Sample records for magnetic properties complexes

  1. Magnetic properties of biacetyldihydrazone complexes

    Microsoft Academic Search

    Montserrat Barquín; María J. González Garmendia

    1996-01-01

    Magnetic susceptibilities of the biacetyldihydrazone (BdH) complexes [M(BdH)3](NO3)2 (M = CoII, NiII, CuII or ZnII), [Fe(BdH)3](NO3)3, [M(BdH)3](Ni(dto)2] (M = CoII, NiII or ZnII; dto = dithiooxalate), [(BdH)2Cu(dto)Ni(dto)] and [Fe(BdH)3]2[Ni(dto)2]3 have been studied in the 4.2–295 K range. ZnII complexes are diamagnetic, and complexes of NiII, CuII and FeIII obey the Curie-Weiss law. The CoII complexes behave anomalously and the results

  2. Magnetic properties and chiral states of a trimetallic uranium complex

    NASA Astrophysics Data System (ADS)

    Carretta, S.; Amoretti, G.; Santini, P.; Mougel, V.; Mazzanti, M.; Gambarelli, S.; Colineau, E.; Caciuffo, R.

    2013-12-01

    The magnetic properties of the triangular molecular nanomagnet [UO2L]3 (L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate) have been investigated through electron paramagnetic resonance spectroscopy, high-field magnetization and susceptibility measurements. The experimental findings are well reproduced by a microscopic model including exchange interactions and local crystal fields. These results show that [UO2L]3 is characterized by a non-magnetic ground doublet corresponding to two oppositely twisted chiral arrangements of the uranium moments. The non-axial character of single-ion crystal fields leads to quantum tunneling of the noncollinear magnetization in the presence of a magnetic field applied perpendicularly to the triangle plane.

  3. Structural, Magnetic and Luminescent Properties of Lanthanide Complexes with N-Salicylideneglycine

    PubMed Central

    Van?o, Ján; Trávní?ek, Zden?k; Kozák, Ond?ej; Bo?a, Roman

    2015-01-01

    A series of anionic heavy lanthanide complexes, involving the N-salicylideneglycinato(2-) Schiff base ligand (salgly) and having the general formula K[Ln(salgly)2(H2O)2]?H2O (1–6), where Ln stands for Gd, Tb, Dy, Ho, Er and Tm, was prepared using the one-pot template synthesis. The complexes were thoroughly characterized by elemental and Thermogravimetric/Differential Thermal Analyses (TG/DTA), Fourier Transform Infrared Spectroscopy (FT-IR), and photoluminescence spectroscopies, electrospray-ionization mass spectrometry, and their magnetic properties were studied by temperature-dependent dc magnetic measurements using the superconducting quantum interference device (SQUID). The X-ray structure of the terbium(III) complex (2), representing the unique structure between the lanthanide complexes of N-salicylideneamino acids, was determined. The results of spectral and structural studies revealed the isostructural nature of the prepared complexes, in which the lanthanide ion is octacoordinated by two O,N,O-donor salgly ligands and two aqua ligands. The analysis of magnetic data confirmed that the complexes behave as paramagnets obeying the Curie law. The results of photoluminescence spectral studies of the complexes showed the different origin in their luminescent properties between the solid state and solution. An antenna effect of the Schiff base ligand was observed in a powder form of the complex only, while it acts as a fluorophore in a solution. PMID:25927576

  4. Magnetic Properties of Some Complexes of Mo5+

    Microsoft Academic Search

    Ibha de; V. P. Desai; A. S. Chakravarty

    1973-01-01

    The paramagnetic susceptibilities of a number of complexes of the second series of the transition-metal ions are analyzed within the framework of the ligand-field theory. In the compounds under present investigation all the metal ions possess one electron in the outermost 4d shell. The symmetry of the crystalline environment surrounding the ions is assumed to be octahedral with slight tetragonal

  5. Magnetic and transport properties of Co-Si-B metallic glasses with complex dopants

    NASA Astrophysics Data System (ADS)

    Yarmoshchuk, Yevhenii I.; Nakonechna, Olesya I.; Semenko, Mykhailo P.; Zakharenko, Mykola I.

    2014-10-01

    The structure, magnetic and resistivity characteristics of Co-Si-B metallic glasses containing complex dopants have been investigated. The intervals of thermal stability of the phases existing in the alloys studied have been determined. The temperature dependences of the resistivity were shown to be essentially nonlinear up to a certain temperature, evidencing for the contribution of several scattering mechanisms. Magnetic and resistivity behavior of these alloys are substantially governed by the phase separation within the region of the amorphous state stability and magnetic clusters formation. In the as-cast alloys these clusters are estimated to contain 2-4 Co atoms. Heat treatment significantly affects the structure and magnetic properties. It leads to increase of the Curie temperature and localized magnetic moment, whereas the crystallization temperature remains almost invariable.

  6. Syntheses, crystal structures, magnetic and luminescence properties of five novel lanthanide complexes of nitronyl nitroxide radical

    SciTech Connect

    Wang, Ya-Li; Gao, Yuan-Yuan [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Ma, Yue, E-mail: maynk@nankai.edu.cn [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Wang, Qing-Lun; Li, Li-Cun [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); Liao, Dai-Zheng [Department of Chemistry and Key Laboratory of Advanced Energy Materials Chemistry (MOE) and TKL of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071 (China); State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005 (China)

    2013-06-01

    Five novel Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized, characterized structurally and magnetically: [Ln(hfac)?(NITPh-3-Br-4-OMe)?] (Ln(III)=Eu(1), Gd(2), Tb(3), Dy(4), Ho(5); hfac=hexafluoroacetylacetonate; and NITPh-3-Br-4-OMe=2-3´-Br-4´-methoxyphenyl-4,4,5,5 -tetramethylimidazoline-1-oxyl-3-oxide). The single-crystal structures analyses show that these complexes have similar mononuclear tri-spin structures, in which central Ln(III) ions are all eight coordinated by three hfac molecules and two NITPh-3-Br-4-OMe radicals. The variable-temperature magnetic susceptibility studies reveal the antiferromagnetic interactions between the paramagnetic ions (Ln(III) and radicals) in complexes 1, 2, 3 and 5 and ferromagnetic interaction in complex 4. The luminescence characterizations of complexes Eu(1), Tb(3) and Dy(4) are also studied in this paper. - Graphical abstract: Using a novel halogen phenyl-substituted nitronyl-nitroxide radical, we obtained and characterized five isostructural lanthanide mononuclear tri-spin compounds. Highlights: • A new halogen phenyl-substituted nitronyl-nitroxide radical was designed. • Five new Ln(III) radical complexes have been synthesized and characterized. • The reasonable evaluation the magnetic interactions between Ln(III) ions and radical is meaningful. • These complexes show good luminescent properties.

  7. CORRELATION BETWEEN THE OPTICAL AND MAGNETIC PROPERTIES OF FERRIC N-ACETYLATED HEME OCTAPEPTIDE COMPLEXES

    SciTech Connect

    Yang, E.K.; Sauer, K.

    1980-05-01

    The room temperature magnetic susceptibility of the complexes of the ferric N-acetylated heme octapeptide (N-H8PT) from horse heart cytochrome c is known to be generally consistent with the absorption and magnetic circular dichroism (MCD) spectra of these complexes. However, the N-acetylated methionine complex of the N-H8PT, which has axial coordination identical to that of the parent molecule, is found to exhibit a thermal mixture of high spin (S=5/2) and low spin (S=1/2) states. The temperature dependence of the magnetic susceptibility of the N-acetylmethionine complex yields {Delta}H{sup 0} = -7.6kca1/mole and {Delta}S° = -25.9 e.u. for a high to low spin transition. The electron spin resonance (ESR) spectrum of the N-acetylmethionine complex indicates a low spin ground state, with g values at 1.51, 2.31, and 2.91, which are distinct from those of cytochrome c. The axial ({Delta}) and rhombic (V) distortion parameters of the {sup 2}T{sub 2g} state correspond to 2.96{lambda} and 1.94{lambda}, respectively, where {lambda} is the spin-orbit coupling constant. A model is proposed to account for the uniqueness of the N-acetylmethionine complex: a change in the Fe-S distance may play a role in regulating the redox properties of cytochrome c.

  8. Complex Nano-objects Displaying Both Magnetic and Catalytic Properties: A Proof of Concept for Magnetically Induced Heterogeneous Catalysis.

    PubMed

    Meffre, Anca; Mehdaoui, Boubker; Connord, Vincent; Carrey, Julian; Fazzini, Pier Francesco; Lachaize, Sébastien; Respaud, Marc; Chaudret, Bruno

    2015-05-13

    Addition of Co2(Co)9 and Ru3(CO)12 on preformed monodisperse iron(0) nanoparticles (Fe(0) NPs) at 150 °C under H2 leads to monodisperse core-shell Fe@FeCo NPs and to a thin discontinuous Ru(0) layer supported on the initial Fe(0) NPs. The new complex NPs were studied by state-of-the-art transmission electron microscopy techniques as well as X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. These particles display large heating powers (SAR) when placed in an alternating magnetic field. The combination of magnetic and surface catalytic properties of these novel objects were used to demonstrate a new concept: the possibility of performing Fischer-Tropsch syntheses by heating the catalytic nanoparticles with an external alternating magnetic field. PMID:25867032

  9. Structurally Diverse Copper(II) Complexes of Polyaza Ligands Containing 1,2,3-Triazoles: Site Selectivity and Magnetic Properties

    E-print Network

    Weston, Ken

    (II) centers in three dinuclear complexes were analyzed via temperature-dependent magnetic susceptibility Selectivity and Magnetic Properties Pampa M. Guha, Hoa Phan, Jared S. Kinyon, Wendy S. Brotherton structural diversity, which includes mononuclear and dinuclear complexes as well as one-dimensional polymers

  10. Magnetism and Magnetic Properties

    NSDL National Science Digital Library

    Roberta Schneck

    2011-10-13

    Students will identify properties of magnetism and begin to develop understanding of their practical applications. Students will also begin to develop understanding of the essential nature of Earth's magnetic fields.

  11. New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties

    SciTech Connect

    Liu Fuchen, E-mail: fuchenliutj@yahoo.co [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xue Min; Wang Haichao [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Ouyang Jie, E-mail: ouyang@tjut.edu.c [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2010-09-15

    Two new manganese complexes, [Mn{sub 3}(L{sup 1}){sub 4}(NO{sub 3}){sub 2}]{sub n} (1, HL{sup 1}=nicotinate N-oxide acid) and [MnL{sup 2}Cl]{sub n} (2, HL{sup 2}=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L{sup 1} ligands take two different coordinated modes bridging four and three Mn{sup II} ions. The nitrate anions take chelating coordination modes, leading one type of the Mn{sup II} ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schlaefli notation {l_brace}4{sup 3{r_brace}}2{l_brace}4{sup 4}; 6{sup 2{r_brace}}4{l_brace}4{sup 6}; 6{sup 6}; 8{sup 3{r_brace}}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L{sup 2} ligand, giving a 3D framework with a {l_brace}3{sup 4}; 5{sup 4{r_brace}} {l_brace}3{sup 2};4;5{sup 6};6{sup 6{r_brace}} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a -J{sub 1}J{sub 1}J{sub 2}- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J{sub 1}=-2.77, J{sub 2}=-0.67 cm{sup -1}. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J{sub 1}=-2.05 and J{sub 2}=0.55 cm{sup -1}, which results in a whole antiferromagnetic state. - Graphical abstract: The synthesis, crystal structure and magnetic properties of two new MnII complexes with pyridyl-carboxylate N-oxide ligands are reported.

  12. Modeling the magnetic properties of lanthanide complexes: relationship of the REC parameters with Pauling electronegativity and coordination number.

    PubMed

    Baldoví, José J; Gaita-Ariño, Alejandro; Coronado, Eugenio

    2015-07-01

    In a previous study, we introduced the Radial Effective Charge (REC) model to study the magnetic properties of lanthanide single ion magnets. Now, we perform an empirical determination of the effective charges (Zi) and radial displacements (Dr) of this model using spectroscopic data. This systematic study allows us to relate Dr and Zi with chemical factors such as the coordination number and the electronegativities of the metal and the donor atoms. This strategy is being used to drastically reduce the number of free parameters in the modeling of the magnetic and spectroscopic properties of f-element complexes. PMID:26105010

  13. Synthesis, spectroscopy and magnetic properties of transition-metal complexes with aminophosphonate derivatives of pyridine

    NASA Astrophysics Data System (ADS)

    ?urowska, B.; Boduszek, B.

    2011-06-01

    The compounds of general formula [ML2](ClO4)2 [M = Cu(II), Ni(II), Co(II)]; L = diethyl 3-pyridylmethyl[N-(butyl)amino]phosphonate (3-pmape) or diethyl 4-pyridylmethyl[N-(butyl)amino]phosphonate (4-pmape) were prepared. The new complexes were identified and characterized by elemental analysis, infrared, electronic spectral studies and magnetic measurements. The complexes are sixcoordinate. Metal ions are octahedrally surrounded by two pyridine and two amine nitrogens, and two oxygens of the phosphoryl groups. The results of the magnetic studies suggest polymeric chain structure of the above complexes and indicate weak antiferromagnetic interaction between the magnetic centers. The magnetic behavior of Co(II) complexes is characteristic for cobalt(II) system with an important orbital contribution via spin-orbit coupling.

  14. Assembly and photonic properties of superparamagnetic colloids in complex magnetic fields.

    PubMed

    He, Le; Hu, Yongxing; Han, Xiaogang; Lu, Yu; Lu, Zhenda; Yin, Yadong

    2011-11-15

    Interparticle magnetic dipole force has been found to drive the formation of dynamic superparamagnetic colloidal particle chains that can lead to the creation of photonic nanostructures with rapidly and reversibly tunable structural colors in the visible and near-infrared spectrum. Although most studies on magnetic assembly utilize simple permanent magnets or electromagnets, magnetic fields, in principle, can be more complex, allowing the localized modulation of assembly and subsequent creation of complex superstructures. To explore the potential applications of a magnetically tunable photonic system, we study the assembly of magnetic colloidal particles in the complex magnetic field produced by a nonideal linear Halbach array. We demonstrate that a horizontal magnetic field sandwiched between two vertical fields would allow one to change the orientation of the particle chains, producing a high contrast in color patterns. A phase transition of Fe(3)O(4)@SiO(2) particles from linear particle chains to three-dimensional crystals is found to be determined by the interplay of the magnetic dipole force and packing force, as well as the strong electrostatic force. While a color pattern with tunable structures and diffractions can be instantly created when the particles are assembled in the form of linear chains in the regions with vertical fields, the large field gradient in the horizontal orientation may destabilize the chain structures and produces a pattern of 3D crystals that compliments that of initial chain assemblies. Our study not only demonstrates the great potential of magnetically responsive photonic structures in the visual graphic applications such as signage and security documents but also points out the potential challenge in pattern stability when the particle assemblies are subjected to complex magnetic fields that often involve large field gradients. PMID:21967666

  15. Magnetic properties of poly(propylene imine)-copper dendromesogenic complexes: An EPR study.

    PubMed

    Domracheva, Natalia; Mirea, Anisoara; Schwoerer, Markus; Torre-Lorente, Laura; Lattermann, Günter

    2006-12-11

    Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns. PMID:17089431

  16. Magnetic properties and electronic structure of neptunyl(VI) complexes: wavefunctions, orbitals, and crystal-field models.

    PubMed

    Gendron, Frédéric; Páez-Hernández, Dayán; Notter, François-Paul; Pritchard, Ben; Bolvin, Hélène; Autschbach, Jochen

    2014-06-23

    The electronic structure and magnetic properties of neptunyl(VI), NpO2(2+), and two neptunyl complexes, [NpO2(NO3)3](-) and [NpO2Cl4](2-), were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO2Cl4](2-), a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. PMID:24848696

  17. Solvent dependent reactivities of di-, tetra- and hexanuclear manganese complexes: syntheses, structures and magnetic properties.

    PubMed

    Yang, Hua; Cao, Fan; Li, Dacheng; Zeng, Suyuan; Song, You; Dou, Jianmin

    2015-04-14

    An unusual solvent effect on the synthesis of five manganese complexes [Mn2(L1)2(Py)4](), [Mn2(L1)2(DMSO)4](), [Mn4(L2)4(OH)4](), [Mn4(L3)2(DMSO)7(H2O)](), and [Mn6O2(L4)4(OAc)2(OMe)2(DMSO)4]·MeOH] (), (H3L1 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid; H2L2 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid amide; H4L3 = di-[5-(2-oxyphenyl)-pyrazole]-3-hydroxamic ether; and H2L4 = 5-(2-oxyphenyl)-pyrazole-3-carboxylic acid methyl ester) has been reported. Five complexes have been characterized by X-ray single crystal diffraction, IR, element analysis, thermogravimetric analysis and UV-vis spectra. The analysis reveals that complexes and are isostructural with a bimetallic six-membered ring and L1 from the decomposition of the original H4ppha (H4ppha = 5-(2-hydroxyphenyl)-pyrazole-3-hydroxamic acid) ligand. Complexes and are two tetranuclear clusters, and possesses an aza12-metallacrown-4 core with L2 from the amide functionalization of the decomposition L1; while represents a novel linear [Mn4N8O2] core with L3 from the condensation of L1 and H4ppha. Complex is the first Mn6 cluster linked by two stacked, off-set 8-azametallacrown-3 subunits with [M-N-N-M-N-N-M-O] connectivity, and L4 derived from the esterification of L1. The magnetic behaviour of complexes show the dominant antiferromagnetic interactions between metal centers, whereas complex further reveals the coexistence of antiferromagnetic and ferromagnetic interactions, and slow magnetic relaxation at T < 6 K with S = 4 ground state, as well as field induced magnetization saturation. PMID:25758136

  18. Structures and magnetic properties of transition metal complexes of 1,3,5-benzenetricarboxylic acid

    Microsoft Academic Search

    Wanru Zhang; Sandra Bruda; Christopher P Landee; Judith L Parent; Mark M Turnbull

    2003-01-01

    Treatment of the potassium salt of 1,3,5-benzenetricarboxylic acid with transition metal ions in aqueous solution produced a series of coordination complexes. Reaction of Ni(ClO4)2·6H2O with K3[C6H3(CO2)3] gave complexes 1, Ni3[C6H3(CO2)3]2(H2O)14·4H2O. The compound crystallized as trimers with two terminal Ni(H2O)5 units bridged by two benzenetricarboxylate ligands to a central Ni(H2O)4. Magnetic susceptibility data indicate the presence of either weak antiferromagnetic interactions

  19. d-Orbital orientation in a dimer cobalt complex: link to magnetic properties?

    PubMed

    Deutsch, Maxime; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Sakiyama, Hiroshi; Tone, Katsuya; Souhassou, Mohamed

    2011-08-01

    The experimental charge-density distribution of the dinuclear cobalt(II) complex [Co(2)(sym-hmp)(2)](BPh(4))(2)·2H(2)O·2C(3)H(6)O was determined at 100 K. When decreasing the temperature, the magnetic susceptibility of this complex deviates from Curie law because of anti-ferromagnetic exchange interactions, but the susceptibility increases sharply at low temperature (< 20 K). To explain this magnetic behaviour a tilt angle between the Co-atom environments was previously theoretically predicted. The structure and experimental charge density determined in this study show a tilt angle. The calculated value, based on the 100 K experimental d-orbital model, is in agreement with the theoretical one. PMID:21775811

  20. Magnetic Properties

    Microsoft Academic Search

    Joachim Wecker; Günther Bayreuther; Gunnar Ross; Roland Grössinger

    \\u000a \\u000a Magnetic materials are one of the most prominent classes of functional materials, as introduced in Sect. 1.3. They are mostly\\u000a inorganic, metallic or ceramic in nature and typically multicomponent when used in applications (e.g. alloys or intermetallic\\u000a phases). Their structure can be amorphous or crystalline with grain sizes ranging from a few nanometers (as in high-end nanocrystalline\\u000a soft magnetic materials) to centimeters

  1. Structure and magnetic properties of a trinuclear nickel(II) complex with benzenetricarboxylate bridge

    Microsoft Academic Search

    Jerzy Mrozi?ski; Alina Bie?ko; Pavel Kopel; Vratislav Langer

    2008-01-01

    Novel trinuclear Ni(II) complex [Ni3(pmdien)3(btc)(H2O)3](ClO4)3·4H2O, 1 where pmdien=N,N,N?,N?,N?-pentamethyldiethylenetriamine, H3btc=1,3,5-benzenetricarboxylic (trimesic) acid, has been prepared and structurally characterized. Three nickel atoms are bridged by btc trianion and their coordination sphere is completed by three N atoms of pmdien and O atom of the water molecule. The three nickel(II) magnetic centers are equivalent and their coordination spheres are completed to deformed octahedrons.

  2. Formation of a G-quartet-Fe complex and modulation of electronic and magnetic properties of the Fe center.

    PubMed

    Wang, Likun; Kong, Huihui; Zhang, Chi; Sun, Qiang; Cai, Liangliang; Tan, Qinggang; Besenbacher, Flemming; Xu, Wei

    2014-11-25

    Although the G-quartet structure has been extensively investigated due to its biological importance, the formation mechanism, in particular, the necessity of metal centers, of an isolated G-quartet on solid surfaces remains ambiguous. Here, by using scanning tunneling microscopy under well-controlled ultra-high-vacuum conditions and density functional theory calculations we have been able to clarify that besides the intraquartet hydrogen bonding a metal center is mandatory for the formation of an isolated G-quartet. Furthermore, by subtly perturbing the local coordination bonding schemes within the formed G-quartet complex via local nanoscale scanning tunneling microscopy manipulations, we succeed in modulating the d orbitals and the accompanying magnetic properties of the metal center. Our results demonstrate the feasibility of forming an isolated G-quartet complex on a solid surface and that the strategy of modulating electronic and magnetic properties of the metal center can be extended to other related systems such as molecular spintronics. PMID:25347538

  3. Preparation and magnetic properties of metal-complexes from N-t-butyl-N-oxidanyl-2-amino-(nitronyl nitroxide).

    PubMed

    Furui, Takanori; Suzuki, Shuichi; Kozaki, Masatoshi; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Okada, Keiji; Tretyakov, Evgeny V; Tolstikov, Svyatoslav E; Romanenko, Galina V; Ovcharenko, Victor I

    2014-01-21

    Metal complexation reactions of N-t-butyl-N-oxidanyl-2-amino(nitronyl nitroxide) diradical (1) with M(hfac)2 (M: Mn or Cu) were investigated. These reactions were found to be very sensitive to the type of metal ion employed. Complex [Mn(hfac)2·1], consisting of Mn(hfac)2 and diradical 1, was readily prepared by mixing the components. However, the reaction of Cu(hfac)2 with 1 or N-t-butyl-N-oxidanyl-2-amino(iminonitroxide) diradical (2) involved the reduction of the diradical to the N-t-butyl-N-oxidanide-2-amino(iminonitroxide) radical anion (3) and finally produced the polymer-chain complex [Cu2(hfac)2·32·Cu(hfac)2]n. The structures of these complexes were elucidated by X-ray analysis, and their magnetic properties were investigated in detail. The temperature dependence of ?pT (?p: magnetic susceptibility) for [Mn(hfac)2·1] exhibited a strong antiferromagnetic interaction (H = -2JS1·S2, J/kB = -217 K) between the Mn(II) spin (S = 5/2) and the diradical 1 spin (S = 1). However, the ?pT-T plots for [Cu2(hfac)2·32·Cu(hfac)2]n indicated the presence of several magnetic interactions: a large ferromagnetic interaction (J/kB = 510 K) between iminonitroxide 3 and the imino-coordinating Cu(II) atom, a moderately large ferromagnetic interaction (J/kB = 58 K) between the iminonitroxide and (iminonitroxide oxygen)-coordinating Cu(hfac)2, and a weak antiferromagnetic interaction (J/kB = -1.4 K) between the two Cu(hfac)-3 moieties within a Cu2O2 square. PMID:24364815

  4. Ligand field influence on the electronic and magnetic properties of quasi-linear two-coordinate iron(ii) complexes.

    PubMed

    Chilton, Nicholas F; Lei, Hao; Bryan, Aimee M; Grandjean, Fernande; Long, Gary J; Power, Philip P

    2015-06-28

    The 2 to 300 K magnetic susceptibilities of Fe{N(SiMe2Ph)2}2, 1, Fe{N(SiMePh2)2}2, 2, and the diaryl complex Fe(Ar(Pr(i)4))2, 3, where Ar(Pr(i)4) is C6H3-2,6(C6H3-2,6-Pr(i)2)2 have been measured. Initial fits of these properties in the absence of an independent knowledge of their ligand field splitting have proven problematic. Ab initio calculations of the CASSCF/RASSI/SINGLE-ANISO type have indicated that the orbital energies of the complexes, as well as those of Fe(Ar(Me6))2, 4, where Ar(Me6) is C6H3-2,6(C6H2-2,4,6-Me3)2), are in the order dxy? dx(2)-y(2) < dxz? dyz < dz(2), and the iron(ii) complexes in this ligand field have the (dxy, dx(2)-y(2))(3)(dxz, dyz)(2)(dz(2))(1) ground electronic configuration with a substantial orbital contribution to their effective magnetic moments. An ab initio-derived ligand field and spin-orbit model is found to yield an excellent simulation of the observed magnetic properties of 1-3. The calculated ligand field strengths of these ligands are placed in the broader context of common coordination ligands in hypothetical two-coordinate linear iron(ii) complexes. This yields the ordering I(-) < H(-) < Br(-)? PMe3 < CH3(-) < Cl(-)? C(SiMe3)3(-) < CN(-)? SAr(Pr(i)6-) < Ar(Pr(i)4-) < Ar(Me6-)? N3(-) < NCS(-)? NCSe(-)? NCBH3(-)? MeCN ? H2O ? NH3 < NO3(-)? THF ? CO ? N(SiMe2Ph)2(-)? N(SiMePh2)2(-) < F(-)? N(H)Ar(Pr(i)6-)? N(SiMe3)Dipp(-) < OAr(Pr(i)4-). The magnetic susceptibility of the bridged dimer, [Fe{N(SiMe3)2}2]2, 5, has also been measured between 2 and 300 K and a fit of ?MT with the isotropic Heisenberg Hamiltonian, ? = -2J?1·?2 yields an antiferromagnetic exchange coupling constant, J, of -131(2) cm(-1). PMID:26006177

  5. Odd-numbered Fe(III) complexes: synthesis, molecular structure, reactivity, and magnetic properties.

    PubMed

    Ako, Ayuk M; Waldmann, Oliver; Mereacre, Valeriu; Klöwer, Frederik; Hewitt, Ian J; Anson, Christopher E; Güdel, Hans U; Powell, Annie K

    2007-02-01

    Three isostructural disklike heptanuclear FeIII compounds of the general formula [FeIII7(mu3-O)3(L)3(mu-O2CCMe3)6(eta1-O2CCMe3)3(H2O)3], where L represents a di- or triethanolamine moiety, display a three-blade propeller topology, with the central Fe atom representing the axle or axis of the propeller. This motif corresponds to the theoretical model of a frustrated Heisenberg star, which is one of the very few solvable models in the area of frustrated quantum-spin systems and can, furthermore, be converted to an octanuclear cage for the case where L is triethanolamine to give [FeIII8(mu4O)3(mu4-tea)(teaH)3(O2CCMe3)6(N3)3].1/2MeCN.1/2H2O or [FeIII8(mu4O)3(mu4-tea)(teaH)3(O2CCMe3)6(SCN)3].2MeCN when treated with excess NaN3 or NH4SCN, respectively. The core structure is formally derived from that of the heptanuclear compounds by the replacement of the three aqua ligands by an {Fe(tea)} moiety, so that the 3-fold axis of the propeller is now defined by two central FeIII atoms. Magnetic studies on two of the heptanulcear compounds established unequivocally S = 5/2 spin ground state for these complexes, consistent with overall antiferromagnetic interactions between the constituent FeIII ions. PMID:17257017

  6. Relationships between electron density and magnetic properties in water-bridged dimetal complexes.

    PubMed

    Overgaard, Jacob; Walsh, James P S; Hathwar, Venkatesha R; Jørgensen, Mads R V; Hoffman, Christina; Platts, Jamie A; Piltz, Ross; Winpenny, Richard E P

    2014-11-01

    The electron densities in two analogous dimetallic transition metal compounds, namely, [M2(?-OH2)((t)BuCOO)4((t)BuCOOH)2(C5H5N)2] (M = Co(1), Ni(2)), were determined from combined X-ray and neutron single-crystal diffraction at 100 K. Excellent correspondence between the thermal parameters from X- and N-derived atomic displacement parameters is found, indicating high-quality X-ray data and a successful separation of thermal and electronic effects. Topological analysis of electron densities derived from high-resolution X-ray diffraction, as well as density functional theory calculations, shows no direct metal-metal bonding in either compound, while the total energy density at the bond critical points suggests stronger metal-oxygen interactions for the Ni system, in correspondence with its shorter bond distances. The analysis also allows for estimation of the relative strength of binding of terminal and bridging ligands to the metals, showing that the bridging water molecule is more strongly bound than terminal carboxylic acid, but less so than bridging carboxylates. Recently, modeling of magnetic and spectroscopic data in both of these systems has shown weak ferromagnetic interactions between the metal atoms. Factors related to large zero-field splitting effects complicate the magnetic analysis in both compounds, albeit to a much greater degree in 1. The current results support the conclusion drawn from previous magnetic and spectroscopic measurements that there is no appreciable direct communication between metal centers. PMID:25330274

  7. Syntheses, structures and magnetic properties of a series of 2D and 3D lanthanide complexes constructed by citric ligand

    NASA Astrophysics Data System (ADS)

    Zhou, Rui-Sha; Song, Jiang-Feng; Yang, Qing-Feng; Xu, Xiao-Yu; Xu, Ji-Qing; Wang, Tie-Gang

    2008-04-01

    A series of lanthanide(III) complexes with citric ligand, [Ln(Hcit)(H 2O)] n (Ln = Ce ( 1), Pr ( 2), Sm ( 3), Dy ( 4) and Er ( 5)), have been synthesized and characterized by elemental analysis, IR, TGA and single-crystal X-ray diffraction. X-ray structural analysis reveals that complexes 1 and 2 are isomorphous and feature 3D networks showing five-connected distorted BN topology, while the isostructural 3- 5 display 2D layer structures with two kinds of 13-membered rings. Variable-temperature magnetic susceptibility measurements for complexes 1 and 5 indicate there exist antiferromagnetic interactions between magnetic centers.

  8. A new tetranuclear copper(II) complex with oximate bridges: Structure, magnetic properties and DFT study

    Microsoft Academic Search

    Sanjib Giri; Debdulal Maity; Jeffrey F. Godsell; Saibal Roy; Michael G. B. Drew; Ashutosh Ghosh; Gurucharan Mukhopadhyay; Shyamal K. Saha

    2011-01-01

    A new tetranuclear complex, [Cu4L4](ClO4)4·2H2O (1), has been synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligand (2E,3E)-3-(2-aminopropylimino) butan-2-one oxime (HL). Single-crystal X-ray diffraction studies reveal that complex 1 consists of a Cu4(NO)4 core where the four copper(II) centers having square pyramidal environment are arranged in a distorted tetrahedral geometry. They are linked together by a

  9. Sandwich transitional metal complexes with tungstobismuthates and 1-methylimidazole ligands: Syntheses, structures and magnetic properties

    Microsoft Academic Search

    Hong Liu; Lin Xu; Guanggang Gao; Fengyan Li; Ning Jiang

    2008-01-01

    Two novel sandwich-type coordination compounds of tungstobismuthate Na9[{Na(H2O)2}3{CoII(mim)}3(BiIIIWVI9O33)2]·36H2O (1) and Na7H2[{Na(H2O)2}3{MnII(mim)}3(BiIIIWVI9O33)2]·21H2O (2) (mim=1-methylimidazole) have been synthesized in alkaline aqueous solution. Their composition and structures were established by elemental analyses, IR spectra, and single crystal X-ray diffraction. These two complexes consist of two tri-vacant [?-B-BiIIIWVI9O33]9? moieties linked through three CuII or MnII and three Na+ ions. These Na+ cations around the

  10. Structure, photochemistry and magnetic properties of tetrahydrogenated Schiff base chromium(III) complexes.

    PubMed

    Liu, Bin; Chai, Jie; Feng, SiSi; Yang, BinSheng

    2015-04-01

    Four mononuclear chromium(III) complexes [Cr(L(1))(en)]Br0.3Cl0.7 (1), [Cr(L(1))(pr)]Cl (2), [Cr(L(2))(en)]ClO4 (3), [Cr(L(2))(pr)]Cl (4) along with one dinuclear ?-methoxo [Cr(?-OMe)(L1)]2 (5) were synthesized (en=1,2-ethanediamine, pr=1,3-diaminopropane H2L(1)=Tetrahydrosalen=H2[H4]salen=N,N'-bis(2-hydroxybenzyl)-1,2-ethanediamine, H2L(2)=Tetrahydrosalpr=H2[H4]salpr=N,N'-bis(2-hydroxybenzyl)-1,3-diaminopropane). The competitive reactions in the presence of EDTA were carried out and the first-order rate constants k(1)=(5.2±0.2)×10(-3) h(-1)complex 5 exhibits a strong antiferromagnetic coupling with the J=-10.8 cm(-1). PMID:25637815

  11. Novel tetranuclear Ni(II) Schiff base complex containing Ni4O4 cubane core: Synthesis, X-ray structure, spectra and magnetic properties

    NASA Astrophysics Data System (ADS)

    Jana, Mahendra Sekhar; Priego, José L.; Jiménez-Aparicio, Reyes; Mondal, Tapan Kumar

    2014-12-01

    Novel tetranuclear nickel(II) Schiff base complex having symmetric Ni4O4 cubane-core, [Ni4O2(OAc)2(L)2] (1) has been synthesized. Single crystal of the complex exhibits four nickel atoms in the alternate corner of the cubane and other four sites are occupied by phenolate-O and ?3-O2-. Variable temperature magnetic moment data suggests the Ni centres are weakly antiferromagnetically coupled with J1 = -4.82 cm-1 and J2 = -4.83 cm-1. The electronic spectra, emission properties and life time measurement of ligand, HL and complex 1 have been studied.

  12. Novel tetranuclear Ni(II) Schiff base complex containing Ni4O4 cubane core: synthesis, X-ray structure, spectra and magnetic properties.

    PubMed

    Jana, Mahendra Sekhar; Priego, José L; Jiménez-Aparicio, Reyes; Mondal, Tapan Kumar

    2014-12-10

    Novel tetranuclear nickel(II) Schiff base complex having symmetric Ni4O4 cubane-core, [Ni4O2(OAc)2(L)2] (1) has been synthesized. Single crystal of the complex exhibits four nickel atoms in the alternate corner of the cubane and other four sites are occupied by phenolate-O and ?3-O(2-). Variable temperature magnetic moment data suggests the Ni centres are weakly antiferromagnetically coupled with J1=-4.82cm(-1) and J2=-4.83cm(-1). The electronic spectra, emission properties and life time measurement of ligand, HL and complex 1 have been studied. PMID:24996213

  13. Uranyl and uranyl-3d block cation complexes with 1,3-adamantanedicarboxylate: crystal structures, luminescence, and magnetic properties.

    PubMed

    Thuéry, Pierre; Rivière, Eric; Harrowfield, Jack

    2015-03-16

    The reaction of 1,3-adamantanedicarboxylic acid (LH2) with uranyl nitrate under solvo-hydrothermal conditions, either alone or in the presence of additional metal cations (Co(2+), Ni(2+), or Cu(2+)) gives a series of nine complexes displaying a wide range of architectures. While [UO2(L)(H2O)]·1.25CH3CN (1) and [UO2(L)(DMF)] (2) are one-dimensional (1D) species analogous to that previously known, [H2NMe2]2[(UO2)2(L)3]·1.5H2O (3), which includes dimethylammonium counterions generated in situ, is a three-dimensional (3D) framework, and [UO2(L)(NMP)] (4) (NMP = N-methyl-2-pyrrolidone) is a braid-shaped 1D polymer. When 3d block metal ions are present and bound to 2,2'-bipyridine (bipy) coligands, their role is reduced to that of decorating species attached to uranyl-containing 1D polymers, as in [UO2M(L)2(bipy)2]·0.5H2O with M = Co (5) or Ni (6), and [(UO2)2Cu2(L)3(NO3)2(bipy)2]·0.5H2O (9), or of counterions, as in [Ni(bipy)3][(UO2)4(O)2(L)3]·3H2O (7), in which a two-dimensional (2D) assembly is built from tetranuclear uranyl-containing building units. In contrast, the heterometallic 3D framework [UO2Cu(L)2] (8) can be isolated in the absence of bipy. The emission spectra measured in the solid state display the usual uranyl vibronic fine structure, with various degrees of resolution and quenching, except for that of complex 7, which shows emission from the nickel(II) centers. The magnetic properties of complexes 5, 6, 8, and 9 were investigated, showing, in particular, the presence of zero-field splitting effects in 6 and weak antiferromagnetic interactions in 9. PMID:25710676

  14. Magnetic properties of the Fe{sup II} spin crossover complex in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol)

    SciTech Connect

    Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.j [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone 522-8533 (Japan); Iguchi, Motoi; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone 522-8533 (Japan); Fujiwara, Motoyasu [Institute for Molecular Science, Okazaki 444-8585 (Japan)

    2010-04-15

    Influence of chemical substitution in the Fe{sup II} spin crossover complex on magnetic properties in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol) as a protective colloid was investigated near its high spin/low spin (HS/LS) phase transition. The obvious bi-stability of the HS/LS phase transition was considered by the identification of multiple spin states between the quintet (S=2) states to single state (S=0) across the excited triplet state (S=1). Magnetic parameters of gradual shifts of anisotropy g-tensor supported by the molecular distortion of the spin crossover complex would arise from a Jahn-Teller effect regarding ligand field theory on the basis of a B3LYP density functional theory using electron spin resonance (ESR) spectrum and X-ray powder diffraction. - Graphical abstract: AFM surface image of the emulsion particles with the spin crossover complex.

  15. Hydrothermal synthesis, structures, luminescence and magnetic properties of Zn(II) and Cu(II) complexes with new hydrazone ligand

    NASA Astrophysics Data System (ADS)

    Zheng, Chang-zheng; Wang, Liang; Liu, Juan

    2012-06-01

    Two new complexes [Zn(HL)2(py)2] (1) and [Cu(HL)]2 (2) have been synthesised from a bidentate Schiff base ligand HL (benzylidene acetophenone benzoyl hydrazone). The crystal structures of complex 1 and complex 2 were determined by single-crystal X-ray diffraction. The data indicate that: the complex 1 crystallizes in the monoclinic space group P2(1)/n, with a (nm) = 1.35816(8), b (nm) = 2.39486(13), c (nm) = 1.41368(8), ? (°) = 90, ? (°) = 96.0840(10), ? (°) = 90, Z = 4. The complex 2 crystallizes in the triclinic space group P-1, with a (nm) = 1.02483(8), b (nm) = 1.35797(11), c (nm) = 1.38271(11), ? (°) = 71.5020(10), ? (°) = 78.5850(10), ? (°) = 74.3110(10), Z = 1. Moreover, the unsaturated coordination site of metal ion is occupied by secondary ligand of pyridine. The mononuclear units in 1 and 2 are packed through weak Csbnd H⋯? and ?-? interactions respectively. The results of analytical, IR and TG analysis studies are presented in this paper. Both the ligand and complex 1 show fluorescence in DMF solutions at room temperature. The complex 2 variable-temperature (300-1.8 K) magnetic test show that there is ferromagnetic intramolecular interaction and weak antiferromagnetic intermolecular interaction.

  16. Chondrule magnetic properties

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Obryan, M. V.

