

SciTech Connect

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS). This has been attributed to stresses in the cladding and one or more aggressive fission products. Stress corrosion cracking by iodines' 6 and LME by cadmium7>8 have been reported, and it is known that Zircaloy can be embrittled by some low-melting metals, (e.g., mercury).g LME is a form of environmentally induced embrittlement that can induce cracking or loss of ductility. LME requties wetting and a tensile stress, but it does not require corrosion penetration. Experimentally, it has been demonstrated that gallium can cause embrittlement of some alloys (e.g., aluminum) at low temperatures,'"' ] ] but experiments relative to LME of zirconium by gallium have been limited and inconclusive.*2 This report describes a series of tests designed to establish the effects of low levels of residual gallium in WG-MOX fhel on its compatibility with Zircaloy. In addition, to establish damage mechanisms it was important to understand types of cladding interactions and available stiety margins with respect to gallium concentration.

D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

1998-09-01

387

A mechanism for Na incorporation in garnet: An example from garnet in orthogneiss from the SuLu terrane, eastern China  

Microsoft Academic Search

Sodian and yttrian (Na-Y) garnet occurs in orthogneisses of the Su-Lu terrane of eastern China with major quartz, microcline, and albite and subordinate biotite, titanite, hematite, and zircon. Acmite-rich pyroxene, muscovite, epidote, allanite, and hastingsitic amphibole occur in a few of the samples. The Na- Y garnet can be divided into almandine-spessartine- grossular (AI > 1.6 per formula unit (pfu)

MASAKI ENAMI; BOLIN CONG; TAKEYOSHI YOSHIDA; IWAO KAWABE

1995-01-01

388

Infrared Response of Impurity Doped Silicon MOSFET's (IRFET's): Fabrication and Characterization of the Gallium Doped Infrared Sensing MOSFET.  

National Technical Information Service (NTIS)

Fabrication and characterization of the gallium doped infrared sensing MOSFET is described. Gallium doped MOSFET device structures have been fabricated by diffusion of gallium from doped oxide sources into n-channel MOSFET's fabricated on a normal boron p...

L. Forbes

1976-01-01

389

Infrared Absorption in Gallium Phosphide-Gallium Arsenide Alloys I. Absorption in n-type Material  

Microsoft Academic Search

There is an absorption band at 3 ?m in n-type gallium phosphide for which a number of explanations have been advanced. These are discussed, and it is shown that a distinction may be made between them by observing the 3 ?m band as a function of composition in GaPxAs1-x alloys. Experimentally it is found that at liquid nitrogen temperatures the

J W Allen; J W Hodby

1963-01-01

390

Epitaxial Growth of Bulk-Quality Gallium Arsenide on Gallium Arsenide and Germanium Substrates  

Microsoft Academic Search

l-4 Efferl has reported high electron mobilities in homoepitaxial gallium arsenide but otherwise little is known about the electrical properties or the crystal perfection of these layers. In our work, epitaxial growth was effected using a hydrogen stream saturated at room temperature with AsCla (p= 10 mm) passing first over metallic Ga at 900°C and then over GaAs or Ge

L. C. Bobb; H. Holloway; K. H. Maxwell; E. Zimmerman

1966-01-01

391

Density functional study of the effects of doping and stoichiometry on gallium diffusion in gallium arsenide  

NASA Astrophysics Data System (ADS)

Previous experimental [1-4] and theoretical [5,6] work on the properties of diffusion of gallium within gallium arsenide has produced some results that are apparently at odds with each other. We present results of a wide theoretical survey of the point defects that form in this material with special attention paid to the formation and diffusion of excess-gallium-related point defects. In this study we applied density functional theory in the local density approximation [7]. Diffusion was examined through the use of the nudged elastic band method [8]. After considering the accuracy of the approximations used, the calculations yield information compatible with the experimental situation and capable of shedding light on areas of apparent disagreement.[4pt] [1] G B"osker et al., Phys. Rev. B 52, 11927 (1995). [2] G B"osker et al., J. Appl. Phys. 86, 791 (1999). [3] H Bracht and S Brotzmann, Phys. Rev. B 71, 115216 (2005). [4] H Bracht et al., Physica B 308-210, 831 (2001). [5] K Levasseur-Smith and N. Mousseau, J. Appl. Phys. 103, 113502 (2008). [6] PA Schultz et al., Mod. and Sim. in Mat. Sci. and Engr. 17, 084007 (2009). [7] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993); ibid. 49, 14251 (1994). [8] H. J'onsson et al., "Classical and quantum dynamics in condensed phase systems," (World Scientific, 1998) Chap. 16, pp. 385-404.

Schick, J. T.; Morgan, C. G.

2011-03-01

392

Production of high-purity gadolinium-153. 2. Removal of samarium, terbium, and microamounts of europium from gadolinium by extraction chromatography  

SciTech Connect

Extraction and extraction-chromatographic behavior of Sm, Eu, Gd, and Tb in the system di-2-ethylhexyl hydrogen phosphate (DEHP)-decane-nitric acid has been studied at various concentrations of nitric acid and lanthanide in aqueous phase. The optimal range of nitric acid concentrations for extraction-chromatographic separation of samarium, europium, gadolinium, and terbium has been determined. The influence of gadolinium concentration on distribution of europium and terbium has been examined. At gadolinium content in solution below 50% of the dynamic exchange capacity of the column, the gadolinium distribution coefficient slightly decreases with increasing gadolinium concentration in the initial solution, the distribution factors of the impurity lanthanides remaining virtually unchanged. With further increase in gadolinium content in the initial solution, the gadolinium distribution factor drastically decreases, and {open_quotes}tails{close_quotes} are formed at the expense of increasing fraction of the extracted complex form GdA{sub 3}. These data allowed a conclusion that composition of extracted complexes is different for Sm, Eu, Gd, and Tb. Conditions proposed for extraction-chromatographic purification of gadolinium in the system DEHP-decane-nitric acid provide for removal of impurity lanthanides (samarium, terbium, and microamounts of europium) with the purification factors greater than 100 (Sm, Tb) and about 2 (Eu) at the column charge of up to 50%.

Mel`nik, M.I.; Karelin, E.A.; Filimonov, V.T. [Research Inst. of Atomic Reactors, Dimitrovgrad (Russian Federation)

1995-03-01

393

Radiation Tolerant, High Speed, Low Power, Gallium Arsenide Logic.  

National Technical Information Service (NTIS)

Gallium Arsenide (GaAs) circuits are largely immune to slowly accumulated radiation doses and therefore do not need the shielding required by complementary metal oxide semiconductor (CMOS) devices. This attribute renders GaAs circuits particularly attract...

K. A. Wolfe

1993-01-01

394

All-optical modulation in gallium arsenide integrated optical waveguides  

SciTech Connect

We have investigated all-optical modulators in gallium arsenide integrated optical waveguides; these modulators use electron-hole pair generation to alter the propagation characteristics of a guided light beam. 6 refs., 6 figs.

McWright, G.; Ross, B.; Guthreau, W.; Lafaw, D.; Lowry, M.; Tindall, W.

1988-01-27

395

Control of Surface Attack by Gallium Alloys in Electrical Contacts.  

National Technical Information Service (NTIS)

Electrical contact between a copper plated steel specimen and brushes of graphite and copper through a film of gallium alloy were investigated. Material compatibility phase changes were studied. Techniques of film renewal were tested as were results in in...

R. A. Burton R. G. Burton

1986-01-01

396

Reversible expansion of gallium-stabilized (delta)-plutonium  

SciTech Connect

It is shown that the transient expansion of plutonium-gallium alloys observed both in the lattice parameter as well as in the dimension of a sample held at ambient temperature can be explained by assuming incipient precipitation of Pu{sub 3}Ga. However, this ordered {zeta}-phase is also subject to radiation-induced disordering. As a result, the gallium-stabilized {delta}-phase, being metastable at ambient temperature, is driven towards thermodynamic equilibrium by radiation-enhanced diffusion of gallium and at the same time reverted back to its metastable state by radiation-induced disordering. A steady state is reached in which only a modest fraction of the gallium present is arranged in ordered {zeta}-phase regions.

Wolfer, W G; Oudot, B; Baclet, N

2006-02-27

397

Quantum-Optical Integrated Circuits of Gallium Arsenide.  