    1994-01-01

    The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

  17. New families of hetero-tri-spin 2p-3d-4f complexes: synthesis, crystal structures, and magnetic properties.

    PubMed

    Escobar, Lívia B L; Guedes, Guilherme P; Soriano, Stéphane; Speziali, Nivaldo L; Jordão, Alessandro K; Cunha, Anna Claudia; Ferreira, Vitor F; Maxim, Catalin; Novak, Miguel A; Andruh, Marius; Vaz, Maria G F

    2014-07-21

    In this work we report the synthesis, crystal structures, and magnetic behavior of 2p-3d-4f heterospin systems containing the nitroxide radical 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl radical (N3tempo). These compounds were synthesized through a one-pot reaction by using [Cu(hfac)2], [Ln(hfac)3] (hfac = hexafluoroacetylacetonate, Ln = Dy(III), Tb(III) or Gd(III)), and the N3tempo radical. Depending on the stoichiometric ratio used, the synthesis leads to penta- or trimetallic compounds, with molecular formulas [Cu3Ln2(hfac)8(OH)4(N3tempo)] (Ln = Gd, Tb, Dy) and [CuLn2(hfac)8(N3tempo)2(H2O)2] (Ln = Gd, Dy). The magnetic properties of all compounds were investigated by direct current (dc) and alternating current (ac) measurements. The ac magnetic susceptibility measurements of Tb(III)- and Dy(III)-containing compounds of both families revealed slow relaxation of the magnetization, with magnetic quantum tunneling in zero field. PMID:24964044

  18. Two types of nitrito support for ??-oxido-bridged [Cu?] complexes: synthesis, crystal structures, magnetic properties and DFT analysis.

    PubMed

    Pait, Moumita; Shatruk, Michael; Lengyel, Jeff; Gómez-Coca, Silvia; Bauzá, Antonio; Frontera, Antonio; Bertolasi, Valerio; Ray, Debashis

    2015-04-01

    Novel nitrito supported and ?4-oxido bridged Cu(II) aggregates have been found in two tetranuclear complexes, [Cu4(?4-O)L2(?(1,3)-ONO)4] (1) and [Cu4(?4-O)L2(?(1,3)-OAc)2(?1,2-NO2)2] (2), of the chiral Schiff base HL (HL = 4-methyl-2,6-bis-(1-phenyl-ethylimino)-methylphenol). The structures contain either in situ generated or externally added peripheral ?-nitrito groups, in ?(2)O/O and ?(2)N/O bridging modes. Four NO2(-) bridges in 1 and two AcO(-) co-ligands along with two NO2(-) bridges in 2 are essential for the stabilization of these tetranuclear aggregates. The complexes have been characterized by X-ray crystal structure determination, spectroscopic and magnetic measurements, and density functional theory (DFT) analysis. They are formed from the assembly of two [Cu2L](3+) fragments around a water-derived oxido ligand under the control of nitrite or mixed nitrite/acetate bridges. Variable temperature magnetic susceptibility measurements reveal strong intramolecular antiferromagnetic exchange interactions within the tetranuclear clusters to yield S(T) = 0 ground state. The capacity of the two different nitrite bridging modes to mediate magnetic coupling has been examined through measurements and numerical fitting procedures, and rationalized by means of DFT calculations. PMID:25729876

  19. Synthesis, structural and magnetic properties of oxo-, chloroacetato-bridged tetra-nuclear iron(III) complex

    NASA Astrophysics Data System (ADS)

    Dutta, Amit Kumar; Maji, Swarup Kumar; Dutta, Supriya; Robert Lucas, C.; Adhikary, Bibhutosh

    2012-12-01

    Oxo- and chloroacetato-bridged tetra-nuclear iron(III) complex [Fe4O2(ClCH2COO)8(bpy)2]·H2O, where bpy = 2,2'-bipyridine, has been synthesized and characterized on the basis of X-ray crystallography, elemental analysis, cyclic voltammetric, UV-vis and IR spectroscopic techniques. X-ray diffraction analysis reveals that the complex crystallizes in the monoclinic space group P2/n with a = 9.629(5) Å, b = 13.742(5), c = 20.437(5) Å, ? = ? = 90.000(5)°, ? = 99.792(5)°, V = 2664.9(18) Å3 and Z = 2. The tetra-nuclear entity consists of a [Fe4(?3-O)2]8+ unit comprising four FeIII atoms with a "butterfly" arrangement. Each pair of iron(III) atoms occupy the "hinge" or "body" sites, and "wing-tip" sites, respectively. It undergoes two stepwise one electron reductions, one is quasi-reversible at E1/2 = +0.061 V vs Ag/AgCl (?Ep = 0.082 V) and the other is irreversible at EP.C = -0.38 V at a scan rates 0.1 V s-1. Variable-temperature magnetic susceptibility data reveals strong antiferromagnetic exchange interactions among the four high-spin FeIII ions. The exchange coupling constant Jbb (body-body interaction) is indeterminate due to prevailing spin frustration, but the 'wing-body' antiferromagnetic interaction (Jwb) was evaluated as -115 cm-1, using the spin Hamiltonion model H = -Jwb (S1?S2 + S2?S1 + S1'?S2' + S2'?S1) -Jbb(S2?S2').

  20. Three tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole and different aromatic carboxylates: Assembly, structures, electrochemical and magnetic properties

    SciTech Connect

    Wang, Xiu-Li, E-mail: wangxiuli@bhu.edu.cn [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)] [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China); Zhao, Wei; Zhang, Ju-Wen; Lu, Qi-Lin [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)] [Department of Chemistry, Bohai University, Liaoning Province Silicon Materials Engineering Technology Research Centre, Jinzhou 121000 (China)

    2013-02-15

    Three new tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole (atrz) and three types of aromatic carboxylates, [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(DNBA){sub 6}] (1), [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(1,3-BDC){sub 3}]{center_dot}2H{sub 2}O (2) and [Cu{sub 4}({mu}{sub 3}-OH){sub 2}(atrz){sub 2}(SIP){sub 2}]{center_dot}4H{sub 2}O (3) (HDNBA=3,5-dinitrobenzoic acid, 1,3-H{sub 2}BDC=1,3-benzenedicarboxylic acid and NaH{sub 2}SIP=sodium 5-sulfoisophthalate), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a single-molecular Cu{sup II}{sub 4} cluster structure, which is further connected by the intermolecular hydrogen-bonding interactions to form a 2D supramolecular layer. In 2, there also exist tetranuclear Cu{sup II}{sub 4} clusters, which are linked by the 1,3-BDC anions to give a 3D NaCl-type framework. In 3, the Cu{sup II}{sub 4} clusters are connected by the carboxyl and sulfo groups of SIP anions to generate 3D (4,8)-connected framework with a (4{sup 10}{center_dot}6{sup 14}{center_dot}8{sup 4})(4{sup 5}{center_dot}6){sub 2} topology. The atrz ligand conduces to the construction of tetranuclear copper(II) clusters and the carboxylates with different non-carboxyl substituent show important effects on the final structures of the title complexes. The electrochemical and magnetic properties of 1-3 have been investigated. - Graphical abstract: Three tetranuclear copper(II) cluster-based complexes based on different carboxylates have been synthesized under hydrothermal conditions. The carboxylate anions play a key role in the formation of three different structures. Highlights: Black-Right-Pointing-Pointer Three new tetranuclear copper(II) cluster-based complexes have been obtained. Black-Right-Pointing-Pointer The atrz conduces to the construction of tetranuclear copper(II) clusters. Black-Right-Pointing-Pointer Carboxylates show important effect on the structures of title complexes. Black-Right-Pointing-Pointer Magnetic properties and electrochemical behaviors have been reported.

  1. Structure and magnetic properties of a copper(II) complex with the schiff base derived from 2,2,6,6-tetramethyl-4-aminopiperidine-1-iminoxyl

    Microsoft Academic Search

    L. O. Atovmyan; N. I. Golovina; G. A. Klitskaya; A. A. Medzhidov; A. V. Zvarykina; V. B. Stryukov; D. N. Fedutin

    1975-01-01

    The crystal structure of a copper(II) complex with a Schiff base containing iminoxyI radicals has been determined. Measurements of magnetic susceptibility in the 1.3-300~ range have shown that the magnetic system of the complex consists of triads of interacting spins. The ESR spectra of single crystals of the complex measured at 1.3-300~ have led to a conclusion about interaction between

  2. Structural, electronic and magnetic properties of Mo (4d)-based complex perovskites Ba2MMoO6 (M=Cr and Fe)

    NASA Astrophysics Data System (ADS)

    Musa Saad H.-E., M.; El-Hagary, M.

    2014-06-01

    We report a study of crystallographic parameters of the Mo-based complex perovskites Ba2MMoO6 (M=Cr and Fe) obtained from analysis of X-ray diffraction (XRD) data and the electronic and magnetic properties prediction using the magnetic measurements and the full-potential linearized muffin-tin orbitals within the plane-wave approximation (LMTO-PLW). The Ba2MMoO6 materials were prepared by the solid state reaction method. XRD analysis reveals that Ba2MMoO6 crystalline in a cubic structure (space group Fm-3m) with lattice parameters (a=8.013 Å) for M=Cr and (a=8.061 Å) for M=Fe. XRD results present a matching of 98% with the theoretical results. The densities of states were calculated using the local spin density approximation (LSDA) and LSDA+U methods. LDOS results show a half-metallic-ferrimagnetic ground state for Ba2MMoO6, which is in majority due to the 4d-t2g and 3d-t2g characters. The structural, electronic and magnetic calculation results are in excellent agreement with the experimental and previous theoretical results.

  3. A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

    SciTech Connect

    Gao, Xue-Miao; Guo, Qian [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)] [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)] [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Liu, Fu-Chen, E-mail: fuchenliutj@yahoo.com [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China) [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Lanzhou Petrochemical College of Vocational Technology, Lanzhou 730060 (China)

    2012-12-15

    A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D framework with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.

  4. Synthesis, crystal structures and magnetic properties of the copper(II) complexes containing isophthalate anion as coligand

    Microsoft Academic Search

    Feng-Mei Nie; Fei Lu; Jing Chen; Yong-Li Yang

    2009-01-01

    Two new dinuclear isophthalato-bridged copper(II) complexes [Cu2(ntb)2(?-ipt)](ClO4)2·4CH3OH·0.33H2O (1), [Cu2(bbma)2(?-ipt)(NO3)(CH3OH)]NO3·CH3OH (2) and one mononuclear complex [Cu(bbma)(ipt)(CH3OH)0.67(H2O)0.33]·2CH3OH (3) containing tetradentate and tridentate poly-benzimidazole ligands were synthesized, where ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine and ipt is isophthalate dianion. All of the complexes were characterized by elemental analysis, IR spectra and X-ray crystallography. The structures of complexes 1 and 2 consist of ?-ipt

  5. Rational Synthesis and Magnetic Properties of a Family of Low-Dimensional Heterometallic Cr-Mn Complexes Based on the

    E-print Network

    Gao, Song

    -Ming Wang, Gang Su, Hao-Ling Sun, and Feng Pan State Key Laboratory of Rare Earth Materials Chemistry and Applications and PKU-HKU Joint Laboratory on Rare Earth Materials and Bioinorganic Chemistry, College has a tetranuclear [Mn2Cr2] square structure. Magnetic studies show antiferromagnetic interaction

  6. Magnetic Properties of Diabase Dikes

    Microsoft Academic Search

    D. W. Strangway

    1961-01-01

    A study has been made of the magnetic properties of several diabase dikes of Precambrian age from the Canadian shield. These dikes are of widely differing ages and belong to several swarms having widely different strike directions. It was found that the direction of reinanent magnetization of the various dikes was quite widely scattered before they were demagnetized in a-c

  7. Crystal structure, spectroscopic and magnetic properties, and antimicrobial activities of cobalt(II) 2-methylthionicotinate complexes with N -heterocyclic ligands

    Microsoft Academic Search

    Peter Segl’a; Jozef Miklovi?; Dušan Mikloš; Ján Titiš; Radovan Herchel; Ján Moncol; Barbora Kali?áková; Daniela Hudecová; Viera Mrázová; Tadeusz Lis; Milan Melník

    2008-01-01

    Synthesis and characterization of 10 new 2-methylthionicotinate (2-MeSnic) Co(II) complexes, namely, [Co(2-MeSnic)2L2(H2O)2] · nH2O (L is N,N-diethylnicotinamide—Et2nia, ethylnicotinate—Etnic, nicotinamide—nia, isonicotinamide—isonia, N-methylnicotinamide—N-Menia, furo[3,2-c]pyridine—fpy, 2,3-dimethylfuro[3,2-c]pyridine—Me2fpy or benzo[4,5]furo[3,2-c]pyridine—Bfp; n is 0, 1 or 2) as well as [Co(2-MeSnic)2L2] (L is ronicol—ron or 2-methylfuro[3,2-c]pyridine—Mefpy), are reported. The characterizations were based on physico-chemical\\u000a and spectroscopic methods. The crystal structure of one of the complexes has been determined.

  8. An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties

    Microsoft Academic Search

    Pritha Talukder; Shyamapada Shit; Ashok Sasmal; Stuart R. Batten; Boujemaa Moubaraki; Keith S. Murray; Samiran Mitra

    2011-01-01

    A novel hexanuclear complex [{(CuL)2Cu}2(?-dca)2](ClO4)2·2L?(1) (where H2L=(OH)C6H4C(CH3)N(CH2)3NC(CH3)C6H4(OH) or N,N?-bis(2-hydroxyacetophenone) propylenediimine and dca=N(CN)2? and L?=2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV–Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals ?2-phenoxo bridges between terminal

  9. A One-dimensional Nickel(III) Chain Complex Showing Ferromagnetic Ordering: Crystal Structure and Magnetic Property

    E-print Network

    Gao, Song

    A One-dimensional Nickel(III) Chain Complex Showing Ferromagnetic Ordering: Crystal Structure-membered nickel- containing rings are slightly puckered, as have been found with other [M(mnt)2]nÀ structures.10 The nearest S... S, S... Ni and Ni... Ni distances are of 3.73, 3.63 and 3.96 A within the [Ni(mnt)2]À anion

  10. Tuning the Magnetic Properties of Nanoparticles

    PubMed Central

    Kolhatkar, Arati G.; Jamison, Andrew C.; Litvinov, Dmitri; Willson, Richard C.; Lee, T. Randall

    2013-01-01

    The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time. PMID:23912237

  11. Magnetic property of the nerve.

    PubMed

    Varga, L; Barrett, J S; Keszthelyi, L; Madarász, E

    1978-01-01

    An electromagnet of inhomogeneous magneticfield has been used to measure the magnetic susceptibility of the frog's nerve. Specimen of frog sciatic nerve were attached to a thin tungsten wire hanging into the inhomogeneous magnetic field, and from the deviation of this pendulum from the perpendicular position the magnetic susceptibility of the nerve has been determined to be -0.8 . 10(-6) cm3g-1 in a good agreement with the known magnetic property of the constituents of the nerve. PMID:754499

  12. Synthesis, structure, and magnetic properties of (6-9)-nuclear Ni(II) trimethylacetates and their heterospin complexes with nitroxides.

    PubMed

    Ovcharenko, Victor; Fursova, Elena; Romanenko, Galina; Eremenko, Igor; Tretyakov, Evgeny; Ikorskii, Vladimir

    2006-07-10

    New polynuclear nickel trimethylacetates [Ni6(OH)4(C5H9O2)8(C5H10O2)4] (6), [Ni7(OH)7(C5H9O2)7(C5H10O2)6(H2O)] x 0.5 C6H14 x 0.5 H2O (7), [Ni8(OH)4(H2O)2(C5H9O2)12] (8), and [Ni9(OH)6(C5H9O2)12(C5H10O2)4] x C5H10O2 x 3 H2O (9), where C5H9O2 is trimethylacetate and C5H10O2 is trimethylacetic acid, have been found. Their structures were determined by X-ray crystallography. Because of their high solubility in low-polarity organic solvents, compounds 6-9 reacted with stable organic radicals to form the first heterospin compounds based on polynuclear Ni(II) trimethylacetate and nitronyl nitroxides containing pyrazole (L(1)-L(3)), methyl (L(4)), or imidazole (L(5)) substituent groups, respectively, in side chain [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(1))2(H2O)] x 0.5 C6H14 x H2O (6+1a), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L2)2(H2O)] x H2O (6+1b), [Ni7(OH)5(C5H9O2)9(C5H10O2)2(L(3))2(H2O)] x H2O (6+1c), [Ni6(OH)3(C5H9O2)9(C5H10O2)4(L(4))] x 1.5 C6H14 (6''), and [Ni4OH)3(C5H9O2)5(C5H10O2)4(L(5))] x 1.5 C7H8 (4). Their structures were also determined by X-ray crystallography. Although Ni(II) trimethylacetates may have varying nuclearity and can change their nuclearity during recrystallization or interactions with nitroxides, this family of compounds is easy to study because of its topological relationship. For any of these complexes, the polynuclear framework may be derived from the [Ni6] polynuclear fragment {Ni6(mu4-OH)2(mu3-OH)2(mu2-C5H9O2-O,O')6(mu2-C5H9O2-O,O)(mu4-C5H9O2-O,O,O',O')(C5H10O2)4}, which is shaped like an open book. On the basis of this fragment, the structure of 7-nuclear compounds (7 and 6+1a-c) is conveniently represented as the result of symmetric addition of other mononuclear fragments to the four Ni(II) ions lying at the vertexes of the [Ni6] open book. The 9-nuclear complex is formed by the addition of trinuclear fragments to two Ni(II) ions lying on one of the lateral edges of the [Ni6] open book. This wing of the 9-nuclear complex preserves its structure in another type of 6-nuclear complex (6'') with the boat configuration. If, however, two edge-sharing Ni(II) ions are removed from [Ni6] (one of these lies at a vertex of the open book and the other, on the book-cover line), we obtain a 4-nuclear fragment recorded in the molecular structure of 4. Twinning of this 4-nuclear fragment forms highly symmetric molecule 8, which is a new chemical version of cubane. PMID:16813397

  13. Magnetic properties of large Apollo lunar samples

    NASA Astrophysics Data System (ADS)

    Gattacceca, Jerome; Eduardo, Lima; Yoann, Quesnel; Benjamin, Weiss; Pierre, Rochette; Minoru, Uehara; Laurent, Baratchart; Juliette, Leblond; Sylvain, Chevillard

    2015-04-01

    Paleomagnetic studies of lunar samples shed light on the existence and timing of the ancient lunar dynamo, with insights to the inner structure and thermal evolution of the Moon, as well as constraints for dynamo modeling [e.g., Weiss and Tikoo 2014 Science]. The intrinsic magnetic properties of lunar rocks also offer clues to their petrogenesis [e.g., Rochette et al. 2010 EPSL]. However, because of curation constraints, these studies are usually performed on small cm-scale samples, typically below 100 mg for paleomagnetism. Such a small size, combined with anisotropy and other spurious effects, have been shown to be the source of additional complexity for paleomagnetic analyses [Tikoo et al. 2012 EPSL] and raises question about how representative their magnetic properties are for the bulk rock. We measure here the natural remanent magnetization and magnetic susceptibility of 105 large Apollo samples (ranging from 40 g to 3 kg) using a portable new instrument. The aim is to gain information about the evolution of the lunar field with time, and identify samples with anomalous magnetic record or magnetic properties. We will discuss how these measurements compare with the existing laboratory measurements, what they tell us about lunar rocks, and how they can be used to select samples for in-depth paleomagnetic study.

  14. Scaling Properties of Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Blanco-Cano, X.; Russell, C. T.

    Magnetic reconnection is a universal process in space plasmas which often dominates the magnetic topology of the system and the flow patterns within and around it This process is operative in systems with vastly different spatial scales such as the Sun planetary magnetospheres and at comets In addition magnetic reconnection operates on plasma scales ranging from those associated with kinetic electrons and ions to fluid and macro-scales A true knowledge of the magnetic reconnection process requires the understanding of the minimum spatial scales at which it can be operative and how its properties scale with the system size Without such an understanding it is not possible to apply our knowledge of reconnection to systems with various sizes and properties In this talk we examine the scaling properties of reconnection using results of global hybrid simulations kinetic ions fluid electrons of solar wind interaction with magnetic dipoles of various strength Focus is on dayside reconnection during purely southward interplanetary magnetic field direction The parameter Dp defined as the standoff distance of the nose magnetopause normalized to solar wind ion skin depth is used to characterize the nature of the resulting magnetosphere as a function of dipole strength It is found that magnetic reconnection generation of reconnection electric field and the associated plasma jetting first occur at small values of Dp sim 2 before a terrestrial like magnetosphere is formed Further evolution of this process is observed with increasing values of

  15. Tetraanionic biphenyl lanthanide complexes as single-molecule magnets.

    PubMed

    Huang, Wenliang; Le Roy, Jennifer J; Khan, Saeed I; Ungur, Liviu; Murugesu, Muralee; Diaconescu, Paula L

    2015-03-01

    Inverse sandwich biphenyl complexes [(NN(TBS))Ln]2(?-biphenyl)[K(solvent)]2 [NN(TBS) = 1,1'-fc(NSi(t)BuMe2)2; Ln = Gd, Dy, Er; solvent = Et2O, toluene; 18-crown-6], containing a quadruply reduced biphenyl ligand, were synthesized and their magnetic properties measured. One of the dysprosium biphenyl complexes was found to exhibit antiferromagnetic coupling and single-molecule-magnet behavior with Ueff of 34 K under zero applied field. The solvent coordinated to potassium affected drastically the nature of the magnetic interaction, with the other dysprosium complex showing ferromagnetic coupling. Ab initio calculations were performed to understand the nature of magnetic coupling between the two lanthanide ions bridged by the anionic arene ligand and the origin of single-molecule-magnet behavior. PMID:25695369

  16. The crystal structure and magnetic properties of 3-pyridinecarboxylate-bridged Re(ii)M(ii) complexes (M = Cu, Ni, Co and Mn).

    PubMed

    Pacheco, Mario; Cuevas, Alicia; González-Platas, Javier; Lloret, Francesc; Julve, Miguel; Kremer, Carlos

    2015-06-17

    The novel Re(ii) complex NBu4[Re(NO)Br4(Hnic)] () and the heterodinuclear compounds [Re(NO)Br4(?-nic)Ni(dmphen)2]·½CH3CN (), [Re(NO)Br4(?-nic)Co(dmphen)2]·½MeOH (), [Re(NO)Br4(?-nic)Mn(dmphen)(H2O)2]·dmphen (), [Re(NO)Br4(?-nic)Cu(bipy)2] () [Re(NO)Br4(?-nic)Cu(dmphen)2] () (NBu4(+) = tetra-n-butylammonium cation, Hnic = 3-pyridinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline, bipy = 2,2'-bipyridine) have been prepared and the structures of determined using single crystal X-ray diffraction. The structure of consists of [Re(NO)Br4(Hnic)](-) anions and NBu4(+) cations. Each Re(ii) is six-coordinate with four bromide ligands, a linear nitrosyl group and a nitrogen atom from the Hnic molecule, in a distorted octahedral surrounding. The structures of are made up of discrete heterodinuclear Re(ii)M(ii) units where the fully deprotonated [Re(NO)Br4(nic)](2-) entity acts as a didentate ligand through the carboxylate group towards the [Ni(dmphen)2](2+) (), [Co(dmphen)2](2+) (), [Mn(dmphen)(H2O)2](2+) () and [Cu(bipy)2](2+) () fragments, the Re-M separation across the nic bridge being 7.8736(8) (), 7.9632(10) (), 7.7600(6) () and 8.2148(7) Å (). The environment of the Re(ii) ion in is the same as that in and all M(ii) are six-coordinate in highly distorted octahedral surroundings, the main source of the distortion being due to the reduced bite of the chelating carboxylate. The magnetic properties of were investigated in the temperature range 1.9-300 K. behaves as a quasi-magnetically isolated spin doublet with very weak antiferromagnetic interactions through space BrBr contacts. Its magnetic susceptibility data were successfully modeled through a deep analysis of the influence of the ligand field, spin-orbit coupling, tetragonal distortion and covalence effects as variable parameters. Compounds exhibit weak antiferromagnetic interactions. The intramolecular exchange pathway in this family being discarded because of the symmetry of magnetic orbitals of the Re(ii) ion (dxy) precludes any spin delocalization on the bridging nic orbitals, the observed magnetic interactions are most likely mediated by ?-? type interactions between the peripheral ligands which occur in them. Only in the case of , short through space BrBr contacts of ca. 4.03 Å (values larger than 5.5 Å in , and ) could be involved in the exchange coupling. PMID:26042855

  17. Magnetic properties of polycrystalline diamonds

    NASA Astrophysics Data System (ADS)

    Collinson, D. W.

    1998-09-01

    The remanent magnetism and bulk magnetic properties of polycrystalline diamonds have been investigated. The diamonds are of two distinct types, those occurring together with gem-grade diamonds in kimberlite pipes in S Africa, and carbonados, found in placer deposits notably in Brazil and the Central African Republic. Both types generally possess measurable remanent magnetization, the former stronger than the latter, and stability tests indicate the presence of primary and secondary components. Magnetite is the dominant carrier of NRM in the kimberlite diamonds, but the very small content of magnetic mineral in the carbonados makes identification of the carrier difficult. Possible contributors are tetrataenite, native iron and cohenite. Anomalous acquisition of isothermal remanence occurs in some carbonados, saturation being unachievable in applied fields in excess of 1 T. The ratio of saturation remanence to initial NRM is anomalously low in some of the kimberlite diamonds, and the possibility of magnetic contamination is investigated.

  18. Synthesis, magnetic, thermal and structural properties of Co(II), Ni(II) and Cu(II) complexes containing isophthalato ligands

    NASA Astrophysics Data System (ADS)

    Rogan, Jelena; Poleti, Dejan; Karanovi?, Ljiljana; Jagli?i?, Zvonko

    2011-01-01

    A series of novel ternary Co(II), Ni(II) and Cu(II) complexes containing 2,2'-dipyridylamine (dipya), 2,2'-bipyridine (bipy), and 1,10-phenanthroline (phen), as aromatic diamine ligands, and dianion of isophthalic acid (ipht) have been prepared by ligand exchange reactions from diluted H 2O/EtOH solutions. The complexes were characterized by elemental analysis, IR spectroscopy, magnetic susceptibility measurements and TG and DSC analysis. Three complexes, Cu(dipya)(ipht)·H 2O ( 1), Co(dipya)(ipht)·2H 2O ( 2) and Cu(ipht)(phen)·2H 2O ( 5) are polymeric with bis-monodentate ipht, while the other two complexes M(bipy)(ipht)·4H 2O, M dbnd Co(II) ( 3) and Ni(II) ( 4), contain ipht as a counter ion. All Co(II) and Ni(II) complexes are (pseudo)octahedral, while Cu(II) complexes have square-pyramidal or distorted octahedral geometry. The variable temperature magnetic susceptibility measurements showed very weak antiferromagnetic behaviour for all complexes. Dehydration processes, decomposition mechanisms and thermal stability of 1- 5 are assumed. One complex from the above series, [Ni(bipy)(H 2O) 4](ipht) ( 4), and one additional complex, [Co(bipy)(ipht)] n ( 6), are obtained as single-crystals and their structures are determined from X-ray diffraction data. In both structures M(II) centers are in deformed octahedral environment and they are linked by hemi-ipht ligands ( 4) and two different bridging ipht ligands ( 6). Three-dimensional networks in 4 and 6 are governed by strong noncovalent interactions. The cations and ipht anions in 4 are connected by hydrogen bonds building double layers parallel to ab-plane that are further packed by ?- ? interactions. In 6 double chains extending along b-axis are strengthened by interchain ?- ? interactions constructing a three-dimensional framework.

  19. Synthesis, crystal structures and magnetic properties of bis(?-dialkoxo)-bridged linear trinuclear copper(II) complexes with aminoalcohol ligands: a theoretical/experimental magneto-structural study.

    PubMed

    Seppälä, Petri; Colacio, Enrique; Mota, Antonio J; Sillanpää, Reijo

    2012-03-01

    The bis(?-dialkoxo)-bridged trinuclear copper(II) complexes [Cu(3)(ap)(4)(ClO(4))(2)EtOH] (1), [Cu(3)(ap)(4)(NO(3))(2)] (2), [Cu(3)(ap)(4)Br(2)] (3) and [Cu(3)(ae)(4)(NO(3))(2)] (4) (ae = 2-aminoethanolato and ap = 3-aminopropanolato) have been synthesised via self-assembly from chelating aminoalcohol ligands with the corresponding copper(II) salts. The complexes are characterised by single-crystal X-ray diffraction analyses and variable temperature magnetic measurements. The crystal structures of complexes 1-4 consist of slightly bent linear or linear trinuclear [Cu(3)(aa)(4)](2+) (aa = aminoalcoholato) units to which the perchlorate, nitrate or bromide anions are weakly coordinated. The adjacent trinuclear units of 1-4 are connected together by hydrogen bonds and bridging nitrate or bromide anions resulting in the formation of 2D layers. Magnetic studies of 1, 2 and 4 show that J values vary from -379 to +36.0 cm(-1) as the Cu-O-Cu angle (?) and the out-of-plane shift of the carbon atom of the bridging alkoxo group (?) vary from 103.7 to 94.4° and from 0.9 to 35.5°, respectively. Magnetic exchange coupling constants calculated by DFT methods are of the same nature and magnitude as the experimental ones. For complexes 1, 2 and 4, which have complementarity effects between the ? and ? angles (small ? values are associated with large ? values and vice versa), an almost linear relationship between the calculated J values with ? angles could be established, thus supporting that the ? and ? angles are the two key structural factors that determine the magnetic exchange coupling for such a type of compounds. Complex 3 does not obey this linear correlation because of the existence of counter-complementarity effects between these angles (small ? values are associated with small ? values and vice versa). It is of interest that the theoretical calculations for the magnetic exchange interaction between next-nearest neighbours indicate that the usual approximation in experimental studies of neglecting the magnetic coupling between the next-nearest neighbours in linear trinuclear complexes could lead to considerable errors, especially when J(1) and J(2) are of the same order of magnitude as J(3). PMID:22234645

  20. Connection between microstructure and magnetic properties of soft magnetic materials

    Microsoft Academic Search

    G. Bertotti

    2008-01-01

    The magnetic behavior of soft magnetic materials is discussed with some emphasis on the connection between macroscopic properties and underlying micromagnetic energy aspects. It is shown that important conceptual gaps still exist in the interpretation of macroscopic magnetic properties in terms of the micromagnetic formulation. Different aspects of hysteresis modeling, power loss prediction and magnetic non-destructive evaluation are discussed in

  1. Formation of octapod MnO nanoparticles with enhanced magnetic properties through kinetically-controlled thermal decomposition of polynuclear manganese complexes

    NASA Astrophysics Data System (ADS)

    Douglas, Fraser J.; MacLaren, Donald A.; Tuna, Floriana; Holmes, William M.; Berry, Catherine C.; Murrie, Mark

    2013-12-01

    Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine.Polynuclear manganese complexes are used as precursors for the synthesis of manganese oxide nanoparticles (MnO NPs). Altering the thermal decomposition conditions can shift the nanoparticle product from spherical, thermodynamically-driven NPs to unusual, kinetically-controlled octapod structures. The resulting increased surface area profoundly alters the NP's surface-dependent magnetism and may have applications in nanomedicine. Electronic supplementary information (ESI) available: Experimental details, TGA, TEM and diffraction data. See DOI: 10.1039/c3nr04832b

  2. Magnetism of the oceanic crust: Evidence from ophiolite complexes

    SciTech Connect

    Banerjee, S.K.

    1980-07-10

    The magnetic properties of six ophiolite complexes from around the world, ranging in age from Jurassic to Miocene, are presented. An emphasis is placed in our study on the petrologic and isotopic data from these ophiolite complexes in order to determine first whether the rock samples presently available represent the pristine ocean crust or whether they have been altered subaerially since their formation. Five of the ophiolites are found to be acceptable, and the conclusion is overwhelmingly in favor of a marine magnetic source layer that includes not only the pillow lavas but also the underlying dikes and gabbro. At the moment, however, our observations do not suggest that the magnetic contributions of the basaltic dikes should be overlooked in favor of gabbro. A second important conclusion is that nearly pure magnetite could indeed be a magnetic carrier which contributes to marine magnetic anomanies. It only awaits discovery by deeper ocean crustal penetration by future Deep Sea Drilling Project legs.

  3. Mononuclear thiocyanate containing nickel(II) and binuclear azido bridged nickel(II) complexes of N4-coordinate pyrazole based ligand: Syntheses, structures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Solanki, Ankita; Monfort, Montserrat; Kumar, Sujit Baran

    2013-10-01

    Two mononuclear nickel(II) complexes [NiL1(NCS)2] (1) and [NiL2(NCS)2] (2) and two azido bridged binuclear nickel(II) complexes [Ni(()2()2] (3) and [Ni(()2()2] (4), where L1, L2, L1? and L2? are N,N-diethyl-N?,N?-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1), N,N-bis((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2), N,N-diethyl-N?-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1?) and N-((1H-pyrazol-1-yl)methyl)-N?,N?-diethylethane-1,2-diamine (L2?) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS- containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (?-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32 cm-1, respectively.

  4. Magnetic Properties of Composite Structures.

    NASA Astrophysics Data System (ADS)

    Taylor, Jeffrey Neel

    1992-08-01

    The study of composite structures is a field of current interest in materials research. New fabrication techniques allow the creation of composite structures not observed in nature and many workers are seeking to associate novel electronic and magnetic properties with them. This thesis is concerned with two very different types of magnetic thin film composites: amorphous and magnetically soft Fe -B-N alloys, and crystalline, magnetically hard Co-Cr-Y, Y = Ta, Nb, V alloys. Samples were mostly studied by theta-2theta x-ray diffraction, scanning and transmission electron microscopy, SQUID and vibrating sample magnetometry, and Mossbauer spectroscopy. All samples were fabricated in thin film fom by magnetron sputter deposition. The first type of film, Fe-B-N alloy, is a two phase, amorphous structure, one phase of which is ferromagnetic. Its magnetic behavior was found to be consistent with that of amorphous Fe-B. Structurally, these films were found to segregate into particles 3-10 nm in size. The films with low Fe concentration were found to exhibit super-paramagnetism, which is characteristic of single domain particles, although the coercivity remained small for all compositions and measuring temperatures. Co-Cr alloy is a hard magnetic materias because of its large magnetic anisotropy energy and segregated structure. The substitutional alloys Co-Cr-Y, where Y = Ta, Nb, V were studied in order to determine the effect of the diluent on the magnetic behavior. The IVA family is interesting to study as diluents of Co-Cr because of their similar chemical properties, but widely differing atomic weight and size. Certain compositions of Co-Cr -Ta alloy were found to have enhanced crystalline texture and coercivity. The differences between the systems are discussed. Multi-layer films composed of high Ta concentration, amorphous layers and ferromagnetic, low Ta concentration layers were studied in order to study the growth behavior of the magnetic layers. The high Ta concentration layers provide a nucleation surface which enhances textured growth. The mechanism of magnetization in the ferromagnetic Co-Cr-Ta films was also studied by examining the dependence of the coercivity on film orientation. A curling mechanism is found to predominarte in high coercivity films.

  5. Complexes of selected transition metal ions with 4-oxo-4-{[3-(trifluoromethyl)phenyl]amino}but-2-enoic acid: Synthesis, structure and magnetic properties

    NASA Astrophysics Data System (ADS)

    Ferenc, Wies?awa; Sadowski, Pawe?; Tarasiuk, Bogdan; Cristóvão, Beata; Drzewiecka-Antonik, Aleksandra; Osypiuk, Dariusz; Sarzy?ski, Jan

    2015-07-01

    The new complexes of 4-oxo-4-{[3-(trifluoromethyl)phenyl]amino}but-2-enoic acid, HL anion with Mn(II), Co(II), Ni(II), Cu(II) and Pr(III), Nd(III), Sm(III), Gd(III), Dy(III), Ho(III), Er(III), Y(III) were synthesized and some of their physico-chemical properties investigated. The complexes form hydrates with two or three molecules of water. The carboxylate groups act as a bidentate bridging or chelating ligand. The compounds of Pr(III), Nd(III), Sm(III), Gd(III), Dy(III), Ho(III), Er(III) and Y(III) are amorphous solids while those of Cu(II), Co(II), Ni(II) and Mn(II) crystalline ones that crystallize in monoclinic system. Complex of Cu(II) is the centrosymmetric dinuclear compound. Around both Cu(II) cations the tetragonal pyramide is formed. Being heated in air at 293-1173 K the complexes are decomposed in three steps. The oxides of appropriate metals are the final products of complex decomposition. All analysed compounds obey Curie-Weiss law. They show the paramagnetic properties with the ferromagnetic interactions between molecular centres.

  6. Magnetic properties of ferromagnetic ilmenites

    Microsoft Academic Search

    T. Nagata; S. Akimoto

    1956-01-01

    Summary Magnetic and crystallographic properties of solid solutionsxFeTiO3. (1?x) Fe2O3 of hematite (Fe2O3) and ilmenite (FeTiO3), which have rhombohedral crystal structure, are examined in detail for the whole range of 0 ?x ? 1. Samples examined are mineral grains separated out from natural rocks and artificially synthesized ones. The minerals of the hematite-ilmenite series for 0.55x are ferromagnetic and their

  7. Hydrothermal syntheses, structures, and magnetic properties of two new Mn(II) complexes with biphenyl-2,3,3?,5?-tetracarboxylic acid

    NASA Astrophysics Data System (ADS)

    Li, Rong-Fang; Liu, Xin-Fang; Zhang, Tian; Zhang, Xiao-Yu; Feng, Xun

    2014-10-01

    Two metal-organic frameworks [Mn4(bptc)2(bpy)2]n (1) (H4bptc = biphenyl-2,3,3?,5?-tetra-carboxylic acid, bpy = 2, 2?-dipyridine) with Mn4 clusters and {[Mn2(bptc)2(H2O)8]?4H2O}(2) were obtained through hydrothermal reaction. X-ray diffraction analysis shows that both complexes 1 and 2 crystallize in the Triclinic system, space group of P-1. The Mn(II) ions have two kinds of coordination mode in complex 1, one is five- coordinated and the other is six-coordinated. Mn(2) ion is bridged to neighboring Mn(2)A(A:1 - x, 1 - y, 2 - z) by two ?2-Ocarboxyl atoms to afford a {Mn}4 cluster together with another two symmetrical Mn(1) and Mn(1)a. The {Mn}4 clusters are further connected through the bptc4- ligands each other, giving rise to a 2D network. There is a Mn2O2 parallelogram-core in every {Mn}4 cluster, and to the best of our knowledge this is the first time observed. Complex 2 consists of the dinuclear manganese (II) unit, which is further linked by hydrogen bonds to form a 3D framework structure. Magnetic measurements show there is a weak anti-ferromagnetic interaction in complex 1. Moreover, the IR, element analysis, and thermal stability of the two complexes have been investigated systemically.

  8. Dynamic rheological properties of viscoelastic magnetic fluids in uniform magnetic fields

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroshi; Niu, Xiao-Dong; Ye, Xiao-Jiang; Li, Mingjun; Iwamoto, Yuhiro

    2012-10-01

    The dynamic rheological properties of viscoelastic magnetic fluids in externally applied uniform magnetic fields are investigated by a laboratory-made cone-plate rheometer in this study. In particular, the effects of the magnetic field on the viscoelastic properties (the complex dynamic modulus) of the viscoelastic magnetic fluids are studied. In the investigation, three viscoelastic magnetic fluids are made by mixing a magnetic fluid and a viscoelastic fluid with different mass ratios. As a supplementation to the experimental investigation, a theoretical analysis is also presented. The present study shows that the viscosity and elasticity of the viscoelastic magnetic fluids are significantly influenced by the magnetic field and the concentrations of the magnetic particles in the test fluids. Theoretical analysis qualitatively explains the present findings.