National Technical Information Service (NTIS)

The report describes quantum-optical logic circuits of gallium arsenide, developed using methods of semiconductor integrated technology. Laser integrated modules were made with electron-hole junctions formed by the diffusion method. The modules are made a...

I. S. Goldobin A. S. Dobkin

1971-01-01

398

On-chip photonic crystals on magnetic garnet films  

NASA Astrophysics Data System (ADS)

By trapping photons in fabricated phase-shift defects magnetic photonic crystals can enhance the Faraday rotation in magneto-optic films. The integration of these structures into on-chip photonic circuits, while advantageous from the point of view of component connectivity in multi-functional systems, faces several challenges. Differences in effective refractive indices between transverse electric (TE) and transverse magnetic (TM) modes engender phase disparities, thus hindering the Faraday response of the material. Moreover, photonic waveguide structures in magnetic films may support more than one mode depending on the waveguide thickness and refractive index. The effects of birefringence and multimodality on the performance of waveguide magnetic photonic crystals in magnetic garnets are discussed in paper. Particular attention is paid to analyzing the effect of Faraday rotation enhancement in magnetophotonic crystals in the presence of waveguide birefringence and modal multiplicity. Multiple stopbands and significant polarization rotation are observed in multimode Bi-substituted iron garnet film waveguides with single-defect photonic crystal structures. A spectrally flat response is predicted for the polarization rotation in first order mode for birefringent waveguides. The photonic crystals for this study are patterned on ridge waveguide films by focused ion beam (FIB) milling.

Li, R.; Levy, M.

2005-08-01

399

Machining of iron–gallium alloy for microactuator  

Microsoft Academic Search

We study the micromachining of iron–gallium alloy for use in a microactuator. Iron–gallium (Galfenol) is an iron-based magnetostrictive material with magnetostriction exceeding 200ppm, Young's modulus of 70GPa, and distinctive ductile and machinable properties. An actuator made by small Galfenol component therefore should be simple, robust against external forces and drivable at low voltage. A rod of Galfenol (Fe81.6Ga18.4) prepared by

T. Ueno; E. Summers; T. Higuchi

2007-01-01

400

Gallium phosphide nanowires as a substrate for cultured neurons.  

PubMed

Dissociated sensory neurons were cultured on epitaxial gallium phosphide (GaP) nanowires grown vertically from a gallium phosphide surface. Substrates covered by 2.5 microm long, 50 nm wide nanowires supported cell adhesion and axonal outgrowth. Cell survival was better on nanowire substrates than on planar control substrates. The cells interacted closely with the nanostructures, and cells penetrated by hundreds of wires were observed as well as wire bending due to forces exerted by the cells. PMID:17880143

Hällström, Waldemar; Mårtensson, Thomas; Prinz, Christelle; Gustavsson, Per; Montelius, Lars; Samuelson, Lars; Kanje, Martin

2007-09-19

401

Light Induced Soliton Switching at the Gallium-Silica Interface  

NASA Astrophysics Data System (ADS)

In the present paper, we have investigated the solitonic characteristics of a pulse passing through an interface separating two nonlinear media. The first media is a thin film of gallium nanoparticles which show switching properties under optical excitation and second is a monomode optical fiber. Soliton propagation in three different phases of gallium nanoparticles have been analyzed by using the method of phase-plane analysis. Also, the critical power required for soliton propagation has been calculated.

Naruka, Preeti; Bissa, Shivangi

402

Positive gallium-67 scintigraphy associated with pulmonary embolism  

SciTech Connect

A 54-year-old man presenting with symptoms and signs of pulmonary embolism demonstrated gallium-67 accumulation within the right lower lung field in the region of a pulmonary embolism with effusion. An associated infectious process was ruled out. This is contrary to the usual clinical experience and identifies a potential pitfall in the use of gallium-67 as an aid in the differential diagnosis of pulmonary embolism and pneumonitis.

Brown, J.M.; Moreno, A.J.; Weisman, I.; Baker, F.J.; Lundy, M.N.; Brown, T.J.

1983-08-01

403

Selective catalytic reduction of NO with methane on gallium catalysts  

Microsoft Academic Search

Gallium species supported on H-ZSM-5 and on H-mordenite are active catalysts for NO reduction with methane in the presence of excess O[sub 2]. Over Ga-H-ZSM-5, the NO reduction rate is first order in NO with a variable, fractional order in CH[sub 4]. The distinct feature of these gallium-based catalysts is their very high CH[sub 4] selectivities for NO[sub x] reduction.

Yuejin Li; J. N. Armor

1994-01-01

404

Role of gallium-67 in the clinical evaluation of cancer  

SciTech Connect

This review is based primarily on historic data, and it examines the indications for and limitations of gallium-67 scanning in the evaluation of patients with neoplasms. The use of gallium-67 scans is discussed according to tumor type, and data from the most representative and comprehensive studies are included. The results described, some of which were obtained primarily with older imaging techniques, should be regarded as representing the minimum that can be expected from application of this imaging procedure.

Bekerman, C.; Hoffer, P.B.; Bitran, J.D.

1984-10-01

405

Gallium arsenide clusters and their interfacial physics and chemistry  

Microsoft Academic Search

Gallium arsenide clusters have been studied on a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer with an external supersonic cluster source. Reaction of GaAs cluster cations with ammonia revealed that all cluster cations larger than seven atoms were most reactive near the 1\\/1 composition ratio of gallium\\/arsenic. The results suggest that even at this small size, the clusters begin

Richard E. Smalley; Robert F. Curl; Frank K. Tittel

1992-01-01

406

Gallium-cooled liquid metallic-fueled fast reactor  

Microsoft Academic Search

We have examined the effects on core characteristics of using two different types of Pu-based metallic alloy fuels in the gallium-cooled fast reactor core. In the proposed concept, the liquid metal fast nuclear reactor uses metallic fuel in the liquid phase and gallium coolant at high temperature (inlet 1700K, outlet 1900K). The liquid fuel is continuously supplied to the reactor

T. Sawada; A. Netchaev; H. Ninokata; H. Endo

2000-01-01

407

Inhalation developmental toxicology studies: Gallium arsenide in mice and rats  

SciTech Connect

Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

1990-12-01

408

An effective interaction potential for gallium phosphide.  

PubMed

An effective interatomic potential consisting of two- and three-body covalent interactions is used here to study the properties of gallium phosphide by molecular dynamics simulations. The many-body interatomic potential accounts for the energy scale, length scale and mechanical properties of GaP. At atmospheric pressure, the calculated melting temperature, linear thermal expansion, vibrational density of states and specific heat are in excellent agreement with experimental results. The structural phase transition induced by hydrostatic pressure at 27 GPa is also in quite good agreement with experimental findings. We also studied the energy of vacancy formation in the GaP lattice and the surface energy, which is in reasonable agreement with experimental data. PMID:21406914

Ribeiro-Silva, C I; Rino, J P; Gonçalves, Luis G V; Picinin, A

2011-01-13

409

Direct band gap wurtzite gallium phosphide nanowires.  

PubMed

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555-690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

Assali, S; Zardo, I; Plissard, S; Kriegner, D; Verheijen, M A; Bauer, G; Meijerink, A; Belabbes, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

2013-03-18

410

Direct Band Gap Wurtzite Gallium Phosphide Nanowires  

PubMed Central

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality.

2013-01-01

411

Gallium-68 lipophilic complexes for labeling platelets  

SciTech Connect

Generator produced 68Ga-labeled platelets could be useful for positron emission tomographic (PET) studies of thrombosis or atherosclerosis. To label platelets with 68Ga, we have studied the effects of trace metals in elutions of 68Ga from 68Ge. Studies were conducted on the formation of lipophilic 68Ga complexes 8-hydroxyquinoline, tropolone, and mercaptopyridine-N-oxide (MPO). Parameters such as pH, buffers, concentration of ligand, and stability with time were investigated. High performance liquid chromatography and instant thin layer chromatography were used to quantitate formation of the 68Ga complex. Platelets from human, dog, and rabbit plasma were incubated with the 68Ga complexes and the percent labeling determined. Accumulation of platelets in the catheter scraped aorta of the rabbit was determined by PET imaging, tissue counting, and autoradiography. Gallium-68 MPO gave 40-60% labeling of rabbit platelets with higher accumulation in the scraped aorta compared to the normal.

Yano, Y.; Budinger, T.F.; Ebbe, S.N.; Mathis, C.A.; Singh, M.; Brennan, K.M.; Moyer, B.R.

1985-12-01

412

Gallium arsenide: Solar panel assembly technology  

SciTech Connect

Gallium arsenide (GaAs) solar cell devices are maturing at 18% AMO efficiencies for liquid phase epitaxy (LPE) technology, and efforts must be intensified placing necessary focus on the development of panel assembly techniques, and ultimately panel manufacturing methods capable of maintaining these high efficiencies for on-panel operation. Key problems and solutions are described which were experienced during the assembly of flight qualified solar panels using Spectrolab's mature (silicon) panel manufacturing processes for assembly of LPE GaAs solar cells. These cells were produced by Hughes Malibu (supplied by the U.S. Air Force WPAFB) ranging in efficiency from 15 to 17 percent, air mass zero (AMO) 28 degrees C. Cell assembly methods for coverglass installation, submodule, and circuit soldering, as well as panel bonding are discussed. The LIPS II satellite, using a GaAs solar cell panel was successfully launched in 1983.

Zemmrich, D.; Loo, R.; Mardesich, N.; McFarlane, B.

1984-05-01

413

The Soviet-American Gallium Experiment (SAGE)  

SciTech Connect

It is a great pleasure for me to have been asked by Louis Rosen to tell you about the Soviet-American Gallium Experiment (SAGE). This undertaking is a multi-institutional collaboration among scientists from the Institute for Nuclear Research, Moscow (INR), Los Alamos National Laboratory (LANL), and several US universities. Its purpose is to measure the number of low-energy electron neutrinos emitted from the Sun that arrive at this planet. As such, it is an extremely important experiment, touching on fundamental physics issues as well as solar dynamics. In contrast to the strategic overviews, plans, and hopes for international collaboration presented earlier today, SAGE is an ongoing working effort with high hopes of producing the first measurement of the Sun's low-energy neutrino flux. This paper reviews this experiment. 3 refs., 3 figs.

Garvey, G.T.

1989-01-01

414

Cathodoluminescence spectra of gallium nitride nanorods  

PubMed Central

Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

2011-01-01

415

Gadolinium Endohedral Metallofullerene-Based MRI Contrast Agents  

NASA Astrophysics Data System (ADS)

With the ability to encapsulate and carry the highly paramagnetic Gd3+ ion, gadolinium endohedral metallofullerenes or "gadofullerenes" are being explored as alternatives to the chelate complexes that are currently used for contrast-enhanced magnetic resonance imaging (MRI). Reviewed here are the various water-soluble derivatives of the gadofullerenes Gd@C82, Gd@C60, and Gd3N@C80 that have been investigated as MRI contrast agents. The water proton r1 relaxivities of gadofullerenes can be more than an order of magnitude higher than those of clinically used chelate agents. Gadofullerene relaxivity mechanisms have been studied, and multiple factors are found to contribute to their high relaxivities. In vitro and in vivoT1-weighted MRI tests of gadofullerene derivatives have shown their utility as bright image-enhancing agents. The gadofullerene MRI contrast agents are a promising new and unique style of gadolinium carrier for advanced imaging applications, including cellular and molecular imaging.

Bolskar, Robert D.

416

About a Gadolinium-doped Water Cherenkov LAGUNA Detector  

SciTech Connect

Water Cherenkov (wC) detectors are extremely powerful apparatuses for scientific research. Nevertheless they lack of neutron tagging capabilities, which translates, mainly, into an inability to identify the anti-matter nature of the reacting incoming anti-neutrino particles. A solution was proposed by R. Beacon and M. Vagins back in 2004: by dissolving in the water a compound with nucleus with very large cross section for neutron capture like the Gadolinium, with a corresponding emission of photons of enough energy to be detected, they can tag thermal neutrons with an efficiency larger than 80%. In this talk we detail the technique and its implications in the measurement capabilities and, as well, the new backgrounds induced. We discuss the improvement on their physics program, also for the case of LAGUNA type detectors. We comment shortly the status of the pioneering R and D program of the Super-Kamiokande Collaboration towards dissolving a Gadolinium compound in its water.

Labarga, Luis [Department of Theoretical Physics, University Autonoma Madrid, 28049 Madrid (Spain)

2010-11-24

417

First principles investigations on the elasticity and phase stability of grossular garnet  

NASA Astrophysics Data System (ADS)

In order to understand the fate of subducted continental materials by means of mechanisms such as tectonic erosion and sediment subduction, it is important to understand the high-pressure stability and elastic properties of grossular garnet. We study these questions using the first principles computation method. Grossular garnet was found to dissociate into an assemblage of CaSiO3 Ca-perovskite (Pv) and Al2O3 corundum (Cor) at about 23.4 GPa, accompanied by remarkable jumps of compressional wave (8.0%), shear wave (11.6%), bulk sound (5.7%) velocities, and density (12.1%). Although Pv with the grossular garnet composition was suggested experimentally after the decomposition reaction, this phase was found to be less stable than an assemblage of CaPv and Cor at pressures higher than 20 GPa. This indicates that observed Pv with the grossular garnet composition is metastable but can be obtained because of the slow kinetics of the garnet decomposition reaction. Our results imply that the dissociation of grossular garnet (as well as that of jadeite) included in continental materials subducted into the deep mantle increases the complexity of the 660 km discontinuity and can explain seismically observed multiple reflections. We have also investigated the anisotropy of elastic velocities of grossular garnet, CaPv, and Cor and found that CaPv is the most anisotropic mineral. This implies that CaPv could produce seismic anisotropy in the uppermost lower mantle.

Kawai, Kenji; Tsuchiya, Taku

2012-02-01

418

Study of the provenance of Belgian Merovingian garnets by PIXE at IPNAS cyclotron  

NASA Astrophysics Data System (ADS)

Recent archaeological excavation in Belgium reveals one of the biggest Merovingian necropolis ever found in this country. This necropolis contains 436 tombs with a period of occupation of almost two centuries. Some of these tombs were very rich, especially two of them, and delivered an important funerary furniture. About 60 jewels inlaid with red garnets have been found, most of them of “cloisonné” style (namely about 450 garnets). The new extracted beam set-up of the IPNAS cyclotron (University of Liège, Belgium) has been improved in order to analyse by PIXE these garnets and try to determine their provenance. These analyses reveal that the garnets found in the necropolis of Grez Doiceau are very homogeneous in composition (almandine garnets) and are coming almost from a unique source. These results have been compared to previous studies led in France during these past five years. This permits to identify the source of almandine garnet situated in India and to highlight differences in garnet supply between France and Belgium in Merovingian times.

Mathis, F.; Vrielynck, O.; Laclavetine, K.; Chêne, G.; Strivay, D.

2008-05-01

419

The effect of fluid and deformation on zoning and inclusion patterns in poly-metamorphic garnets  

NASA Astrophysics Data System (ADS)

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 1000?m) 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 ?m) 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.

Erambert, Muriel; Austrheim, Håkon

1993-11-01

420

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

USGS Publications Warehouse

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.

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

2003-01-01

421

Improved dissolution and chemical separation methods for Lu-Hf garnet chronometry  

NASA Astrophysics Data System (ADS)

Garnet-based Lu-Hf geochronology using conventional (HF-HNO3) dissolution methods may be compromised by full or partial digestion of Hf-rich zircon inclusions. This study integrates two complimentary methods to substantially reduce zircon digestion while assuring complete digestion of garnet and sample-spike equilibration. Handpicked garnet fractions are heat treated to >1000°C in an evacuated silica glass ampoule to anneal zircon inclusions and then dissolved with 12 M HCl at 210°C and cold 28 M HF. Analyses of heat-treated garnet (and their high-temperature breakdown products orthopyroxene-spinel-quartz) from Gore Mountain, New York, demonstrate the method is capable of complete dissolution of garnet and routinely achieving sample-spike equilibration. Independent analyses of annealed and unannealed zircons dissolved by HCl - cold HF demonstrate the benefit of heat treatment prior to dissolution. Analyses of zircon-rich garnets from peletic paragneisses of Labrador, Canada, show the potential of this method by returning Lu-Hf ratios commensurate with the degree of heat treatment. Finally, a complementary chemical separation method for Lu and Hf is presented that supports analysis of garnet by MC-ICP-MS.

Connelly, J. N.