  9. Cyano-bridged Mn(III)3M(III) (M(III) = Fe, Cr) complexes: synthesis, structure, and magnetic properties.

    PubMed

    Miyasaka, Hitoshi; Takahashi, Hitomi; Madanbashi, Tomokura; Sugiura, Ken-ichi; Clérac, Rodolphe; Nojiri, Hiroyuki

    2005-08-22

    Two cyano-bridged tetranuclear complexes composed of Mn(III) salen (salen = N,N'-ethylene bis(salicylideneiminate)) and hexacyanometalate(III) (M = Fe, Cr) in a stoichiometry of 3:1 have been selectively synthesized using {NH2(n-C12H25)2}3[M(III)(CN)6] (M(III) = Fe, Cr) starting materials: [{Mn(salen)(EtOH)}3{M(CN)6}] (M = Fe, 1; Cr, 2). Compounds 1 and 2 are isostructural with a T-shaped structure, in which [M(CN)6]3- assumes a meridional-tridentate building block to bind three [Mn(salen)(EtOH)]+ units. The strong frequency dependence and observation of hysteresis on the field dependence of the magnetization indicate that 1 is a single-molecule magnet. PMID:16097811

  10. Structure and magnetic properties of a one-dimensional chain complex {[Mn 2(TPA) 2( o-phth)](ClO 4) 2} n

    Microsoft Academic Search

    Lei Yang; Fang Bian; Shi-ping Yan; Dai-zheng Liao; Peng Cheng; Zong-hui Jiang

    2003-01-01

    A terephthalate-bridged chain complex of {[Mn2(TPA)2(o-phth)](ClO4)2}n (TPA=tris(2-pyridylmethyl)amine, o-phth=terephthalato dianion) was synthesized and characterized by X-ray crystallography and magnetic measurements. In the compound, each terephthalate acts as tetrakis(monodentate) ligand and links manganese(II) pairs to yield a one-dimensional chain. The manganese(II) ion coordinates with four nitrogen atoms of TPA and two oxygen atoms of two carboxylate groups from two terephthalate ligands and

  11. 2,2?-Oxydiacetato-bridged complexes containing Sm(III) and bivalent cations. Synthesis, structure, magnetic properties and chemical speciation

    NASA Astrophysics Data System (ADS)

    Torres, J.; Peluffo, F.; Domínguez, S.; Mederos, A.; Arrieta, J. M.; Castiglioni, J.; Lloret, F.; Kremer, C.

    2006-12-01

    Heterometallic compounds containing Sm(III), bivalent cations M (M = Cu, Ni, Co, Mn, Ca, Mg), and 2',2'-oxydiacetate (oda) as connecting ligand have been prepared and characterized. The complexes can be formulated as [Sm 2M 3(oda) 6] · xH 2O. The structure of [Sm 2Cu 3(oda) 6(H 2O) 6] shows the presence of the Sm(III) coordinated by six carboxy and three ether oxygen atoms, and the Cu(II) cation bonded to four carboxy oxygens and two molecules of water. An open 3D framework is observed, containing large hexagonal channels. At room temperature, the polynuclear complexes behave as built by magnetically isolated paramagnetic ions, but at low temperatures, very weak antiferromagnetic interactions M - M are predominant. The chemical systems were also investigated in solution (25.0 °C, I = 0.5 M Me 4NCl) by potentiometry. The same kind of polynuclear species have been found.

  12. BASIC PROPERTIES OF MUTUAL MAGNETIC HELICITY

    E-print Network

    Demoulin, Pascal

    BASIC PROPERTIES OF MUTUAL MAGNETIC HELICITY P. DEMOULIN1, E. PARIAT1, M.A. BERGER2 1 Observatoire flux tubes weighted by their magnetic fluxes. We emphasize that these mutual helicities have properties Abstract. We derive the magnetic helicity for configurations formed by flux tubes contained fully or only

  13. Electronic and magnetic properties of nanographite ribbons

    Microsoft Academic Search

    Katsunori Wakabayashi; Mitsutaka Fujita; Hiroshi Ajiki; Manfred Sigrist

    1999-01-01

    Electronic and magnetic properties of ribbon-shaped nanographite systems with zigzag and armchair edges in a magnetic field are investigated by using a tight binding model. One of the most remarkable features of these systems is the appearance of edge states, strongly localized near zigzag edges. The edge state in magnetic field, generating a rational fraction of the magnetic flux (\\\\phi=

  14. The Magnetic Properties Experiments on Mars Pathfinder

    NASA Astrophysics Data System (ADS)

    Knudsen, J. M.; Gunnlaugsson, H. P.; Hviid, S. F.; Madsen, M. B.

    1996-09-01

    A remarkable result from the Viking missions was the discovery that the Martian soil is highly magnetic, in the sense that the soil is attracted by permanent magnets. Both the strong and weak magnets on the Viking landers were saturated with dust throughout the mission. Appropriate limits for the spontaneous magnetization sigma_S were advanced: 1 Am(2) (kg soil)(-1) < sigma_S < 7 Am(2) (kg soil)(-1) . The essential difference between the Magnet Arrays for Mars Pathfinder and the Viking Magnetic Properties Experiment is that Magnet Arrays on Pathfinder will include magnets of lower strengths that the weakest Viking magnet. The five magnets consist of small ring magnets concentric with oppositely polarized cylindrical magnets. The outer diameter of the ring magnets is 18 mm. Discrete (single phase) particles of strongly magnetic minerals (gamma -Fe2O3 or Fe3O4) will stick to all five magnets, while composite (multiphase) particles will stick preferentially to the strongest magnets. Two Magnet Arrays are placed on the Pathfinder lander, with a distance of 1180 and 1450 mm, respectively, from the Imager for Mars Pathfinder (IMP). The magnets will attract airborne dust, and the dust on the magnets will be periodically viewed by the IMP. The images transmitted to Earth are the data on which conclusions on the magnetic properties of the dust will be based. Besides the Magnet Arrays the Pathfinder lander carries two other types of magnets. The Tip Plate Magnet is placed at a distance of 10 cm from the IMP, and thus allows a rather high resolution imaging of the dust clinging to the magnet. The Ramp Magnets are placed near the end of the ramps by which the micro-rover will descend to the surface. The dust on the Ramp Magnets will be studied by the APX-spectrometer of the micro-rover.

  15. Magnetic properties in graphene-graphane superlattices

    E-print Network

    Lee, Joo-Hyoung

    The magnetic properties of graphene-graphane superlattices with zigzag interfaces and separately varying widths are investigated by first-principles density functional calculations. It is demonstrated that magnetic states ...

  16. Magnetic properties of hydrothermally recrystallized magnetite crystals

    Microsoft Academic Search

    Franz Heider; David J. Dunlop; Naoji Sugiura

    1987-01-01

    The discrepancy between the magnetic hysteresis properties of magnetite crystals that are precipitated from solution and of crushed sifted grains (larger than 300 nm) is not an inherent property of magnetite but is caused by the highly stressed state of crushed material and by adhering finer fragments. The size trends of magnetic properties exhibited by submicron-size precipitated grains continue in

  17. Modeling Magnetic Properties in EZTB

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon; vonAllmen, Paul

    2007-01-01

    A software module that calculates magnetic properties of a semiconducting material has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure. [EZTB is designed to model the electronic structures of semiconductor devices ranging from bulk semiconductors, to quantum wells, quantum wires, and quantum dots. EZTB implements an empirical tight-binding mathematical model of the underlying physics.] This module can model the effect of a magnetic field applied along any direction and does not require any adjustment of model parameters. The module has thus far been applied to study the performances of silicon-based quantum computers in the presence of magnetic fields and of miscut angles in quantum wells. The module is expected to assist experimentalists in fabricating a spin qubit in a Si/SiGe quantum dot. This software can be executed in almost any Unix operating system, utilizes parallel computing, can be run as a Web-portal application program. The module has been validated by comparison of its predictions with experimental data available in the literature.

  18. Magnetic Properties of Gadolinium Ortho-Aluminate

    Microsoft Academic Search

    J. D. Cashion; A. H. Cooke; T. L. Thorp; M. R. Wells

    1970-01-01

    An account is given of specific heat, magnetic susceptibility and magnetic moment measurements on gadolinium ortho-aluminate, GdAlO3, at temperatures in the liquid helium range. This compound orders antiferromagnetically at 3.87 K. In the antiferromagnetic state, its properties can be accounted for satisfactorily as those of an array of S-state magnetic ions with isotropic magnetic properties, coupled together by exchange interaction

  19. Magnetic properties of submicron circular permalloy dots

    Microsoft Academic Search

    Gianluca Gubbiotti; Giovanni Carlotti; Fabrizio Nizzoli; Roberto Zivieri; Takuya Okuno; Teruya Shinjo

    2002-01-01

    Both the static and the dynamical magnetic properties of a square array of circular permalloy dots, characterized by a magnetic vortex configuration of the magnetization, have been investigated by means of magneto-optical Kerr effect and Brillouin light scattering (BLS) from thermally excited spin waves. The measured hysteresis loop can be satisfactorily reproduced by micromagnetic simulations, showing that the vortex configuration

  20. Magnetic and electrical properties of Martian particles

    NASA Technical Reports Server (NTRS)

    Olhoeft, G. R.

    1991-01-01

    The only determinations of the magnetic properties of Martian materials come from experiments on the two Viking Landers. The results suggest Martian soil containing 1 to 10 percent of a highly magnetic phase. Though the magnetic phase mineral was not conclusively identified, the predominate interpretation is that the magnetic phase is probably maghemite. The electrical properties of the surface of Mars were only measured remotely by observations with Earth based radar, microwave radiometry, and inference from radio-occultation of Mars orbiting spacecraft. No direct measurements of electrical properties on Martian materials have been performed.

  1. Effective magnetization of the dust particles in a complex plasma

    NASA Astrophysics Data System (ADS)

    Kählert, Hanno

    2012-10-01

    The large mass and size of the dust particles in a complex plasma has several advantages, including low characteristic frequencies on the order of a few Hz and the ability to record their motion with video cameras. However, these properties pose major difficulties for achieving strong magnetization. While the light electrons and ions can be magnetized by (superconducting) magnets, magnetizing the heavy dust component is extremely challenging. Instead of further increasing the magnetic field strengths or decreasing the particle size, we use the analogy between the Lorentz force and the Coriolis force experienced by particles in a rotating reference frame to create ``effective magnetic fields'' which is a well-established technique in the field of trapped quantum gases [1]. To induce rotation in a complex plasma, we take advantage of the neutral drag force, which allows to transmit the motion of a rotating neutral gas to the dust particles [2]. The equations of motion in the rotating frame agree with those in a stationary gas except for the additional centrifugal and Coriolis forces [3]. Due to the slow rotation frequencies (˜ Hz) and contrary to the situation in a strong magnetic field, only the properties of the heavy dust particles are notably affected. Experiments with a rotating electrode realize the desired velocity profile for the neutral gas and allow us to verify the efficiency of the concept [3].[4pt] This work was performed in collaboration with J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel.[4pt] [1] A. L. Fetter, Rev. Mod. Phys. 81, 647 (2009)[0pt] [2] J. Carstensen, F. Greiner, L.-J. Hou, H. Maurer, and A. Piel, Phys. Plasmas 16, 013702 (2009)[0pt] [3] H. K"ahlert, J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel, submitted for publication, arXiv:1206.5073

  2. Magnetic Properties of the Bay of Islands Ophiolite Suite and Implications for the Magnetization of Oceanic Crust

    Microsoft Academic Search

    B. Ann Swift; H. Paul Johnson

    1984-01-01

    Rock magnetic properties, opaque mineralogy, and degree of metamorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex, Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetization of the underlying sheeted dike

  3. Hexa- and heptacoordinated manganese(II) dicyanamide complexes containing a tetradentate N-donor Schiff base: Syntheses, composition tailored architectures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Bhar, Kishalay; Sutradhar, Dipu; Choubey, Somnath; Ghosh, Rajarshi; Lin, Chia-Her; Ribas, Joan; Ghosh, Barindra Kumar

    2013-11-01

    Two 1D coordination polymers [Mn(L)(?1,5-dca)(MeOH)]n(ClO4)n (1) and [Mn(L)(?1,5-dca)]n(PF6)n (2) and a dinuclear compound [Mn2(L)2(?1,5-dca)2(dca)2]?H2O (3) [L = N,N'-(bis-(pyridin-2-yl)benzylidene)-ethane-1,2-diamine; dca = dicyanamide] have been isolated using one-pot synthesis of the building components in appropriate molar ratios and characterized. X-ray structural studies reveal that 1 forms a zigzag 1D chain through single Mn-(NCNCN)-Mn units in which each heptacoordinated manganese(II) center adopts a distorted pentagonal bipyramidal geometry with an MnN6O chromophore occupied with four N atoms of L, two nitrile N atoms of monobridged ?1,5-dca and one O atom of MeOH. In 2, each hexacoordinated metal(II) center has a distorted octahedral coordination environment with an MnN6 chromophore bound by four N atoms of L and two nitrile N atoms of two different single bridged ?1,5-dca units; the latter connects other neighboring metal centers in a non-ending fashion affording a linear 1D chain. Complex 3 is dinuclear where two [Mn(L)]2+ units are connected by double ?1,5-dca bridges with a distorted pentagonal bipyramidal environment. Variable-temperature magnetic susceptibility measurements of 1-3 show weak antiferromagnetic interactions among the metal centers through ?1,5-dca bridges.

  4. Magnetism in Complex Oxide Heterostructures Determined with Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Te Velthuis, Suzanne G. E.

    2009-03-01

    With the creation of high quality superlattices consisting of complex oxide materials novel materials exhibiting a wide range of interesting phenomena are emerging. Due to the diverse physical properties of complex oxides, (e.g., ferromagnetism, antiferromagnetism, superconductivity), some of which can be varied by doping, the versatility in their applications is large. The physical properties in these new materials, often is tied to the behavior at the interfaces between the different components of the superlattice, and therefore requires detailed knowledge of the relationship between the chemical and electronic composition. Polarized neutron reflectometry (PNR) provides access to the depth-dependent magnitude and orientation of the magnetization and can therefore link the magnetic to the electronic and chemical properties, especially close to these interfaces. Several examples of our work will be presented, including that on La0.7Ca0.3MnO3/ YBa2Cu3O7-?/ La0.7Ca0.3MnO3 trilayers which exhibit the inverse superconducting spin switch behavior, and where suppression of the magnetization close to the interface, as well as a varying anisotropy axis have been determined [1]. Another example is work on digitally layered analogs of La1-xSrxMnO3, where PNR reveals an asymmetric distribution of the magnetization across the two components (antiferromagnetic) LaMnO3and SrMnO3, which has been linked to structural properties at the interfaces [2]. [4pt] [1] V. Peña, Z. Sefrioui, D. Arias, C. Leon, J. Santamaria, J. L. Martinez, S. G. E. te Velthuis, A. Hoffmann, Phys. Rev. Lett. 94 (2005) 057002. [0pt] [2] S. J. May, A. B. Shah, S. G. E. te Velthuis, M. R. Fitzsimmons, J. M. Zuo, X. Zhai, J. N. Eckstein, S. D. Bader, and A. Bhattacharya, Phys. Rev. B 77 (2008) 174409.

  5. Magnetic field properties of SSC model dipole magnets

    SciTech Connect

    Wake, M.; Bossert, R.; Carson, J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Lamm, M.J.; Strait, J. (Fermi National Accelerator Lab., Batavia, IL (United States)); Butteris, J.; Sims, R.; Winters, M. (Superconducting Super Collider Lab., Dallas, TX (United States))

    1992-09-01

    SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.

  6. Thermal and magnetic properties of manganese oxides

    NASA Astrophysics Data System (ADS)

    Smolyaninova, Vera Nikolaevna

    This thesis reports a study of the thermal, magnetic and transport properties of perovskite manganese oxides A1-xBxMnO3 (A = La, Nd, and Pr; B = Ca, Ba, and Sr). The ferromagnetic (FM) metallic (low x) and the charge-ordered (CO) (high x) doping regimes were studied in order to better understand the complex behavior of these materials. In the metallic doping range the low temperature magnetization was found to be in agreement with the Bloch law for ferromagnetic spin waves, and the spin-wave stiffness was determined. Important parameters such as the Debye temperature and the effective mass of the charge carriers were determined from low temperature specific heat experiments. The effective mass of the charge carriers was found to be 2--4 times heavier than the mass obtained from band structure calculations suggesting an important role of electron-phonon interactions in these materials. In order to better understand the nature of the metal-insulator transition at the ferromagnetic TC the resistivity and magnetization of epitaxial thin films of La0.67Ca 0.33MnO3 and Nd0.7Sr0.3MnO3 were studied. It was found that the behavior of the resistivity and magnetization near TC is inconsistent with Anderson localization as proposed by several theories. Various compositions of charge-ordered La1-xCaxMnO3 and Pr1-xCa1-xMnO 3 were studied to better understand the CO transition and its ground state. From powder neutron diffraction measurements we found that the CO antiferromagnetic (AFM) and ferromagnetic metallic phases coexist at low temperatures. Charge ordered Pr1-xCaxMnO3 and La1-xCax MnO3 (x ? 0.5) were found to have an anomalous excess specific heat ( C') at low temperatures (T < 20 K). This C' contribution has a temperature dependence consistent with non-magnetic excitations with a dispersion relation e = Delta' + Bq2. Surprisingly, it was found that a magnetic field sufficient to induce the transition from the insulating CO (and AFM) state to the metallic FM state is not sufficient to eliminate the C' contribution to the specific heat. The possible origin of these excitations and their relation to the CO ground state is discussed.

  7. Thermoelectric Properties of Complex Zintl Phases

    Microsoft Academic Search

    G. Jeffrey Snyder

    2008-01-01

    Complex Zintl phases make ideal thermoelectric materials because they can exhibit the necessary ``electron-crystal, phonon-glass'' properties required for high thermoelectric efficiency. Complex crystal structures can lead to high thermoelectric figure of merit (zT) by having extraordinarily low lattice thermal conductivity. A recent example is the discovery that Yb14MnSb11, a complex Zintl compound, has twice the zT as the SiGe based

  8. Properties of Simulated Magnetized Galaxy Clusters

    E-print Network

    Dolag, K

    2000-01-01

    We study the evolution of magnetized clusters in a cosmological environment using magneto-hydro dynamical simulations. Large scale flows and merging of subclumps generate shear flows leading to Kelvin-Helmholtz instabilities, which, in addition to the compression of the gas where the magnetic field is frozen in, further amplify the magnetic field during the evolution of the cluster. Therefore, well-motivated initial magnetic fields of $^{1/2}=10^{-9} {\\rm G}$ reach the observed $\\sim\\mu{\\rm G}$ field strengths in the cluster cores at $z=0$. These magnetized clusters can be used to study the final magnetic field structure, the dynamical importance of magnetic fields for the interpretation of observed X-Ray properties, and help to constrain further processes in galaxy clusters like the population of relativistic particles giving rise to the observed radio halos or the behavior of magnetized cooling flows.

  9. Structure, magnetic behavior, and anisotropy of homoleptic trinuclear lanthanoid 8-quinolinolate complexes.

    PubMed

    Chilton, Nicholas F; Deacon, Glen B; Gazukin, Olga; Junk, Peter C; Kersting, Berthold; Langley, Stuart K; Moubaraki, Boujemaa; Murray, Keith S; Schleife, Frederik; Shome, Mahasish; Turner, David R; Walker, Julia A

    2014-03-01

    Three complexes of the form [Ln(III)3(OQ)9] (Ln = Gd, Tb, Dy; OQ = 8-quinolinolate) have been synthesized and their magnetic properties studied. The trinuclear complexes adopt V-shaped geometries with three bridging 8-quinolinolate oxygen atoms between the central and peripheral eight-coordinate metal atoms. The magnetic properties of these three complexes differ greatly. Variable-temperature direct-current (dc) magnetic susceptibility measurements reveal that the gadolinium and terbium complexes display weak antiferromagnetic nearest-neighbor magnetic exchange interactions. This was quantified in the isotropic gadolinium case with an exchangecoupling parameter of J = -0.068(2) cm(-1). The dysprosium compound displays weak ferromagnetic exchange. Variable-frequency and -temperature alternating-current magnetic susceptibility measurements on the anisotropic cases reveal that the dysprosium complex displays single-molecule-magnet behavior, in zero dc field, with two distinct relaxation modes of differing time scales within the same molecule. Analysis of the data revealed anisotropy barriers of Ueff = 92 and 48 K for the two processes. The terbium complex, on the other hand, displays no such behavior in zero dc field, but upon application of a static dc field, slow magnetic relaxation can be observed. Ab initio and electrostatic calculations were used in an attempt to explain the origin of the experimentally observed slow relaxation of the magnetization for the dysprosium complex. PMID:24520896

  10. Complex Mechanical Properties of Steel

    E-print Network

    Dimitriu, Radu

    ?i friction stress ?y stress necessary to propagate yield ? bias A number of models in the committee CONTENTS ix a crack length a1 reliability constant a2 material fatigue properties constant a3 lubricant constant C material constant ci chemical... 2.2 ROLLING CONTACT FATIGUE Contact fatigue is a common type of failure encountered in bearings, rails, gears and valves. It differs from structural fatigue (bending or torsion) in that the cyclic stress originates in Hertzian contact, when a curved...

  11. Magnetic properties of Np 2T 3X 4 compounds

    NASA Astrophysics Data System (ADS)

    Colineau, E.; Wastin, F.; Rebizant, J.; Boulet, P.

    2001-05-01

    The magnetic and electronic properties of Np 2T 3X 4 compounds, as inferred from 237Np Mössbauer spectroscopy, magnetization and resistivity measurements, are reported. Np 2Mo 3Si 4 orders at TN?47 K into an AF phase and becomes ferrimagnetic at T''?38 K, Np 2Tc 3Si 4 and Np 2Tc 3Ge 4 order antiferromagnetically, respectively, at TN?19 K and TN?15 K. All compounds exhibit complex Mössbauer spectra which were reproduced assuming the occurrence of three distinct Np 3+ sites with different magnetic moments and moreover an extra, zero-moment Np 3+ site is always associated with the AF-phases. The variation of the magnetic properties along the series may be explained by Np-transition metal hybridization and Kondo effect.

  12. Magnetic properties of anisotropic Sr-La-system ferrite magnets

    SciTech Connect

    Yamamoto, H.; Nagakura, M. (School of Science and Technology, Meiji Univ., 1-1-1 Higashi-mita, Tama-ku, Kawasaki 214 (JP)); Terada, H. (College of Engineering, Chubu Univ., 1200 Matsumoto-cho, Kasugai 487 (JP))

    1990-05-01

    This paper presents an experiment carried out to investigate the effect of La{sub 2}O{sub 3} addition to the magnetic and physical properties of strontium ferrite magnets. It was found that the La{sub 2}O{sub 3} addition to SrO {center dot} 6Fe{sub 2}O{sub 3} (stoichiometric composition) was very useful in stabilizing the magnetoplumbite structure and that these Sr-La-system ferrites had excellent properties as a permanenent magnet. Compositions were chosen according to the formula ((SrO){sub 1/n+1}(Fe{sub 2}O{sub 3}){sub n/n+1}){sub 100{minus}x}(La{sub 2}O{sub 3}){sub x}, where n was varied between 5.0 and 6.5, and x between 0 and 5.0. The optimum conditions for making magnets and some properties of typical specimens are discussed.

  13. MAGNETIC PROPERTIES OF DYSPROSIUM SINGLE CRYSTALS

    Microsoft Academic Search

    D. R. Behrendt; S. Legvold; F. H. Speddin

    1958-01-01

    Single crystals of metallic dysprosium have been grown by the Bridgman ; method and their magnetic properties have been determined in different ; crystallographic directions of the hexagonal close-packed structure. Below the ; Neel point of 178.5 deg K the individual magnetic moments are aligned ; perpendicular to the c\\/sub o\\/ axis. The moments are aligned in an ; antiferromagnetic

  14. Static magnetic properties of Maghemite nanoparticles

    NASA Astrophysics Data System (ADS)

    Zulfiqar; Rahman, Muneeb Ur; Usman, M.; Hasanain, Syed Khurshid; Zia-ur-Rahman; Ullah, Amir; Kim, Ill Won

    2014-12-01

    We report the static magnetic properties of Maghemite (?-Fe2O3) nanoparticles with an average crystallite size of 14 ± 1.8 nm synthesized via a co-precipitation method. The zero-field-cooled (ZFC) and the field-cooled (FC) magnetization measurements were performed using a physical properties measurements system (PPMS) at temperatures from 5 K to 300 K. The ZFC/FC measurements showed a typical superparamagnetic behavior with a narrow size distribution.

  15. Fast magnetic relaxation in an octahedral dysprosium tetramethyl-aluminate complex.

    PubMed

    König, Sonja N; Chilton, Nicholas F; Maichle-Mössmer, Cäcilia; Pineda, Eufemio Moreno; Pugh, Thomas; Anwander, Reiner; Layfield, Richard A

    2014-02-28

    Ab initio calculations on the octahedral dysprosium aluminate complex [Dy(AlMe4)3] (1) predict weak SMM properties. Dynamic magnetic susceptibility measurements on 1 confirm the theoretical predictions, revealing fast relaxation of the magnetization via quantum tunnelling. PMID:24121786

  16. Magnetic properties of nanosize iron clusters

    SciTech Connect

    Venturini, E.L.; Wilcoxon, J.P.; Newcomer, P.P.

    1993-12-31

    Isolated, monodisperse {alpha}-Fe clusters between 1.4 and 15 nm in diameter were prepared inside inverse micelles using an oil-continuous, nonaqueous system. The magnetic properties of these clusters were studied in a SQUID magnetometer as a function of cluster size, temperature and applied magnetic field. The blocking temperature, coercive field and remanent moment of 12.5 nm Fe clusters in inverse micelles are significantly lower than those reported for clusters of similar {alpha}-Fe core size but with a surface oxide. The novel synthesis technique may yield metallic clusters with essentially intrinsic magnetic properties.

  17. Spin-crossover iron(II) complexes [Fe(Medpq)(py) 2(NCS) 2] and [Fe(Medpq)(py) 2(NCSe) 2]: syntheses, characterization and magnetic properties

    Microsoft Academic Search

    Jian-Qing Tao; Zhi-Guo Gu; Tian-Wei Wang; Qiao-Fang Yang; Jing-Lin Zuo; Xiao-Zeng You

    2007-01-01

    Two new spin-crossover complexes, [Fe(Medpq)(py)2(NCS)2]·py·0.5H2O (1) and [Fe(Medpq)(py)2(NCSe)2]·py (2) (Medpq=2-methyldipyrido[3,2-f:2?,3?-h]-quinoxaline, py=pyridine), have been synthesized. The crystal structures were determined at both room temperature (298K) and low temperature (110K). Complexes 1 and 2 crystallize in the orthorhombic space group Pbca and monoclinic space group P21\\/n, respectively. In both complexes, the distorted [FeN6] octahedron is formed by six nitrogen atoms from Medpq,

  18. Magnetic properties and magnetic domains of Nd-Fe-B thin films

    SciTech Connect

    Chen, S. L.; Liu, W.; Zhang, Z. D. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, and International Centre for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016 (China); Gunaratne, G. H. [Department of Physics, University of Houston, Houston, Texas 77204 (United States)

    2008-01-15

    Anisotropic Nd-Fe-B thin films are fabricated by direct current magnetron sputtering on Si substrates heated to temperatures over a wide range. Surface morphology and magnetic domains of the Nd-Fe-B thin films prepared at different sputtering temperatures (25-600 deg. C) are observed by a scanning probe microscopy. The magnetic domains exhibit a rich variety of textures, changing from striped via maze to cloudlike as the sputtering temperature is increased. Variations in magnetic domains with substrate temperature are discussed using phase components and magnetic anisotropies of the thin films. In addition, patterns of magnetic domains are analyzed using the 'disorder functions', a set of characterizations of complex patterns with labyrinthine structures. The disorder function {delta}(1) and the structure factor {delta}k do not change appreciably until a substrate temperature of 350 deg. C, but increases significantly beyond 400 deg. C. The disorder in magnetic domains increases with increasing sputtering temperature. A simultaneous enhancement of the anisotropic c texture and the hard-magnetic properties of the thin films are observed. The significant change of the disorder function at T{sub s}=400 deg. C appears to be a precursor to the hardening of the Nd-Fe-B film. The most disordered magnetic domains of the film with the substrate temperature of 600 deg. C correspond to the optimum magnetic properties, with the maximum energy product (BH){sub max} of 22.4 MG Oe.

  19. Magnetic property and thermal analysis of a Mn(II) complex with [Mn(CO2)]n chains based on 4,4?-bis(1H-imidazol-1-yl-methyl)biphenyl

    NASA Astrophysics Data System (ADS)

    Zhang, Ming-Dao; Zheng, Bao-Hui; Wang, Zhe; Jiao, Yan; Chen, Min-Dong

    2014-11-01

    Magnetic coordination polymers have attracted considerable interest due to their novel structures and potential applications. In this paper, one new 2D magnetic manganese coordination polymer {[Mn(bimb)(OBA)]}n (1) was synthesized under solvothermal conditions based on 4,4?-bis(1H-imidazol-1-yl-methyl)biphenyl (bimb) and 4,4?-oxybis(benzoate) (H2OBA). Complex 1 contains [Mn(CO2)]n 1D chains and magnetic susceptibility measurements indicate that compound 1 exhibits an antiferromagnetic coupling interaction. In addition, complex 1 exhibits solid-state photoluminescence and high thermal stability.

  20. Magnetic properties of ZnO-based diluted magnetic semiconductors

    Microsoft Academic Search

    S. W. Yoon; S.-B. Cho; S. C. We; B. J. Suh; H. K. Song; Y. J. Shin

    2003-01-01

    We report a study of the magnetic properties of transition-metal doped Zn1-xTMxO (TM=Mn, Co, Fe). Polycrystalline powder samples were synthesized by both solid-state and liquid-phase reactions. From the Curie-Weiss behavior of susceptibility at high temperatures, it was found that the TM-TM interaction is dominated by antiferromagnetic coupling with effective nearest-neighbor exchange constants J=-90 to -30 K. The magnetization data measured

  1. Magnetic properties of ZnO-based diluted magnetic semiconductors

    Microsoft Academic Search

    S. W. Yoon; S.-B. Cho; S. C. We; B. J. Suh; H. K. Song; Y. J. Shin

    2003-01-01

    We report a study of the magnetic properties of transition-metal doped Zn1?xTMxO (TM=Mn, Co, Fe). Polycrystalline powder samples were synthesized by both solid-state and liquid-phase reactions. From the Curie–Weiss behavior of susceptibility at high temperatures, it was found that the TM–TM interaction is dominated by antiferromagnetic coupling with effective nearest-neighbor exchange constants J=?90 to ?30 K. The magnetization data measured

  2. Dynamics of a complex quantum magnet.

    SciTech Connect

    Landry, James W.; Coppersmith, S. N. (University of Wisconsin, Madison, WI)

    2003-01-01

    We have computed the low energy quantum states and low frequency dynamical susceptibility of complex quantum spin systems in the limit of strong interactions, obtaining exact results for system sizes enormously larger than accessible previously. The ground state is a complex superposition of a substantial fraction of all the classical ground states, and yet the dynamical susceptibility exhibits sharp resonances reminiscent of the behavior of single spins. These results show that strongly interacting quantum systems can organize to generate coherent excitations and shed light on recent experiments demonstrating that coherent excitations are present in a disordered spin liquid. The dependence of the energy spectra on system size differs qualitatively from that of the energy spectra of random undirected bipartite graphs with similar statistics, implying that strong interactions are giving rise to these unusual spectral properties.

  3. Testing Low Complexity Affine-Invariant Properties

    E-print Network

    Bhattacharyya, Arnab; Lovett, Shachar

    2012-01-01

    Invariance with respect to linear or affine transformations of the domain is arguably the most common symmetry exhibited by natural algebraic properties. In this work, we show that any low complexity affine-invariant property of multivariate functions over finite fields is testable with a constant number of queries. This immediately reproves, for instance, that the Reed-Muller code over F_p of degree d =2 and fixed integer R >= 2, any affine-invariant property P of functions f: F_p^n -> [R] is testable, assuming the complexity of the property is less than p. Our proof involves developing analogs of graph-theoretic techniques in an algebraic setting, using tools from higher-order Fourier analysis.

  4. Magnetic properties of iron yoke laminations for SSC dipole magnets

    SciTech Connect

    Kahn, S.A.; Morgan, G.H.

    1991-01-01

    We examine the magnetic properties for the iron used in the SSC yoke laminations so that the accelerator tolerances can be met. The accelerator requirements for field quality specify a tolerance on the variation in the central field. At machine injection the variation in field is attributed to coercivity, H{sub c}. Requirements on the magnitude and the variation of H{sub c} are presented. At the 6.65 tesla operating field the variation in the saturation magnetization dominates the magnetic tolerance for the iron. 4 refs., 3 figs., 2 tabs.

  5. Magnetic properties of metallic ferromagnetic nanoparticle composites

    NASA Astrophysics Data System (ADS)

    Ramprasad, R.; Zurcher, P.; Petras, M.; Miller, M.; Renaud, P.

    2004-07-01

    Magnetic properties of nanoparticle composites, consisting of aligned ferromagnetic nanoparticles embedded in a nonmagnetic matrix, have been determined using a model based on phenomenological approaches. Input materials parameters for this model include the saturation magnetization (Ms), the crystal anisotropy field (Hk), a damping parameter (?) that describes the magnetic losses in the particles, and the conductivity (?) of the particles; all particles are assumed to have identical properties. Control of the physical characteristics of the composite system—such as the particle size, shape, volume fraction, and orientation—is necessary in order to achieve optimal magnetic properties (e.g., the magnetic permeability) at GHz frequencies. The degree to which the physical attributes need to be controlled has been determined by analysis of the ferromagnetic resonance (FMR) and eddy current losses at varying particle volume fractions. Composites with approximately spherical particles with radii smaller than 100 nm (for the materials parameters chosen here), packed to achieve a thin film geometry (with the easy magnetization axes of all particles aligned parallel to each other and to the surface of the thin film) are expected to have low eddy current losses, and optimal magnetic permeability and FMR behavior.

  6. Magnetic properties of the Bay of Islands Ophiolite suite and implications for the magnetization of oceanic crust

    Microsoft Academic Search

    B. Ann Swift; H. Paul Johnson

    1984-01-01

    Rock magnetic properties, opaque mineralogy, and degree of metomorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex. Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetizaiton of the underlying sheeted dike

  7. Complex Autoregressive Model and Its Properties

    Microsoft Academic Search

    Iwao SEKITA; Takio KURITA; Nobuyuki OTSU

    1991-01-01

    This paper shows the following three properties of the CAR (complex autoregressive) model which were proposed by the authors for shape description and recognition. The CAR coefficients estimated by the least squares fit are shown to be the maximum likelihood estimates and also the estimates obtained by maximizing the mutual infor- mation between boundary point zj and the previous m

  8. Complex Weldment Properties: Trends in Predictive Power

    E-print Network

    Cambridge, University of

    Complex Weldment Properties: Trends in Predictive Power H. K. D. H. Bhadeshia University about the optimum scheme for modelling materials failure. Introduction Our theoretical understanding of the various as- pects of welding varies in the solidity of its foundations and in its predictive powers [1

  9. Magnetic properties of colloidal cobalt nanoclusters

    NASA Astrophysics Data System (ADS)

    Torchio, R.; Meneghini, C.; Mobilio, S.; Capellini, G.; García Prieto, A.; Alonso, J.; Fdez-Gubieda, M. L.; Turco Liveri, V.; Longo, A.; Ruggirello, A. M.; Neisius, T.

    2010-01-01

    Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co3O4with metallic Co and some Co2+ bound to the surfactant. The presence of antiferromagnetic Co3O4 explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

  10. Ordered Magnetic Nanostructures. Fabrication and Properties

    Microsoft Academic Search

    J. I. Martin; J. Nogues; Kai Liu; J. L. Vicent; Ivan K. Schuller

    2003-01-01

    Abstract The fabrication,methods,and,physical properties,of ordered,magnetic,nanostructures,with,dimensions,on the submicron to nanometer scale are reviewed. First, various types of nanofabrication techniques are described, and their capabilities and limitations in achieving magnetic nanostructures are discussed. Specifically, we address electron beam lithography, X-ray lithography, laser interference lithography, scanning probe lithography, step growth methods, nanoimprint, shadowmasks, radiation damage, self-assembled structures, and the use of nanotemplates. Then

  11. Magnetic properties of ultrafine iron particles

    Microsoft Academic Search

    S. Gangopadhyay; G. C. Hadjipanayis; B. Dale; C. M. Sorensen; K. J. Klabunde; V. Papaefthymiou; A. Kostikas

    1992-01-01

    The magnetic and morphological properties of fine Fe particles have been studied. Ultrafine particles of Fe were prepared using a vapor deposition technique under an argon atmosphere. The argon pressure was varied from 0.5 to 8 Torr during evaporation, and samples with a median diameter in the range 50-200 Å were obtained having a log-normal distribution. The dependence of magnetic

  12. Microstructure characterization and magnetic properties of nanomaterials

    Microsoft Academic Search

    Xiang-Cheng Sun

    2002-01-01

    The microstructure and superparamagnetic properties of two systems of magnetic nanoparticles are reviewed. A new type of magnetic core-shell Ni-Ce nanocomposite particle (15-50nm) has been prepared. Typical HREM images and FFT patterns of HREM images showed that many planar defects (nanotwins and stacking faults) exist in the large Ni core zone (10-45nm). The shell layers (3-5nm) consist of an innermost

  13. Magnetic properties and anisotropy in magnetic thin films and superlattices

    NASA Astrophysics Data System (ADS)

    Guo, Wenli

    A systematic study of the magnetic properties and anisotropy in magnetic thin films as well as superlattices is presented in this thesis. The main objective is to investigate by means of the Green function technique the order-disorder phase transition and reorientation transition in a non-perturbative microscopic theory valid in the whole temperature range of interest. We consider the magnetic systems that may consist of an arbitrary number of layers with any spin. We start with a discussion of general properties and origins of anisotropies of the magnetic systems, and a list of questions that we are trying to answer. A comparison between different theoretical approaches follows. The Green function method is used to derive analytical expressions for various anisotropies. The energy spectrum and the spontaneous magnetization are obtained as well. Based on these results, the transition temperature and the Curie temperature are calculated as functions of the Fe film thickness. It is shown that the condition for the reorientation transition is equivalent to that for the zero energy gap at the bottom of the spin-wave spectrum. Special features under the influence of normal external field, anisotropic exchange couplings and next-nearest-neighbor couplings on the magnetization reorientation of magnetic thin films are then investigated in detail. It is demonstrated that the nature of perpendicular remanent (PR) depends primarily on the surface anisotropy and film thickness. The magnetic properties of Tb/Fe superlattices are also studied. It shows ferrimagnetic properties and normal uniaxial anisotropy. An approximation is proposed to treat magnetic Ni films of arbitrary thickness and arbitrary lattice structure for general spin. It is a much simpler way of calculation, in which one does not have to solve the determinant equation, especially the one with off-diagonal elements. The temperature and thickness dependence of various anisotropies are then investigated. There exists a PR magnetization for a medium size of film thickness. Finally, a summary and conclusion are given and some general perspectives of the field are discussed.

  14. Magnetic properties of rapidly quenched soft magnetic materials

    Microsoft Academic Search

    G. Bertotti; E. Ferrara; F. Fiorillo; P. Tiberto

    1997-01-01

    The discovery and large scale investigation of rapidly solidified alloys have brought to light, in the last two decades, a new scenario in basic and applied magnetism. With a range of compositions and microstructural states unavailable to conventional materials, the rapidly quenched alloys have in fact demonstrated unprecedented versatile properties, provided unique opportunities in applications and stirred up the domain

  15. Magnetic properties of iron yoke laminations for SSC dipole magnets

    Microsoft Academic Search

    S. A. Kahn; G. H. Morgan

    1991-01-01

    The authors examine the magnetic properties for the iron used in the SSC (Superconducting Super Collider) yoke laminations so that the accelerator tolerance can be met. The accelerator requirements for field quality specify a tolerance on the variation in the central field. At machine injection the variation in field is attributed to coercivity, Hc. Requirements on the magnitude and the

  16. Magnetic Properties of Electrically Contacted Fe4 Molecular Magnets

    NASA Astrophysics Data System (ADS)

    Burgess, Jacob; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Totti, Frederico; Ninova, Silviya; Yan, Shichao; Choi, Deung-Jang; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-03-01

    Single molecule magnets (SMMs) are often large and fragile molecules. This poses challenges for the construction of SMM based spintronics. Device geometries with two electronic leads contacting a molecule may be explored via scanning tunneling microscopy (STM). The Fe4 molecule stands out as a robust, thermally evaporable SMM, making it ideal for such an experiment. Here we present the first STM investigations of individual Fe4 molecules thermally evaporated onto a monolayer of Cu2N on a Cu (100) crystal. Using inelastic electron tunneling spectroscopy (IETS), spin excitations in single Fe4 molecules can be detected at meV energies. Analysis using a Spin Hamiltonian allows extraction of magnetic properties of individual Fe4 molecules, and investigation of the influence of the electronic leads. The tip and sample induce small changes in the magnetic properties of Fe4 molecules, making Fe4 a promising candidate for the development of spintronics devices based on SMMs.