2006-04-01

422

Modified permittivity observed in bulk Gallium Arsenide and Gallium Phosphide samples at 50 K using the Whispering Gallery mode method  

Microsoft Academic Search

Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium\\u000aPhosphide samples have been examined both in darkness and under white light at\\u000a50 K. In both samples we observed change in permittivity under light and dark\\u000aconditions. This results from a change in the polarization state of the\\u000asemiconductor, which is consistent with a free electron-hole\\u000acreation\\/recombination process. The

John G. Hartnett; David Mouneyrac; Jean-Michel Le Floch; Jerzy Krupka; Michael E. Tobar; D. Cros

2009-01-01

423

Use of Whispering-Gallery Modes and Quasi Modes for Broadband Characterization of Bulk Gallium Arsenide and Gallium Phosphide Samples  

Microsoft Academic Search

The complex permittivity of bulk crystals of semiinsulating gallium arsenide (GaAs) and gallium phosphide (GaP) were measured over the frequency range from 4 to 30 GHz and at temperatures from 30 up to 300 K employing whispering-gallery-mode (WGM) and quasi-TE0 np-mode dielectric-resonator techniques. At temperatures about 40 K, dielectric loss tangent values were below 10 -6 for GaAs and below

Jerzy Krupka; David Mouneyrac; John G. Hartnett; Michael E. Tobar

2008-01-01

424

Gallium-induced magnesium enrichment on grain boundary and the gallium effect on degradation of tensile properties of aluminum alloys  

Microsoft Academic Search

By applying a controlled amount of gallium (3 mg or 5 mg) to double-notched samples, the effects of the gallium on the grain\\u000a boundary chemistry and tensile properties of AA6061-T4 alloy were investigated. Commercial-purity aluminum AA1050 was used\\u000a for comparison to determine whether alloying elements would correlate with Ga-induced embrittlement and to elucidate the physical\\u000a reason that governed the occurrence

Jun-Yen Uan; Cheng-Chia Chang

2006-01-01

425

Hysteresis in gadolinium oxide metal-oxide-semiconductor capacitors  

NASA Astrophysics Data System (ADS)

This investigation explores how oxidation affects the gadolinium oxide capacitor and the corresponding Gd2O3 hysteresis phenomenon. The current-voltage varied with Gd2O3 thickness and a charged capacitance voltage (C-V) curve with a left shift is also observed in experimental results. The breakdown voltages rise with increasing oxidation time, while the corresponding C-V hysteresis gaps decrease with increasing oxidation time.

Hsieh, Li-Zen; Ko, Hong-Hsi; Kuei, Ping-Yu; Chang, Liann-Be; Jeng, Ming-Jer

2005-10-01

426

Electrochemical kinetics of hydrogen intercalation in gadolinium switchable mirrors  

NASA Astrophysics Data System (ADS)

Potential-step experiments on gadolinium thin-film electrodes provide current and optical transmission transients, whose time constants are related to effective hydrogen diffusion coefficients according to a standard diffusion model. The diffusion coefficients and switching kinetics depend on temperature, hydrogen concentration, potential, and film thickness. A thickness dependence of the kinetics is observed in which the diffusion coefficient and optical switching time are linearly dependent.

di Vece, M.; Swart, I.; Kelly, J. J.

2003-10-01

427

Control and application of domain wall motion in gadolinium molybdate  

Microsoft Academic Search

Sideways motion of ferroelectric-ferroelastic domain walls in gadolinium and terbium molybdates can be produced with electric fields as low as 200 volts\\/cm, in relatively defect-free crystals. Crystal mounting and electroding techniques are described that suppress intersections of perpendicular walls, a primary source of crystal failure. Using these techniques, a GMO crystal has been switched successfully over 109 times with no

J. R. Barkley; L. H. Brixner; E. M. Hogan; R. K. Waring Jr

1972-01-01

428

Control and Application of Domain Wall Motion in Gadolinium Molybdate  

Microsoft Academic Search

Sideways motion of ferroelectric-ferroelastic domain walls in gadolinium and terbium molybdates can be produced with electric fields as low as 200 volts\\/cm, in relatively defect-free crystals. Crystal mounting and electroding techniques are described that suppress intersections of perpendicular walls, a primary source of crystal failure. Using these techniques, a GM0 crystal has been switched successfully over IO9 times with no

J. R. Barkley; L. H. Brixner; E. M. Hogan

1972-01-01

429

Magnons as a Bose-Einstein Condensate in Nanocrystalline Gadolinium  

SciTech Connect

The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.

Kaul, S. N.; Mathew, S. P. [School of Physics, University of Hyderabad, Central University P.O., Hyderabad-500 046 (India)

2011-06-17

430

Late gadolinium enhancement: precursor to cardiomyopathy in Duchenne muscular dystrophy?  

Microsoft Academic Search

Background Progressive cardiomyopathy is a common cause of death in Duchenne muscular dystrophy (DMD), presumably secondary to fibrosis\\u000a of the myocardium. The posterobasal and left lateral free wall of the left ventricle (LV) are initial sites of myocardial\\u000a fibrosis pathologically. The purposes of this study were to assess whether cardiac magnetic resonance imaging (CMRI), utilizing\\u000a late gadolinium enhancement (LGE), could

Michael D. Puchalski; Richard V. Williams; Bojana Askovich; C. Todd Sower; Kan H. Hor; Jason T. Su; Nathan Pack; Edward Dibella; William M. Gottliebson

2009-01-01

431

Electrical Properties of the Cerium and Gadolinium Hydrogen Systems  

Microsoft Academic Search

Conductivities of polycrystalline solid samples of cerium hydride and gadolinium hydride were measured over the composition ranges H\\/Ce=0–2.5 and H\\/Gd=0–2.13 at room temperature and at elevated temperatures (400°—750°C). Conduction is metallic and the results for the two systems are very similar. The conductivity in the variable composition dihydride phase of each system decreases with increasing hydrogen content and is explained

Richard C. Heckman

1964-01-01

432

Electron Spin Resonance in Two Salts containing Gadolinium  

Microsoft Academic Search

The electron spin resonance spectra of Gd3+ have been measured in gadolinium hexa-antipyrene iodide (HAPI), lanthanum HAPI, and cadmium fluoride. In CdF2 the Gd3+ ions are sometimes in sites of cubic and sometimes in sites of tetragonal symmetry. In the latter the zero field splitting is remarkably small, being about 0.05 cm-1. In the HAPI there is a large zero

J. M. Baker; F. I. B. Williams

1961-01-01

433

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)

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 ? m thick and 10 ? 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.

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

2001-12-01

434

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

NASA Astrophysics Data System (ADS)

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.

Karimzadeh Somarin, Alireza

2010-03-01

435

Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy (abstract)  

NASA Astrophysics Data System (ADS)

The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd2O3) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

Lee, Dongkyu; Maeng, Inhee; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol; Son, Joo-Hiuk

2009-04-01

436

Magnetization of 2.6 T in gadolinium thin films  

NASA Astrophysics Data System (ADS)

There is renewed interest in rare-earth elements and gadolinium in particular for a range of studies in coupling physics and applications. However, it is still apparent that synthesis impacts understanding of the intrinsic magnetic properties of thin gadolinium films, particularly for thicknesses of topicality. We report studies on 50 nm thick nanogranular polycrystalline gadolinium thin films on SiO2 wafers that demonstrate single-crystal like behavior. The maximum in-plane saturation magnetization at 4 K was found to be 4?MS4 K = (2.61 +/- 0.26) T with a coercivity of HC4 K = (160 +/- 5) Oe. A maximum Curie point of TC = (293 +/- 2) K was measured via zero-field-cooled-field-cooled magnetization measurements in close agreement with values reported in bulk single crystals. Our measurements revealed magnetic transitions at T1 = (12 +/- 2) K (as deposited samples) and T2 = (22 +/- 2) K (depositions on heated substrates) possibly arising from the interaction of paramagnetic face-centred cubic grains with their ferromagnetic hexagonal close-packed counterparts.

Scheunert, G.; Hendren, W. R.; Ward, C.; Bowman, R. M.

2012-10-01

437

Homoleptic gadolinium amidinates as precursors for MOCVD of oriented gadolinium nitride (GdN) thin films.  