  17. Electrostatic complexation of polyelectrolyte and magnetic nanoparticles: from wild clustering to controllable magnetic wires.

    PubMed

    Yan, Minhao; Qu, Li; Fan, Jiangxia; Ren, Yong

    2014-01-01

    We present the electrostatic complexation between polyelectrolytes and charged nanoparticles. The nanoparticles in solution are ?-Fe2O3 (maghemite) spheres with 8.3 nm diameter and anionic surface charges. The complexation was monitored using three different formulation pathways such as direct mixing, dilution, and dialysis. In the first process, the hybrids were obtained by mixing stock solutions of polymers and nanoparticles. A 'destabilization state' with sharp and intense maximum aggregation was found at charges stoichiometry (isoelectric point). While on the two sides of the isoelectric point, 'long-lived stable clusters state' (arrested states) were observed. Dilution and dialysis processes were based on controlled desalting kinetics according to methods developed in molecular biology. Under an external magnetic field (B?=?0.3 T), from dialysis at isoelectric point and at arrested states, cationic polyelectrolytes can 'paste' these magnetic nanoparticles (NPs) together to yield irregular aggregates (size of 100 ?m) and regular rod-like aggregates, respectively. These straight magnetic wires were fabricated with diameters around 200 nm and lengths comprised between 1 ?m and 0.5 mm. The wires can have either positive or negative charges on their surface. After analyzing their orientational behavior under an external rotating field, we also showed that the wires made from different polyelectrolytes have the same magnetic property. The recipe used a wide range of polyelectrolytes thereby enhancing the versatility and applied potentialities of the method. This simple and general approach presents significant perspective for the fabrication of hybrid functional materials. PMID:24910569

  18. Electrostatic complexation of polyelectrolyte and magnetic nanoparticles: from wild clustering to controllable magnetic wires

    NASA Astrophysics Data System (ADS)

    Yan, Minhao; Qu, Li; Fan, Jiangxia; Ren, Yong

    2014-05-01

    We present the electrostatic complexation between polyelectrolytes and charged nanoparticles. The nanoparticles in solution are ?-Fe2O3 (maghemite) spheres with 8.3 nm diameter and anionic surface charges. The complexation was monitored using three different formulation pathways such as direct mixing, dilution, and dialysis. In the first process, the hybrids were obtained by mixing stock solutions of polymers and nanoparticles. A `destabilization state' with sharp and intense maximum aggregation was found at charges stoichiometry (isoelectric point). While on the two sides of the isoelectric point, `long-lived stable clusters state' (arrested states) were observed. Dilution and dialysis processes were based on controlled desalting kinetics according to methods developed in molecular biology. Under an external magnetic field ( B = 0.3 T), from dialysis at isoelectric point and at arrested states, cationic polyelectrolytes can `paste' these magnetic nanoparticles (NPs) together to yield irregular aggregates (size of 100 ?m) and regular rod-like aggregates, respectively. These straight magnetic wires were fabricated with diameters around 200 nm and lengths comprised between 1 ?m and 0.5 mm. The wires can have either positive or negative charges on their surface. After analyzing their orientational behavior under an external rotating field, we also showed that the wires made from different polyelectrolytes have the same magnetic property. The recipe used a wide range of polyelectrolytes thereby enhancing the versatility and applied potentialities of the method. This simple and general approach presents significant perspective for the fabrication of hybrid functional materials.

  19. Crystal structure and magnetic properties of a three-dimensional complex constructed from [CuL] 2+ and [Fe(CN) 6 ] 3? precursors

    Microsoft Academic Search

    Ai-hua Yuan; Xiao-ping Shen; Hu Zhou

    2008-01-01

    Self-assembly of the precursor [Cu(L)]2+ (L = 3,10-dipropyl-1,3,5,8,10,12-hexaazacyclotetradecane) with hexacyanometalate [Fe(CN)6]3? produces a 3-D cyano-bridged Cu(II)–Fe(III) bimetallic assembly, [CuL]2[Fe(CN)6]ClO4 · H2O (1), characterized by single-crystal X-ray diffraction studies, and magnetic measurements. The crystallographic determination\\u000a reveals that each hexacyanoferromate(III) ion connects four copper(II) ions using four co-planar CN? groups which axially coordinate to the copper ion in a trans fashion forming trans-CuL(N?C)2 moieties in (1).

  20. On the Effective Magnetic Properties of Magnetorheological Fluids \\Lambda

    E-print Network

    On the Effective Magnetic Properties of Magnetorheological Fluids \\Lambda November 9, 1998 Tammy M of the interparticle distance. To this end, we present and employ a model for the effective magnetic properties of MR interparticle distance affects the overall magnetic properties of the fluids [2]. Understanding the magnetic re

  1. New application of complex magnetic materials to the magnetic refrigerant in an Ericsson magnetic refrigerator

    SciTech Connect

    Hashimoto, T.; Kuzuhara, T.; Sahashi, M.; Inomata, K.; Tomokiyo, A.; Yayama, H.

    1987-11-01

    A complex new magnetic refrigerant, suitable for the ideal Ericsson cycle, has been investigated. Above --15 K it is necessary to use ferromagnets as a magnetic refrigerant. However, temperature variation for the magnetic entropy change in a homogeneous ferromagnet is not suitable for the Ericsson cycle. The present paper verifies, from theoretical analysis, that a complex ferromagnetic material, for instance, (ErAl/sub 2/)/sub 0.312/(HoAl/sub 2/)/sub 0.198/ (Ho/sub 0.5/Dy/sub 0.5/Al/sub 2/)/sub 0.490/, has the most suitable characteristics for the ideal Ericsson cycle, including two kinds of isomagnetic field processes. On the basis of the above consideration, a sintered layer structural complex has been prepared, composed of three kinds of RAl/sub 2.15/ layers, where R's are rare-earth atoms. From specific heat measurements made on this complex, its entropy and entropy change have been determined. It has been concluded that the complex magnetic material is the most hopeful refrigerant for the Ericsson cycle.

  2. Domain structures in complex 3D magnetic fields

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Priest, E. R.

    The numerous magnetic fragments that populate the mixed-polarity, quiet-Sun photosphere give rise to many interesting topological features in the corona. In light of this, much recent work has gone into classifying the configurations that arise from simple, point-source potential-field models in efforts to determine the nature of the quiet-Sun magnetic field. These studies have ranged from systematic and detailed examinations of magnetic fields arising from only a handful of sources, involving classifying the configurations that arise (and how some states may bifurcate into other states), to statistical studies of the overall properties of fields arising from hundreds of magnetic sources. Such studies have greatly increased our understanding of what we might expect the magnetic field over the quiet Sun to behave like; the purpose of the study presented here is to extend this understanding further by examining the structure of the individual domains (the regions in space through which pairs of opposite-polarity sources are connected). In particular, the features of lesser-known domain structures that are absent from fields arising from only a few sources and overlooked by sweeping statistical studies are documented. In spite of the incredible complexity of the coronal field, previous studies have shown that there are only two types of building block in a potential field arising from coplanar point sources: namely, an isolated dome, bounded by a single unbroken separatrix surface, and a separator-ring domain, engirdled by a ring of separators. However, it is demonstrated here how both isolated domains and separator-ring domains may be categorised further depending upon their particular geometrical and topological traits. As many models predict coronal heating at topologically distinct features in magnetic fields such as null points, separators and separatrices, for any such models to be applied to general fields would require a scheme for identifying which topological features are related to a given domain. The study here explores some of the issues that would need to be taken into account by such a scheme, and in particular the problems associated with trying to deduce the properties of a general magnetic field from knowledge of domain footprints alone. Animated 3D-rotational views of some of the figures in this manuscript may be viewed in AVI, MPEG and animated-GIF formats by visiting http://www-solar.mcs.st-and.ac.uk/robertc/animations/blocks.html and following the desired link.

  3. Syntheses, structures and magnetic properties of two new water bridged dinuclear nickel(II) complexes containing derivatives of 1,2,4-triazole and pivalate ligands

    Microsoft Academic Search

    Jian-Hao Zhou; Ru-Mei Cheng; You Song; Yi-Zhi Li; Zhi Yu; Xue-Tai Chen; Xiao-Zeng You

    2006-01-01

    Two new water bridged dinuclear nickel(II) complexes containing derivatives of 1,2,4-triazole and pivalate ligands, [Ni2(?-H2O)(?-admtrz)2(piv)4(H2O)2]·13H2O (1·13H2O) (admtrz=4-amino-3,5-dimethyl-1,2,4-triazole, piv=pivalate anion) and [Ni2(?-H2O)(?-adetrz)2(piv)4]·3H2O (2·3H2O) (adetrz=4-amino-3,5-diethyl-1,2,4-triazole) were prepared and structurally characterized. Both 1 and 2 have similar unprecedented dinuclear Ni(II) units with one water and two triazole bridges, in which each six-coordinated Ni(II) ion is further coordinated with terminal pivalate ligand and in

  4. Magnetic properties and energy-mapping analysis.

    PubMed

    Xiang, Hongjun; Lee, Changhoon; Koo, Hyun-Joo; Gong, Xingao; Whangbo, Myung-Hwan

    2013-01-28

    The magnetic energy levels of a given magnetic solid are closely packed in energy because the interactions between magnetic ions are weak. Thus, in describing its magnetic properties, one needs to generate its magnetic energy spectrum by employing an appropriate spin Hamiltonian. In this review article we discuss how to determine and specify a necessary spin Hamiltonian in terms of first principles electronic structure calculations on the basis of energy-mapping analysis and briefly survey important concepts and phenomena that one encounters in reading the current literature on magnetic solids. Our discussion is given on a qualitative level from the perspective of magnetic energy levels and electronic structures. The spin Hamiltonian appropriate for a magnetic system should be based on its spin lattice, i.e., the repeat pattern of its strong magnetic bonds (strong spin exchange paths), which requires one to evaluate its Heisenberg spin exchanges on the basis of energy-mapping analysis. Other weaker energy terms such as Dzyaloshinskii-Moriya (DM) spin exchange and magnetocrystalline anisotropy energies, which a spin Hamiltonian must include in certain cases, can also be evaluated by performing energy-mapping analysis. We show that the spin orientation of a transition-metal magnetic ion can be easily explained by considering its split d-block levels as unperturbed states with the spin-orbit coupling (SOC) as perturbation, that the DM exchange between adjacent spin sites can become comparable in strength to the Heisenberg spin exchange when the two spin sites are not chemically equivalent, and that the DM interaction between rare-earth and transition-metal cations is governed largely by the magnetic orbitals of the rare-earth cation. PMID:23128376

  5. Maria Goeppert-Mayer Award Talk: Novel Magnetism and Transport in Complex Oxide Thin Films, Multilayers and Nanostructures

    Microsoft Academic Search

    Yuri Suzuki

    2005-01-01

    In epitaxial complex oxide systems, epitaxial strain, cation substitution and nanofabrication are just some ways in which their magnetic, electronic and optical properties may be tuned. In addition, their surfaces and interfaces provide a rich playground for the exploration of novel magnetic properties not found in the bulk constituents and the development of functional interfaces to be incorporated into technological

  6. Magnetic properties of Martian surface material

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.

    1984-01-01

    The hypothesis that the magnetic properties of the Martian surface material are due to the production of a magnetic phase in the clay mineral nontronite by transient shock heating is examined. In the course of the investigation a magnetic material is produced with rather unusual properties. Heating from 900 C to 1000 C, of natural samples of nontronite leads first to the production of what appears to be Si doped maghemite gamma (-Fe2O3). Although apparently metastable, the growth of gamma -Fe2O3 at these temprtures is unexpected, and its relative persistence of several hours at 1000 C is most surprising. Continued annealing of this material for longer periods promote the crystallization of alpha Fe2O3 and cristobalite (high temperature polymorph of SiO2). All available data correlate this new magnetic material with the cristobalite hence our naming it magnetic ferri cristobalite. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.

  7. Magnetic properties of dispersed magnetite powders

    Microsoft Academic Search

    L. G. Parry

    1965-01-01

    Measurements have been made of coercive force, susceptibility, isothermal remanence, thermoremanence and thermal and alternating field demagnetization of annealed magnetite powders in nine size ranges from 1·5 ? to 120 ?. The samples were dispersed in plaster to occupy a few per cent by volume of the specimens and thus to simulate the magnetic properties of rocks. The results are

  8. Magnetic Properties of Dy in Pb

    SciTech Connect

    Skanthakumar, S.; Soderholm, L.; Movshovich, R.

    1999-07-10

    Superconductivity can be induced at high temperatures in Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8} (R - rare earth) by partially doping Ca{sup 2+} for R{sup 3+}. In order to understand the interplay between magnetism and superconductivity, the magnetic properties of the parent compounds, Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8}, have been studied. The work presented here includes magnetic susceptibility and specific heat measurements on R=Dy and extends the previous studies on R=Ce, Pr, Tb, Ho and Er. Specific heat experiments suggest that the Dy ions order antiferromagnetically with an ordering temperature of 1.3K. The magnetic susceptibility data are in good agreement with the susceptibility calculated using crystal field parameters that are extrapolated from previous modeling of the R=Er and Ho analogs of this series.

  9. Spectroscopic properties of transition elements and their related magnetic properties

    Microsoft Academic Search

    P. Porcher

    1988-01-01

    Optical and magnetic properties of transition elements (nd and nf ions) are re-analysed. The aim of this work is to see how far a unique set of phenomenological parameters, those introduced by crystal-ligand field theory described on the ??SLJM> kets, can describe the experimental data.

  10. Magnetic dipole discharges. I. Basic properties

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States); Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R. [Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck (Austria)] [Institute for Ion Physics and Applied Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

    2013-08-15

    A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup ?3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.

  11. Effect of coupling strength on magnetic properties of exchange spring magnets

    E-print Network

    Liu, J. Ping

    Effect of coupling strength on magnetic properties of exchange spring magnets Vamsi M. Chakka, Z. S, is a key parameter in controlling the spring magnet properties. A ferromagnetically coupled hard that correlate the magnetic properties of a FCB and its layer parameters. These analytical expressions have been

  12. Magnetic properties of heterotrophic bacteria (abstract)

    NASA Astrophysics Data System (ADS)

    Verkhovceva, Nadezda V.; Glebova, Irina N.; Romanuk, Anatoly V.

    1994-05-01

    The magnetic properties (magnetic susceptibility and saturation magnetization) of six species of heterotrophic bacteria were studied: alcaligenes faecalis 81, arthrobacter globiformis BKM 685, bacillus cereus 8, leptothrix pseudo-ochracea D-405, proteus vulgaris 14, and seliberia stellata. It has been shown that the magnetic properties of bacteria depend on (1) the peculiarity of the micro-organism (species-specific and connected with cultivation conditions); (2) the source of the iron in the media. Most of the bacteria are diamagnetic in media with a minimum of iron (??=-7.2-0.3×10-6 sm3/g). The spore forming species (bacillus cereus) has increased diamagnetism. Usually the bacteria are paramagnetic in iron-containing media because they concentrate into Fe compounds. The paramagnetism of the iron-concentrating species (anthrobacter globiformis -?par=2.4×10-6, leptothrix pseudo-ochtracea ?par=11.0×10-6 and seliberia stellata ?par=3.2×10-6 sm3/g) depends, in general, on magnetically ordered compounds. Iron compounds not accumulated by proteus vulgaris and these species are always diamagnetic .

  13. Magnetic properties of Pt Ir nanowires

    NASA Astrophysics Data System (ADS)

    Sondón, Tristana; Saúl, Andrés; Guevara, Javier

    2007-09-01

    We study the magnetic properties of Pt 1- xIr x nanowires by using the ab-initiowien2k code, being 0 ? x ? 1. It has been established in the literature that Pt and Ir nanowires show very different behaviors if spin-orbit coupling (SOC) is considered or not in the calculation of their electronic structure. Pt nanowires have magnetic order only if SOC is considered, but Ir ones show the opposite behavior. In the case of Pt 1- xIr x nanowires and without considering SOC, the spin magnetic moment as a function of the Ir concentration ( ? vs. x) shows an almost linear behavior between the spin magnetic moments of pure wires. While ? Ir is relatively high, the ? Pt presents very low values. On the contrary, if SOC is taken into account, a very interesting behavior is found. While the pure wires have low average magnetic moment values, being zero for Ir one and 0.15 ? B for the Pt one, the curve ? vs. x shows a maximum at x = 1/2 of about 0.75 ? B. We discuss the influence of equilibrium bond length and hybridization effects on the electronic properties of Pt 1- xIr x nanowires.

  14. PHYSICAL PROPERTIES OF COMPLEX C HALO CLOUDS

    SciTech Connect

    Hsu, W.-H. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Putman, M. E.; Peek, J. E. G. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Heitsch, F.; Clark, S. E. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Stanimirovic, S., E-mail: wenhsin@umich.edu [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706-1582 (United States)

    2011-02-15

    Observations from the Galactic Arecibo L-band Feed Array H I (GALFA-H I) Survey of the tail of Complex C are presented and the halo clouds associated with this complex are cataloged. The properties of the Complex C clouds are compared to clouds cataloged at the tail of the Magellanic Stream to provide insight into the origin and destruction mechanism of Complex C. Magellanic Stream and Complex C clouds show similarities in their mass distributions (slope = -0.7 and -0.6 log (N( log (mass)))/ log (mass), respectively) and have a common line width of 20-30 km s{sup -1} (indicative of a warm component), which may indicate a common origin and/or physical process breaking down the clouds. The clouds cataloged at the tail of Complex C extend over a mass range of 10{sup 1.1}-10{sup 4.8} M{sub sun}, sizes of 10{sup 1.2}-10{sup 2.6} pc, and have a median volume density and pressure of 0.065 cm{sup -3} and (P/k) = 580 K cm{sup -3}. We do not see a prominent two-phase structure in Complex C, possibly due to its low metallicity and inefficient cooling compared to other halo clouds. Assuming that the Complex C clouds are in pressure equilibrium with a hot halo medium, we find a median halo density of 5.8 x 10{sup -4} cm{sup -3}, which given a constant distance of 10 kpc is at a z-height of {approx}3 kpc. Using the same argument for the Stream results in a median halo density of 8.4 x 10-{sup 5} (60 kpc/d) cm{sup -3}. These densities are consistent with previous observational constraints and cosmological simulations. We also assess the derived cloud and halo properties with three-dimensional grid simulations of halo H I clouds and find that the temperature is generally consistent within a factor of 1.5 and the volume densities, pressures, and halo densities are consistent within a factor of three.

  15. Magnetic Properties of Mesoporous and Nano-particulate Metal Oxides 

    E-print Network

    Hill, Adrian H

    2009-01-01

    The magnetic properties of the first row transition metal oxides are wide and varied and have been studied extensively since the 1930’s. Observations that the magnetic properties of these material types change with the ...

  16. Ris-PhD-30(EN) The Magnetic properties of

    E-print Network

    Risø-PhD-30(EN) The Magnetic properties of antiferromagnetic nanoparticles: NiO and -Fe2 O3: Christian Robert Haffenden Bahl Title: The Magnetic properties of antiferromagnetic nanoparticles: Ni, have magnetic properties which at nanoscale differ from those of the bulk materials. With emphasis

  17. Electron holography and magnetic properties of exsolved synthetic titanomagnetites

    E-print Network

    Dunin-Borkowski, Rafal E.

    Electron holography and magnetic properties of exsolved synthetic titanomagnetites Church, N S nc-scale exsolution structures, but the contribution to bulk magnetic properties of these assemblages of iron magnetic properties and subsequently resintered under oxidizing conditions to create two-phase systems

  18. Complexity and diffusion of magnetic flux surfaces in anisotropic turbulence

    SciTech Connect

    Servidio, S. [Dipartimento di Fisica, Università della Calabria, I-87036 Cosenza (Italy); Matthaeus, W. H.; Wan, M.; Rappazzo, A. F. [Department of Physics and Astronomy, University of Delaware, Newark, DE (United States); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok (Thailand); Oughton, S., E-mail: sergio.servidio@fis.unical.it [Department of Mathematics, University of Waikato, Hamilton (New Zealand)

    2014-04-10

    The complexity of magnetic flux surfaces is investigated analytically and numerically in static homogeneous magnetic turbulence. Magnetic surfaces are computed to large distances in magnetic fields derived from a reduced magnetohydrodynamic model. The question addressed is whether one can define magnetic surfaces over large distances when turbulence is present. Using a flux surface spectral analysis, we show that magnetic surfaces become complex at small scales, experiencing an exponential thinning that is quantified here. The computation of a flux surface is of either exponential or nondeterministic polynomial complexity, which has the conceptual implication that global identification of magnetic flux surfaces and flux exchange, e.g., in magnetic reconnection, can be intractable in three dimensions. The coarse-grained large-scale magnetic flux experiences diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established explicitly through multiple scale analysis. The Kubo number controls both large and small scale limits. These results have consequences for interpreting processes such as magnetic reconnection and field-line diffusion in astrophysical plasmas.

  19. Research into europium complexes as magnetic resonance imaging contrast agents (Review)

    PubMed Central

    HAN, GUOCAN; DENG, YANGWEI; SUN, JIHONG; LING, JUN; SHEN, ZHIQUAN

    2015-01-01

    Europium (Eu) is a paramagnetic lanthanide element that possesses an outstanding luminescent property. Eu complexes are ideal fluorescence imaging (FI) agents. Eu2+ has satisfactory relaxivity and optical properties, and can realize magnetic resonance (MRI)-FI dual imaging applications when used with appropriate cryptands that render it oxidatively stable. By contrast, based on the chemical exchange saturation transfer (CEST) mechanism, Eu3+ complexes can provide enhanced MRI sensitivity when used with optimal cryptands, incorporated into polymeric CEST agents or blended with Gd3+. Eu complexes are promising in MRI-FI dual imaging applications and have a bright future. PMID:26136858

  20. Thickness dependent properties of magnetic ultrathin films

    NASA Astrophysics Data System (ADS)

    Cong, Bach Thanh; Thao, Pham Huong

    2013-10-01

    The dependence of magnetic properties on the thickness of few-layer thin films is investigated at finite temperature using the functional integral method for solving the Heisenberg spin model. The temperature dependence of the ultra-thin film's magnetization and Curie temperature are calculated in terms of the mean field theory and of the Gaussian spin fluctuation approximations. It has been shown that both Curie temperature and temperature interval, where the magnetization is non-zero, are strongly reduced with the thickness reduction by using the spin fluctuation approximations in comparison with the mean field results. Curie temperature dependence on the film thickness calculated numerically well agrees with the experimental data for Ni/Cu(1 0 0) and Ni/Cu(1 1 1) ultrathin films.

  1. Magnetic properties of artificially synthesized ferritins

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Lee, H. I.; Cho, S.-B.; Yoon, S.; Suh, B. J.; Jang, Z. H.; St. Pierre, T. G.; Kim, S.-W.; Kim, K.-S.

    2005-05-01

    Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H ) data to a modified Langevin function: M(H )=M0L(?pH/kBT)+?aH, the effective magnetic moment ?p is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins.

  2. Correcting Aberrations in Complex Magnet Systems for Muon Cooling Channels

    SciTech Connect

    J.A. Maloney, B. Erdelyi, A. Afanaciev, R.P. Johnson, Y.S. Derbenev, V.S. Morozov

    2011-03-01

    Designing and simulating complex magnet systems needed for cooling channels in both neutrino factories and muon colliders requires innovative techniques to correct for both chromatic and spherical aberrations. Optimizing complex systems, such as helical magnets for example, is also difficult but essential. By using COSY INFINITY, a differential algebra based code, the transfer and aberration maps can be examined to discover what critical terms have the greatest influence on these aberrations.

  3. Measuring Viscosity with a Levitating Magnet: Application to Complex Fluids

    ERIC Educational Resources Information Center

    Even, C.; Bouquet, F.; Remond, J.; Deloche, B.

    2009-01-01

    As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10[superscript 6] mPa s are obtained. This experiment is used as an introduction to complex

  4. Electron spin resonance and magnetic studies on some copper(II) azobarbituric and azothiobarbituric acid complexes.

    PubMed

    Masoud, M S; Khalil, E A; Hafez, A M; El-Husseiny, A F

    2005-03-01

    Electron spin resonance and magnetic susceptibility on some copper(II) complexes prepared from phenylazobarbituric and phenylazothiobarbituric acid compounds containing 2,5-dichloro and 2,5-dimethyl groups were discussed. The thio complexes exist in dimer-monomer mixture. The corresponding copper(II) complexes of the oxygen homologous failed to exhibit association. Singlet-triplet separation values equal to -321 and -263 cm(-1) for the 2,5-dimethyl and 2,5-dichloro complexes, respectively, of the thio series. An empirical measure of the amount of tetrahedral deformation based on the values of g||/A|| assigned the square-planar geometry of the dimethyl-oxygen complex while the other complexes are with tetrahedral planar geometries. The effect of temperature on the ESR data was discussed. The diamagnetic properties of the complexes derived from 2,5-dichloro and 2,5-dimethyl thiobarbituric acid suggested the formation of Cu(I) complexes. PMID:15683807

  5. The influence of magnetic ordering on the transport properties of Cr–Fe–Mn alloys

    Microsoft Academic Search

    K. Perzynska; M. Biernacka; L. Dobrzynski; D. Satula; K. Szymanski; J. Waliszewski; P. Zaleski

    2002-01-01

    In order to understand conditions in which magnetic ordering affects the electric transport properties in magnetically disordered Cr–Fe–Mn alloys, GMR was investigated in two series of samples: Cr75+xFe16+xMn9?x and Cr75+yFe16?yMn9. Magnetic structure of these alloys turned out to be very complex. The observed magnetoresistivity is shown to be particularly sensitive to the FM ordering.

  6. An instrument for measuring complex magnetic susceptibility of soils

    NASA Astrophysics Data System (ADS)

    West, Gordon F.; Bailey, Richard C.

    2005-06-01

    To improve the success of electromagnetic induction (EMI) metal detectors in identifying anti-personnel land mines buried in slightly ferromagnetic natural soils, we need to know what range of soil physical properties must be dealt with. We have therefore built a laboratory instrument for measuring complex magnetic susceptibility in inch-sized samples over a frequency range from 100 Hz to ~ 70 kHz with errors of a few percent of the sample susceptibility in a sample of ~1 milli-SIU volume susceptibility, (i.e. ~30 micro-SIU). The instrument is a symmetrical, six coil, induction spectrometer. A pair of transmitter coils in Helmholtz configuration generates a uniform magnetic field over the sample region. The magnetic moment induced in the sample is detected (mainly) by a pair of receiver coils which are closer to the sample than the transmitter pair and also (nearly) in Helmholtz configuration, so as to provide uniform sensitivity over the whole sample region. The coupling of the main receiver pair to the transmitter pair is annulled with a second pair of coils (called the reference receiver pair) situated outside the transmitter pair. The transmitter coils are energized with a wideband current. Data acquisition is by a PC computer with a 192 kHz, 24 bit, 2 channel sound card using software in written in MatLab. Although our instrument is still a prototype and its design continues to evolve, we have measured susceptibility spectra of some samples from de-mining projects in areas where false alarms are a problem and have found dispersive susceptibilities.

  7. Intrinsic Magnetic Properties of L10 Derivates

    NASA Astrophysics Data System (ADS)

    Skomski, Ralph; Manchanda, Priyanka; Sahota, Pankaj K.; Kashyap, Arti; Balasubramanian, Balamurugan; Shield, J. E.; Sellmyer, D. J.

    2012-02-01

    It is investigated how atomic substitutions modify the magnetization, exchange and anisotropy of L10-ordered ferromagnets. Emphasis is on properties of interest in permanent magnetism, including the reduction of raw-materials costs by substituting iron-series transition metals for expensive heavy (4d/5d) transition-metal elements. In particular, VASP calculations are used to determine the magnetizations of the Fe-Co-Pt, Mn-Al-C and Fe-Ni-S systems. We perform supercell calculations to determine the moments of Fe and Co in various L10 derivates with chemical disorder. The local magnetic moments exhibit a subtle dependence on the environment, not only in each Fe-Co layer but also through alternating 4d/5d layers. However, the magnitude of these spatial fluctuations is not very large, and after configurational averaging, the moments exhibit very simple dependencies on the concentrations of the involved atoms. The FeNi system is also interesting because L10-ordered FeNi was originally discovered in meteorites (tetrataenite), formed with cooling times in excess of one million years.

  8. Magnetic properties of substituted barium ferrite powders

    SciTech Connect

    Gruskova, A. [Slovak Univ. of Technology, Bratislava (Slovakia). Dept. of Electrotechnology] [Slovak Univ. of Technology, Bratislava (Slovakia). Dept. of Electrotechnology

    1994-03-01

    Hexagonal barium ferrites were prepared using the citrate method. Cobalt and titanium were added in the amounts x from 0.2 to 1.1 ion/f.u. related to the formula BaCo{sub x}Ti{sub x}Fe{sub 12{minus}2x}O{sub 19}. The heat treatment has been applied in three steps of 550 C/5 hrs, 850 C/2 hrs and 1,100 C/2 hrs. The following magnetic properties have been achieved: H{sub c} {approximately} 80 kA/m, J{sub s} {approximately} 120 {times} 10{sup {minus}6} Tkg{sup {minus}1} m{sup 3}, and J{sub r} {approximately} 60 {times} 10{sup {minus}6} Tkg{sup {minus}1} m{sup 3} in the composition for which x is equal to 0.5 ion/f.u. The magnetic parameters have been measured by the vibration magnetometer.

  9. Synthesis and magnetic properties of nanostructured maghemite

    SciTech Connect

    Vollath, D.; Szabo, D.V. [Institut fuer Materialforschung III, Forschungszentrum Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe (Germany); Taylor, R.D.; Willis, J.O. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    1997-08-01

    Nanocrystalline maghemite, {gamma}{endash}Fe{sub 2}O{sub 3}, can be synthesized in a microwave plasma using FeCl{sub 3} or Fe{sub 3}(CO){sub 12} as the precursor. Electron microscopy revealed particle sizes in the range of 5 to 10 nm. In general, this material is superparamagnetic. The magnetic properties are strongly dependent on the precursor. In both cases the production process leads to a highly disordered material with the consequence of a low magnetization. The assumption of a disordered structured is also supported by electron energy loss (EEL) and Moessbauer spectroscopy. The structure of this material shows a nearly identical number of cations on tetrahedral and octahedral lattice sites. {copyright} {ital 1997 Materials Research Society.}

  10. Optical, magnetic and electronic properties of graphene quantum dots

    Microsoft Academic Search

    A. Devrim Guclu

    2011-01-01

    We present a theory of optical, magnetic and electronic properties of graphene quantum dots. We demonstrate that there exists a class of triangular graphene quantum dots with zigzag edges [1-8] which combines magnetic, optical and transport properties in a single-material structure. These dots exhibit robust magnetic moment and optical transitions simultaneously in the THz, visible and UV spectral ranges due

  11. Magnetic susceptibility of Mn(III) complexes of hydroxamate siderophores.

    PubMed

    Springer, Stephen D; Butler, Alison

    2015-07-01

    The hydroxamate siderophores putrebactin, desferrioxamine B, and desferrioxamine E bind Mn(II) and promote the air oxidation of Mn(II) to Mn(III) at pH>7.1. The magnetic susceptibility of the manganese complexes were determined by the Evans method and the stoichiometry was probed with electrospray ionization mass spectrometry (ESIMS). The room temperature magnetic moments (?eff) for the manganese complexes of desferrioxamines B and E were 4.85BM and 4.84BM, respectively, consistent with a high spin, d(4), Mn(III) electronic configuration. The manganese complex of putrebactin had a magnetic moment of 4.98BM, consistent with incomplete oxidation of Mn(II), as confirmed by X band EPR spectroscopy. Mass spectra of the Mn(III) desferrioxamine B and E complexes showed complexes at m/z 613.26 and 653.26, respectively, consistent with 1:1 complexation. Mass spectral peaks for manganese putrebactin at m/z 797.31 and 1221.41 corresponds to 1:2 and 2:3 Mn:putrebactin complexation. This study directly confirms the Mn(III) oxidation state in hydroxamate siderophore complexes. PMID:25978931

  12. Magnetic field properties of the ISABELLE Project superconducting dipole magnets

    SciTech Connect

    Kirk, H.G.; Engelmann, R.; Herrera, J.; Jaeger, K.; Robins, K.; Willen, E.

    1981-01-01

    A series of prototype superconducting dipole magnets have been constructed and tested as part of the ISABELLE Project research and development program. Results of magnetic field measurements are presented with emphasis placed on the DC and AC components of the main field. Magnetization and the effects of the magnetic fields at the ends of the magnet are displayed.

  13. Rapidly solidified alloys and their mechanical and magnetic properties

    Microsoft Academic Search

    B. C. Giessen; D. E. Polk; A. I. Taub

    1986-01-01

    This book is organized under the following headings: Processing; Amorphous Alloys Formation; Amorphous Alloys-Relaxation and Phase Transformation; Amorphous Alloys-Consolidation, Mechanical, and Chemical Properties; Amorphous Alloys-Magnetic Properties; Crystalline Magnetic Materials; Quasicrystals; Microstructure and Properties of Crystalline RSP Alloys-Light Metals: Aluminum, Magnesium, Titanium; Microstructure and Properties of Crystalline RSP Alloys-Nickel, Iron and Cobalt Alloysl; Microstructure and Properties of Crystallilne RSP Alloys-Other Systems.

  14. Magnetic properties and microstructure of bulk Nd-Fe-B magnets solidified in magnetic field

    SciTech Connect

    Wang, C. [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108 (China); Lai, Y. S.; Hsieh, C. C.; Chang, W. C. [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); Chang, H. W. [Department of Physics, Tunghai University, Taichung 407, Taiwan (China); Sun, A. C. [Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li 32003, Taiwan (China)

    2011-04-01

    The Nd-Fe-B bulk magnets with a slab shape of 0.9 x 4 x 15 mm{sup 3} were prepared by injection casting into a copper mold. The effects of applying a magnetic field during the casting process on the magnetic properties and microstructure of Nd{sub 9.5}Fe{sub 71.5}Ti{sub 2.5}Zr{sub 0.5}Cr{sub 1}B{sub 14.5}C{sub 0.5} alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd{sub 2}Fe{sub 14}B phase with the c-axis perpendicular to the slab plane than the sample cast without magnetic field. The intensity of the texture weakens from surface to inner region of the bulk magnets. Applying a magnetic field during the casting process is helpful to refine the grain size effectively. As a result, the magnetic properties are improved from B{sub r} = 5.8 kG, {sub i}H{sub c} = 6.5 kOe, and (BH){sub max} = 5.9 MGOe for thesample cast without magnetic field to B{sub r} = 6.1 kG, {sub i}H{sub c} = 10.3 kOe, and (BH){sub max} = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

  15. Structure and magnetic properties of MnZn nanoferrites synthesized under a high magnetic field

    Microsoft Academic Search

    Yongsheng Liu; Yunbo Zhong; Jincang Zhang; Zhongming Ren; Shixun Cao; Zhenglong Yang; Tian Gao

    2011-01-01

    Mn0.6Zn0.4Fe2O4 nanoparticles are fabricated by a phase transformation method in a high dc magnetic field of 60 kOe, and their structural and magnetic properties are investigated. For the 60 kOe sample, the average particle size increases and the particle size becomes uniform. Magnetic investigation displays the magnetic field enhances its saturation magnetization and decreases its magnetic loss. Results of a.c.

  16. Thermodynamic Properties of Organometallic Dihydrogen Complexes for Hydrogen Storage Applications

    NASA Astrophysics Data System (ADS)

    Abrecht, David Gregory

    The mechanism and thermodynamic properties of hydrogen binding to the solid-state complexes [M(CO)dppe2][BArF24] (M = Mn, Re, Tc) and [M'Hdppe2][NTf2] (M' = Fe, Ru, Os) were investigated experimentally and computationally over the temperature range 298K-373K and pressure range 0-2800 torr, based on the Sieverts method. The bulk absorption behavior was found to be accurately described by Langmuir isotherms. Enthalpy and entropy values of ?H° = -52.2 kJ/mol and ?S° = -99.6 J/mol-K were obtained experimentally for hydrogen absorption onto [Mn(CO)dppe2][BArF24] from the Langmuir equilibrium constant, and values obtained from electronic structure calculations using the LANL2DZ-ECP basis set were found to successfully reproduce both the pressure-temperature-composition behavior and the thermodynamic values to within 5% of those obtained through experiment. Results from simulations for all complexes yielded large enthalpy values similar to metal hydride formation enthalpies for all complexes studied, and the substitution of the metal center reproduced qualitative binding strength trends of 5d>3d>4d consistent with those previously reported for the group 6 metals. X-ray diffraction patterns and Mössbauer spectra were taken to determine the thermal decomposition pathway for [FeH(?2-H 2)dppe2][NTf2]. Simulations at the B3LYP/TZVP level of theory and experimental Mössbauer spectra confirmed the direct thermal decomposition from singlet-state [FeH(?2-H 2)dppe2][NTf2] to triplet-state [FeHdppe 2][NTf2] under vacuum conditions at 398K. Evaluation of the partial quadrupole splitting values of Q(H2) = -0.245 mm/s from Mössbauer spectroscopy significantly differ from typical values obtained for hydrides, indicating an underutilized mechanism for identification of dihydrogen ligands. Singlet-state thermodynamic values from simulation were consistent with experimental observations for Ru and Os, and ruthenium complexes were found to have thermodynamic properties within appropriate ranges for hydrogen storage applications. Simulated thermodynamic values for Fe complexes were found to significantly underestimate experimental behavior, demonstrating the importance of the magnetic spin state of the molecule to hydrogen binding properties.

  17. Dosimetric properties of magnetically collimated electron beams for radiation therapy

    Microsoft Academic Search

    Lijun Ma

    2004-01-01

    A method of generating magnetically collimated electron beams is developed and the dosimetric properties of magnetically collimated electrons are investigated. An in-air magnetic collimator device was designed and constructed for the study. The magnetic collimator was placed above the exit port of a 14x14 cm² electron cone. Axial magnetic field of approximately 0.6 Tesla is generated inside the collimator via

  18. Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles

    SciTech Connect

    Mao, Yuanbing; Parsons, Jason; McCloy, John S.

    2013-03-31

    Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by x-ray diffraction and transmission electron microscopy. Magnetic properties were evaluated using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field. The magnetization curve shows a paramagnetic-ferromagnetic transition at TC ~275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO had a single magnetic transition indicative of Co2+-O2--Mn4+ ordering, whereas the LNMO showed more complex magnetic behavior suggesting a re-entrant spin glass.

  19. Effect of an Oscillating Magnetic Field on the Release Properties of Magnetic Collagen Gels

    E-print Network

    Spinu, Leonard

    Effect of an Oscillating Magnetic Field on the Release Properties of Magnetic Collagen Gels Vania M properties of collagen gels containing magnetic nanoparticles and microparticles and fluorescent drug analogues. Collagen gels were prepared through fibrillogenesis of collagen in the presence of iron oxide

  20. Magnetic twist: a source and property of space weather

    E-print Network

    Warnecke, Jörn; Mitra, Dhrubaditya

    2012-01-01

    We present evidence for finite magnetic helicity density in the heliosphere and numerical models thereof, and relate it to the magnetic field properties of the dynamo in the solar convection zone. We use simulations and solar wind data to compute magnetic helicity either directly from the simulations, or indirectly using time series of the skew-symmetric components of the magnetic correlation tensor. We find that the solar dynamo produces negative magnetic helicity at small scales and positive at large scales. However, in the heliosphere these properties are reversed and the magnetic helicity is now positive at small scales and negative at large scales. This is explained in terms of the magnetic helicity equation where magnetic helicity production is balanced against the divergence of magnetic helicity fluxes.