PubMed

Five new homoleptic gadolinium tris-amidinate complexes are reported, which were synthesized via the salt-elimination reaction of GdCl(3) with 3 equiv of lithiated symmetric and asymmetric amidinates at ambient temperature. The Gd-tris-amidinates [Gd{(N(i)Pr)(2)CR}(3)] [R = Me (1), Et (2), (t)Bu (3), (n)Bu (4)] and [Gd{(NEt)(N(t)Bu)CMe}(3)] (5) are solids at room temperature and sublime at temperatures of about 125 °C (6 × 10(-2) mbar) with the exception of compound 4, which is a viscous liquid at room temperature. According to X-ray diffraction analysis of 3 and 5 as representative examples of the series, the complexes adopt a distorted octahedral structure in the solid state. Mass spectrometric (MS) data confirmed the monomeric structure in the gas phase, and high-resolution MS allowed the identification of characteristic fragments, such as [{(N(i)Pr)(2)CR}GdCH(3)](+) and [{(N(i)Pr)(2)CR}GdNH](+). The alkyl substitution patterns of the amidinate ligands clearly show an influence on the thermal properties, and specifically, the introduction of the asymmetric carbodiimide leads to a lowering of the onset of volatilization and decomposition. Compound 5, which is the first Gd complex with an asymmetric amidinate ligand system to be reported, was, therefore, tested for the MOCVD of GdN thin films. The as-deposited GdN films were capped with Cu in a subsequent MOCVD process to prevent postdeposition oxidation of the films. Cubic GdN on Si(100) substrates with a preferred orientation in the (200) direction were grown at 750 °C under an ammonia atmosphere and exhibited a columnar morphology and low levels of C or O impurities according to scanning electron microscopy, Rutherford backscattering, and nuclear reaction analysis. PMID:23231638

Krasnopolski, Michael; Hrib, Cristian G; Seidel, Rüdiger W; Winter, Manuela; Becker, Hans-Werner; Rogalla, Detlef; Fischer, Roland A; Edelmann, Frank T; Devi, Anjana

2012-12-11

438

Separation of bone from iodine- and gadolinium-based contrast agents using dual energy CT  

Microsoft Academic Search

This study aims to evaluate the separability of bone from iodine- and gadolinium-based intravenous contrast agents using dual energy CT techniques in a phantom. The phantom was prepared containing varying concentrations of iodine-based contrast, gadolinium-based contrast, and calcium hydroxyapatite (to simulate bone). Thirteen iodine concentrations from 0.1 to 12 mg\\/mL, twelve gadolinium concentrations from 0.72 to 34.42 mg\\/mL, and four

Daniel Y. Chong; Erin Angel; Hyun J. Kim; Graham B. Cole; Lousine Boyadzhyan; Christoph Panknin; Ana M. Gomez; Jonathan G. Goldin; Matthew S. Brown; Michael F. McNitt-Gray

2008-01-01

439

Experimental investigation of the creep behavior of garnet at high temperatures and pressures  

Microsoft Academic Search

To provide constraints on the rheological properties of garnet, we have experimentally investigated the creep behavior of\\u000a garnet at high pressures and temperatures using a deformation-DIA. Samples were cold-pressed from a garnet powder and deformed\\u000a at constant displacement rates ranging from 1.1×10?5 to 2.6×10?5 s?1 at high temperatures (1 273–1 473 K) and high pressures (2.4–4.1 GPa). Differential stress and

Shenghua Mei; Ayako M. Suzuki; David L. Kohlstedt; Lili Xu

2010-01-01

440

A predictive thermodynamic model of garnet-melt trace element partitioning  

NASA Astrophysics Data System (ADS)

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 (?Gf) 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 ?Gf 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 between 2.5 and 5.0 GPa and temperatures between 1,430 and 1,640 °C. In conjunction with our new parameterisation for DMg, and previously published equations linking r0(3+) and EX(3+) to garnet major element composition, this model gives a description of trivalent REE, Y, In and Sc partitioning between garnets and anhydrous melts over a range of pressures, temperatures and compositions relevant to melting of garnet-bearing sources in the Earth's upper mantle.

Westrenen, Wim; Wood, Bernard; Blundy, Jonathan

2001-08-01

441

Synthesis of garnet structure compounds using aqueous sol–gel processing  

Microsoft Academic Search

The sol–gel method based on metal chelates in aqueous solvents has been developed to prepare different oxides having garnet crystal structure. This synthetic approach has been used to prepare rare-earth doped yttrium aluminum garnet Y3Al5O12:Ce, Y3Al5O12:Nd, Y3Al5O12:Ho, and Y3Al5O12:Er samples (YAG:Ln). The polycrystalline powders sintered at 1000 °C are formed as single-phase garnet materials. The formation of pure and neodymium-doped

A. Leleckaite; A. Kareiva

2004-01-01

442

Sulfides in the Garnet Pyroxenite xenoliths from Oahu, Hawaii  

NASA Astrophysics Data System (ADS)

Oahu is known for its garnet bearing xenoliths that occur in the Honolulu Volcanics. Clinopyroxene is the dominant minerals of these rocks, and modes of other silicate minerals - orthopyroxene, olivine, garnet, amphibole, and phlogopite vary considerably. Ilmenite and Spinels of diverse variety also occur (Keshav et al. 2007, J. Petrol.). In this report we present new electron microprobe and LA-ICPMS data on the sulfides that are always present in these xenoliths although they make up only trace amounts. In terms of morphology and mode of occurrence the sulfides can be divided fundamentally into two types - Type I occurs as poikilitic inclusions in the silicate phases mostly in clinopyroxene and Type II occurs in the interstitial spaces between the silicates, along grain boundaries and along cracks within individual silicate grains. Sizes of both types vary considerably. Type I sulfides are generally globular and appear to have formed from immiscible sulfide melts that got enclosed by the silicate minerals that grew from the main body of silicate melt. Keshav et al. (2007) estimate the average solidus temperatures of garnet pyroxenites from Oahu to range from 1215 to 1600°C (average 1325°C) at 3-5 GPa. Therefore, the Type I sulfides are high temperature sulfides that formed above the silicate solidus. Type II sulfides take various forms - from vein-like to dendritic. Compositionally, both types include Ni rich pyrrhotites (Ni content varies from 3-5 wt%) and monosulfide solid solutions(MSS). The MSS are divided into Ni rich MSS containing as much as 20 wt% of Ni, the average is 15 wt% while the Ni poor MSS has 5-9 wt% of Ni in it. We have limited data on PGE so far but the Type II sulfides have a very low PGE content. Two recent papers have noted that Hawaiian plume-derived shield tholeiites are too rich in Ni for a given SiO2% to be produced by partial melting of a peridotite and called for an unusual Ni-rich pyroxenite source in which the large Ni content is locked in clinopyroxene. The many experiments that have been conducted on pyroxenites have not been able to generate such high Ni clinopyroxenes. We propose that the Ni actually comes from the high Ni monosulfide solid solutions similar to those in the pyroxenites studied. However, we do not think that these pyroxenites are the source of Hawaiian shield lavas because their isotopic composition is distinct from shield lavas.

Sen, I. S.; Sen, G.; Bizimis, M.

2007-12-01

443

Combination of boron and gadolinium compounds for neutron capture therapy. An in vitro study.  

PubMed

In neutron capture therapy, the therapeutic effect of the boron compound is based on alpha particles produced by the B(n, alpha) reaction while with the gadolinium compound the main radiation effect is from gamma rays derived from the Gd(n, gamma) reaction. The uptake and distribution within the tumor may be different among these compounds. Thus, the combination of the boron and gadolinium compounds may be beneficial for enhancing the radiation dose to the tumor. Chinese hamster fibroblast V79 cells were used. For the neutron targeting compounds, 10B (BSH) at 0, 5, 10, and 15 ppm, and 157Gd (Gd-BOPTA) at 0, 800, 1600, 2400, 3200, and 4800 ppm, were combined. The neutron irradiation was performed with thermal neutrons for 30 min. (neutron flux: 0.84 x 10(8) n/cm2/s in free air). The combination of the boron and gadolinium compounds showed an additive effect when the gadolinium concentration was lower than 1600 ppm. This additive effect decreased as a function of gadolinium concentration at 2400 ppm and resulted in no additive effect at more than 3200 ppm of gadolinium. In conclusion, the combination of the boron and gadolinium compounds can enhance the therapeutic effect with an optimum concentration ratio. When the gadolinium concentration is too high, it may weaken the boron neutron capture reaction due to the high cross-section of gadolinium compound against neutrons. PMID:15943038

Matsumura, A; Zhang, T; Nakai, K; Endo, K; Kumada, H; Yamamoto, T; Yoshida, F; Sakurai, Y; Yamamoto, K; Nose, T

2005-03-01

444

71Ga Chemical Shielding and Quadrupole Coupling Tensors of the Garnet Y(3)Ga(5)O(12) from Single-Crystal (71)Ga NMR.  

PubMed

A single-crystal (71)Ga NMR study of the garnet Y(3)Ga(5)O(12) (YGG) has resulted in the determination of the first chemical shielding tensors reported for the (71)Ga quadrupole. The single-crystal spectra are analyzed in terms of the combined effect of quadrupole coupling and chemical shielding anisotropy (CSA). (71)Ga quadrupole coupling and CSA parameters for the two (tetrahedrally and octahedrally coordinated) gallium sites with axial symmetry in YGG (Ga(IV), C(Q) = 13.1 +/- 0.2 MHz and delta(sigma) = 54 +/- 50 ppm; Ga(VI), C(Q) = 4.10 +/- 0.06 MHz and delta(sigma) = 24 +/- 3 ppm) are fully consistent with its cubic crystal structure which supports the reliability of the experimental data. In addition, the (71)Ga and (27)Al isotropic chemical shifts for YGG and YAG give further support to the linear correlation observed earlier between (71)Ga and (27)Al isotropic chemical shifts. PMID:11669884

Vosegaard, Thomas; Massiot, Dominique; Gautier, Nathalie; Jakobsen, Hans J.

1997-05-21

445

An AEM study of garnet clinopyroxenite from the Sulu ultrahigh-pressure terrane: formation mechanisms of oriented ilmenite, spinel, magnetite, amphibole and garnet inclusions in clinopyroxene  

NASA Astrophysics Data System (ADS)

Optical microscopy, secondary electron microscopy and analytical electron microscopy were used to characterize crystallographic orientation relationships between oriented mineral inclusions and clinopyroxene (Cpx) host from the Hujialing garnet clinopyroxenite within the Sulu ultrahigh-pressure (UHP) terrane, eastern China. One garnet clinopyroxenite sample (2HJ-2C) and one megacrystic garnet-bearing garnet clinopyroxenite (RZ-11D) were studied. Porphyroblastic clinopyroxene from sample 2HJ-2C contains oriented inclusions of ilmenite (Ilm), spinel (Spl), magnetite and garnet, whereas clinopyroxene inclusions within megacrystic garnet from sample RZ-11D contain oriented inclusions of ilmenite and amphibole. Specific crystallographic relationships were observed between ilmenite/spinel plates and host clinopyroxene in sample 2HJ-2C and between ilmenite plates and host clinopyroxene in sample RZ-11D, i.e. [ 1bar{1}00 ]Ilm//[ 0bar{1}0 ]Cpx (0001)Ilm//(100)Cpx; and [110]Spl//[ 0bar{1}0 ]Cpx ( bar{1}11 )Spl//(100)Cpx. These inclusions are suggested to be primary precipitates via solid-state exsolutions. Most of the needle-like magnetite/spinel inclusions generally occur at the rims or along fractures of clinopyroxene within sample 2HJ-2C. Despite the epitaxial relation with host clinopyroxene, these magnetite/spinel needles would have resulted from fluid/melt infiltrations. Non-epitaxial garnet lamellae in clinopyroxene of sample 2HJ-2C were formed via fluid infiltration-deposition primarily along (010) and subordinately along (100) partings. Epitaxial amphibole plates (with a thickness <1 ?m) and lamellae (with a thickness = 1-10 ?m) in host clinopyroxene of sample RZ-11D were probably results of hydration processes, although amphibole plates could otherwise be interpreted as exsolution products. Temporal relations between mineral inclusions in each sample can be established, and a semi-quantitative P-T path for this garnet clinopyroxenite body was derived accordingly. The present results show that the Hujialing garnet clinopyroxenite may not have subducted to mantle depths as deep as 250 km during UHP metamorphism as suggested by previous studies. This study demonstrates that the crystallographic and temporal/spatial relationships between aligned inclusions and host minerals are essential to a correct genetic interpretation of metamorphic rocks.

Hwang, Shyh-Lung; Yui, Tzen-Fu; Chu, Hao-Tsu; Shen, Pouyan; Zhang, Ru-Yuan; Liou, Juhn G.

2011-06-01

446

Application of ultrasound in solvent extraction of nickel and gallium  

SciTech Connect

The effects of ultrasound on the rate of solvent extraction of nickel with Lix 65N and Lix 70, and gallium with Kelex 100 were investigated. These solvent extraction systems are noted by their sluggish nature. Low frequency (20 kHz) ultrasound increased the rates of extraction of nickel by factors of four to seven. The ultrasound had no effect on the final chemical equilibrium. Gallium extraction rates were enhanced with the use of ultrasound by as much as a factor of 15. Again, the ultrasound had no effect on extraction equilibrium. For both nickel and gallium, the enhanced rates were attributed to increased interfacial surface area associated with ultrasonically induced cavitation and microdroplet formation. The stability of the microdroplets permitted intermittent application of ultrasound with corresponding decreases in ultrasonic energy requirements. The lowest energy consumption was observed with short (0.25 to 5 s) bursts of high power (41 to 61 W) ultrasonic inputs. The study also provided insight into the factors that affect the complex extraction of gallium from sodium aluminate solutions. The rate controlling step was found to be the dehydration of the gallate ion, Ga(OH)4, and the first complex formation between gallium and Kelex 100. Sodium was found to enhance the extraction rate up to a point, beyond which increased concentration was detrimental. Increasing aluminum concentration was found to slow extraction rates. Modifiers and diluents were shown to markedly affect extraction rates even without ultrasound. Ketone modifiers, particularly 2-undecanone, when used with Kermac 470B or Escaid 200 diluents enhanced extraction rates of gallium to the point that the use of ultrasound provided no additional benefits. The positive effects of ketone modifiers for the solvent extraction of gallium had not been previously reported.

Pesic, B.

1996-07-01

447

Gallium a unique anti-resorptive agent in bone: Preclinical studies on its mechanisms of action  

SciTech Connect

The discovery of gallium as a new and unique agent for the treatment of metabolic bone disorders was in part fortuitous. Gallium is an exciting new therapeutic agent for the treatment of pathologic states characterized by accelerated bone resorption. Compared to other therapeutic metal compounds containing platinum or germanium, gallium affects its antiresorptive action without any evidence of a cytotoxic effect on bone cells. Gallium is unique amongst all therapeutically available antiresorptive agents in that it favors bone formation. 18 refs., 1 fig.

Bockman, R.; Adelman, R.; Donnelly, R.; Brody, L.; Warrell, R. (Hospital for Special Surgery, New York, NY (USA)); Jones, K.W. (Brookhaven National Lab., Upton, NY (USA))

1990-01-01

448

Magnetoelectric Coupling and Relaxation in Yttrium Iron Garnet  

NASA Astrophysics Data System (ADS)

We report the results of the magnetic and dielectric relaxation measurement on yttrium iron garnet Y3Fe5O12 which shows the 2nd order magneto-electric (ME) effect under an applied electric field [1] and the 1st order ME effect by an electric field cooling procedure [2]. We found that the temperature dependence of the dielectric relaxation dynamics coincides with that of magnetic one. This suggests a strong magneto-electric coupling between dielectric and magnetic relaxation dynamics. Indeed the dielectric relaxation strengths are enhanced by an applied magnetic field; namely the amplitude of electric dipole moment can be tuned by magnetic field. This effect accounts for the magnetic field induced change of the static dielectric permittivity and thereby the gigantic 2nd order ME effect as observed. [1] T.H. O'Dell, Phil. Mag. 16, 487 (1967), [2] H. Ogawa et al., JPSJ 56, 452 (1987).

Yamasaki, Yuichi; Kohara, Yuki; Tokura, Yoshinori

2009-03-01

449

Phase Diagram for Magnon Condensate in Yttrium Iron Garnet Film  

PubMed Central

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??m 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.