  1. Magnetic and magnetoelastic properties of amorphous ribbons

    SciTech Connect

    Chiriac, H.; Ciobotaru, I.; Mohorianu, S. [Inst. of Technical Physics, Iasi (Romania)] [Inst. of Technical Physics, Iasi (Romania)

    1994-03-01

    A phenomenological model for the magnetic and magnetoelastic behavior of the field-annealed magnetostrictive ribbon is proposed. The basic hypothesis is that the magnetic domain coupling energy due to the inhomogeneity inherent to amorphous state is dependent on the reduced magnetization. The model takes into account the anisotropy energy, Zeeman energy, magnetoelastic energy and magnetic domain coupling energy. The magnetization, engineering magnetostriction and Young`s modulus are derived as continuous functions of the applied magnetic field and stress.

  2. Synthesis, crystal structures, magnetic properties and catecholase activity of double phenoxido-bridged penta-coordinated dinuclear nickel(II) complexes derived from reduced Schiff-base ligands: mechanistic inference of catecholase activity.

    PubMed

    Biswas, Apurba; Das, Lakshmi Kanta; Drew, Michael G B; Aromí, Guillem; Gamez, Patrick; Ghosh, Ashutosh

    2012-08-01

    Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni(2)(L(1))(2)(NCS)(2)] (1), [Ni(2)(L(2))(2)(NCS)(2)] (2), and [Ni(2)(L(3))(2)(NCS)(2)] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL(1)), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL(2)), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL(3)), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter ? = 0.47) and 3 (? = 0.29), while it is almost perfect for 2 (? = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm(3) K mol(-1), in the convention H = -2JS(1)S(2)). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes. PMID:22759340

  3. Pseudostreamers: Formation, Magnetic Topology and Plasma Properties

    NASA Astrophysics Data System (ADS)

    Panasenco, O.; Velli, M. M. C.

    2014-12-01

    A traditional view of the origins of the solar wind states that slow wind streams arise from coronal hole boundaries due to the larger expansion factor. It is hard in this explanation to understand why the slow wind occupies so much space in the heliosphere. Pseudostreamers are multipolar features which develop into fields that are unipolar at greater heights. There is debate as to the speed and nature of the wind from pseudostreamers: it could be fast, slow, or in between. And, in general, they might form a network of slow wind which may or may not connect in the heliosphere to slow wind coming from around the heliospheric current sheet. Here we discuss the relationship between the expansion factor along PFSS extrapolated magnetic field lines of pseudostreamers and wind speed and plasma properties calculated with numeral modeling. We demonstrate how the resulting wind type depends on the stage of pseudostreamer development in the context of the global coronal environment: factors in determining wind speed include the height of the pseudostreamer null point, the presence or absence of filament channels, and the expansion of coronal magnetic field lines in the neighborhood of the pseudostreamer spine. This study helps to better understand the sources of slow and fast solar wind for the Solar Probe Plus mission.

  4. Severe to Extreme Solar Storms: Magnetic Field Complexity and Warnings

    NASA Astrophysics Data System (ADS)

    Lundstedt, H.

    2014-12-01

    The most pressing space weather warnings are those of the most intense solar flares and coronal mass ejections. By now we have studied the extreme solar storms in May 1921, October-November 2003 and July 2012. A solid torus model was developed to explain the extreme solar storms of May 1921. The most recent extreme solar storm in July 2012 makes it possible to use magnetic field data of Solar Dynamics Observatory (SDO) and derived magnetic field complexity parameters of the SHARP system. Preliminary daily probabilistic warnings of severe solar flares, based on SDO magnetic field complexity and SHARP parameters will be presented. The general goal is to try to integrate the topological with the probabilistic approach into a daily warning system of severe to extreme solar storms.

  5. Magnetic memory in an isotopically enriched and magnetically isolated mononuclear dysprosium complex.

    PubMed

    Pointillart, Fabrice; Bernot, Kevin; Golhen, Stéphane; Le Guennic, Boris; Guizouarn, Thierry; Ouahab, Lahcène; Cador, Olivier

    2015-01-26

    The influence of nuclear spin on the magnetic hysteresis of a single-molecule is evidenced. Isotopically enriched Dy(III) complexes are synthesized and an isotopic dependence of their magnetic relaxation is observed. This approach is coupled with tuning of the molecular environment through dilution in an amorphous or an isomorphous diamagnetic matrix. The combination of these approaches leads to a dramatic enhancement of the magnetic memory of the molecule. This general recipe can be efficient for rational optimization of single-molecule magnets (SMMs), and provides an important step for their integration into molecule-based devices. PMID:25486900

  6. Magnetic properties modeling of soft magnetic composite materials using two-dimensional vector hybrid hysteresis model

    NASA Astrophysics Data System (ADS)

    Li, Dandan; Liu, Fugui; Li, Yongjian; Zhao, Zhigang; Zhang, Changgeng; Yang, Qingxin

    2014-05-01

    A 2-D vector hybrid hysteresis model for a soft magnetic composite (SMC) material is established, which is combined with classical Preisach model and Stoner-Wohlfarth (S-W) model. The rotational magnetic properties of SMC materials were studied using the vector model, and the computed results were compared with the experimental measurement. It is shown that the vector hybrid model can effectively simulate the rotational magnetic properties under low magnetization fields.

  7. A new Cu–cysteamine complex: structure and optical properties

    SciTech Connect

    Ma, Lun; Chen, Wei; Schatte, Gabriele; Wang, Wei; Joly, Alan G.; Huang, Yining; Sammynaiken, Ramaswami; Hossu, Marius

    2014-06-07

    Here we report the structure and optical properties of a new Cu–cysteamine complex (Cu–Cy) with a formula of Cu3Cl(SR)2 (R ¼ CH2CH2NH2). This Cu–Cy has a different structure from a previous Cu–Cy complex, in which both thio and amine groups from cysteamine bond with copper ions. Single-crystal X-ray diffraction and solid-state nuclear magnetic resonance results show that the oxidation state of copper in Cu3Cl(SR)2 is +1 rather than +2. Further, Cu3Cl(SR)2 has been observed to show intense photoluminescence and X-ray excited luminescence. More interesting is that Cu3Cl(SR)2 particles can produce singlet oxygen under irradiation by light or X-ray. This indicates that Cu3Cl(SR)2 is a new photosensitizer that can be used for deep cancer treatment as X-ray can penetrate soft tissues. All these findings mean that Cu3Cl(SR)2 is a new material with potential applications for lighting, radiation detection and cancer treatment.

  8. Magnetic Properties of Lunar Geologic Terranes: New Statistical Results

    NASA Technical Reports Server (NTRS)

    Halekas, J. S.; Mitchell, D. L.; Lin, R. P.; Frey, S.; Hood, L. L.; Acuna, M. H.; Binder, A.

    2002-01-01

    We use global magnetic field data and digitized geologic maps to determine the magnetic properties of lunar terranes. Average fields vary by a factor of 100 from demagnetized impact basins and craters to strongly magnetized antipodal regions. Additional information is contained in the original extended abstract.

  9. Properties of microturbulence in toroidal plasmas with reversed magnetic shear

    E-print Network

    Lin, Zhihong

    Properties of microturbulence in toroidal plasmas with reversed magnetic shear Wenjun Deng wave turbulence in tokamak plasmas with reversed magnetic shear is studied using global gyrokinetic for the formation of internal transport barriers in the reversed magnetic shear when qmin crossing an integer

  10. On the magnetic properties of some industrial metal aerosols

    Microsoft Academic Search

    M. Moilanen; K. Kalliomäki; R. Kivelä; P.-L. Kalliomäki

    1983-01-01

    The magnetic properties of some dusts and fumes collected from different work environments are studied. The specific magnetic remanent and saturation moments, pulse coercive forces and iron contents of the dusts are given and regression equations for the relation between the results are calculated. Some examples of the remanent magnetization curves of the dust are illustrated. A change in the

  11. Microstructure and magnetic properties of cobalt ferrite thin films

    Microsoft Academic Search

    G. Hu; V. G. Harris; Y. Suzuki

    2001-01-01

    In contrast to films grown on spinel structure substrates, epitaxial cobalt ferrite films grown on MgO substrates provide a model system to study the effects of microstructural defects on the magnetic properties. The anomalous magnetic behaviors observed in as-grown films are explained by the structural and magnetic disorder across the antiphase boundaries. During post deposition annealing, magnesium interdiffusion between the

  12. Syntheses, structures, and magnetic properties of diphenoxo-bridged M(II)Ln(III) complexes derived from N,N'-ethylenebis(3-ethoxysalicylaldiimine) (M = Cu or Ni; Ln = Ce-Yb): observation of surprisingly strong exchange interactions.

    PubMed

    Koner, Rajesh; Lin, Hsin-Huang; Wei, Ho-Hsiang; Mohanta, Sasankasekhar

    2005-05-16

    A series of heterodinuclear Cu(II)Ln(III) and Ni(II)Ln(III) complexes, [M(II)L(1)Ln(III)(NO(3))(3)] (M = Cu or Ni; Ln = Ce-Yb), with the hexadentate Schiff base compartmental ligand N,N'-ethylenebis(3-ethoxysalicylaldiimine) (H(2)L(1)) have been synthesized and characterized. The X-ray crystal structure determinations of 13 of these compounds reveal that they are all isostructural. All of these complexes crystallize with the same orthorhombic P2(1)2(1)2(1) space group with closely similar unit cell parameters. Typically, the structure consists of a diphenoxo-bridged 3d-4f dinuclear core, self-assembled to two dimensions due to the intermolecular nitrate...copper(II) or nitrate...nickel(II) semicoordination and weak C-H...O hydrogen bonds. Despite that, the metal centers of the neighboring units are well separated (the ranges of the shortest intermolecular contacts (A) are (M...M) 7.46-7.60, (Ln...Ln) 8.56-8.69, and (M...Ln) 6.12-6.20). Variable-temperature (5-300 K) magnetic susceptibility measurements of all the complexes have been made. The nature of exchange interactions in the Cu(II)Ln(III) systems has been inferred from the Deltachi(M)T versus T plots, where Deltachi(M)T is the difference between the values of chi(M)T for a Cu(II)Ln(III) system and its corresponding Ni(II)Ln(III) analogue. Ferromagnetic interactions seem to be exhibited by the Cu(II)Gd(III), Cu(II)Tb(III), Cu(II)Dy(III), Cu(II)Ho(III), Cu(II)Tm(III), and Cu(II)Yb(III) complexes, while, for the Cu(II)Er(III) complex, no definite conclusion could be reached. On the other hand, among the lower members of the series, the complexes of Ce(III), Nd(III), and Sm(III) exhibit antiferromagnetic interactions, while the Cu(II)Pr(III) and Cu(II)Eu(III) analogues behave as spin-uncorrelated systems. The observations made here vindicate the proposition of Kahn (Inorg. Chem. 1997, 36, 930). The Deltachi(M)T versus T plots also suggest that, for most of the Cu(II)Ln(III) complexes, the exchange interactions are fairly strong, which probably could be related to the small dihedral angle (ca. 4 degrees) between the CuO(2) and LnO(2) planes. PMID:15877435

  13. Matching Martian Magnetic Anomalies and Snc Magnetic Properties

    Microsoft Academic Search

    P. Rochette; V. Sautter; F. Brunet; V. Chevrier; J. P. Lorand

    2002-01-01

    Understanding the origin of Martian magnetic anomalies is a major challenge for Martian studies, both in terms of planetary geodynamics and of magnetic petrology. Present models require a crustal magnetization of 15-30 A\\/m with a thickness of 20-50 km [e.g. 1]. SNC meteorites are the only material available to make a magnetominer- alogical model for this crustal magnetization. Here will

  14. Mimicking the magnetic properties of rare earth elements using superatoms

    PubMed Central

    Cheng, Shi-Bo; Berkdemir, Cuneyt; Castleman, A. W.

    2015-01-01

    Rare earth elements (REs) consist of a very important group in the periodic table that is vital to many modern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel “magic boron” counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters. PMID:25848014

  15. Electrodeposition and magnetic properties of polypyrrole–Fe nanocomposites

    Microsoft Academic Search

    Mircea Chipara; Ralph Skomski; David J. Sellmyer

    2007-01-01

    The synthesis, structure, and magnetic properties of a new composite material obtained by the codeposition of polypyrrole and iron, in the galvanostatic mode, using square wave potentials are reported. The effect of electrodeposition conditions (voltage and concentration of the electrolytes) on the magnetic properties of the nanocomposite is analyzed.

  16. Magnetic properties of frictional volcanic materials

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie E.; Lavallée, Yan; Biggin, Andrew; Ferk, Annika; Leonhardt, Roman

    2015-04-01

    During dome-building volcanic eruptions, highly viscous magma extends through the upper conduit in a solid-like state. The outer margins of the magma column accommodate the majority of the strain, while the bulk of the magma is able to extrude, largely undeformed, to produce magma spines. Spine extrusion is often characterised by the emission of repetitive seismicity, produced in the upper <1 km by magma failure and slip at the conduit margins. The rheology of the magma controls the depth at which fracture can occur, while the frictional properties of the magma are important in controlling subsequent marginal slip processes. Upon extrusion, spines are coated by a carapace of volcanic fault rocks which provide insights into the deeper conduit processes. Frictional samples from magma spines at Mount St. Helens (USA), Soufriere Hills (Montserrat) and Mount Unzen (Japan) have been examined using structural, thermal and magnetic analyses to reveal a history of comminution, frictional heating, melting and cooling to form volcanic pseudotachylyte. Pseudotachylyte has rarely been noted in volcanic materials, and the recent observation of its syn-eruptive formation in dome-building volcanoes was unprecedented. The uniquely high thermal conditions of volcanic environments means that frictional melt remains at elevated temperatures for longer than usual, causing slow crystallisation, preventing the development of some signature "quench" characteristics. As such, rock-magnetic tests have proven to be some of the most useful tools in distinguishing pseudotachylytes from their andesite/ dacite hosts. In volcanic pseudotachylyte the mass normalised natural remanent magnetisation (NRM) when further normalised with the concentration dependent saturation remanence (Mrs) was found to be higher than the host rock. Remanence carriers are defined as low coercive materials across all samples, and while the remanence of the host rock displays similarities to an anhysteretic remanent magnetisation (ARM), as expected for a thermal origin, the remanence of volcanic pseudotachylyte has been found to be comparable to an isothermal remanent magnetisation (IRM). Thus, the pseudotachylyte has experienced a strong magnetic field that overwrote the previous thermoremanent magnetisation of the magma, such as the strong local electric current that occurs in faults (e.g. Ferré et al., 2005). Additionally, the pseudotachylyte seems more often to comprise of uniaxial non-interacting single-domain particles compared to pseudo-single in the host, and to have a single Curie temperature whereas the host more commonly exhibits multiple phases. Differences in rock-magnetic parameters between the pseudotachylyte and host are significant, but not as high as those observed in granites by Nakamura et al. (2002) or Ferré et al. (2005), probably because granitic host rocks do not already carry a strong and stable remanence as do these extrusive volcanic rocks. The application of rock-magnetic tests in volcanology will undoubtedly continue to be a "go-to" tool for identification of pseudotachylytes, which are increasingly being recognised to play an important role in dome-building eruptions. Refs: Ferré, E.C., Zechmeister, M.S., Geissman, J.W., MathanaSekaran, N. and Kocak, K., 2005. The origin of high magnetic remanence in fault pseudotachylites: Theoretical considerations and implication for coseismic electrical currents. Tectonophysics, 402(1-4): 125-139. Nakamura, N., Hirose, T. and Borradaile, G.J., 2002. Laboratory verification of submicron magnetite production in pseudotachylytes: relevance for paleointensity studies. . Earth and Planetary Science Letters, 201(1): 13-18.

  17. Electrostatic Properties of Protein-Protein Complexes

    Microsoft Academic Search

    Petras J. Kundrotas; Emil Alexov

    2006-01-01

    Statistical electrostatic analysis of 37 protein-protein complexes extracted from the previously developed database of protein complexes (ProtCom, http:\\/\\/www.ces.clemson.edu\\/compbio\\/protcom) is presented. It is shown that small interfaces have a higher content of charged and polar groups compared to large interfaces. In a vast majority of the cases the average pKa shifts for acidic residues induced by the complex formation are negative,

  18. Synthesis, Characterization, In Vitro Cytotoxicity, and Apoptosis-Inducing Properties of Ruthenium(II) Complexes

    PubMed Central

    Xu, Li; Zhong, Nan-Jing; Xie, Yang-Yin; Huang, Hong-Liang; Jiang, Guang-Bin; Liu, Yun-Jun

    2014-01-01

    Two new Ru(II) complexes, [Ru(bpy)2(FAMP)](ClO4)2 1 and 2, are synthesized and characterized by elemental analysis, electrospray mass spectrometry, and 1H nuclear magnetic resonance. The in vitro cytotoxicities and apoptosis-inducing properties of these complexes are extensively studied. Complexes 1 and 2 exhibit potent antiproliferative activities against a panel of human cancer cell lines. The cell cycle analysis shows that complexes 1 and 2 exhibit effective cell growth inhibition by triggering G0/G1 phase arrest and inducing apoptosis by mitochondrial dysfunction. The in vitro DNA binding properties of the two complexes are investigated by different spectrophotometric methods and viscosity measurements. PMID:24804832

  19. Soft magnetic properties of metallic glasses-recent developments

    Microsoft Academic Search

    R. Hasegawa; R. C. O'Handley

    1979-01-01

    Two major aspects of the soft magnetic properties of metallic glasses, i.e., high magnetic permeability and high saturation induction, are discussed. Recent development in the area of high permeability materials is centered around the zero-magnetostriction Co-rich metallic glasses having Si and B as metalloids. The heat treated materials studied thus far show low-field magnetic properties comparable or superior to those

  20. Magnetic properties of the Tertiary red clay from Gansu

    Microsoft Academic Search

    Xiuming Liu; Zhisheng An; Tim Rolph; Xiaoke Qiang; Paul Hesse; Huayu Lu; Jie Zhou; Yanjun Cai

    2001-01-01

    The study on magnetic properties of the red clay indicates that the red clay and loesspaleosol sequence have a common magnetic\\u000a mineralogy, with magnetite, maghemite, hematite (and possibly goethite) contributing to the magnetic behavior. The red clay\\u000a magnetic susceptibility is also found to have a positive relation with extrafine superparamagnetic grains. This suggests that,\\u000a like the Quaternary loess-paleosols, an ultrafine

  1. Structural and Magnetic Properties of Co-Mn-Sb Thin films

    SciTech Connect

    Meinert, M.; Schmalhorst, J.-M.; Ebke, D.; Liu, N. N.; Thomas, A.; Reiss, G.; Kanak, J.; Stobiecki, T.; Arenholz, E.

    2009-12-17

    Thin Co-Mn-Sb films of different compositions were investigated and utilized as electrodes in alumina based magnetic tunnel junctions with CoFe counterelectrode. The preparation conditions were optimized with respect to magnetic and structural properties. The Co-Mn-Sb/Al-O interface was analyzed by x-ray absorption spectroscopy and magnetic circular dichroism with particular focus on the element-specific magnetic moments. Co-Mn-Sb crystallizes in different complex cubic structures depending on its composition. The magnetic moments of Co and Mn are ferromagnetically coupled in all cases. A tunnel magnetoresistance ratio of up to 24% at 13 K was found and indicates that Co-Mn-Sb is not a ferromagnetic half-metal. These results are compared to recent works on the structure and predictions of the electronic properties.

  2. The synthesis, structure, magnetic and luminescent properties of a new tetranuclear dysprosium (III) cluster

    NASA Astrophysics Data System (ADS)

    Chen, Yen-Han; Tsai, Yun-Fan; Lee, Gene-Hsian; Yang, En-Che

    2012-01-01

    The synthesis and characterization of [Dy4(dhampH3)4(NO3)2](NO3)2 (1), a new tetranuclear dysprosium (III) complex, is described. The compound was characterized by its X-ray structure, magnetic properties as well as the luminescent spectra. The compound crystallizes in a P1¯ space group with a zig-zag linear form of geometry. The ac magnetic susceptibilities of the molecule indicate that it is a magnetic molecule with a slow magnetization relaxation. The molecule also exhibits an emission spectrum that was confirmed to be ligand based. These results indicate that this molecule has both a slow magnetization relaxation (that could be potentially a SMM) and luminescent properties.

  3. Influence of complexing agent on the electrodeposited Co Pt W magnetic thin films

    NASA Astrophysics Data System (ADS)

    Wei, Guoying; Ge, Hongliang; Huang, Lihong; Wu, Qiong; Wang, Xinqing; Huang, Liming

    2008-03-01

    Complexing agents are often used to improve the quality of electrodeposited alloys. Influence of different complexing agents with hydroxycarboxylic acid group on the electrodeposited Co-Pt-W thin films has been investigated. Cathodic polarization curves show that the polarization behaviors of electroplating bath with different complexing agents are very different. Surface morphology, phase composition and magnetic properties are observed by means of FESEM, XRD and vibrating sample magnetometer (VSM), respectively. It has been found out that, if citrate was used as complexing agent, the Co-Pt-W thin films were homogeneous and the granular crystals with the average grain size of 2 ?m have been observed. Co-Pt-W thin films exhibited hexagonal close packed (hcp) lattice and strong perpendicular anisotropic magnetic behavior ( Hc? = 215.5 kA/m; Hc? = 55.4 kA/m). In the presence of gluconate, needle-like deposits were obtained and a strong face centered cubic (fcc(1 1 1)) texture was measured. The Co-Pt-W thin films showed isotropic magnetic behavior. In the case of tartate and malate, the coexistence of needle-like deposits and cellular deposits appeared. The XRD patterns showed that the mixed fcc and hcp phase formed. Perpendicular anisotropic magnetic behaviors of thin films, from malate or tartate baths, were not obvious.

  4. Magnetic Properties Experiments on the Mars Exploration Rover mission

    NASA Astrophysics Data System (ADS)

    Madsen, M. B.; Bertelsen, P.; Goetz, W.; Binau, C. S.; Olsen, M.; Folkmann, F.; Gunnlaugsson, H. P.; Kinch, K. M.; Knudsen, J. M.; Merrison, J.; Nørnberg, P.; Squyres, S. W.; Yen, A. S.; Rademacher, J. D.; Gorevan, S.; Myrick, T.; Bartlett, P.

    2003-12-01

    The Mars Exploration Rovers each carry a set of Magnetic Properties Experiments designed with the following objectives in mind: (1) to identify the magnetic mineral(s) in the dust, soil and rocks on Mars, (2) to establish if the magnetic material is present in the form of nanosized (d < 10 nm) superparamagnetic crystallites embedded in the micrometer sized airborne dust particles, and (3) to establish if the magnets are culling a subset of strongly magnetic particles or if essentially all particles of the airborne dust are sufficiently magnetic to be attracted by the magnets. To accomplish these goals, the Mars Exploration Rovers each carry a set of permanent magnets of several different strengths and sizes. Each magnet has its own specific objective. The dust collected from the atmosphere by the Capture magnet and the Filter magnet (placed on the front of each rover) will be studied by the Mössbauer spectrometer and the Alpha Particle X-ray Spectrometer, both of which are instruments located on the rover's Instrument Deployment Device. The captured dust particles will also be imaged by the Pancam and Microscopic Imager. The Sweep magnet will be imaged by Pancam and is placed near the Pancam calibration target. The four magnets in the Rock Abrasion Tool (RAT) are designed to capture magnetic particles originating from the grinding of Martian surface rocks. The magnetic particles captured by the RAT magnets will be imaged by Pancam.

  5. 2.20 Properties of Rocks and Minerals -Magnetic Properties of Rocks and Minerals

    E-print Network

    Dunin-Borkowski, Rafal E.

    2.20 Properties of Rocks and Minerals - Magnetic Properties of Rocks and Minerals R. J. Harrison, R 621 622 623 623 579 #12;580 Magnetic Properties of Rocks and Minerals 2.20.5.3 2.20.5.4 2, and are present in all types of rocks, sediments, and soils. These minerals retain a memory of the geomagnetic

  6. Low-dimensional compounds containing cyano groups. XIV. Crystal structure, spectroscopic, thermal and magnetic properties of [CuL {sub 2}][Pt(China){sub 4}] complexes (L=ethylenediamine or N,N-dimethylethylenediamine)

    SciTech Connect

    Potocnak, Ivan [Department of Inorganic Chemistry, Institute of Chemistry, P.J. Safarik University, Moyzesova 11, SK-04154 Kosice (Slovakia)]. E-mail: ivan.potocnak@upjs.sk; Vavra, Martin [Department of Inorganic Chemistry, Institute of Chemistry, P.J. Safarik University, Moyzesova 11, SK-04154 Kosice (Slovakia); Cizmar, Erik [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Tibenska, Katarina [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Orendacova, Alzbeta [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Steinborn, Dirk [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Wagner, Christoph [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Dusek, Michal [Institute of Physics, Na Slovance 2, CZ-182 21 Praha 8 (Czech Republic); Fejfarova, Karla [Institute of Physics, Na Slovance 2, CZ-182 21 Praha 8 (Czech Republic); Schmidt, Harry [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Muller, Thomas [Institute of Inorganic Chemistry, Martin-Luther-University, Halle-Wittenberg, Kurt-Mothes-Street 2, D-06120 Halle (Germany); Orendac, Martin [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia); Feher, Alexander [Centre of Low Temperature Physics of the Faculty of Science of P.J. Safarik University and IEP SAS, Park Angelinum 9, SK-04154 Kosice (Slovakia)

    2006-07-15

    Violet crystals of [Cu(en){sub 2}][Pt(China){sub 4}] and blue crystals of [Cu(dmen){sub 2}][Pt(China){sub 4}] were crystallized from the water-methanol solution containing CuCl{sub 2}.2H{sub 2}O, ethylenediamine (en) or N,N-dimethylethylenediamine (dmen) and K{sub 2}[Pt(China){sub 4}].3H{sub 2}O. Both compounds were characterized using elemental analysis, infrared and UV-VIS spectroscopy, magnetic measurements, specific heat measurements and thermal analysis. X-ray structure analysis revealed chain-like structure in both compounds. The covalent chains are built of Cu(II) ions linked by [Pt(China){sub 4}]{sup 2-} anions in the [111] and [101] direction, respectively. The Cu(II) atoms are hexacoordinated by four nitrogen atoms in the equatorial plane from two molecules of bidentate ligands L with average Cu-N distance of 2.022(2) and 2.049(4) A, respectively. Axial positions are occupied by two nitrogen atoms from bridging [Pt(China){sub 4}]{sup 2-} anions at longer Cu-N distance of 2.537(2) and 2.600(5) A, respectively. Both materials are characterized by the presence of weak antiferromagnetic exchange coupling. Despite the one-dimensional (1D) character of the structure, the analysis of magnetic properties and specific heat at very low temperatures shows that [Cu(en){sub 2}][Pt(China){sub 4}] behaves as two-dimensional (2D) spatially anisotropic square lattice Heisenberg magnet, while more pronounced influence of interlayer coupling is observed in [Cu(dmen){sub 2}][Pt(China){sub 4}]. - Graphical abstract: Chain-like structure in [Cu(en){sub 2}][Pt(China){sub 4}] (R=H) and [Cu(dmen){sub 2}][Pt(China){sub 4}] (R=CH{sub 3}) compounds.

  7. Redox-active porous coordination polymers prepared by trinuclear heterometallic pivalate linking with the redox-active nickel(II) complex: synthesis, structure, magnetic and redox properties, and electrocatalytic activity in organic compound dehalogenation in heterogeneous medium.

    PubMed

    Lytvynenko, A S; Kolotilov, S V; Kiskin, M A; Cador, O; Golhen, S; Aleksandrov, G G; Mishura, A M; Titov, V E; Ouahab, L; Eremenko, I L; Novotortsev, V M

    2014-05-19

    Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv(-) = pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (SBET = 50 m(2) g(-1), VDR = 0.017 cm(3) g(-1) estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm(3) g(-1)) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of ?MT of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin-orbit coupling of Co(II), and in the second model the spin-orbit coupling of Co(II) was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product. PMID:24779588

  8. Magnetic properties of the Bay of Islands ophiolite suite and implications for the magnetization of oceanic crust

    USGS Publications Warehouse

    Swift, B. Ann; Johnson, H. Paul

    1984-01-01

    Rock magnetic properties, opaque mineralogy, and degree of metamorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex, Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetization of the underlying sheeted dike complex appears to have been destroyed by hydrothermal alteration soon after formation. The magnetic intensity of the gabbroic samples increases as the degree of alteration increases, with the highly altered upper metagabbros having an average intensity of 3×10?3 emu/c3. Because magnetization of the metagabbro samples is related to nonpervasive, variable alteration, these crustal units are unlikely to make a significant contribution to lineated magnetic anomalies. A compilation of our results and other studies suggests a model in which oceanic crust magnetization results from an upper extrusive basalt source layer, roughly 600 m thick, with no contribution from a deeper source layer recognizable from these Bay of Islands data.

  9. Cis-trans isomerism in diphenoxido bridged dicopper complexes: role of crystallized water to stabilize the cis isomer, variation in magnetic properties and conversion of both into a trinuclear species.

    PubMed

    Biswas, Apurba; Drew, Michael G B; Diaz, Carmen; Bauzá, Antonio; Frontera, Antonio; Ghosh, Ashutosh

    2012-10-21

    The trans-[Cu(2)L(2)Cl(2)] (1), and cis-[Cu(2)L(2)Cl(2)]·H(2)O (2) isomers of a diphenoxido bridged Cu(2)O(2) core have been synthesized using a tridentate reduced Schiff base ligand 2-[(2-dimethylamino-ethylamino)-methyl]-phenol. The geometry around Cu(II) is intermediate between square pyramid and trigonal bipyramid (Addison parameter, ? = 0.463) in 1 but nearly square pyramidal (? = 0.049) in 2. The chloride ions are coordinated to Cu(II) and are trans oriented in 1 but cis oriented in 2. Both isomers have been optimized using density functional theory (DFT) calculations and it is found that the trans isomer is 7.2 kcal mol(-1) more favorable than the cis isomer. However, the hydrogen bonding interaction of crystallized water molecule with chloride ions compensates for the energy difference and stabilizes the cis isomer. Both complexes have been converted to a very rare phenoxido-azido bridged trinuclear species, [Cu(3)L(2)(?(1,1)-N(3))(2)(H(2)O)(2)(ClO(4))(2)] (3) which has also been characterized structurally. All the complexes are antiferromagnetically coupled but the magnitude of the coupling constants are significantly different (J = -156.60, -652.31, and -31.54 cm(-1) for 1, 2, 3 and respectively). Density functional theory (DFT) calculations have also been performed to gain further insight into the qualitative theoretical interpretation on the overall magnetic behavior of the complexes. PMID:22930034

  10. Approach to saturation and magnetic properties of melt-spun Fe?Cu granular systems

    NASA Astrophysics Data System (ADS)

    Hernando, A.; El Ghannami, M.; Gómez-Polo, C.; García Escorial, A.

    1997-09-01

    The aim of the work is to analyze the correlation between structure, shape and volume distribution of magnetic aggregates and magnetic properties in Fe xCu 100- x ( x = 30, 50, 70) melt-spun ribbons. The structural analysis, performed by X-ray diffraction and scanning electron microscopy, shows that the sample is mainly composed of a mixture of Cu rich, non-magnetic, and BCC-Fe ferromagnetic aggregates widely distributed in size. Evidence of a partial mutual solubility between both immiscible elements is found in the as-cast state, so the main effect of the thermal treatment is to produce an almost complete segregation of both pure BCC-Fe and FCC-Cu immiscible phases, and thus, an increase in the corresponding mean grain sizes. The magnetization process of the samples reflects the complex magnetic behavior associated with a wide distribution in size of magnetic aggregates. The law of approach to saturation has been found to be an excellent complementary technique to correlate nanostructure and magnetic properties. The observed magnetic behavior can be interpreted as the contribution of superparamagnetic particles, single domain and multidomain aggregates, the multidomain being the first-order contribution. The results show that the shape of the magnetic aggregates governs through the internal demagnetizing field the macroscopic magnetization curve. This shape can be controlled through the Fe content, since as the Fe content increases the ferromagnetic aggregates evolve from spherical to ribbon-shaped.

  11. Magnetic properties of Cr Fe Mn alloys

    Microsoft Academic Search

    B. Li; H. L. Alberts; A. M. Strydom; B. M. Wu; A. R. E. Prinsloo; Zh. J. Chen

    2009-01-01

    The magnetic behaviour of a Cr80-xFe20Mnx alloy system with x=2, 7, 10, 13 and 22 has been investigated in the temperature range 2 400 K through measurements of magnetization, electrical resistivity, magnetoresistivity, specific heat and thermal expansion. The temperature vs. Mn concentration magnetic phase diagram of the system is rich in magnetic behaviour with ferromagnetic (FM), antiferromagnetic (AFM) and paramagnetic

  12. Magnetic properties of intermediate-mass stars

    E-print Network

    G. A. Wade

    2006-01-30

    Magnetic fields play an important role in producing and modifying the photospheric chemical peculiarities of intermediate-mass main sequence stars. This article discusses the basic theory and methods of measurement used to detect and characterise stellar magnetic fields, and reviews our current knowledge of selected characteristics of magnetic fields in intermediate-mass stars.

  13. Magnetic and Superconducting Properties of Vanadium Nanoconstrictions

    NASA Astrophysics Data System (ADS)

    Takata, Hiroki; Inagaki, Yuji; Kawae, Tatsuya; Ienaga, Koichiro; Tsujii, Hiroyuki

    2015-03-01

    We study the magnetic and superconducting properties in a paramagnetic vanadium (V) nanoconstriction with changing its size using a mechanically controllable break junction technique. In the normal state the magnetoresistance effect is observed below the diameter d ~ 8 nm. Moreover, a Fano resonance appears around zero-bias voltage in the differential conductance for the atomic-size contacts and changes shape as the size of the constriction changes. On the other hand, below the superconducting critical temperature the superconducting gap features in V contacts are largely different from those in Pb contacts which exhibit typical features expected in superconducting point contacts. Only a single Andreev anomaly at 2?, where ? is the superconducting energy gap, is observed in the spectra of the V contacts, while two anomalies at ? and 2? appear in the case of the Pb contacts. In the tunnel conductance regime, the structure of the superconducting quasiparticle tunneling density of states is not seen in the V spectra in contrast to the Pb spectra. The origin of these features is discussed.

  14. Evaluating climate change by multivariate statistical techniques on magnetic and chemical properties of marine sediments

    E-print Network

    Utrecht, Universiteit

    ; accepted 28 May 2004 Abstract Regression models and cluster analyses are used to link magnetic properties. Keywords: Climate change; Multivariate statistical analysis; Magnetic properties; Chemical composition 1 environmental study, based on a combination of magnetic properties and elemen

  15. Viking magnetic properties investigation - Preliminary results

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.; Collinson, D. W.; Spitzer, C. R.

    1976-01-01

    Three permanent-magnet arrays are aboard the Viking lander. By sol 35, one array, fixed on a photometric reference test chart on top of the lander, has clearly attracted magnetic particles from airborne dust; two other magnet arrays, one strong and one weak, incorporated in the backhoe of the surface sampler, have both extracted considerable magnetic mineral from the surface as a result of nine insertions associated with sample acquisition. The loose Martian surface material around the landing site is judged to contain 3 to 7 per cent highly magnetic mineral which, pending spectrophotometric study, is thought to be mainly magnetite.

  16. New complex magnetic materials for an application in Ericsson refrigerator

    NASA Astrophysics Data System (ADS)

    Othmani, S.; Blel, R.; Bejar, M.; Sajieddine, M.; Dhahri, E.; Hlil, E. K.

    2009-07-01

    In this paper, a new complex magnetic materials La 0.70Ca 0.15Sr 0.15Mn 1-xFe xO 3 ( x= 0.000, 0.025, 0.050, 0.075 and 0.100), suitable for the Ericsson cycle, has been investigated. For these materials, the effect of Fe doping can be attributed to a combination of doping disorder, Fe-Mn super exchange interactions and a site-percolation mechanism, which suppress the metallic conduction and ferromagnetism. We have found that these compounds crystallize in the rhombohedral structure with the R3¯ c space group. We have also verified that the substitution of the manganese with iron leads to an important decrease of the Curie temperature TC from 335 to 225 K for 0%-10% of Fe. The magnetocaloric study exposes a quite large value of the magnetic entropy change, which decreases when increasing Fe concentration. For an applied magnetic field of 2 T, the Relative Cooling Power (RCP) values are found to vary between 80 and 125 J/kg. As a result, the studied compounds could be considered as potential material for magnetic Ericsson refrigeration by using complex magnetocaloric compounds.

  17. Magnetic properties of mafics and ultramafics from Eastern Ghats

    NASA Astrophysics Data System (ADS)

    Bhaskara Rao, V.; Raju, A. Lakshmipati

    1981-11-01

    Magnetic properties, namely intensity of natural remanent magnetisation (NRM) and magnetic susceptibility, of mafic and ultramafic formations of Eastern Ghats belt in the Godavari Districts, Andhra Pradesh are studied. The formations sampled for the study are, iron-ore, chromite-ore, amphibolite, gabbro, charnockite and khondalite gneiss. Mineralogical differences in iron-ore and the degree of martitisation are reflected in magnetic susceptibility. NRM and susceptibility of chromite-ore are feeble. The gabbro exhibits strong magnetic properties because of its contiguity with iron formation. The Koenigsberger ratio is found to indicate relative palaeomagnetic stability.

  18. Magnetic and microstructural properties of some lodestones

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.

    1977-01-01

    A lodestone is an iron ore that behaves as a permanent magnet. A protolodestone is an iron ore capable of being charged sufficiently strongly to behave as a permanent magnet. In the present paper, important criteria are established which distinguish lodestones from other iron ores. Magnetic hysteresis-loop data provide evidence that the massive pieces of lodestone behave magnetically as fine intergrowths rather than coarse multidomain material. This means that the iron ores have been magnetically hardened. The nature and scale of the hardening microstructure is illustrated by photo micrographs. The mechanism of charging the protolodestone appears to be either transient magnetic fields with lightning-discharge currents, or presently obscure aspects of magnetization intensity enhancement associated with maghemitization of massive iron ores.

  19. Improvement of the magnetic properties of nanocomposite permanent magnetic alloys with Dy and Ga substitutions

    Microsoft Academic Search

    Mingang Zhang; Gang Sun; Dongcheng Guo; Zhihao Jin

    2002-01-01

    The Dy and Ga substituted NdFeB nanocomposite permanent magnetic alloys with high magnetic properties have been prepared by appropriate wheel speed of melt-spinning and post-annealing treatment. Under optimal conditions, compared with the best magnetic properties of ternary NdFeB alloy of Jr=1.18T, Hci=379.5kA\\/m and (BH)max=119.5kJ\\/m3, the best magnetic properties of the alloy with Dy and Ga substitutions are Jr=1.16T, Hci=580.5kA\\/m, and

  20. Novel heterometallic Schiff base complexes featuring unusual tetranuclear {Co(III)2Fe(III)2(?-O)6} and octanuclear {Co(III)4Fe(III)4(?-O)14} cores: direct synthesis, crystal structures, and magnetic properties.