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

2013-01-01

450

Garnet-Perovskite transformation in CaGeO3  

NASA Astrophysics Data System (ADS)

The phase transitions and physical properties of the garnet and the perovskite structure at high P-T conditions have attracted attention to understand the dynamics of the Earth's interior because major compositions (MgSiO3 or CaSiO3) have these structures in the Earth's mantle. It is known that some ABO3 compounds are excellent analogues of MgSiO3 or CaSiO3. Calcium germinate (CaGeO3) exhibits a sequence of phase transitions from a pyroxenoid to a tetragonal garnet phase, and subsequently to an orthorhombic perovskite phase. The phase boundaries in CaGeO3 have been also used as a pressure calibration point at high temperatures in high-pressure experiments, such as for SiO2 and Mg2SiO4. Therefore, the precise phase boundary of CaGeO3 needs to be determined. The transition pressure of CaGeO3 has been investigated in static high-pressure experiments using quench [1] and in situ methods [2]. According to previous high-pressure experiments, the transition pressure is ~6 GP and this boundary had a negative slope. In contrast, Ross et al. [1] also estimated the value of dP/dT slope of this transition using calorimetry data, and calculated the slope to be 2-3 times more negative than the value determined from high-pressure experiments. Therefore, we reinvestigated the dP/dT slope of garnet-perovskite transition in CaGeO3 using the high-pressure experiments. In this study, the use of a multi-anvil high-pressure system combined with a synchrotron radiation source made it possible to acquire precise data from samples under high-pressure and high-temperature conditions [3]. After reaching the required pressure and temperature, we performed in situ measurements using the synchrotron X-rays. The duration of heating was 0.5-2.0 hours. At the end of the experimental runs, the sample was quenched by cutting off the electrical power. This heating procedure was the same as that used in typical quench experiments. We performed approximately 30 experimental runs, and the boundary determined in this study is in general agreement with that reported in previous high-pressure experiments [1,2]. However, the value of our dP/dT slope was 2-3 times more negative than that in previous experiments [3]. The calculated value of the dP/dT slope using calorimetry data [1] is consistent with our value of dP/dT [3]. It is likely that the discrepancy between previous and our high-pressure experiments dues to the kinetics of the structural phase transition. In previous in situ experiments [2], the P-T condition was changed several times during each run while observing the transition from the garnet to the perovskite structure. It is known that a metastable overshoot (?P or ?T) is required to provide a sufficiently large energy driving force to overcome a nucleation and/or growth barrier for the transition in previous experiments [2]. To avoid any influence of the kinetic effect, we used the same heating cycle as that used in conventional quench experiments.

Ono, S.

2012-04-01

451

Mixed Garnet laser crystals for water vapour DIAL transmitter  

NASA Astrophysics Data System (ADS)

There are more or less well established technologies such as the optical-parametric-oscillator (OPO), the Raman-laser, and the Ti-Sapphire laser, which are able to emit laser light in the region of the water vapour absorption lines. For WALES the regions of about 935 nm, 942 nm, and 944 nm have been identified as the most suitable wavelength ranges. However, each of these laser designs is highly sophisticated. Current baseline for WALES is the Ti-Sapphire laser. A fourth possibility to achieve these wavelength ranges is to shift the groundstate laser lines (938 nm and 946 nm) of the Nd:YAG laser by replacing Aluminium and Yttrium by other rare earth elements. Changes of the host lattice characteristics lead to a shift of the upper and lower laser levels. These modified crystals are summarized under the name of "Mixed Garnet" crystals. Only the Mixed Garnet lasers can be pumped directly with diode laser and use a direct approach to generate the required laser pulses without frequency conversion. Therefore no additional non-linear crystals are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons. Such lasers have the great potential to fulfil the requirements and to become the preferred transmitter concept for WALES as well as for follow up missions. Within a ESA study several crystal compositions have been grown, spectrally characterised and analysed. Absorbed space radiation energy in the crystal lattice causes colour centres, which can reabsorb the pump and laser wavelength and consequently reduce the laser gain considerably. Co-dopants such as Chromium and Cerium are able to suppress the colour centres and are candidates for effective radiation hardening. The results of the crystal tuning, the co-doping with different radiation hardeners and the radiation tests will be presented. There applicability for a space based water vapour DIAL transmitter will be discussed.

Treichel, Rainer; Czeranowsky, Christoph; Ileri, Bilge; Petermann, Klaus; Huber, Günter

2004-06-01

452

Calibrating the Spinel/Garnet transition in CMAS  

NASA Astrophysics Data System (ADS)

Previous investigations of the spinel-garnet lherzolite transition (SGT) in the CMAS system have yielded wildly discrepant pressures for the SGT at temperatures between 1400° C and the solidus (~1570° C) depending upon the pressure medium. Melting experiments on compositions in the Di-Wo join have been used to determine the stability of pressure with time in experiments BaCO3 and talc/pyrex assemblies. No variation in eutectic liquid composition (hence pressure) was observed with time up to 24 hours for either assembly. However, in the course of mapping out the trace of the Diopside-Wollastonite eutectic curve in P-T space with both piston-in and piston-out experiments it became obvious that sample pressure in BaCO3 assemblies was being intensified at high temperatures in contrast to frictional loss of pressure at lower temperatures along the gold melting. A new pressure correction algorithm, derived by multiple regression analysis, incorporates both effects. When applied to a barium carbonate run at the intersection of the CMAS spinel-lherzolite to garnet-lherzolite transition (SGT) with the model peridotite solidus, the model pressure increases from 2.25 to 2.82 GPa. There appears to be a similar effect, but much smaller in magnitude, for talc/pyrex assemblies. Experiments with BaCO3 assemblies in the MAS system produce enstatites with AL2O3 concentrations that agree exactly with the data of Perkins et al. (1981, Contrib. Min. Petrol.) when the new pressure algorithm is applied.

Longhi, J.

2004-05-01

453

[Studies on gallium alloys for dental restorations. 2. Electron probe microanalysis for hardened gallium alloys].  

PubMed

Hardened gallium alloys were analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The cores, matrix and white irregular shape phases were visible with SEM. The round or irregular shape cores contained Ag, Pd, Cu and Zn but did not contain Ga and In. The dark irregular shape matrix, which surrounded the core, consisted of Ga-Ag, Ga-Pd, Ga-Cu and Ga-Sn phases. However, the amount of Ga-Sn phase was very low. The white phase in the matrix was Ag-In phase. PMID:2135533

Horibe, T; Okamoto, Y; Miyazaki, K

1990-05-01

454

Ultraviolet light-driven epitaxial growth of gallium arsenide at reduced substrate temperatures  

Microsoft Academic Search

We report on the photodeposition of gallium arsenide on gallium arsenide and silicon at low substrate temperatures utilizing ultraviolet radiation. A 1000 W Hg-Xe arc lamp serves as the light source with triethylgallium and arsine serving as the reactants. In this study, single crystal gallium arsenide thin films are obtained at substrate temperatures of approximately 357°. The electrical, chemical and

D. P. Norton; P. K. Ajmera

1990-01-01

455

Coesite and diamond inclusions, exsolution microstructures and chemical patterns in ultrahigh pressure garnet from Ceuta (Northern Rif, Spain)  

NASA Astrophysics Data System (ADS)

Garnet from diamondiferous granulites of Ceuta (Betic–Rif cordillera, Spain and Morocco) contains a variety of inclusion types. To better understand the evolution of these rocks during the ultrahigh pressure event, two samples (1 and 2) were selected for the detailed study of garnet. Primary inclusions of apatite, quartz, coesite, rutile and retrograded pyroxene, and exsolution microstructures of rutile characterize garnet from sample 1, whereas exsolution microstructures of quartz, coesite, apatite and rutile, and inclusions formed from a melt characterize garnet from sample 2, indicating that peak metamorphic conditions were recorded by sample 2. In contrast, the chemical patterns of garnet suggest an inverse situation. Garnet from sample 1 has high Ca- and low Mn contents and high XMg, characteristic of growth at high pressure and temperature whereas garnet from sample 2 shows high Mn and low Ca contents and low XMg, characteristic of garnet formed at lower temperature and pressure. The contrasting compositions are interpreted as reflecting differences in the position of the metamorphic path followed by both samples relative to the solidus: Garnets from sample 1 are interpreted as formed below the solidus whereas garnets from sample 2 are interpreted as formed in the presence of a melt, which caused notable enrichment of garnet in Mn and depletion in Ca relative to garnet from sample 1. Due to extensive low-pressure Hercynian melting that caused generalized migmatization and melt mobilization, whole-rock composition of the samples notably changed, thus preventing the accurate estimation of the physical conditions characterizing the older ultrahigh pressure event. Estimations based on experimental determinations of the phosphorous solubility in garnet suggest that peak pressure conditions were on the order of 6–7 GPa, which put the origin of the studied crustal rocks at depths greater than 200 km.