    PubMed

    Chygorin, Eduard N; Nesterova, Oksana V; Rusanova, Julia A; Kokozay, Vladimir N; Bon, Volodymyr V; Bo?a, Roman; Ozarowski, Andrew

    2012-01-01

    A one-pot reactions of cobalt powder with iron(II) chloride in dimethylformamide (DMF; 1) or dimethyl sulfoxide (DMSO; 2) solutions of polydentate salicylaldimine Schiff base ligands (H(2)L(1), 1; H(4)L(2), 2) based on 2-aminobenzyl alcohol (1) or tris(hydroxymethyl)aminomethane (2), formed in situ, yielded two novel heterometallic complexes, [Co(III)(2)Fe(III)(2)(L(1))(6)]·4DMF (1) and [Co(III)(4)Fe(III)(4)(HL(2))(8)(DMSO)(2)]·18DMSO (2). Crystallographic investigations revealed that the molecular structure of 1 is based on a tetranuclear core, {Co(III)(2)Fe(III)(2)(?-O)(6)}, with a chainlike metal arrangement, while the structure of 2 represents the first example of a heterometallic octanuclear core, {Co(III)(4)Fe(III)(4)(?-O)(14)}, with a quite rare manner of metal organization, formed by two pairs of {CoFe(HL(2))(2)} and {CoFe(HL(2))(2)(DMSO)} moieties, which are joined by O bridges of the Schiff base ligands. Variable-temperature (1.8-300 K) magnetic susceptibility measurements showed a decrease of the ?(B) value at low temperature, indicative of antiferromagnetic coupling (J/hc = -32 cm(-1) in 1; J/hc = -20 cm(-1) in 2) between the Fe(III) magnetic centers in both compounds. For 2, three J constants between Fe(III) centers were assumed to be identical. High-frequency electron paramagnetic resonance spectra allowed one to find spin Hamiltonian parameters in the coupled-spin triplet and quintet states of 1 and estimate them in 2. The "outer" and "inner" Fe atoms in 2 appeared separately in the Mössbauer spectra. PMID:22129107

  1. Magnetic anisotropy determination and magnetic hyperthermia properties of small Fe nanoparticles in the superparamagnetic regime

    Microsoft Academic Search

    B. Mehdaoui; A. Meffre; L.-M. Lacroix; J. Carrey; S. Lachaize; M. Respaud; M. Gougeon; B. Chaudret

    2009-01-01

    We report on the magnetic and hyperthermia properties of iron nanoparticles\\u000asynthesized by organometallic chemistry. They are 5.5 nm in diameter and\\u000adisplay a saturation magnetization close to the bulk one. Magnetic properties\\u000aare dominated by the contribution of aggregates of nanoparticles with respect\\u000ato individual isolated nanoparticles. Alternative susceptibility measurements\\u000aare been performed on a low interacting system obtained

  2. Tuning the photophysical properties of amidophosphine complexes of copper

    E-print Network

    Mickenberg, Seth F. (Seth Fox)

    2009-01-01

    A series of monomeric copper complexes that allow for the tuning of the emission properties is reported. Luminescence lifetimes up to 150 [mu]s are observed in benzene solution at ambient temperature, which are comparable ...

  3. Viking magnetic properties investigation - Further results

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.; Collinson, D. W.; Arvidson, R. E.; Spitzer, C. R.

    1976-01-01

    The amounts of magnetic particles held on the reference test chart and backhoe magnets on lander 2 and lander 1 are comparable, indicating the presence of an estimated 3 to 7 percent by weight of relatively pure, strongly magnetic particles in the soil at the lander 2 sampling site. Preliminary spectrophotometric analysis of the material held on the backhoe magnets on lander 1 indicates that its reflectance characteristics are indistinguishable from material within a sampling trench with which it has been compared. The material on the RTC magnet shows a different spectrum, but it is suspected that the difference is the result of a reflectance contribution from the magnesium metal covering on the magnet. It is argued that the results indicate the presence, now or originally, of magnetite, which may be titaniferous.

  4. Complex Fuzzy Set-Valued Complex Fuzzy Measures and Their Properties

    PubMed Central

    Ma, Shengquan; Li, Shenggang

    2014-01-01

    Let F*(K) be the set of all fuzzy complex numbers. In this paper some classical and measure-theoretical notions are extended to the case of complex fuzzy sets. They are fuzzy complex number-valued distance on F*(K), fuzzy complex number-valued measure on F*(K), and some related notions, such as null-additivity, pseudo-null-additivity, null-subtraction, pseudo-null-subtraction, autocontionuous from above, autocontionuous from below, and autocontinuity of the defined fuzzy complex number-valued measures. Properties of fuzzy complex number-valued measures are studied in detail. PMID:25093202

  5. Correlation Between Domain Behavior and Magnetic Properties of Materials

    SciTech Connect

    Jeffrey Scott Leib

    2003-05-31

    Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, H{sub c} in cases 1, 3, and 5, and the uniaxial character of the Gd{sub 5}(Si{sub 2}Ge{sub 2}), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, M{sub s}, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected from theory and calculation, and provided such information in a matter of minutes. In fact, typical characterization in each of these studies was far more complete and reliable with domain imagery to back it up--especially the single crystal and applied field pictures. In these simple cases, it appears that domain imagery may be close to standing alone in magnetic characterization. The surprises in the 10 nm CoFeHfO film, the complexity seen in the polycrystalline Gd-Si-Ge sample and the broad range predictions of the K{sub 1} of the same reinforce the unreliability of making concrete statements based purely on domain imagery of any type, but it may be possible to create standards similar to the types used in optical microscopy for metallography in these complex cases.

  6. Synthesis and magnetic properties of Co–Zn magnetic fluid

    Microsoft Academic Search

    G. Vaidyanathan; S. Sendhilnathan

    2008-01-01

    Co1?xZnxFe2O4 (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization (Ms) and the size of the particles were measured at room temperature. The magnetization (Ms) was found to decrease with the increase

  7. EM Properties of Magnetic Minerals at RADAR Frequencies

    NASA Technical Reports Server (NTRS)

    Stillman, D. E.; Olhoeft, G. R.

    2005-01-01

    Previous missions to Mars have revealed that Mars surface is magnetic at DC frequency. Does this highly magnetic surface layer attenuate RADAR energy as it does in certain locations on Earth? It has been suggested that the active magnetic mineral on Mars is titanomaghemite and/or titanomagnetite. When titanium is incorporated into a maghemite or magnetite crystal, the Curie temperature can be significantly reduced. Mars has a wide range of daily temperature fluctuations (303K - 143K), which could allow for daily passes through the Curie temperature. Hence, the global dust layer on Mars could experience widely varying magnetic properties as a function of temperature, more specifically being ferromagnetic at night and paramagnetic during the day. Measurements of EM properties of magnetic minerals were made versus frequency and temperature (300K- 180K). Magnetic minerals and Martian analog samples were gathered from a number of different locations on Earth.

  8. Six-coordinate lanthanide complexes: slow relaxation of magnetization in the dysprosium(III) complex.

    PubMed

    Na, Bo; Zhang, Xue-Jing; Shi, Wei; Zhang, Yi-Quan; Wang, Bing-Wu; Gao, Chen; Gao, Song; Cheng, Peng

    2014-11-24

    A series of six-coordinate lanthanide complexes {(H3O)[Ln(NA)2]?H2O}n (H2NA=5-hydroxynicotinic acid; Ln=Gd(III) (1?Gd); Tb(III) (2?Tb); Dy(III) (3?Dy); Ho(III) (4?Ho)) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3?Dy. To suppress the quantum tunneling of the magnetization, 3?Dy diluted by diamagnetic Y(III) ions was also synthesized and magnetically studied. Interesting butterfly-like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3?Dy. The energy barrier (?(?)) and pre-exponential factor (?0) of the diluted 3?Dy are 75?K and 4.21×10(-5) s, respectively. This work illustrates a successful way to obtain low-coordination-number lanthanide complexes by a framework approach to show single-ion-magnet-like behavior. PMID:25297951

  9. Study of magnetic properties of copolymer of 3-dodecylthiophene and 2,3-R,R-thieno[3,4-b]pyrazine

    Microsoft Academic Search

    G ???k; F Šerše?; L Dlhá?; I ?erve?; A Staško; D Végh

    2002-01-01

    The EPR spectroscopy and the measurement of AC magnetic susceptibility (?), magnetization and of specific heat capacity were used to study magnetic properties of the copolymer (COP) of 3-dodecylthiophene (DDT) and 2,3-R,R-thieno[3,4-b]pyrazine (TTP). The copolymer exhibits antiferromagnetic properties at the Nèel temperature of ca. 38K. At maximum complex, magnetic susceptibility achieved value of 6.5×10?6m3kg?1. That behaviour was ascribed to the

  10. Dynamics of dust-ion acoustic shock waves in a magnetized charge variable superthermal complex plasma

    NASA Astrophysics Data System (ADS)

    Shahmansouri, Mehran

    2014-07-01

    A theoretical investigation is carried out to study the characteristic properties of dust-ion acoustic (DIA) shock waves in a magnetized, charge varying, complex (dusty) plasma which consists of immobile dust grains, fluid ions and superthermal electrons. The effects of collisions are not included here, but the dissipation leading to the formation of stable shock structures is provided by the dust charge fluctuations. The Korteweg-de Vries-Burgers (KdV-Burgers) equation is derived using the reductive perturbation technique. The combined effects of obliqueness, magnitude of the magnetic field, and electron superthermality on the DIA shock waves are then investigated. It is shown that the effects of obliqueness, electron non-thermality and dust charge fluctuation significantly modify the basic properties of DIA shock waves.

  11. Bimetallic anionic formyl complexes: synthesis and properties

    SciTech Connect

    Tam, W.; Marsi, M.; Gladysz, J.A.

    1983-05-11

    Three bimetallic anionic complexes, (2) lithium + dimanganese nonacarbonyl formyl/sup -/, (3) lithium + rhenium manganese nonacarbonyl formyl/sup -/, and (4) lithium + cisdirhenium nonacarbonyl formyl, are prepared by the reaction of lithium triethylboron hydride with the corresponding neutral metal carbonyl dimers, dimanganese decacarbonyl and manganese rhenium decarbonyl. 2 has a half-life of ca 8 min at room temperature, 4 is stable for days and is easily isolated as a tetrahydrofuran solvate. When 2 - 4 are treated with electrophiles such as benzaldehyde, iron pentacarbonyl, n-octyl iodide, hydride transfer occurs to produce benzyl alcohol, lithium + iron tetracarbonyl formyl/sup -/ complex, and octane, respectively. 3 is the weakest hydride donor. Reaction of 4 with methyl iodide produces ca 52% methane. The only identifiable product from the pyrolysis of 4 is dirhenium decacarbonyl; photolysis of 4 produces lithium + dirhenium nonacarbonyl hydride. 1 figure.

  12. Matching Martian Magnetic Anomalies and Snc Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Sautter, V.; Brunet, F.; Chevrier, V.; Lorand, J. P.

    Understanding the origin of Martian magnetic anomalies is a major challenge for Martian studies, both in terms of planetary geodynamics and of magnetic petrology. Present models require a crustal magnetization of 15-30 A/m with a thickness of 20-50 km [e.g. 1]. SNC meteorites are the only material available to make a magnetominer- alogical model for this crustal magnetization. Here will be presented a synthesis based on 16 independant SNCs, with all the falls and non Antarctic finds except NWA480. Titanomagnetite is the major magnetic carrier only in the four Nakhlites, Los Angeles, ALH75005 and Chassigny. Due to high titanium substitution, the Curie point based on high temperature magnetic measurements or microprobe analysis is only about 150C in the nakhlites and Los Angeles. High coercivity pyrrhotite is the major car- rier in the other eight basaltic shergottites measured. We estimate in-situ NRM for SNCs Noachian equivalent by using saturation remanent magnetization and use the proposed upper bound of 5% for NRM/IRM in case of TRM in an Earth-like field for magnetite or pyrrhotite Taking the lower bound of 15 A/m for crustal NRM and a density of 3 leads to a minimum Mrs of 10-1 Am2/kg. Only Los Angeles, NWA817 and 1068, i.e. the most magnetic Nakhlites and basaltic shergottites, are above this threshold. ALH84001, the only SNC with the right age, is two orders of magnitude below, like Chassigny, while lherzolitic ALH75005 is one order of magnitude below. This confirms the contention that magnetic sources are rather mafic than ultramafic rocks. Titanomagnetite is the preferred candi-date mineral in the litterature but the Curie point of 150C found on SNCs is at odd with a Curie depth of 20-50 km during NRM acquisition. Although fundamental drawbacks exist in the use of SNCs to put forward a magnetomineralogical model for magnetic anomalies, sulfides appear as a serious alternative to oxydes in the martian case.

  13. Magnetic properties of fine NiO Particles

    Microsoft Academic Search

    P. Mollard; P. Briane; P. Germi; F. Fievet

    1978-01-01

    The partial thermo-remanent magnetizations and the apparent susceptibility have been obtained on fine NiO particle in connection with physicochemical properties. The results are interpreted with Néels model of fine antiferromagnetic particles.

  14. Magnetic properties of highT(sub c) superconductors

    Microsoft Academic Search

    Junho Gohng; Junho

    1992-01-01

    Magnetic properties of high-T(sub c) superconductors have been studied in order to determine the free-energy surface, the characteristic critical fields, order parameters structure, and the grain size effect on magnetization. Studies of the thermodynamic reversibility for YBa2Cu3O(7-delta) show the rounding in magnetization vs. temperature curves is a reflection of the thermodynamic fluctuations near T(sub c). Specific heat jump C(0)-C(H) values

  15. Magnetic properties of highT(c) superconductors

    Microsoft Academic Search

    Junho Gohng; Junho

    1992-01-01

    Magnetic properties of high-Tc superconductors have been studied in order to determine the free energy surface, the characteristic critical fields, order parameter structure, and the grain size effect on magnetization. Studies of the thermodynamic reversibility for YBa2Cu3O(7-delta) show the rounding in magnetization vs. temperature curves is a reflection of thermodynamic fluctuations near (Tc). Specific heat jump C(O)-C(H) values that have

  16. Magnetic Properties of High Critical Transition Temperature Superconductors

    Microsoft Academic Search

    Junho Gohng

    1992-01-01

    Magnetic properties of high-T_ {rm c} superconductors have been studied in order to determine the free-energy surface, the characteristic critical fields, order parameters structure, and the grain size effect on magnetization. Studies of the thermodynamic reversibility for rm YBa _2Cu_3O_{7-delta} show the rounding in magnetization vs. temperature curves is a reflection of the thermodynamic fluctuations near T_{rm c}. Specific heat

  17. Transport and Superconducting Properties of Rare Earth Magnetic Superconductors

    Microsoft Academic Search

    Hu. Zhou

    1988-01-01

    An investigation of transport and magnetic properties of two groups of magnetic superconductors, tetragonal {cal R}Rh_4 B_4 and orthorhombic high -T_{rm c} oxides {cal R}Ba_2 Cu_3O_{7 -delta}, where {cal R} represents rare earth elements and Y, was carried out by means of electrical resistance and magnetic measurements. Single crystals of {cal R} Rh_4B_4 were successfully synthesized using a copper flux

  18. High temperature permeameter for measuring magnetic properties

    NASA Technical Reports Server (NTRS)

    Barranger, J. P.

    1972-01-01

    Instrument for measuring magnetic permeability of materials undergoing heat treatment as method for monitoring stress relief and tempering is described. Procedure is based on magnetic potentiometer principle with yoke compensating coils to cancel effects of reluctance of yoke and joint gaps. Instrument is heated with specimen being heat treated.

  19. Mechanical properties of insulators for Accelerator Magnets

    E-print Network

    McDonald, Kirk

    such as flexural strength and shear strength ­ Generally in a composite the polymer will be radiation damaged well;Outline · Accelerator Magnet Insulation · Nb3Sn Insulation · Glass fibre/epoxy composites · Irradiation ­ ~Mylar, glass fibre, epoxy resin ­ ~2mm thick · NbTi Superconducting Magnets ­ ~Kapton & epoxy ­ ~40µm

  20. Magnetic Properties and Structure of Oxyhemoglobin

    Microsoft Academic Search

    Linus Pauling

    1977-01-01

    A review of the published evidence reinforces the conclusion reached by Pauling and Coryell in 1936 (Proc. Natl. Acad. Sci. USA 22, 210-216) that oxyhemoglobin in blood or in solution at 20 degrees has zero magnetic moment and fails to support a recent contradictory suggestion based on magnetic susceptibility of frozen samples at temperatures below 250 K. Predicted values of

  1. Magnetic properties of aligned Fe-filled carbon nanotubes

    Microsoft Academic Search

    T. Mühl; D. Elefant; A. Graff; R. Kozhuharova; A. Leonhardt; I. Mönch; M. Ritschel; P. Simon; S. Groudeva-Zotova; C. M. Schneider

    2003-01-01

    We report on the magnetic properties of Fe-filled multiwalled carbon nanotubes (MWNTs) grown by chemical vapor deposition (CVD) on Si substrates with ferrocene as precursor. The MWNTs are aligned perpendicularly to the substrate plane. X-ray diffraction analyses indicate the presence of both bcc and fcc iron with a relatively strong texture. Magnetometry measurements show a pronounced magnetic anisotropy with the

  2. Magnetic properties of sedimentary greigite (Fe 3S 4)

    Microsoft Academic Search

    Andrew P. Roberts

    1995-01-01

    New data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite (Fe3S4). Several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite. Such discriminants are necessary because greigite displays a similar (or higher) range of coercivities compared to most ferrimagnetic minerals and the commonly used method

  3. MAGNETIC PROPERTIES OF MAGHEMITE: A HEISENBERG-MONTE CARLO APPROACH

    Microsoft Academic Search

    J. Restrepo

    Magnetic properties of bulk maghemite are addressed by means of the Monte Carlo method in the framework of a three dimensional classical Heisenberg model with cubic crystalline anisotropy. The crystalline structure has been simulated in the most realistic way and different sets of exchan- ge integrals have been taken from literature in order to check their influence upon the magnetic

  4. Structural, magnetic, and magnetoelastic properties of magnesium substituted cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Nlebedim, I. C.; Hadimani, R. L.; Prozorov, R.; Jiles, D. C.

    2013-05-01

    The effects of substituting Mg on the structural, magnetic, and magnetostrictive properties of cobalt ferrite have been investigated. Comparable values of lattice parameter were obtained for the Mg-substituted samples. Saturation magnetization continuously decreased with increase in Mg concentration. Peak-to-peak magnetostriction amplitude and strain sensitivity had a similar dependence on Mg concentration.

  5. Viking magnetic properties experiment - Extended mission results

    NASA Technical Reports Server (NTRS)

    Hargraves, R. B.; Collinson, D. W.; Arvidson, R. E.; Cates, P. M.

    1979-01-01

    The backhoe magnets on Viking Lander (VL) 2 were successfully cleaned, followed by a test involving successive insertions of the cleaned backhoe into the surface. Rapid saturation of the magnets confirmed evidence from primary mission results that the magnetic mineral in the Martian surface is widely distributed, most probably in the form of composite particles of magnetic and nonmagnetic minerals. An image of the VL 2 backhoe taken via the X4 magnifying mirror demonstrates the fine-grained nature of the attracted magnetic material. The presence of maghemite and its occurrence as a pigment in, or a thin coating on, all mineral particles or as discrete, finely divided and widely distributed crystallites, are consistent with data from the inorganic analysis experiments and with laboratory simulations of results of the biology experiments on Mars.

  6. Magnetic properties of dense holographic QCD

    E-print Network

    Oren Bergman; Gilad Lifschytz; Matthew Lippert

    2009-04-30

    We investigate the Sakai-Sugimoto model at nonzero baryon chemical potential in a background magnetic field both in the confined phase and in the deconfined phase with restored chiral symmetry. In this case the 8-brane Chern-Simons term becomes important. In the confined phase it generates a gradient of the pseudo-scalar "pion", which carries a non-vanishing baryon charge. Above a critical value of the chemical potential there is a second order phase transition to a mixed phase which includes also ordinary baryonic matter. However, at fixed baryon charge density the matter is purely "pion"-gradient above a critical magnetic field. In the deconfined chiral-symmetric phase at nonzero chemical potential the magnetic field induces an axial current. We also compute the magnetization of the baryonic matter and find that it is paramagnetic in all three phases but with nonlinear behavior at large magnetic field.

  7. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    NASA Astrophysics Data System (ADS)

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  8. Rotational dynamics of magnetic silica spheres studied by measuring the complex magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Claesson, E. M.; Erné, B. H.; Philipse, A. P.

    2007-07-01

    The weak permanent magnetic dipole moment of cobalt ferrite-doped colloidal silica spheres was increased by exposure to a saturating magnetic field. The resulting change of the rotational dynamics of the magnetic microspheres in a weak alternating field was measured from low to high volume fraction in ethanol, using a frequency-dependent complex magnetic susceptibility setup. At low volume fractions, the increased dipolar attraction slows down Brownian rotation. At higher volume fractions, however, rotation is no longer slowed down as rapidly with increasing concentration, likely due to dipolar coupling between the particles which accelerates their partial alignment with the alternating field. This explanation is supported by the unexpected finding that salt addition accelerates particle rotation rather than slowing it down. At the highest volume fraction, colloidal crystals and glasses were formed in which only a small fraction of the spheres exhibit rotational mobility.

  9. Induction of Biogenic Magnetization and Redox Control by a Component of the Target of Rapamycin Complex 1 Signaling Pathway

    PubMed Central

    Nishida, Keiji; Silver, Pamela A.

    2012-01-01

    Most organisms are simply diamagnetic, while magnetotactic bacteria and migratory animals are among organisms that exploit magnetism. Biogenic magnetization not only is of fundamental interest, but also has industrial potential. However, the key factor(s) that enable biogenic magnetization in coordination with other cellular functions and metabolism remain unknown. To address the requirements for induction and the application of synthetic bio-magnetism, we explored the creation of magnetism in a simple model organism. Cell magnetization was first observed by attraction towards a magnet when normally diamagnetic yeast Saccharomyces cerevisiae were grown with ferric citrate. The magnetization was further enhanced by genetic modification of iron homeostasis and introduction of ferritin. The acquired magnetizable properties enabled the cells to be attracted to a magnet, and be trapped by a magnetic column. Superconducting quantum interference device (SQUID) magnetometry confirmed and quantitatively characterized the acquired paramagnetism. Electron microscopy and energy-dispersive X-ray spectroscopy showed electron-dense iron-containing aggregates within the magnetized cells. Magnetization-based screening of gene knockouts identified Tco89p, a component of TORC1 (Target of rapamycin complex 1), as important for magnetization; loss of TCO89 and treatment with rapamycin reduced magnetization in a TCO89-dependent manner. The TCO89 expression level positively correlated with magnetization, enabling inducible magnetization. Several carbon metabolism genes were also shown to affect magnetization. Redox mediators indicated that TCO89 alters the intracellular redox to an oxidized state in a dose-dependent manner. Taken together, we demonstrated that synthetic induction of magnetization is possible and that the key factors are local redox control through carbon metabolism and iron supply. PMID:22389629

  10. Coordination properties of hydralazine Schiff base. Synthesis and equilibrium studies of some metal ion complexes

    NASA Astrophysics Data System (ADS)

    Shoukry, Azza A.; Shoukry, Mohamed M.

    2008-08-01

    In the present study, a new ligand is prepared by condensation of hydralazine (1-Hydralazinophthalazine) with 2-butanon-3-oxime. The acid-base equilibria of the schiff-base and the complex formation equilibria with the metal ions as Cu(II), Ni(II), Co(II), Cd(II), Mn(II) and Zn(II) are investigated potentiometrically. The stability constants of the complexes are determined and the concentration distribution diagrams of the complexes are evaluated. The effect of metal ion properties as atomic number, ionic radius, electronegativity and ionization potential are investigated. The isolated solid complexes are characterized by conventional chemical and physical methods. The potential coordination sites are assigned using the i.r. and 1H NMR spectra. The structures of the isolated solid complexes are proposed on the basis of the spectral and magnetic studies.

  11. Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates

    NASA Astrophysics Data System (ADS)

    Antropov, V. P.; Antonov, V. N.

    2014-09-01

    We present a first-principles investigation of the electronic structure and physical properties of doped lithium nitridometalates Li2(Li1-xMx)N (LiMN) with M = Cr, Mn, Fe, Co, and Ni. The diverse properties include the equilibrium magnetic moments, magneto-crystalline anisotropy, magneto-optical Kerr spectra, and x-ray magnetic circular dichroism. We explain the colossal magnetic anisotropy in LiFeN by its unique electronic structure which ultimately leads to a series of unusual physical properties. The most unique property is a complete suppression of relativistic effects and freezing of orbital moments for in-plane orientation of the magnetization. This leads to the colossal spatial anisotropy of many magnetic properties including energy, Kerr, and dichroism effects. LiFeN is identified as an ultimate single-ion anisotropy system where a nearly insulating state can be produced by a spin orbital coupling alone. A very nontrivial strongly fluctuating and sign changing character of the magnetic anisotropy with electronic 3d-atomic doping is predicted theoretically. A large and highly anisotropic Kerr effect due to the interband transitions between atomic-like Fe 3d bands is found for LiFeN. A giant anisotropy of the x-ray magnetic circular dichroism for the Fe K spectrum and a very weak one for the Fe L2,3 spectra in LiFeN are also predicted.

  12. Structural and electronic dependence of the single-molecule-magnet behavior of dysprosium(III) complexes.

    PubMed

    Campbell, Victoria E; Bolvin, Hélène; Rivière, Eric; Guillot, Regis; Wernsdorfer, Wolfgang; Mallah, Talal

    2014-03-01

    We investigate and compare the magnetic properties of two isostructural Dy(III)-containing complexes. The Dy(III) ions are chelated by hexadentate ligands and possess two apical bidendate nitrate anions. In dysprosium(III) N,N'-bis(imine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (1), the ligand's donor atoms are two alkoxo, two pyridine, and two imine nitrogen atoms. Dysprosium(III) N,N'-bis(amine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (2) is identical with 1 except for one modification: the two imine groups have been replaced by amine groups. This change has a minute effect on the structure and a larger effect the magnetic behavior. The two complexes possess slow relaxation of the magnetization in the presence of an applied field of 1000 Oe but with a larger barrier for reorientation of the magnetization for 1 (Ueff/kB = 50 K) than for 2 (Ueff/kB = 34 K). First-principles calculations using the spin-orbit complete active-space self-consistent-field method were performed and allowed to fit the experimental magnetization data. The calculations gave the energy spectrum of the 2J + 1 sublevels issued from the J = 15/2 free-ion ground state. The lowest-lying sublevels were found to have a large contribution of MJ = ±15/2 for 1, while for 2, MJ = ±13/2 was dominant. The observed differences were attributed to a synergistic effect between the electron density of the ligand and the small structural changes provoked by a slight alteration of the coordination environment. It was observed that the stronger ligand field (imine) resulted in complex 1 with a larger energy barrier for reorientation of the magnetization than 2. PMID:24533673

  13. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals

    PubMed Central

    2012-01-01

    Ferronematic materials composed of 4-cyano-4?-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (?n) and figure of merit of optical properties (Q?=??n/?, where ? is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. PMID:22587542

  14. Complex windmill transformation producing new purely magnetic fluids

    NASA Astrophysics Data System (ADS)

    Lozanovski, C.; Wylleman, L.

    2011-04-01

    Minimal complex windmill transformations of G2IB(ii) spacetimes (admitting a two-dimensional Abelian group of motions of the so-called Wainwright B(ii) class) are defined and the compatibility with a purely magnetic Weyl tensor is investigated. It is shown that the transformed spacetimes cannot be perfect fluids or purely magnetic Einstein spaces. We then determine which purely magnetic perfect fluids (PMpfs) can be windmill-transformed into purely magnetic anisotropic fluids (PMafs). Assuming separation of variables, complete integration produces two, algebraically general, G2I-B(ii) PMpfs: a solution with zero 4-acceleration vector and spatial energy-density gradient, previously found by the authors, and a new solution in terms of Kummer's functions, where these vectors are aligned and non-zero. The associated windmill PMafs are rotating but non-expanding. Finally, an attempt to relate the spacetimes to each other by a simple procedure leads to a G2I-B(ii) one-parameter PMaf generalization of the previously found metric.

  15. The magnetic properties experiments on Mars Pathfinder

    NASA Astrophysics Data System (ADS)

    Madsen, M. B.; Hviid, S. F.; Gunnlaugsson, H. P.; Knudsen, J. M.; Goetz, W.; Pedersen, C. T.; Dinesen, A. R.; Mogensen, C. T.; Olsen, M.; Hargraves, R. B.

    1999-04-01

    The Mars Pathfinder lander carried two magnet arrays, each containing five small permanent magnets of varying strength. The magnet arrays were passively exposed to the wind borne dust on Mars. By the end of the Mars Pathfinder mission a bull's-eye pattern was visible on the four strongest magnets of the arrays showing the presence of magnetic dust particles. From the images we conclude that the dust suspended in the atmosphere is not solely single phase particles of hematite (?-Fe2O3) and that single phase particles of the ferrimagnetic minerals maghemite (?-Fe2O3) or magnetite (Fe3O4) are not present as free particles in any appreciable amount. The material on the strongest magnets seems to be indistinguishable from the bright surface material around the lander. From X-ray fluorescence it is known that the soil consists mainly of silicates. The element iron constitutes about 13% of the soil. The particles in the airborne dust seem to be composite, containing a few percent of a strongly magnetic component. We conclude that the magnetic phase present in the airborne dust particles is most likely maghemite. The particles thus appear to consist of silicate aggregates stained or cemented by ferric oxides, some of the stain and cement being maghemite. These results imply that Fe2+ ions were leached from the bedrock, and after passing through a state as free Fe2+ ions in liquid water, the Fe2+ was oxidized to Fe3+ and then precipitated. It cannot, however, be ruled out that the magnetic particles are titanomagnetite (or titanomaghemite) occurring in palagonite, having been inherited directly from the bedrock.

  16. Magnetic Properties and Corrosion Resistance Studies on Hybrid Magnetic Overcoats for Perpendicular Recording Media

    Microsoft Academic Search

    Wei Choong Poh; S. N. Piramanayagam; T. Liew

    2010-01-01

    Magnetic properties and corrosion inhibition properties of hybrid magnetic overcoats (Hy-MOC) that are suitable for ultra-high-density recording are investigated. Two types of Hy-MOC using different types of Co-based alloys were investigated for the magnetic overcoat (MOC). Hy- MOC(??) used CoCrPt:SiO2 (14% SiO2) while Hy-MOC(??) used CoCr22 as the sputtering targets for the reactive sputtering with N2. Magnetic hysteresis loops indicated

  17. Experimental evidence for magnetic exchange in di- and trinuclear uranium(IV) ethynylbenzene complexes.

    PubMed

    Newell, Brian S; Rappé, Anthony K; Shores, Matthew P

    2010-02-15

    We report the preparation and magnetic property investigations of a structurally related family of mono-, di-, and trinuclear U(IV) aryl acetylide complexes. The reaction between [(NN'(3))UCl] and lithiated aryl acetylides leads to the formation of the hexacoordinate complexes [(NN'(3))U(CCPh)(2)(Li.THF)] (1) and [(NN'(3))(2)U(2)(p-DEB)(THF)] (2) as red-brown and yellow-green crystalline solids, respectively. In contrast, combining the uranacycle [(bit-NN'(3))U] (bit-NN'(3) = [N(CH(2)CH(2)NSi(t)BuMe(2))(2)(CH(2)CH(2)Si(t)BuMeCH(2)]) with stoichiometric amounts of mono-, bis-, and tris(ethynyl) benzenes affords the yellow-green pentacoordinate arylacetylide complexes [(NN'(3))U(CCPh)] (3), [(NN'(3))(2)U(2)(m-DEB)] (4), [(NN'(3))(2)U(2)(p-DEB)] (5), and [(NN'(3))(3)U(3)(TEB)] (6), where NN'(3) = [N(CH(2)CH(2)NSi(t)BuMe(2))(3)]. The measured magnetic susceptibilities for 1-6 trend toward non-magnetic ground states at low temperatures. Nevertheless, the di- and trinuclear pentacoordinate compounds 4-6 appear to display weak magnetic communication between the uranium centers. This communication is modeled by fitting of the direct current (DC) magnetic susceptibility data, using the spin Hamiltonian H = -2J(S(i) x S(j)). These results are consistent with weak ferromagnetic coupling for complexes 4-6 (J = 4.76, 2.75, and 1.11 cm(-1), respectively), while the fit for 2 is consistent with a near-negligible exchange interaction (J = -0.05 cm(-1)). Geometry-optimized Stuttgart/6-31 g* B3LYP hybrid DFT calculations were carried out (spin-orbit coupling omitted) on model complexes of 3-5. The mononuclear complex shows a triplet ground state with singly occupied degenerate f orbitals. The meta- and para-bridged species are computed to show very weak ferro- and antiferromagnetic coupling, respectively. All three complexes show only small net spin density on the acetylide-containing ligands. The monomeric phenylacetylide complex 3 undergoes a reversible redox couple at -1.02 V versus [Cp(2)Fe](+/0), assignable to an oxidation of U(IV) to U(V). PMID:20085270

  18. Structural and Magnetic Properties of Thin Film of Iron Nitride

    NASA Astrophysics Data System (ADS)

    Kayani, Zohra Nazir; Riaz, Saira; Naseem, Shahzad

    2014-12-01

    The nano-crystalline iron nitride films with a mixture of ?-Fe4N, ?Fe3N and ?Fe2N phases were synthesized on copper substrate by sol-gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm3, respectively.

  19. Magnetic properties of alluvial soils polluted with heavy metals

    NASA Astrophysics Data System (ADS)

    Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

    2012-04-01

    Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (P?íbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on magnetic extracts indicated the presence of magnetite/maghemite in the uppermost layers, and strong mineralogical transformation of iron oxyhydroxides during heating. Magnetic techniques give valuable information about the soil Fe oxides, which are useful for investigation of the environmental effects in soil. Key words: magnetic methods, Fe oxides, pollution, alluvial soils.

  20. Magnetic properties of NdAu 2Ge 2

    NASA Astrophysics Data System (ADS)

    Szytu?a, A.; Kaczorowski, D.; Gondek, ?.; Arulraj, A.; Baran, S.; Penc, B.

    2009-10-01

    Physical properties of NdAu 2Ge 2, crystallising with the tetragonal ThCr 2Si 2-type crystal structure, were investigated by means of magnetic, calorimetric and electrical transport measurements as well as by neutron diffraction. The compound exhibits antiferromagnetic ordering below TN=4.5 K with a collinear magnetic structure of the AFI-type. The neodymium magnetic moments are parallel to the c-axis and amount to 1.04(4) ? B at 1.5 K. The observed magnetic behaviour is strongly influenced by crystalline electric field effect.

  1. Thermal to electricity conversion using thermal magnetic properties

    DOEpatents

    West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

    2010-04-27

    A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

  2. Functional hyperbranched polymers with advanced optical, electrical and magnetic properties.

    PubMed

    Wu, Wenbo; Tang, Runli; Li, Qianqian; Li, Zhen

    2015-06-01

    As one kind of important functional material, those with advanced optical, electrical and magnetic characteristics have attracted increasing attention due to their essential and irreplaceable role in the daily life of humans. In particular, optical, electrical and magnetic hyperbranched polymers (HBPs) exhibit some unique properties, partially derived from their highly branched topological structures. This review summarizes the recent progress in the field of functional HBPs and their application in optics, electronics and magnetics, including light-emitting polymers, nonlinear optical materials, chemosensors, solar cells, magnetic materials, etc., and also gives some outlooks for further exploration in this field at the end of this paper. PMID:25170592

  3. Properties of magnetic double perovskites, silicide intermetallics and molybdenum-doped vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Holman, Katherine Leigh

    Chemists and condensed matter physicists alike have long searched for compounds that can shed light on electronic behavior in solids. Electronic behavior is usually assessed by two straightforward ways: conductivity and magnetism. The interactions that determine magnetic states give clues as to the lattice contribution and the atomic orbital interactions. This thesis investigates three systems for their electronic, magnetic, and structural properties: firstly, three double perovskites with very similar structures but different magnetic properties; secondly, a family of compounds with a cubic structure that theoretically should superconduct but doesn't; and lastly, the effects of molybdenum on the structure, magnetic, and electronic properties of VO2. Two new compounds, La2NiVO6 and La2CoVO 6 were synthesized along with the previously studied La2CoTiO 6. While all three compounds have the double perovskite structure, they exhibit very different magnetic properties. Only La2CoTiO 6 was found to have an ordered magnetic structure, the result of the transition metals ordering. The other two compounds had antiferromagnetic interactions, but with Ni and V mixed on a site and Co and V mixed on a site, neither exhibited long-range magnetic ordering. From theory, M6Ni16Si7 (M=Mg, Sc, Ti, Nb, or Ta), should be superconducting. These five compounds were synthesized, and their magnetic and electronic properties were measured with surprisingly consistent magnetic behavior over the wide range of electron counts. Measurements revealed no superconductivity, contrary to expectations. VO2 has a rather unique metal-insulator transition that occurs just above room temperature, which has been studied for decades. The insulator phase of VO2 contains V-V dimers and little magnetic activity is expected. By adding Mo, local magnetic states are created by disrupting these V-V dimers. For every Mo4+ added, an equal number of V 4+ ions displayed a magnetic moment, indicating the breaking up of V-V pairs. Doping also results in an increase in the density of states coinciding with a decrease in the number of magnetic moments on the lattice. These results suggest that chemical manipulation of simple systems, like VO2, provide an excellent framework for the development and testing of modern ideas about complex electronic matter and state-of-the-art theoretical treatments of correlated electron systems.

  4. Magnetic properties of a metal-organic network Fe,,N3...2,,4,4 -bpy... Tan Yuen and C. L. Lin

    E-print Network

    Li, Jing

    Magnetic properties of a metal-organic network Fe,,N3...2,,4,4 -bpy... Tan Yuen and C. L. Lin of Chemistry, Rutgers University, Camden, New Jersey 08102 The results of magnetic susceptibility, isothermal magnetization, and heat capacity measurements on a newly discovered iron complex with mixed ligands Fe(N3

  5. The synthesis, structure, magnetic and luminescent properties of a new tetranuclear dysprosium (III) cluster

    SciTech Connect

    Chen, Yen-Han; Tsai, Yun-Fan [Department of Chemistry, Fu Jen Catholic University, Hsinchuang, Taipei, 24205 Taiwan (China); Lee, Gene-Hsian [Instrument Centre, College of Science, National Taiwan University, Taipei, 106 Taiwan (China); Yang, En-Che, E-mail: 071549@mail.fju.edu.tw [Department of Chemistry, Fu Jen Catholic University, Hsinchuang, Taipei, 24205 Taiwan (China)

    2012-01-15

    The synthesis and characterization of [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} (1), a new tetranuclear dysprosium (III) complex, is described. The compound was characterized by its X-ray structure, magnetic properties as well as the luminescent spectra. The compound crystallizes in a P1-bar space group with a zig-zag linear form of geometry. The ac magnetic susceptibilities of the molecule indicate that it is a magnetic molecule with a slow magnetization relaxation. The molecule also exhibits an emission spectrum that was confirmed to be ligand based. These results indicate that this molecule has both a slow magnetization relaxation (that could be potentially a SMM) and luminescent properties. - Graphical Abstract: A new tetranuclear dysprosium (III) complex [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} is synthesized and reported in this paper. This molecule has luminescence and can potentially act as a SMM. Highlights: Black-Right-Pointing-Pointer A new designed ligand (dhampH{sub 5}) was syntheisized. Black-Right-Pointing-Pointer A new tetra-dysprosium cluster [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} was made. Black-Right-Pointing-Pointer Slow magnetization relaxation phenomenon was observed. Black-Right-Pointing-Pointer Ligand-based luminescence was observed.