Ruiz-Cruz, M. D.; Sanz de Galdeano, C.

2013-09-01

456

Iron Site Population in Garnets from the Arabo-Nubian Shield  

NASA Astrophysics Data System (ADS)

Recently it has been found in two different locations in South Eastern Desert of Egypt that some pegmatitic veins which invaded in gneissic rocks are associated with Yttrium bearing garnets with the general chemical composition c3a2d3O12. The concentration of Yttrium in these garnets reached 10,000 ppm. Garnets with lower concentration up to 300 ppm were also found in south Sinai peninsula, and are associated with metamorphosed sedimentary rocks. Both locations are part of the Arabo-Nubian Shield, and were mapped using Landsat images (TM) and extensive field work. In the present study our main concern was to determine the cation site population and chemical composition of all samples. Two different garnets structure models were identified. The typical occurrence of spessartine, almandine and pyrope were present and confirm the site population.

Bahgat, A. A.; Ramadan, T. M.; Mostafa, M. A.

1998-12-01

457

Constraints on transport and kinetics in hydrothermal systems from zoned garnet crystals.  

PubMed

Zonation of oxygen isotope ratios, fluorine, and rare earth element abundances across garnet crystals from the Permian Oslo Rift reflect temporal variation of the hydrothermal system in which the garnets grew. A sharp rimward decrease in the (18)O/(16)O ratio (of 5 per mil) across the interface between aluminum-rich garnet cores and iron-rich rims indicates influx of meteoric fluids to a system initially dominated by magmatic fluids. This influx may record the transition from ductile to brittle deformation of the hydrothermally altered rocks. In contrast, fluorine and light rare earth element concentrations increase at the core-rim interface. These data may reflect enhanced advective transport and notable kinetic control on trace element uptake by the garnets during brittle deformation. PMID:17754883

Jamtveit, B; Hervig, R L

1994-01-28

458

Using garnet peridotites as tools to reconstruct paleo-geodynamic settings of fossil continental collision zones  

NASA Astrophysics Data System (ADS)

Orogenic garnet peridotites (metamorphic rocks containing the characteristic HP garnet-olivine mineral assemblage) form volumetrically minor, but important components of (ultra)high pressure (UHP) metamorphic terranes. Such terranes form along convergent plate margins where two adjacent plates collide and one of the plates is subducted below the other. After eduction back to the surface such fossil continental subduction/collision zones form the basic components of exposed (U)HP metamorphic terranes. In the absence of significant amounts of tectonic overpressure (Vrijmoed et al., 2010), the discovery of diamond and majoritic garnet in (U)HP metamorphic terranes provide evidence that subduction of continental crust into the mantle was deep enough to reach the garnet stability field in the overlying mantle wedge above the subduction zone. Brueckner (1998) was the first author who noticed that garnet peridotite bodies, present in such mantle wedges, could be transferred during collision from the mantle wedge into the subducted continental crust. Subsequent buoyancy, most likely generated by slab break off of previously subducted oceanic crust, is the most likely candidate to enable the subducted continental crust and its garnet peridotite "cargo" to return back to (sub)crustal levels. During the latter process mantle wedge garnet peridotite may recrystallize (partly or completely) into what will be called here subduction zone garnet peridotite. Alternatively subduction zone garnet peridotite may be formed by prograde subduction of ultramafic protoliths (serpentinites, Fe-Ti peridotite) that may be present in subducting continental crust prior to subduction. Subdivision between these two basic types of orogenic garnet peridotites (mantle wedge - versus subduction zone peridotite) allows however that in mantle wedge garnet peridotite the subcontinental lithospheric mantle (SCLM) - versus crustal-incorporation processes can be identified which a.o. has lead to the recent recognition of a complete new, deep-seated, subcratonic, lithospheric mantle setting. In addition better characterization of SCLM processes in mantle wedge garnet peridotite will also allow for further subdivision of SCLM wedges into different subtypes that all may be present during collision in the hanging wall of a fossil collision/subduction system. In the following we will present the basic outlines of such a mantle wedge classification system. A simple "conceptual" model will be presented that will allow orogenic mantle wedge garnet peridotite to be used as a tool to reconstruct the former paleo-geodynamic setting of the collision/subduction system. Using field, petrological, geochemical, geochronological and geothermobarometric criteria, all of which can be analysed directly in the mantle wedge garnet peridotite body itself, the model allows for discrimination between four different end-member types within the SCLM (equivalent to young/hot/dynamic- versus cold/old/static mantle in thick or thin garnet-olivine bearing mantle wedges). In addition our conceptual model is based on the fundamental assumption that all SCLM was once formed by rising, accretion and cooling of hot asthenospheric mantle. Note also that all mantle wedge end member types may become overprinted by the subduction zone type. The latter, when complete, may evidently erase all former mantle wedge evidences. To test the applicability of our model we have applied the proposed mantle wedge classification system to well studied orogenic garnet peridotites of the Caledonian Orogeny in Scandinavia and the Triassic Sulu-Dabie Orogeny in China. Results will be presented. References: Brueckner (1998). Geology 26, 631-634; Vrijmoed et al. (2010). Eur. J. Mineralogy.

Zhang, Cong; van Roermund, Herman; Zhang, Lifei

2010-05-01

459

Obtaining Age Information on Metamphic Process Using Mn and HREE Diffusion in Garnets  

NASA Astrophysics Data System (ADS)

Garnet is the main mineral containing Mn and HREE in metamorphic rocks. Usually Mn and HREE exhibits some zoning in garnets. Both Mn and HREE contents increase with temperature drop. Garnets from the polymetamorphic Belomorian complex (Tupaya Guba region) were studied using ion microprobe. These garnets from the gneisses are related to high pressure granulite stage I2 followed without interruption by high pressure amphibolite stage I3 (Drugova, 1999). The garnets are untypical zoned in HREE as low-grade garnets. HREE drop rimward significantly. The minimum temperatures of metamorphism were determined as 730-760° for garnet core and 680-700° for garnet rim by garnet-biotite thermometer. The pressure was constant - about 6.5-8 kbar. HREE exhibit a Rayleigh fractionation profile, Mn concentration has been homogenised to flat profile (1,18 wt. per cent at the core and increase in the outer rim upto 1,73 wt. per cent). It can be explained only by quick time (approximately 10-15 Ma) estimated for the metamorphic event. HREE diffusion rates more than two orders of magnitude slower than Mn diffusion rate (Van Orman et al., 2002), and more time of metamorphic event is required to homogenise the HREE profiles. The alike results of modelling of trace element and Mn data were presented for garnets from the Zanskar area of the Indian Himalaya - 3-10 Ma estimate for the metamorphic event (Ayres & Vance, 1994). References Drugova, G.M., Principal stages in metamorphic evolution of Chupinskaya series in Belomorsky folded belt. Proc. Rus. Min. Soc., No 3, 49-57 (1999). Van Orman, J. A., Grove, T. L., Shimizu, N. et al., Rare earth element diffusion in a natural pyrope single crystal at 2.8 Gpa. Contribs Mineral. Petrol., Vol. 142, 416-424. (2002). Ayres, M. and Vance, D., Constraints on the thermal evolution of the Indian Himalaya from manganese and erbium distributions in metapelitic garnets. Mineral. Mag., Vol. 58A, 34-35. (1994).

Skublov, S.

2003-12-01

460

Garnet Lu–Hf dating of retrograde fluid activity during ultrahigh-pressure metamorphic eclogites exhumation  

Microsoft Academic Search

Previous studies on the atoll-shaped garnets in ultrahigh-pressure (UHP) metamorphic eclogites from the Dabie orogen, east-central\\u000a China, suggest a fluid-enhanced overgrowth origin at the onset of exhumation. The atoll-garnets bearing eclogite place better\\u000a constraints on the timing of the retrograde fluid activity and are a straightforward target to gain insight into the isotopic\\u000a equilibrium and\\/or disequilibrium during exhumation. Comprehensive textural,

Hao Cheng; Eizo Nakamura; Zuyi Zhou

2009-01-01