  6. Controlling electronic and magnetic properties of ultra narrow multilayered nanowires

    NASA Astrophysics Data System (ADS)

    Panigrahi, Puspamitra

    Interest in the study of magnetic/non-magnetic multilayered structures took a giant leap since Grunberg and his group established that the interlayer exchange coupling (IEC) is a function of the non-magnetic spacer width. This interest was further fuelled by the discovery of the phenomenal Giant Magnetoresistance (GMR) effect. In fact, in 2007 Albert Fert and Peter Grunberg were awarded the Nobel Prize in Physics for their contribution to the discovery of GMR. GMR is the key property that is being used in the read-head of the present day computer hard drive as it requires a high sensitivity in the detection of magnetic field. The recent increase in demand for device miniaturization encouraged researchers to look for GMR in nanoscale multilayered structures. In this context, one dimensional (1-D) multilayered nanowire structure has shown tremendous promise as a viable candidate for ultra sensitive read head sensors. In fact, the phenomenal giant magnetoresistance (GMR) effect, which is the novel feature of the currently used multilayered thin film, has already been observed in multilayered nanowire systems at ambient temperature. Geometrical confinement of the supper lattice along the 2-dimensions (2-D) to construct the 1-D multilayered nanowire prohibits the minimization of magnetic interaction-offering a rich variety of magnetic properties in nanowire that can be exploited for novel functionality. In addition, introduction of non-magnetic spacer between the magnetic layers presents additional advantage in controlling magnetic properties via tuning the interlayer magnetic interaction. Despite of a large volume of theoretical works devoted towards the understanding of GMR and IEC in super lattice structures, limited theoretical calculations are reported in 1-D multilayered systems. Thus to gauge their potential application in new generation magneto-electronic devices, in this thesis, I have discussed the usage of first principles density functional theory (DFT) in predicting the equilibrium structure, stability as well as electronic and magnetic properties of one dimensional multilayered nanowires. Particularly, I have focused on the electronic and magnetic properties of Fe/Pt multilayered nanowire structures and the role of non-magnetic Pt spacer in modulating the magnetic properties of the wire. It is found that the average magnetic moment per atom in the nanowire increases monotonically with an ˜ 1N(Fe) dependance, where N(Fe) is the number of iron layers in the nanowire. A simple model based upon the interfacial structure is given to explain the 1N(Fe) trend in magnetic moment obtained from the first principle calculations. A new mechanism, based upon spin flip with in the layer and multistep electron transfer between the layers, is proposed to elucidate the enhancement of magnetic moment of Iron atom at the Platinum interface. The calculated IEC in the Fe/Pt multilayered nanowire is found to switch sign as the width of the non-magnetic spacer varies. The competition among short and long range direct exchange and the super exchange has been found to play a key role for the non-monotonous sign in IEC depending upon the width of the Platinum spacer layer. The calculated magnetoresistance from Julliere's model also exhibit similar switching behavior as that of IEC. The universality of the behavior of exchange coupling has also been looked into by introducing different non-magnetic spacers like Palladium, Copper, Silver, and Gold in between magnetic Iron layers. The nature of hybridization between Fe and other non-magnetic spacer is found to dictate the inter layer magnetic interaction. For example, in Fe/Pd nanowire the d-p hybridization in two spacer layer case favors anti-ferromagnetic (AFM) configuration over ferromagnetic (FM) configuration. However, the hybridization between half-filled Fe(d) and filled Cu(p) state in Fe/Cu nanowire favors FM coupling in the 2-spacer system.

  7. 2236 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Magnetic Properties and Crystallization Kinetics of a

    E-print Network

    Laughlin, David E.

    /nanocrystalline nanocom- posite soft ferromagnetic material that has been suggested for such magnetic components precursors to nanocrystalline soft magnets contributes to the understanding of microstructural development and its influence on soft magnetic properties. FINEMET was one of the first amorphous

  8. Effects of External Magnetic Fields on the Excited States of (ND)8 Metal Complexes.

    NASA Astrophysics Data System (ADS)

    Helms, Charles Alan

    Large changes in the steady state emissions and lifetimes as a function of external magnetic field strength have been observed for (nd)^8 mononuclear and binuclear complexes. These unusually pronounced effects are attributed to a field-induced symmetry reduction leading to a relaxation of transition dipole selection rules. Both spin-orbit coupling and magnetic field strength appear to play a role in determining the magnitude of the observed effect. A theoretical model has been developed to rationalize the results obtained for the Pt_2(H _2P_2O _5)_sp{4}{4-} ion. An analogous model should pertain to the mononuclear systems. Closed-shell (La(III), Lu(III)) rare earth salts of the Pt_2(H_2P _2O_5)_sp{4 }{4-} ion show the same dependence on an externally applied magnetic field as the previously examined K and Ba analogs, in all respects. However, the luminescence properties of the openshell salts are markedly different, even in the absence of a magnetic field. The zero-field phosphorescence lifetime of GdKPt_2 (H_2P_2O _5)_4 is one-tenth that of the closed-shell lifetime, but the position of the phosphorescence is unchanged from the closed-shell case. The application of an external magnetic field produces no further changes in the electronic properties of the open-shell salts. Salts containing rare earth ions with low-lying atomic states (Eu(III)) exhibit complete quenching of the Pt _2(H_2P_2 O_5)_sp{4}{4 -} phosphorescence, indicating efficient energy transfer. Results from complexes containing rare earth ions are analyzed in terms of an angular momentum coupling scheme. A recently published derivation of basis functions for the Pt_2(H_2 P_2O_5)_sp {4}{4-} ion including spin-orbit interactions was repeated and confirmed.

  9. The effects of magnetic nanoparticle properties on magnetic fluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Kappiyoor, Ravi; Liangruksa, Monrudee; Ganguly, Ranjan; Puri, Ishwar K.

    2010-11-01

    Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material used for hyperthermia should be one that is readily produced and is nontoxic while providing sufficient heating. We examine six materials that have been considered as candidates for MFH use. Examining the heating produced by nanoparticles of these materials, barium-ferrite and cobalt-ferrite are unable to produce sufficient MFH heating, that from iron-cobalt occurs at a far too rapid rate to be safe, while fcc iron-platinum, magnetite, and maghemite are all capable of producing stable controlled heating. We simulate the heating of ferrofluid-loaded tumors containing nanoparticles of the latter three materials to determine their effects on tumor tissue. These materials are viable MFH candidates since they can produce significant heating at the tumor center yet maintain the surrounding healthy tissue interface at a relatively safe temperature.

  10. Magnetic and magnetocaloric properties and the magnetic phase diagram of single-crystal dysprosium

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. S.; Tsokol, A. O.; Tishin, A. M.; Gschneidner, K. A., Jr.; Pecharsky, V. K.

    2005-05-01

    Magnetic materials exhibiting magnetic phase transitions simultaneously with structural rearrangements of their crystalline lattices hold promise for numerous practical applications including magnetic refrigeration, magnetomechanical devices, and sensors. We undertook a detailed study of a single crystal of dysprosium metal, which is a classical example of a system where magnetic and crystallographic sublattices can be either coupled or decoupled from one another. Magnetocaloric effect, magnetization, ac magnetic susceptibility, and heat capacity of high-purity single crystals of dysprosium have been investigated over broad temperature and magnetic field intervals with the magnetic field vector parallel to either the a or c axes of the crystal. Notable differences in the behavior of the physical properties when compared to Dy samples studied in the past have been observed between 110 and 125 K, and between 178 and ˜210K . A plausible mechanism based on the formation of antiferromagnetic clusters in the impure Dy has been suggested in order to explain the reduction of the magnetocaloric effect in the vicinity of the Néel point of relatively impure samples. Experimental and theoretical investigations of the influence of commensurability effects on the magnetic phase diagram and the value of the magnetocaloric effect have been conducted. The presence of newly found anomalies in the physical properties has been considered as evidence of previously unreported states of Dy. The refined magnetic phase diagram of dysprosium with the magnetic field vector parallel to the a axis of a crystal has been constructed and discussed.

  11. Vacuum properties of sintered SmCo/sub 5/ magnets

    SciTech Connect

    Warren, R.W.; DePaula, R.F.; Hansborough, L.D.

    1981-12-01

    There are many desirable applications of powerful, rare-earth permanent magnets made of sintered SmCo/sub 5/ material within vacuum systems. One application is the use of large numbers of SmCo/sub 5/ magnets to provide the undulating magnetic field in a free-electron-laser wiggler structure. Tests were conducted at Los Alamos to determine the suitability of SmCo/sub 5/ magnets in a vacuum environment of approx. 10/sup -6/ torr. The vacuum performances of the wiggler system, with and without the SmCo/sub 5/ magnets (having approx. 11% of the total surface area) installed, were essentially identical. These tests indicate that SmCo/sub 5/ magnets have good vacuum properties and are suitable for use in many vacuum systems.

  12. Transport properties of hadronic matter in magnetic field

    E-print Network

    Guru Kadam

    2015-03-06

    We study the effect of magnetic field on the transport properties like shear and bulk viscosities of hot and dense hadronic matter within hadron resonance gas model. We estimate the bulk viscosity using low energy theorems for bilocal correlators of the energy momentum tensor generalized to finite temperature, density and magnetic field. We use Gaussian ansatz for the spectral function at low frequency. We estimate shear viscosity coefficient using molecular kinetic theory. We find that vacuum contribution due to finite magnetic field dominates the bulk viscosity ({\\zeta}) for the temperatures up to 0.1GeV and increases with magnetic field while ratio {\\zeta}/s decreases with magnetic field. We also find that shear viscosity coefficient of hadronic matter decreases with magnetic field.

  13. Magnetic properties of Co Rh and Ni Rh nanowires

    NASA Astrophysics Data System (ADS)

    Sondón, Tristana; Saúl, Andrés; Guevara, Javier

    2007-09-01

    We have calculated the magnetic properties of pure Ni, Co and Rh, and alloyed Co-Rh and Ni-Rh free-standing nanowires by an ab initio method. We have found that the pure Co and Ni wires present an enhanced magnetic moment with respect to their bulk values, and we have obtained that a magnetic order appears for pure Rh wires. For concentrations up to 50%Rh, in the alloyed Ni-Rh linear chains there is an enhancement of the total magnetic moment with respect to the pure nanowires, and in the case of Co-Rh the alloying with Rh enhances the Co magnetic moment. In both systems we obtain very high Rh magnetic moments.

  14. PREDICTION OF THERMODYNAMIC PROPERTIES OF COMPLEX FLUIDS

    SciTech Connect

    Marc Donohue

    2006-01-05

    ABSTRACT The goal of this research has been to generalize Density Functional Theory (DFT) for complex molecules, i.e. molecules whose size, shape, and interaction energies cause them to show significant deviations from mean-field behavior. We considered free energy functionals and minimized them for systems with different geometries and dimensionalities including confined fluids (such as molecular layers on surfaces and molecules in nano-scale pores), systems with directional interactions and order-disorder transitions, amphiphilic dimers, block copolymers, and self-assembled nano-structures. The results of this procedure include equations of equilibrium for these systems and the development of computational tools for predicting phase transitions and self-assembly in complex fluids. DFT was developed for confined fluids. A new phenomenon, surface compression of confined fluids, was predicted theoretically and confirmed by existing experimental data and by simulations. The strong attraction to a surface causes adsorbate molecules to attain much higher densities than that of a normal liquid. Under these conditions, adsorbate molecules are so compressed that they repel each other. This phenomenon is discussed in terms of experimental data, results of Monte Carlo simulations, and theoretical models. Lattice version of DFT was developed for modeling phase transitions in adsorbed phase including wetting, capillary condensation, and ordering. Phase behavior of amphiphilic dimers on surfaces and in solutions was modeled using lattice DFT and Monte Carlo simulations. This study resulted in predictive models for adsorption isotherms and for local density distributions in solutions. We have observed a wide variety of phase behavior for amphiphilic dimers, including formation of lamellae and micelles. Block copolymers were modeled in terms of configurational probabilities and in the approximation of random mixing entropy. Probabilities of different orientations for the segments were considered as order parameters and the free energy was written as a functional of these parameters. Imposing boundary conditions allowed us to apply this approach to confined fluids. Equilibrium self-assembly in fluids was studied in the framework of the lattice density functional theory (DFT). In particular, DFT was used to model the phase behavior of anisotropic monomers. Though anisotropic monomers are a highly idealized model system, the analysis presented here demonstrates a formalism that can be used to describe a wide variety of phase transitions, including processes referred to as self-assembly. In DFT, the free energy is represented as a functional of order parameters. Minimization of this functional allows modeling spontaneous nano-scale phase transitions and self-assembly of supramolecular structures. In particular, this theory predicts micellization, lamellization, fluid – glass phase transitions, crystallization, and more. A classification of phase transitions based on general differences in self-assembled structures is proposed. The roles of dimensionality and intermolecular interactions in different types of phase transitions are analyzed. The concept of “genetic” codes is discussed in terms of structural variety of self-assembled systems.

  15. Influencing the properties of dysprosium single-molecule magnets with phosphorus donor ligands

    PubMed Central

    Pugh, Thomas; Tuna, Floriana; Ungur, Liviu; Collison, David; McInnes, Eric J.L.; Chibotaru, Liviu F.; Layfield, Richard A.

    2015-01-01

    Single-molecule magnets are a type of coordination compound that can retain magnetic information at low temperatures. Single-molecule magnets based on lanthanides have accounted for many important advances, including systems with very large energy barriers to reversal of the magnetization, and a di-terbium complex that displays magnetic hysteresis up to 14?K and shows strong coercivity. Ligand design is crucial for the development of new single-molecule magnets: organometallic chemistry presents possibilities for using unconventional ligands, particularly those with soft donor groups. Here we report dysprosium single-molecule magnets with neutral and anionic phosphorus donor ligands, and show that their properties change dramatically when varying the ligand from phosphine to phosphide to phosphinidene. A phosphide-ligated, trimetallic dysprosium single-molecule magnet relaxes via the second-excited Kramers' doublet, and, when doped into a diamagnetic matrix at the single-ion level, produces a large energy barrier of 256?cm?1 and magnetic hysteresis up to 4.4?K. PMID:26130418

  16. Influencing the properties of dysprosium single-molecule magnets with phosphorus donor ligands.

    PubMed

    Pugh, Thomas; Tuna, Floriana; Ungur, Liviu; Collison, David; McInnes, Eric J L; Chibotaru, Liviu F; Layfield, Richard A

    2015-01-01

    Single-molecule magnets are a type of coordination compound that can retain magnetic information at low temperatures. Single-molecule magnets based on lanthanides have accounted for many important advances, including systems with very large energy barriers to reversal of the magnetization, and a di-terbium complex that displays magnetic hysteresis up to 14?K and shows strong coercivity. Ligand design is crucial for the development of new single-molecule magnets: organometallic chemistry presents possibilities for using unconventional ligands, particularly those with soft donor groups. Here we report dysprosium single-molecule magnets with neutral and anionic phosphorus donor ligands, and show that their properties change dramatically when varying the ligand from phosphine to phosphide to phosphinidene. A phosphide-ligated, trimetallic dysprosium single-molecule magnet relaxes via the second-excited Kramers' doublet, and, when doped into a diamagnetic matrix at the single-ion level, produces a large energy barrier of 256?cm(-1) and magnetic hysteresis up to 4.4?K. PMID:26130418

  17. Magnetic properties and microstructure of Co-Cr-Pr vertically magnetized films

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Yoshida, N.; Hwang, U.; Uchiyama, Y.; Ishibashi, K.

    1988-04-01

    The effect of Pr on both the magnetic properties and microstructure of Co-Cr alloys is discussed. The saturation magnetization Ms and perpendicular magnetic anisotropy Ku at room temperature is found to increase with Pr, becoming maximum at about 0.5 wt. % Pr, and then decreases monotonously. The microstructure is also changed with Pr, leading to a less-defined columnar structure. However, no significant change is found in the Auger spectra for various contents.

  18. Effect of poly (ethylene glycol) coating on the magnetic and thermal properties of biocompatible magnetic liquids

    Microsoft Academic Search

    Arkadiusz Józefczak; Tomasz Hornowski; Andrzej Skumiel; Miko?aj ?abowski; Milan Timko; Peter Kopcanský; Martina Koneracká; Andrzej Szlaferek; Wojciech Kowalski

    2009-01-01

    The aim of this study was to investigate the influence of poly(ethylene glycol) surface-active coating on the magnetic and thermal properties of biocompatible magnetic liquids. The data were analyzed using the high-temperature approximation model taking into account polydispersity of a system. Heating ability of the PEG-stabilized magnetic fluids was determined by the calorimetric measurement of specific absorption rate (SAR) at

  19. The annealing influence onto the magnetic and energetic properties in soft magnetic material after punching process

    Microsoft Academic Search

    A. Boglietti; A. Cavagnino; L. Ferraris; M. Lazzari

    2003-01-01

    The paper presents a method to determine the deterioration effects due to the punching process on soft magnetic materials used in electrical machines. Furthermore the possibility to recovery the magnetic and energetic original properties by mean of subsequent annealing treatments is reported too. The proposed methodology is based on a full experimental approach. Five toroidal cores, with the same geometrical

  20. Maria Goeppert-Mayer Award Talk: Novel Magnetism and Transport in Complex Oxide Thin Films, Multilayers and Nanostructures

    NASA Astrophysics Data System (ADS)

    Suzuki, Yuri

    2005-03-01

    In epitaxial complex oxide systems, epitaxial strain, cation substitution and nanofabrication are just some ways in which their magnetic, electronic and optical properties may be tuned. In addition, their surfaces and interfaces provide a rich playground for the exploration of novel magnetic properties not found in the bulk constituents and the development of functional interfaces to be incorporated into technological applications. We have probed magnetism in complex oxide materials through studies of epitaxial oxide thin films, nanostructures and junction devices. With our ability to control oxide film growth as well as our expertise in nanofabrication, we have been able to study the effects of surfaces and interfaces on magnetism in ultra-thin magnetic oxide films and magnetic oxide nanostructures. For example, we have found that the nature of local magnetic structure in submicron islands of colossal magnetoresistance (CMR) material reveals the importance of shape anisotropy as well as magnetostriction in determining the micromagnetics in such small CMR structures. We have also studied epitaxial oxide trilayer junctions composed of magnetite (Fe3O4) and doped manganite (La0.7Sr0.3MnO3) in which we have confirmed the theoretically predicted negative spin polarization of Fe3O4. Transport through the barrier can be understood in terms of hopping transport through localized states that preserves electron spin information.

  1. Structure, composition and magnetic properties of carbon nanotubes doped by Fe during the growth process

    NASA Astrophysics Data System (ADS)

    Labunov, V. A.; Shulitski, B. G.; Prudnikava, A. L.; Yanushkevich, K. I.

    2008-03-01

    The results of complex investigations of the crystalline structure, composition and specific magnetization of the multi-wall carbon nanotubes (CNTs) filled by magnetic nanocomposite are performed. CNT arrays have been synthesized by the high temperature pyrolysis of fluid hydrocarbon - p-xylole [C8H10] in the presence of volatile catalyst - ferrocene [Fe(C5H5)2] at the walls of tubular-type quartz reactor of specially constructed equipment. It was revealed that the obtained CNTs constitute complex nanocomposite: C - Fe3C - Fe5C2 - Fe. The magnetic properties of such CNTs in the temperature region of 78<=T<=1060 K are conditioned by the ferric carbide (in the form Fe3C H Fe5C2) and Fe.

  2. Petrophysical Properties (Density and Magnetization) of Rocks from the Suhbaatar-Ulaanbaatar-Dalandzadgad Geophysical Profile in Mongolia and Their Implications

    PubMed Central

    Gao, Jintian; Gu, Zuowen; Dagva, Baatarkhuu; Tserenpil, Batsaikhan

    2013-01-01

    Petrophysical properties of 585 rock samples from the Suhbaatar-Ulaanbaatar-Dalandzadgad geophysical profile in Mongolia are presented. Based on the rock classifications and tectonic units, petrophysical parameters (bulk density, magnetic susceptibility, intensity of natural remanent magnetization, and Köenigsberger ratio) of these rocks are summarized. Results indicate that (1) significant density contrast of different rocks would result in variable gravity anomalies along the profile; (2) magnetic susceptibility and natural remanent magnetization of all rocks are variable, covering 5-6 orders of magnitude, which would make a variable induced magnetization and further links to complex magnetic anomalies in ground surface; (3) the distribution of rocks with different lithologies controls the pattern of lithospheric magnetic anomaly along the profile. The petrophysical database thus provides not only one of the keys to understand the geological history and structure of the profile, but also essential information for analysis and interpretation of the geophysical (e.g., magnetic and gravity) survey data. PMID:24324382

  3. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King

    2005-01-01

    (1) First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite,

  4. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King; David Heslop

    2005-01-01

    First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite, which

  5. Spatial variability of magnetic soil properties

    NASA Astrophysics Data System (ADS)

    van Dam, Remke L.; Hendrickx, Jan M.; Harrison, Bruce; Borchers, Brian; Norman, David I.; Ndur, Samuel; Jasper, Chris; Niemeyer, Patrick; Nartey, Robert; Vega, David N.; Calvo, Lucas; Simms, Janet E.

    2004-09-01

    The presence of magnetic iron oxides in the soil can seriously hamper the performance of electromagnetic sensors for the detection of buried land mines and unexploded ordnance (UXO). Previous work has shown that spatial variability in soil water content and texture affects the performance of ground penetrating radar and thermal sensors for land mine detection. In this paper we aim to study the spatial variability of iron oxides in tropical soils and the possible effect on electromagnetic induction sensors for buried low-metal land mine and UXO detection. We selected field sites in Panama, Hawaii, and Ghana. Along several horizontal transects in Panama and Hawaii we took closely spaced magnetic susceptibility readings using Bartington MS2D and MS2F sensors. In addition to the field measurements, we took soil samples from the selected sites for laboratory measurements of dual frequency magnetic susceptibility and textural characteristics of the material. The magnetic susceptibility values show a significant spatial variation in susceptibility and are comparable to values reported to hamper the operation of metal detectors in parts of Africa and Asia. The absolute values of susceptibility do not correlate with both frequency dependence and total iron content, which is an indication of the presence of different types of iron oxides in the studied material.

  6. Magnetic properties of biosynthesized magnetite nanoparticles

    Microsoft Academic Search

    Lucas W. Yeary; Ji-Won Moon; L. J. Love; J. R. Thompson; C. J. Rawn; T. J. Phelps

    2005-01-01

    Magnetic nanoparticles, which are unique because of both structural and functional elements, have various novel applications. The popularity and practicality of nanoparticle materials create a need for a synthesis method that produces quality particles in sizable quantities. This paper describes such a method, one that uses bacterial synthesis to create nanoparticles of magnetite. The thermophilic bacterial strain Thermoanaerobacter ethanolicus TOR-39

  7. Preparation and property of polyurethane/nanosilver complex fibers

    NASA Astrophysics Data System (ADS)

    Qu, Rongjun; Gao, Jingjing; Tang, Bo; Ma, Qianli; Qu, Baohan; Sun, Changmei

    2014-03-01

    Utilizing terminal reactive groups in polyurethane, nanometer silvers were reduced in situ. The formation mechanism of nanosilver in PU was under preliminary discussion. UV-vis spectroscopy and TEM analysis were used to monitor reduction process; and the PU/nanosilver complex fibers were produced by dry spinning, which were characterized by X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis, differential scanning calorimetry and so on. The influence of nanosilver on the thermal, mechanical and antimicrobial properties of PU was studied. It is inferred that 0.030% Ag should be a proper concentration for the PU/nanosilver complex fibers with favorable mechanical properties and highly effective antibacterial activities.

  8. Magnetic properties of Fe on vicinal Pt(111)

    NASA Astrophysics Data System (ADS)

    Cheng, Ruihua; Bader, S. D.; Fradin, F. Y.

    2008-04-01

    A magnetic system such as Fe /Pt shows strong magnetic anisotropy due to the contribution of the interface. Pt is known to be nearly ferromagnetic and can have an induced magnetic moment when it is in proximity to 3d ferromagnetic atoms. Both the magnetic moment and the magnetic anisotropy of the materials are enhanced on the step surface due to the symmetry breaking by the introduction of atomic steps on vicinal substrate. In order to study the effect of step-induced anisotropy, we investigate the magnetic properties of Fe grown on a curved Pt(111) single crystal that provides a continuous gradient in step density. Fe grown on high vicinal angle surfaces has larger values of both the saturation magnetization Ms and coercivity HC compared with the flat surface. The atomic steps of the vicinal surface greatly affect the magnetic properties of ultrathin Fe films. The anisotropy of Fe on the curved Pt(111) surface is related to the step density of the substrate.

  9. The rheological properties of magnetic field excited magnetic powders sheared between two parallel plates

    NASA Astrophysics Data System (ADS)

    Chen, Kaikai; Tian, Yu; Shan, Lei; Zhang, Xiangjun; Meng, Yonggang

    2013-11-01

    The rheological properties of magnetic powders (MPs) excited by magnetic fields under parallel-plate shear were experimentally studied. The results showed that the shear stress increased with increasing magnetic field strength and volume fraction. It was also influenced by the plate gap distance, and was independent of the shear rate. The shear stress could be ascribed to the contributions of magnetic force and friction force, dominated by the normal force, the shear strain and the friction coefficient. The ratio of shear stress to normal stress, a form of friction coefficient, was influenced by volume fraction, magnetic field strength and gap distance. These results provide a better understanding of the mechanisms of magnetic field excited magnetic powders under parallel-plate shear.

  10. Magnetic and magnetization properties of electrodeposited fcc CoPt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Shamaila, S.; Sharif, R.; Riaz, S.; Ma, M.; Khaleeq-ur-Rahman, M.; Han, X. F.

    Magnetic and magnetization properties of fcc Co 1-xPt x ( x?0.3) alloy nanowires fabricated by electrodeposition into self-synthesized anodic alumina templates are investigated. Magnetization curves, measured for varying wire geometries, show a crossover of easy axis of magnetization from parallel to perpendicular to the nanowire axis as a function of the diameter and length. The measured values of coercivity ( Hc) and remanent squareness (SQ) of CoPt nanowire arrays, as a function of angle ( ?) between the field and wire axis, support the crossover of easy axis of magnetization. The curling mode of the magnetization reversal process is observed for CoPt nanowire arrays. At low temperatures, the easy axis for magnetization of the nanowires is observed to deviate from the room-temperature orientation.

  11. Polymorphism and magnetic properties of Li2MSiO4 (M = Fe, Mn) cathode materials.

    PubMed

    Bini, Marcella; Ferrari, Stefania; Ferrara, Chiara; Mozzati, Maria Cristina; Capsoni, Doretta; Pell, Andrew J; Pintacuda, Guido; Canton, Patrizia; Mustarelli, Piercarlo

    2013-01-01

    Transition metal-based lithium orthosilicates (Li2MSiO4, M = Fe, Ni, Co, Mn) are gaining a wide interest as cathode materials for lithium-ion batteries. These materials present a very complex polymorphism that could affect their physical properties. In this work, we synthesized the Li2FeSiO4 and Li2MnSiO4 compounds by a sol-gel method at different temperatures. The samples were investigated by XRPD, TEM, (7)Li MAS NMR, and magnetization measurements, in order to characterize the relationships between crystal structure and magnetic properties. High-quality (7)Li MAS NMR spectra were used to determine the silicate structure, which can otherwise be hard to study due to possible mixtures of different polymorphs. The magnetization study revealed that the Néel temperature does not depend on the polymorph structure for both iron and manganese lithium orthosilicates. PMID:24316682

  12. Structural and magnetic properties of TM-SiO2 (TM = Fe, Co, Ni) films

    NASA Astrophysics Data System (ADS)

    Socolovsky, L. M.; Denardin, J. C.; Brandl, A. L.; Knobel, M.; Zhang, X. X.

    2003-05-01

    TMx-(SiO2)1-x (TM=Fe, Co, Ni) thin films were prepared in a wide concentration range (0.35 ?x?1). Structure was studied with transmission electron microscopy (TEM), X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Magnetic and magnetotransport properties were investigated by means of magnetization and Hall effect measurements. TEM images display nanometric spherical structures embedded in a SiO2 amorphous matrix, with typical sizes increasing from 3 to 5nm when TM volume concentration x is increased. SAXS measurements indicate a complex structure formed by nanosized objects. XRD measurements show that the structure is composed by amorphous SiO2 and TM crystallites. Slightly above the percolation threshold all samples display giant Hall effect. The observed magnetic properties are dependent on x, and display an evolution resulting from the progressive increase of the mean particle size.

  13. Experimental Shocks on Rock Samples and Their Effects on Magnetic Properties and Remanent Magnetization

    NASA Astrophysics Data System (ADS)

    Gattacceca, J.; Bezaeva, N.; Berthe, L.; Boustie, M.; Rochette, P.; Lamali, A.

    2006-12-01

    Hypervelocity impacts play a key role in the magnetic records of many extraterrestrial bodies (asteroids, Mars, the Moon...). The understanding of magnetization changes induced by hypervelocity impacts is crucial for the interpretation of planetary magnetic anomalies and of the paleomagnetic signal of meteorites. Shocks may also permanently modify the intrinsic magnetic properties of rocks. In this work, we investigate the effects of shocks on both the intrinsic (hysteresis, susceptibility, magnetic anisotropy) and extrinsic (remanent magnetization) magnetic properties of magmatic and metamorphic terrestrial rocks, meteorites (ordinary chondrites and Martian meteorites) and synthetic samples. In order to span a large spectrum of shock duration bracketing the natural case (10-3 to 1 s), we use different experimental techniques: pulsed laser (~10-9-10-8s, up to 50 GPa), high-order explosives (~10-6s, up to 25 GPa) and measurement under pressure in a non-magnetic pressure cell (~102-103 s, up to 1.5 GPa). In order to calibrate experimentally the pressure profile in the impacted materials, we applied shocks induced by laser on rock slices of different thickness (0.5-4mm) to evaluate material response under strong and short pressure loading. Rear free surface velocity has been measured with VISAR (Velocimeter Interferometry for Any Reflector) technique. Velocity profiles are reproduced by simulation using hydrodynamic code including elasto-plastic behaviour of material. The agreement between calculations and experiment is rather good allowing an estimation of the pressure seen by the impacted rocks. The shock experiments demonstrate that above ~10 GPa, the intrinsic properties of all investigated magnetic minerals (magnetite, titanomagnetite, pyrrhotite) are permanently modified: coercivity increases, susceptibility decreases and in some cases a magnetic foliation is created perpendicular to the direction of shock. Therefore, the magnetic properties of shocked meteorites (e.g. Martian meteorites) may not be representative of the magnetism of their parent body. The effects on remanent magnetization are already noticeable at ~1 GPa. The efficiency of the shock remagnetization is strongly dependent on the magnetic mineralogy. For pressure of a few GPa, most magnetic minerals present in meteorites (taenite, kamacite, titanomagnetite, magnetite, pyrrhotite) are already largely demagnetized and/or remagnetized. Therefore, in the vast majority of cases, the paleomagnetic signal of meteorites cannot be original. Records of the possible original magnetic fields may only be looked for in very weakly shocked meteorites. Nevertheless the paleomagnetic signal of shocked meteorites can provide clues on the magnetic fields present during the impacts.

  14. Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties.

    PubMed

    Ma, Longfei; Sun, Jibin; Lu, Xiaofeng; Zhang, Shangxi; Qi, Hui; Liu, Lei; Shao, Yongliang; Shao, Xiangfeng

    2015-01-01

    The combination of CuBr2 and arylthio-substituted tetrathiafulvalene derivatives (1-7) results in a series of charge-transfer (CT) complexes. Crystallographic studies indicate that the anions in the complexes, which are derived from CuBr2, show diverse configurations including linear [Cu(I)Br2](-), tetrahedral [Cu(II)Br4](2-), planar [Cu(II)2Br6](2-), and coexistence of planar [Cu(II)Br4](2-) and tetrahedral [Cu(II)Br3](-) ions. On the other hand, the TTFs show either radical cation or dication states that depend on their redox potentials. The central TTF framework on most of TTFs is nearly planar despite the charge on them, whereas the two dithiole rings on molecule 4 in complex 4·CuBr4 are significantly twisted with a dihedral angle of 38.3°. The magnetic properties of the complexes were elucidated. The temperature-dependent magnetic susceptibility of complex 5·Cu2Br6 shows the singlet-triplet transition with coupling constant J = -248 K, and that of 3·(CuBr4)0.5·CuBr3·THF shows the abrupt change at 270 K caused by the modulation of intermolecular interactions. The thermo variation of magnetic susceptibility for the other complexes follows the Curie-Weiss law, indicating the weak antiferromagnetic interaction at low temperature. PMID:26124886

  15. Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties

    PubMed Central

    Ma, Longfei; Sun, Jibin; Lu, Xiaofeng; Zhang, Shangxi; Qi, Hui; Liu, Lei; Shao, Yongliang

    2015-01-01

    Summary The combination of CuBr2 and arylthio-substituted tetrathiafulvalene derivatives (1–7) results in a series of charge-transfer (CT) complexes. Crystallographic studies indicate that the anions in the complexes, which are derived from CuBr2, show diverse configurations including linear [Cu(I)Br2]–, tetrahedral [Cu(II)Br4]2–, planar [Cu(II)2Br6]2–, and coexistence of planar [Cu(II)Br4]2– and tetrahedral [Cu(II)Br3]– ions. On the other hand, the TTFs show either radical cation or dication states that depend on their redox potentials. The central TTF framework on most of TTFs is nearly planar despite the charge on them, whereas the two dithiole rings on molecule 4 in complex 4·CuBr4 are significantly twisted with a dihedral angle of 38.3°. The magnetic properties of the complexes were elucidated. The temperature-dependent magnetic susceptibility of complex 5·Cu2Br6 shows the singlet–triplet transition with coupling constant J = ?248 K, and that of 3·(CuBr4)0.5·CuBr3·THF shows the abrupt change at 270 K caused by the modulation of intermolecular interactions. The thermo variation of magnetic susceptibility for the other complexes follows the Curie–Weiss law, indicating the weak antiferromagnetic interaction at low temperature.

  16. Recent advances in magnetic nanoparticles with bulk-like properties

    NASA Astrophysics Data System (ADS)

    Batlle, Xavier

    2013-03-01

    Magnetic nanoparticles (NP) are an excellent example of nanostructured materials and exhibit fascinating properties with applications in high-density recording and biomedicine. Controlling the effects of the nanostructure and surface chemistry and magnetism at the monolayer level have become relevant issues. As the size is reduced below 100 nm, deviations from bulk behavior have been attributed to finite-size effects and changes in the magnetic ordering at the surface, thus giving rise to a significant decrease in the magnetization and increase in the magnetic anisotropy. The existence of a surface spin glass-like state due to magnetic frustration has been widely suggested in ferrimagnetic NP. However, in this talk, we will show that high crystal quality magnetite Fe3-xO4 NP of about a few nanometers in diameter and coated with different organic surfactants display bulk-like structural, magnetic and electronic properties. Magnetic measurements, transmission electron microscopy, X-ray absorption and magnetic circular dichroism and Monte Carlo simulations, evidenced that none of the usual particle-like behavior is observed in high quality NP of a few nm. Consequently, the magnetic and electronic disorder phenomena typically observed in those single-phase ferrimagnetic NP should not be considered as an intrinsic effect. We also performed a real-space characterization at the sub-nanometer scale, combining scanning transmission electron microscopy, electron energy loss spectroscopy and electron magnetic chiral dichroism. For the first time, we found that the surface magnetization is as high as about 70% of that of the core. The comparison to density functional theory suggested the relevance of the strong surface bond between the Fe ions and the organic surfactant. All the foregoing demonstrates the key role of both the crystal quality and surface bond on the physical properties of ferrimagnetic NP and paves the way to the fabrication of the next generation of NP with optimal magnetic properties. Some bio-applications will also be discussed. In collaboration with A Labarta, N Perez, O Iglesias, A Fraile, C Moya(U Barcelona); A Roca, MP Morales, CJ Serna (ICMM-CSIC); F Bartolome, LM Garcia, J. Bartolome (CSIC-U Zaragoza); R Mejias, DF Barber (CNB-CSIC); M Varela, J Gazquez, J Salafranca, SJ Pennycook (ORNL), ST Pantelides (Vanderbilt U).

  17. Geometric properties of the magnetic Laplacian on the Euclidean 4-space

    SciTech Connect

    Kazmierowski, Dominique [Universite Lille I - Sciences et Technologies, 59655 Villeneuve d'Ascq Cedex (France); Zinoun, Azzouz [Laboratoire de Physique des Lasers, Atomes et Molecules, Unite Mixte de Recherche de l'Universite de Lille 1 et du CNRS - UMR 8523, Universite Lille I - Sciences et Technologies, 59655 Villeneuve d'Ascq Cedex (France); Intissar, Ahmed [Departement de Mathematiques, Faculte des Sciences de Rabat, BP 1014 (Morocco)

    2010-12-15

    When the four-dimensional Euclidean space is endowed with a covariant derivative that is either self-dual or antiself-dual and of constant curvature, the corresponding magnetic Laplacian is closely related to the sub-Laplacian of the quaternionic Heisenberg group. Some geometric properties of this operator are studied. In particular, it is proved that there exists a canonical orthogonal complex structure which provides a factorization in the sense of Schroedinger.

  18. Analytical calculation for estimation of magnetic film properties for a 3GHz thin film inductor

    Microsoft Academic Search

    Terumitsu Tanaka; Yang-Ki Hong; Sung-Hoon Gee; Mun-Hyoun Park; Dustin W. Erickson; Chongwon Byun

    2004-01-01

    Thickness, resistivity, and the Gilbert damping constant are estimated using Maxwell and Landau-Lifshitz-Gilbert (LLG) equations to meet operating parameters of ferromagnetic thin film inductors in the gigahertz frequency range. The following properties of soft magnetic film are calculated to satisfy a quality factor of 10 at 3 GHz: 4?MS=21.3 kG; Hk=215 Oe; and ?dc'=100. The complex permeability was not influenced

  19. Photometric properties of resolved and unresolved magnetic elements

    E-print Network

    Serena Criscuoli; Mark Rast

    2008-12-09

    We investigate the photometric signature of magnetic flux tubes in the solar photosphere. We developed two dimensional, static numerical models of isolated and clustered magnetic flux tubes. We investigated the emergent intensity profiles at different lines-of-sight for various spatial resolutions and opacity models. We found that both geometric and photometric properties of bright magnetic features are determined not only by the physical properties of the tube and its surroundings, but also by the particularities of the observations, including the line/continuum formation height, the spatial resolution and the image analyses techniques applied. We show that some observational results presented in the literature can be interpreted by considering bright magnetic features to be clusters of smaller elements, rather than a monolithic flux tube.

  20. Adsorption-induced magnetic properties and metallic behavior of graphene

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Lv, H. F.; Xiao, Haiyan J.

    2009-09-21

    Magnetic properties and electronic structures of graphene with Cl, S, and P adsorption have been investigated using ab initio calculations. The adsorption of Cl leads to Fermi level shifting to valence band, which results in metallic graphene. A band gap of 0.6 eV emerges in a S-absorbed graphene, leading to the semiconducting graphene. The unpaired electrons in the absorbed P atom is polarized and thus, exhibits a magnetic moment of 0.86 ?B, while no magnetic moment has been observed after Cl and S adsorption. This demonstrates that the magnetic properties and conductive behavior of graphene can be modified via atom adsorption. Specially, P-absorbed graphene may be useful for spintronic applications, such as tunneling magnetoresistance.

  1. Magnetic, dielectric and complex impedance spectroscopic studies of nanocrystalline Cr substituted Li-ferrite

    NASA Astrophysics Data System (ADS)

    Hankare, P. P.; Patil, R. P.; Sankpal, U. B.; Garadkar, K. M.; Sasikala, R.; Tripathi, A. K.; Mulla, I. S.

    2010-09-01

    Nanocrystalline Li 0.5Fe 2.5- xCr xO 4 (2.5? x?0) ferrites were prepared by a sol-gel autocombustion route. X-ray diffraction was employed to confirm the cubic spinel phase formation of the ferrites. The lattice parameter decreases with increase in Cr content. The saturation magnetization, coercivity and remanance were studied as a function of Cr content. The dielectric constant and dielectric loss were measured as a function of frequency in the frequency range 20 Hz-1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. In order to understand the conduction mechanism, complex impedance measurements were carried out. The substitution of chromium plays an important role in changing the dielectric and magnetic properties of lithium ferrites.

  2. Investigation of structural, thermal and magnetic properties of cadmium substituted cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Venkata Reddy, Ch.; Byon, Chan; Narendra, B.; Baskar, D.; Srinivas, G.; Shim, Jaesool; Prabhakar Vattikuti, S. V.

    2015-06-01

    Cd substituted Cobalt ferrite nano particles are synthesis using co-precipitation method. The as prepared samples are calcinated at 300 and 600 °C respectively. The existence of single phase spinal cubic structure of the prepared ferrite material is confirmed by the powder XRD measurement. The surface morphology images, compositional features are studied by SEM with EDX, and TEM. From the FT-IR spectra the absorption bands observed at 595 and 402 cm-1 are attributed to vibrations of tetrahedral and octahedral complexes respectively. From the VSM data, parameters like magnetization, coercivity, remanent magnetization and remanent squareness are measured. The saturation magnetization value is increases with increasing calcination temperature. The DSC and TG-DTA curves reveal that the thermal stability of the prepared ferrite nanoparticles. The calcination temperature affects the crystallite size, morphology and magnetic properties of the samples.

  3. Basic magnetic properties of bituminous coal

    USGS Publications Warehouse

    Alexander, C.C.; Thorpe, A.N.; Senftle, F.E.

    1979-01-01

    Magnetic susceptibility and other static magnetic parameters have been measured on a number of bituminous coals from various locations in the United States. The paramagnetic Curie constant correlates negatively with carbon concentration on a moisture-free basis. The major contribution to the total paramagnetism comes from the mineral matter rather than from free radicals or broken bonds. Analysis of the data indicates that the specific paramagnetism is generally lower in the mineral matter found in high-ash compared to low-ash coal. A substantial number of the coal specimens tested also had a ferromagnetic susceptibility which appeared to be associated with magnetite. Magnetite and ??-iron spherules, possibly of meteoritic or volcanic origin, were found in several specimens. ?? 1979.

  4. The symmetry properties of planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Raedler, Karl-Heinz; Ness, Norman F.

    1990-01-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For earth, Jupiter, and Saturn, the centered dipole, quadrupole, and octupole contributions are included, while at Uranus only the dipole and quadrupole contributions are considered. It is found that there are a number of common features of the magnetic fields of earth and Jupiter. Compared to earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets.

  5. Properties of a novel magnetized alginate for magnetic resonance imaging.

    PubMed

    Shen, Feng; Poncet-Legrand, Celine; Somers, Sat; Slade, Andrea; Yip, Christopher; Duft, Andy M; Winnik, Françoise M; Chang, Patricia L

    2003-08-01

    Implanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once implanted, these microcapsules cannot be assessed without invasive surgery. We now report the preparation and characterization of a novel ferrofluid to render these microcapsules visible with magnetic resonance imaging (MRI). The ferrofluid was prepared as a colloidal iron oxide stabilized in water by alginate. The presence of iron particles in the ferrofluid was verified with chemical titration, dynamic light scattering, and magnetization measurement. The microcapsules fabricated with various concentrations of the ferrofluid in the core, or on the surface of alginate microcapsules, or both, all produced microcapsules with smooth surfaces as shown with light and scanning electron microscopy. However, at the nanoscale level, as revealed with atomic force microscopy, the ferrofluid-fabricated microcapsules demonstrated increased granularity, particularly when the ferrofluid was used to laminate the surface. From the force spectroscopy measurements, these modified microcapsules showed increasing surface rigidity in the following order: traditional alginate < ferrofluid in the core < ferrofluid on the surface. Although the mechanical stability of low-concentration ferrofluid (0.1%) microcapsules was reduced, increasing concentrations, up to 20%, were able to improve stability. When these ferrofluid microcapsules were examined with MRI, their T(2) relaxation time was reduced, thereby producing increased contrast readily detectable with MRI, whereas the traditional alginate microcapsules showed no difference when compared with water. In conclusion, such ferrofluid-enhanced alginate is suitable for fabricating microcapsules that offer the potential for in vivo tracking of implanted microcapsules without invasive surgery. PMID:12783484

  6. Structural and Magnetic Properties of Polypyrrole Nanocomposites

    Microsoft Academic Search

    R. Turcu; I. Peter; O. Pana; L. Giurgiu; N. Aldea; B. Barz; M. N. Grecu; A. Coldea

    2004-01-01

    We report the synthesis and characterization of conducting polymer nanocomposites based on polypyrrole(PPY)and Fe2O3magnetic particles. The global structure of PPY nanocomposites was obtained by X-ray Diffraction(XRD)method using a new approximation based on Generalized Fermi Function. The local structural parameters of Fe sites in Fe2O3nanocrystallites embedded in PPY were determined by X-ray Absorption Spectroscopy(EXAFS). The lack of hysteresis loop for the

  7. Sintered soft magnetic materials. Properties and applications

    Microsoft Academic Search

    J. A Bas; J. A Calero; M. J Dougan

    2003-01-01

    A comparison is presented of the characteristics and production requirements of a variety of materials used to produce sintered soft magnetic parts. These include pure iron, phosphorous–iron, silicon–iron, nickel–iron, and cobalt–iron, together with new coated materials based on encapsulated iron powders. In these bonded materials an organic and\\/or inorganic insulator is used to coat the metallic powder particles giving a

  8. Some Magnetic Properties of YTiFe Si C Carbides

    Microsoft Academic Search

    Corneliu-Bazil Cizmas; Lotfi Bessais; Catherine Djega-Mariadassou

    2008-01-01

    The effect of carbonation on the structure and the magnetic properties of polycrystalline YTiFe11-x Six (0 les x les 2) have been investigated by means of x-ray diffraction (XRD) at room temperature and magnetic measurements at low temperature. The alloys were prepared by typical induction melting and the carbonation was performed by solid-solid reaction. The cell volume of ThMn12 structure

  9. Transport and magnetic properties of BaVSe3

    Microsoft Academic Search

    Ana Akrap; Vladan Stevanovic; Mirta Herak; Marko Miljak; Neven Barisic; Helmuth Berger; László Forró

    2008-01-01

    We report a comprehensive study of transport, magnetotransport, and magnetic properties of single crystals of BaVSe3 . The paramagnetic metal-ferromagnetic metal transition at 43 K was followed as a function of pressure by measuring the electrical resistivity and the thermoelectric power. The exponent of the low-temperature power-law dependence of the resistivity increases with pressure. The effective magnetic moment obtained from

  10. Nonlinear optical properties of the magnetized QED Vacuum

    E-print Network

    J. T. Mendonca

    2007-04-12

    New processes associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics are described. We consider the presence of a static and a rotating magnetic field. The cases of harmonic generation and two different types of sideband cascades are considered. First order and second order effects with respect to the external magnetic field are discussed in detail. Possible experimental configurations using ultra-intense lasers are compared with the alternative use of cw lasers in stable optical cavities.

  11. Fe–FeO Nanocomposites: Preparation, Characterization and Magnetic Properties

    Microsoft Academic Search

    Jamshid Amighian; Morteza Mozaffari; Mehdi Gheisari

    \\u000a To date, nano-magnetic materials have gain great attention by the research community due to their importance for future applications.\\u000a A brief introduction of Fe–FeO nanocomposites in the form of particles and thin films is given in the first part of this chapter.\\u000a This includes definition, magnetic properties, preparation, structure and applications. Different preparation methods of Fe–FeO\\u000a are then introduced in

  12. Optical and magnetic properties of a nonconjugated conducting polymer

    Microsoft Academic Search

    M. Thakur; B. S. Elman

    1989-01-01

    The magnetic and optical properties of a nonconjugated conducting polymer (1,4 cis-polyisoprene) at different doping levels of iodine are discussed in this report. The EPR and static magnetic susceptibility measurements show that cation radical (spin 1\\/2) species are generated as a consequence of doping. The concentration of the cation radicals increases approximately linearly with the dopant concentration until saturation. The

  13. Magnetic properties of aerosol synthesized Co-substituted spinel ferrites

    Microsoft Academic Search

    W. A. Kaczmarek; A. Calka; B. W. Ninham

    1993-01-01

    An aerosol technique and pyrolysis of a mixture of cobalt-nickel-zinc-magnesium and iron nitrates with a fixed stoichiometric composition are used to prepare submicron spherical particles of Co substituted ferrite powders with a spinel-type structure. The magnetic properties are studied using vibrating sample magnetometry (VSM) and ferrimagnetic resonance (FMR). Important parameters such as saturation magnetization, FMR linewidth, and spectroscopic splitting factor

  14. Morphology and properties of magnetic fractals

    NASA Astrophysics Data System (ADS)

    Günther, Bernd

    The inert-gas condensation (IGC) process offers a large variety in the synthesis of nano-particulate metals. In the present work the agglomeration of nickel nanoparticles is studied after evaporation/condensation of ingot material in a laminar Argon gas flow in the pressure range of 50-300 mbar. It is observed that the nickel nanoparticles tend to form large and loosely bound aggregates due to diffusional effects and attractive interparticle forces. A transition from an irregular type to a chain-like morphology is observed, which depends on particle size and can be formally described by a reduction in the fractal dimension. Such necklace-like chains could be deposited in a well-aligned manner in the presence of external magnetic fields. Numerical modeling of magnetically induced aggregation suggests that the interaction energy between the magnetic dipoles leads to chain-formation, if it overcomes the thermal energy of the individ-ual particles. In order to achieve well-defined conditions during extended agglomeration time, buoyancy effects must be suppressed, which usually exist due to strong thermal gradients inside the flow tube chamber. Therefore experiments on parabolic flights were performed to sample agglomerates that were unaffected by convection for up to 10s.

  15. Magnetic properties of NdFeB-coated rubberwood composites

    NASA Astrophysics Data System (ADS)

    Noodam, Jureeporn; Sirisathitkul, Chitnarong; Matan, Nirundorn; Rattanasakulthong, Watcharee; Jantaratana, Pongsakorn

    2013-01-01

    Magnetic properties of composites prepared by coating lacquer containing neodymium iron boron (Nd-Fe-B) powders on rubberwood were characterized by vibrating sample magnetometry (VSM), magnetic moment measurements, and attraction tests with an iron-core solenoid. The Nd-Fe-B powders were recycled from electronic wastes by the ball-milling technique. Varying the milling time from 20 to 300 min, the magnetic squareness and the coercive field of the Nd-Fe-B powders were at the minimum when the powders were milled for 130 min. It followed that the coercive field of the magnetic wood composites was increased with the milling time increasing from 130 to 300 min. For the magnetic wood composites using Nd-Fe-B obtained from the same milling time, the magnetic squareness and the coercive field were rather insensitive to the variation of Nd-Fe-B concentration in coating lacquer from 0.43 to 1.00 g/cm3. By contrast, the magnetization and magnetic moment were increased with the Nd-Fe-B concentration increasing. Furthermore, the electrical current in the solenoid required for the attraction of the magnetic wood composites was exponentially reduced with the increase in the amount of Nd-Fe-B used in the coating.

  16. Growth, structure, morphology, and magnetic properties of Ni ferrite films

    PubMed Central

    2013-01-01

    The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

  17. Magnetic Behaviour of the Ferrimagnetic (1B\\/2,5\\/2,1\\/2) Linear Trimer in Complexes of Mn(hfac)2 with Bis and Trisnitroxide Radicals

    Microsoft Academic Search

    A. S. Markosyan; H. Iwamura; K. Inoue

    1999-01-01

    Characterisation and magnetic properties of new metal-radical complexes with bivalent Mn having a general formula {[Mn(hfac)2]m(R)n} are given. In these complexes, the aminoxyl radicals have magnetic, triplet or quartet, ground state and form with Mn heterospin structures. They show 1D, 2D and 3D behaviour depending on the crystal structure, chemical formula and molecular structure of radical. In the ordered state,

  18. Improvements of magnetic properties of Sr ferrite magnets by substitutions of La and Co

    SciTech Connect

    Ogata, Yasunobu; Kubota, Yutaka; Takami, Takashi; Tokunaga, Masaaki; Shinohara, Tadashi

    1999-09-01

    Recently, it is intensively required to improve the magnetic properties of Sr ferrite magnets in order to decrease the weight of motors used in automobiles and to improve the efficiency of motors used in electric appliances such as air conditioners. The effect of the simultaneous partial substitution of Co{sup 2+} for Fe{sup 3+} and of La{sup 3+} for Sr{sup 2+} ion in Sr ferrite on the magnetic properties of anisotropic Sr ferrite magnets was investigated. It was found that the coercive force of Sr ferrite magnets is increased without significant decrease in residual flux density by La-Co substitution. Temperature coefficients of coercive force were found to be also improved by La-Co substitution.

  19. Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation

    NASA Astrophysics Data System (ADS)

    Volkov, N. V.; Eremin, E. V.; Tarasov, A. S.; Rautskii, M. V.; Varnakov, S. N.; Ovchinnikov, S. G.; Patrin, G. S.

    2012-10-01

    Different phenomena that give rise to a spin-polarized current in some systems with magnetic tunnel junctions are considered. In a manganite-based magnetic tunnel structure in CIP geometry, the effect of current-channel switching was observed, which causes bias-driven magnetoresistance, rf rectification, and the photoelectric effect. The second system under study, ferromagnetic/insulator/semiconductor, exhibits the features of the transport properties in CIP geometry that are also related to the current-channel switching effect. The described properties can be controlled by a bias, a magnetic field, and optical radiation. At last, the third system under consideration is a cooperative assembly of magnetic tunnel junctions. This system exhibits tunnel magnetoresistance and the magnetic-field-driven microwave detection effect.

  20. Complex magnetic order in Pr?Pd?Ge?: a single crystal study.

    PubMed

    Anand, V K; Thamizhavel, A; Ramakrishnan, S; Hossain, Z

    2012-11-14

    We have investigated the magnetic and electronic transport properties of single crystal Pr(2)Pd(3)Ge(5) grown by the Czochralski method. Complex magnetic behaviour (multiple magnetic transitions) is clearly seen in this compound from the magnetic susceptibility ?(T), isothermal magnetization M(H) and electrical resistivity ?(T) data. For the magnetic field applied along the crystallographic c-axis (H ? [001]) the ?(T) data exhibit two sharp transitions at 6.9 and 6.3 K and a broad hump near 8 K. Four anomalies at 8.0, 7.3, 6.2 and 4.9 K are observed for the magnetic field along both a- and b-directions (H ? [100] and H ? [010]). Further, the ordered state ?(T) presents a large anisotropy with an easy axis along the c-axis. The presence of magnetocrystalline anisotropy is also inferred from the isothermal M(H) data. The M(H) data measured at 1.9 K for H ? [001] exhibit a step-like increase due to field-induced metamagnetic transitions at [Formula: see text] T and [Formula: see text] T. For H ? [100] and H ? [010] sharp step-like field-induced metamagnetic transitions occur at [Formula: see text] T and [Formula: see text] T which are accompanied by a weak S-shaped spin-flop metamagnetic transition at [Formula: see text] T. We have extracted the H-T phase diagram from the M(H) data collected at different temperatures in the magnetically ordered state which shows the existence of three magnetic phases below T(N) for H ? [100] and H ? [010], and two magnetic phases for H ? [001]. A sharp transition due to the onset of long range antiferromagnetic order is also seen in the ?(T) data which also exhibit anisotropic behaviour. The observation of an upturn near T(N) in the ?(T) data suggests the formation of a super-zone gap and hence the existence of incommensurate magnetic structure. Further, in the ordered state, the ?(T) data present a gap in the excitation spectrum of magnons with a characteristic energy gap ? ? 0.23 meV. PMID:23086193

  1. Low Temperature Crystal Structure and Magnetic Properties of RAl2

    SciTech Connect

    Pathak, Arjun K. [Ames Laboratory; Paudyal, Durga [Ames Laboratory; Gschneidner, Karl A. [Ames Laboratory; Pecharsky, Vitalij K. [Ames Laboratory

    2014-01-08

    Low temperature crystal structure and magnetic properties of RAl2 (R?=?Pr and Nd) have been studied using temperature dependent powder x-ray diffraction, magnetization, and heat capacity measurements. Unlike PrAl2, NdAl2 retains cubic MgCu2-type structure from room temperature down to 5?K, which is also confirmed from first principles electronic structure calculations. The magnetization measurements show both PrAl2 and NdAl2 order ferromagnetically at TC?=?32?K and 77?K, respectively. However, the magnetization measurements show the former is a hard ferromagnet compared to the latter which is a soft ferromagnetic material. The magnetic entropy change obtained from heat capacity measurements at ?H?=?30 kOe for PrAl2 and NdAl2 are 3.15?J?mol?1 K?1 and 1.18?J?mol?1 K?1, respectively.

  2. Chiral Properties of Strong Interactions in a Magnetic Background

    E-print Network

    Massimo D'Elia; Francesco Negro

    2011-04-18

    We investigate the chiral properties of QCD in presence of a magnetic background field and in the low temperature regime, by lattice numerical simulations of N_f = 2 QCD. We adopt a standard staggered discretization, with a pion mass around 200 MeV, and explore a range of magnetic fields (180 MeV)^2 \\leq|e|B \\leq (700 MeV)^2, in which we study magnetic catalysis, i.e. the increase of chiral symmetry breaking induced by the background field. We determine the dependence of the chiral condensate on the external field, compare our results with existing model predictions and show that a substantial contribution to magnetic catalysis comes from the modified distribution of non-Abelian gauge fields, induced by the magnetic field via dynamical quark loop effects.

  3. Structure, synthetic methods, magnetic properties and biomedical applications of ferrofluids.

    PubMed

    Shokrollahi, H

    2013-07-01

    This paper is aimed at conducting a survey of the synthetic methods and magnetic properties of nanoparticles as ferrofluids used in biomedicine. As compared with other works in the field, the distinctive feature of the current work is the systematic study of recent advances in ferrofluids utilized in hyperthermia and magnetic resonance imaging (MRI). The most important feature for application of ferrofluids is super-paramagnetic behavior of magnetic cores with relatively high saturation magnetization. Although Fe3O4 nanoparticles have traditionally been used in medicine; the modified Mn-ferrite has recently received special attention due to its higher saturation magnetization and r2-relaxivity as a contrast agent in MRI. Co-ferrite nanoparticles are also good candidates for hyperthermia treatment because of their high coercivity and magnetocrystalline anisotropy. The thermal decomposition and hydrothermal methods are good candidates for obtaining appropriate super-paramagnetic particles. PMID:23623058

  4. Properties of hyperonic matter in strong magnetic fields

    E-print Network

    P. Yue; F. Yang; H. Shen

    2009-02-21

    We study the effects of strong magnetic fields on the properties of hyperonic matter. We employ the relativistic mean field theory, which is known to provide excellent descriptions of nuclear matter and finite nuclei. The two additional hidden-strangeness mesons, $\\sigma^{\\ast}$ and $\\phi$, are taken into account, and some reasonable hyperon potentials are used to constrain the meson-hyperon couplings, which reflect the recent developments in hypernuclear physics. It is found that the effects of strong magnetic fields become significant only for magnetic field strength $B>5 \\times 10^{18}$ G. The threshold densities of hyperons can be significantly altered by strong magnetic fields. The presence of hyperons makes the equation of state (EOS) softer than that in the case without hyperons, and the softening of the EOS becomes less pronounced with increasing magnetic field strength.

  5. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John [Ames Laboratory

    2012-11-02

    GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd{sub 2}O{sub 3} W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

  6. Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

    PubMed Central

    Issa, Bashar; Obaidat, Ihab M.; Albiss, Borhan A.; Haik, Yousef

    2013-01-01

    Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 ?m), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents. PMID:24232575

  7. Tunable dynamic response of magnetic gels: impact of structural properties and magnetic fields

    E-print Network

    Mitsusuke Tarama; Peet Cremer; Dmitry Y. Borin; Stefan Odenbach; Hartmut Löwen; Andreas M. Menzel

    2014-09-24

    Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

  8. Magnetic properties and microstructure of Co-Cr bulk alloys

    NASA Astrophysics Data System (ADS)

    Chan, L. H.; Thomas, G.; Gau, J.-S.

    1989-04-01

    The effect of Cr addition on the microstructural changes and magnetic properties of bulk Co-Cr alloys has been investigated. Several interrelated microstructural and magnetic changes result from Cr additions. While Cr additions enhance the fcc phase retention and subsequently the fault density, they cause a decrease in grain size for a given thermal treatment. The addition also decrease saturation magnetization monotonically. Furthermore, the intrinsic coercivity is fairly insensitive to Cr additions for a given grain size and the coercivity increases with decreasing grain size.

  9. Magnetic Properties of Cd Substituted Ni-Cu Ferrites

    NASA Astrophysics Data System (ADS)

    Belavi, P. B.; Chavan, G. N.; Bammannavar, B. K.; Naik, L. R.; Kotnala, R. K.

    2011-07-01

    Cadmium substituted Ni-Cu Ferrites with the general formula Ni0.95-xCdxCu0.05Fe2O4 (x = 0.1, 0.2 and 0.3) were prepared by the standard double sintering ceramic method. The existences of single phase formation with crystalline size of 25-38 nm were confirmed from XRD measurements. The magnetic properties such as saturation magnetization (Ms) and Magnetic moment (?B) were studied by VSM analysis. The existence of multidomain (MD) particles in the samples was revealed from the small values of Mr/Ms.

  10. Optical, magnetic and electronic properties of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Guclu, A. Devrim

    2011-03-01

    We present a theory of optical, magnetic and electronic properties of graphene quantum dots. We demonstrate that there exists a class of triangular graphene quantum dots with zigzag edges [1-8] which combines magnetic, optical and transport properties in a single-material structure. These dots exhibit robust magnetic moment and optical transitions simultaneously in the THz, visible and UV spectral ranges due to the existence of a band of degenerate states lying at the Fermi level in the middle of the energy gap [1-6]. The magnetic and optical properties[5,7] are determined by strong electron-electron and excitonic interactions in the degenerate band, treated exactly using numerical techniques combining tight-binding, DFT, Hartree-Fock and configuration interactions methods. We show that the spin polarized degenerate band leads to quenching of the absorption spectrum at half-filling, while addition of a single electron fully depolarizes all electron spins and turns the absorption on. It is thus possible to design gate and size tunable graphene quantum dots with desired optical and magnetic properties for optoelectronic and photo-voltaic applications. Collaborators: P. Potasz, O. Voznyy, M. Korkusinski, and P. Hawrylak. The author thanks NRC-CNRS CRP, Canadian Institute for Advanced Research, Institute for Microstructural Sciences, and QuantumWorks for support.

  11. THE PROPERTIES OF HORIZONTAL MAGNETIC ELEMENTS IN QUIET SOLAR INTRANETWORK

    SciTech Connect

    Jin Chunlan; Wang Jingxiu; Zhou Guiping [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)], E-mail: jinchunlan@ourstar.bao.ac.cn, E-mail: wangjx@ourstar.bao.ac.cn, E-mail: gpzhou@ourstar.bao.ac.cn

    2009-05-20

    Using the data observed by the Solar Optical Telescope/Spectropolarimeter aboard the Hinode satellite, the horizontal and vertical fields are derived from the wavelength-integrated measures of Zeeman-induced linear and circular polarizations. The quiet intranetwork regions are pervaded by horizontal magnetic elements. We categorize the horizontal intranetwork magnetic elements into two types: one is the nonisolated element which is accompanied by the vertical magnetic elements during its evolution; another is the isolated element which is not accompanied by the vertical magnetic elements. Their properties, such as lifetime, size, and magnetic flux density, are studied, and the relationships among various magnetic parameters are investigated. We identify 446 horizontal intranetwork magnetic elements among them 87 elements are isolated and 359 are nonisolated. Quantitative measurements reveal that the isolated elements have relatively weaker horizontal magnetic fields, almost equal size, and shorter lifetime compared with the nonisolated elements. Most nonisolated horizontal intranetwork magnetic elements are identified to associate with the emergence of {omega}-shaped flux loops. A few nonisolated elements seem to indicate scenarios of submergence of {omega} loops or emergence of U-like loops. There is a positive correlation between the lifetime and the size for both the isolated and nonisolated horizontal intranetwork field elements (HIFs). Positive correlation between the lifetime and the magnetic flux density for nonisolated HIFs is also found, but no correlation for isolated HIFs. Even though the horizontal elements show lower magnetic flux density, they could carry the total magnetic flux in the order of magnitude close to 10{sup 25} Mx to the solar surface each day.

  12. Structural and magnetic properties of bulk MnBi permanent magnets

    NASA Astrophysics Data System (ADS)

    Zhang, D. T.; Cao, S.; Yue, M.; Liu, W. Q.; Zhang, J. X.; Qiang, Y.

    2011-04-01

    Structural and magnetic properties of bulk nanostructural Mn100-xBix (x = 40, 45, 52) permanent magnets prepared by spark plasma sintering technique were studied. The effect of the Mn/Bi ratio on the MnBi low temperature phase (LTP) formation and its magnetic properties were investigated. An increase of the bismuth amount in the magnets leads to better formation of LTP, resulting in the improvement of both magnetization (Ms) and remanence (Mr), but decreasing the coercivity (Hc) of the magnets. At room temperature, Ms increases from 27.87 emu/g for Mn60Bi40 to 45.31 emu/g for Mn48Bi52, whereas Hc decreases from 12 to 7.9 kOe. The microstructure of Mn48Bi52 magnet is composed of fine and uniform grains with an average size of 140 nm as shown in the TEM image. The Mn48Bi52 magnet shows a high Hc of 19 kOe at 423 K, indicating a strong positive temperature coefficient of coercivity for the MnBi magnet.

  13. Vibrational spectra, powder X-ray diffractions and physical properties of cyanide complexes with 1-ethylimidazole

    NASA Astrophysics Data System (ADS)

    Kürkçüo?lu, Güne? Süheyla; Kiraz, Fulya Çetinkaya; Say?n, Elvan

    2015-10-01

    The heteronuclear tetracyanonickelate(II) complexes of the type [M(etim)Ni(CN)4]n (hereafter, abbreviated as M-Ni-etim, M = Mn(II), Fe(II) or Co(II); etim = 1-ethylimidazole, C5H8N2) were prepared in powder form and characterized by FT-IR and Raman spectroscopy, powder X-ray diffraction (PXRD), thermal (TG; DTG and DTA), and elemental analysis techniques. The structures of these complexes were elucidated using vibrational spectra and powder X-ray diffraction patterns with the peak assignment to provide a better understanding of the structures. It is shown that the spectra are consistent with a proposed crystal structure for these compounds derived from powder X-ray diffraction measurements. Vibrational spectra of the complexes were presented and discussed with respect to the internal modes of both the etim and the cyanide ligands. The C, H and N analyses were carried out for all the complexes. Thermal behaviors of these complexes were followed using TG, DTG and DTA curves in the temperature range 30-700 °C in the static air atmosphere. The FT-IR, Raman spectra, thermal and powder X-ray analyses revealed no significant differences between the single crystal and powder forms. Additionally, electrical and magnetic properties of the complexes were investigated. The FT-IR and Raman spectroscopy, PXRD, thermal and elemental analyses results propose that these complexes are similar in structure to the Hofmann-type complexes.

  14. Structure, Transport Properties, and Magnetism of Artificially-Structured Materials

    Microsoft Academic Search

    John Q. Xiao

    1993-01-01

    Structural, magnetic, and magneto-transport properties of three different classes of artificially structured materials: (1) multilayers (Fe(110)\\/Ag(111) and Fe(110)\\/W(110)), (2) Fe-nitrides, and (3) metallic granular solids (Co\\/Ag, Co\\/Cu Fe\\/Ag and (Ni-Fe)\\/Ag), prepared by magnetron sputtering are presented. In the multilayers, the structure has been characterized using both low-angle and high-angle x-ray diffraction together with theoretical modeling. The magnetic properties of the

  15. Temporal properties of dynamic processes on complex networks

    NASA Astrophysics Data System (ADS)

    Turalska, Malgorzata A.

    Many social, biological and technological systems can be viewed as complex networks with a large number of interacting components. However despite recent advancements in network theory, a satisfactory description of dynamic processes arising in such cooperative systems is a subject of ongoing research. In this dissertation the emergence of dynamical complexity in networks of interacting stochastic oscillators is investigated. In particular I demonstrate that networks of two and three state stochastic oscillators present a second-order phase transition with respect to the strength of coupling between individual units. I show that at the critical point fluctuations of the global order parameter are characterized by an inverse-power law distribution and I assess their renewal properties. Additionally, I study the effect that different types of perturbation have on dynamical properties of the model. I discuss the relevance of those observations for the transmission of information between complex systems.

  16. Magnetic Properties of Nanoferrites Near Ferromagnetic Resonance in Millimeter Waves

    Microsoft Academic Search

    Konstantin A. Korolev; Mohammed N. Afsar

    2011-01-01

    Complex magnetic permeability and dielectric permittivity of nano-sized pure powdered and solid diluted barium and strontium ferrites have been studied in a broadband millimeter wave frequency range for the first time. Transmittance measurements have been performed using a free space quasi-optical millimeter wave spectrometer, equipped with a set of high power backward wave oscillators. Backward wave oscillators have been used

  17. Microstructural origin of soft magnetic properties of sendust films prepared by N2 reactive sputtering

    E-print Network

    Laughlin, David E.

    , and 5 wt % Al is a well known soft magnetic material. Usually soft magnetic properties in sendust alloyMicrostructural origin of soft magnetic properties of sendust films prepared by N2 reactive in a mixture of Ar and N2 gas. The soft magnetic properties of the sendust films were, in general, improved

  18. Effect of shock on the magnetic properties of pyrrhotite, the Martian crust, and meteorites

    E-print Network

    Stewart, Sarah T.

    Effect of shock on the magnetic properties of pyrrhotite, the Martian crust, and meteorites Karin L changes in magnetic properties include increasing saturation isothermal remanent magnetization, bulk: Louzada, K. L., S. T. Stewart, and B. P. Weiss (2007), Effect of shock on the magnetic properties

  19. Connecting disorder and magnetic properties in CoFe thin films J. W. Freeland

    E-print Network

    Idzerda, Yves

    Connecting disorder and magnetic properties in CoFe thin films J. W. Freeland Experimental disorder in conjunction with magnetic property measurements, evidence is presented that the grain size' magnetic properties. This is complicated even further with the realization that chemical and magnetic

  20. Characterization of Magnetic Viral Complexes for Targeted Delivery in Oncology

    PubMed Central

    Almstätter, Isabella; Mykhaylyk, Olga; Settles, Marcus; Altomonte, Jennifer; Aichler, Michaela; Walch, Axel; Rummeny, Ernst J.; Ebert, Oliver; Plank, Christian; Braren, Rickmer

    2015-01-01

    Oncolytic viruses are promising new agents in cancer therapy. Success of tumor lysis is often hampered by low intra-tumoral titers due to a strong anti-viral host immune response and insufficient tumor targeting. Previous work on the co-assembly of oncolytic virus particles (VPs) with magnetic nanoparticles (MNPs) was shown to provide shielding from inactivating immune response and improve targeting by external field gradients. In addition, MNPs are detected by magnet resonance imaging (MRI) enabling non-invasive therapy monitoring. In this study two selected core-shell type iron oxide MNPs were assembled with adenovirus (Ad) or vesicular stomatitis virus (VSV). The selected MNPs were characterized by high r2 and r2* relaxivities and thus could be quantified non-invasively by 1.5 and 3.0 tesla MRI with a detection limit below 0.001 mM iron in tissue-mimicking phantoms. Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2* compared to free MNPs. The relaxivity changes could be attributed to the clusterization of particles and complexes shown by transmission electron microscopy (TEM). In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model. In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies. Furthermore, our study provides first evidence of the in vivo applicability of selected MNP-VPs in cancer therapy. PMID:25897333

  1. Theoretical studies on the electronic structure and properties of complex ceramic crystals and glasses

    SciTech Connect

    Ching, Wai-Yim.

    1991-01-24

    This progress report summarizes the accomplishment of the DOE-support research program at the University of Missouri-Kansas City for the period July 1, 1991--June 30, 1992. This is the second year of a three-year renewal. The major accomplishments for the year are: (a) Initiation of fundamental studies on the electronic properties of C{sub 60} and related crystals; (b) study of electronic structures and optical properties of several important ceramic crystals, especially on AlN, SiO{sub 2} and Al{sub 2}O{sub 3}; (c) first-principles calculation of total energies and structural phase transitions in oxides, nitrides, and borides; (d) theory of magnetism in Nd{sub 2}Fe{sub 14}B permanent magnetic alloy. The major focus for the next year's effort will be on the following areas: (1) Continuation of the fundamental studies on the buckminsterfullerene system with particular emphasis on the alkali-doped superconducting fullerides. (2) Fundamental studies on the structure and properties of Boron and B-related compounds. (3) Basic studies on the structural and electronic properties of metallic glasses with particular emphasis on the magnetic glasses. (4) Further development of the first-principles OLCAO method for applications to super-complex systems.

  2. The effect of titanium on microstructure and magnetic properties of Fe-Cr-Co hard magnetic materials

    Microsoft Academic Search

    S. Sugimoto; M. Okada; Y. Ohtani; T. Tanaka; M. Homma

    1985-01-01

    Fe-Cr-Co ductile alloys produce magnetic properties comparable to those of Alnico permanent magnets family, up to (BH)max=91.2 kJ\\/m3(11.4 MGOe). It is technologically known that the addition of Ti to the Fe-Cr-Co alloys extends the ?-phase region of system and improves the magnetic properties. The purpose of this work is to study the effect of Ti on microstructures and magnetic properties

  3. Synthesis of metal-Bis(N-(3-ethylphenyl)-pyridine-2-acetyl-hydrazine complexes and evaluation of their magnetic and antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Singh, Jagvir; Kumari, Kamelesh; Singh, Prashant; Mehrotra, Gopal K.; Singh, Netra Pal

    2012-07-01

    Manganese (II), Cobalt (II), Nickel (II) and Copper (II) complexes, having the general composition [M(L)2X2], have been synthesized [where L= Bis(N-(3-ethylphenyl)-pyridine-2-acetyl-hydrazine (L), and X = Cl-] and have been characterized by elemental analysis, molar conductance, magnetic moments, FTIR, 1H & 13C NHR and UV/visible studies. The possible geometries of the complexes were assigned on the basis of electronic magnetic and infrared spectral studies. Molar conductance values of these complexes show non electrolytic natures. The ligand, as well as their complexes, also shows the significant antimicrobial properties.

  4. Estimation of hydrothermal deposits location from magnetization distribution and magnetic properties in the North Fiji Basin

    NASA Astrophysics Data System (ADS)

    Choi, S.; Kim, C.; Park, C.; Kim, H.

    2013-12-01

    The North Fiji Basin is belong to one of the youngest basins of back-arc basins in the southwest Pacific (from 12 Ma ago). We performed the marine magnetic and the bathymetry survey in the North Fiji Basin for finding the submarine hydrothermal deposits in April 2012. We acquired magnetic and bathymetry datasets by using Multi-Beam Echo Sounder EM120 (Kongsberg Co.) and Overhouser Proton Magnetometer SeaSPY (Marine Magnetics Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly, reduce to the pole(RTP), analytic signal and magnetization. The study areas composed of the two areas(KF-1(longitude : 173.5 ~ 173.7 and latitude : -16.2 ~ -16.5) and KF-3(longitude : 173.4 ~ 173.6 and latitude : -18.7 ~ -19.1)) in Central Spreading Ridge(CSR) and one area(KF-2(longitude : 173.7 ~ 174 and latitude : -16.8 ~ -17.2)) in Triple Junction(TJ). The seabed topography of KF-1 existed thin horst in two grabens that trends NW-SE direction. The magnetic properties of KF-1 showed high magnetic anomalies in center part and magnetic lineament structure of trending E-W direction. In the magnetization distribution of KF-1, the low magnetization zone matches well with a strong analytic signal in the northeastern part. KF-2 area has TJ. The seabed topography formed like Y-shape and showed a high feature in the center of TJ. The magnetic properties of KF-2 displayed high magnetic anomalies in N-S spreading ridge center and northwestern part. In the magnetization distribution of KF-2, the low magnetization zone matches well with a strong analytic signal in the northeastern part. The seabed topography of KF-3 presented a flat and high topography like dome structure at center axis and some seamounts scattered around the axis. The magnetic properties of KF-3 showed high magnetic anomalies in N-S spreading ridge center part. In the magnetization of KF-2, the low magnetization zone mismatches to strong analytic signal in this area. The difference of KF-3 between the low magnetization zones and the analytic signals is considered that the submarine magnetic strength of KF-3 is lower than that of KF-1 and KF-2. The spreading ridges of the study areas showed common Central Anomaly Magnetization Highs (CAMH). As a whole, the previous studies on the structure of this study area (Auzende et al, 1990) support our results of the magnetic properties (Magnetic Anomaly and RTP). We can expect to have the better results by comparing with the other study like geophysics (seismic), geology, and geochemistry in this area. Reference Auzende, J.M., and 29 others, Active Spreading and Hydrothermalism in North Fiji Basin(SW Pacific). Results of Japanese French Cruise Kaiyo 87, Marine Geophysical Researches., 12, 269-283, 1990.

  5. Mobile testing complex based on an explosive magnetic generator

    NASA Astrophysics Data System (ADS)

    Shurupov, A. V.; Kozlov, A. V.; Gusev, A. N.; Shurupova, N. P.; Zavalova, V. E.; Chulkov, A. N.; Bazelyan, E. M.

    2015-01-01

    A mobile testing complex prototype on the basis of an explosive magnetic generator (MTC EMG) is developed to simulate a lightning current pulse. The main element of this complex is a current pulse generator comprising a EMG with a pulse transformer for energy release into the load. The electric chain of the MTC EMG is theoretically analyzed taking into consideration energy losses in active resistances in the primary circuit of the transformer and the inductive-resistive nature of the load, which resulted in the minimization of energy losses in the primary circuit depending on the electric chain parameters. It was found that, if the energy losses are minimized, the efficiency of transferring the EMG energy into the load exceeds 50%. As a result of the field tests of the MTC EMG, its basic characteristics were determined and the waveforms of the current pulses and voltages in the load were obtained. It is shown that the results of the mathematical simulation of current pulses in the load are in good agreement with the experimental data.

  6. Effects of Hydrostatic Pressure on the Properties of Magnetic Materials

    Microsoft Academic Search

    R. E. Alley; V. E. Legg

    1960-01-01

    A review of the literature on hydrostatic pressure effects on magnetic materials showed a lack of information on technologically important properties such as initial permeability, and the hysteresis loop. Measurements of these properties up to 20000 psi showed that most solid materials are only slightly affected. These include tape cores of supermalloy, supermendur, 4–79 Mo-permalloy and grain-oriented Si-steel, as well

  7. Magnetic properties of xenoliths from Yakut kimberlite pipes

    NASA Astrophysics Data System (ADS)

    Tselebrovskiy, Alexey; Maksimochkin, Valeriy

    2014-05-01

    Lower continental crust is poorly known due to its limited availability. One source of information about the formation of the lower crust is the study of xenoliths found in kimberlites, mainly peridotites, eclogites and other rocks made by the kimberlite magma to the surface from great depths. Magnetic methods can solve problems related on the one hand, the definition of the phase composition of natural ferrimagnetics responsible for the magnetic properties of rocks, and on the other - with the establishment of the thermodynamic conditions in which they were formed - their genesis. For example, in [1, 2], there were differences in the magnetic properties of kimberlites taken from tubes with different diamond productivity. In this work, studies have been conducted of the magnetic properties and mineralogy of xenoliths from 10 Yakut kimberlit pipes, courtesy of Doctor of Geological and Mineralogical Sciences V. K. Garanin. Found that the natural remanent magnetization (NRM) and magnetic susceptibility (k0) of the investigated samples varies widely: NRM = (0.002-12.59) A/m, k0 = (0.23-59.9)*10-3 SI. Magnetic properties vary by species: average NRM peridotites (0.002-0.32) A/m order of magnitude smaller eclogitic rocks (0.58-12.59) A/m. Thermomagnetic analysis (TMA) of the test samples showed the presence of xenoliths of the ferromagnetic phase with a Curie point close to Tc magnetite. Because of the high correlation between the values of NRM, k0 and ferrimagnetic saturation magnetization (SM) can be inferred that the magnetic properties of the rocks studied at temperatures above ambient is basically determined by the concentration of magnetite in them. Besides magnetite TMA were also identified ferrimagnetic phase with Curie temperatures from -50°C to -125°C. Mineralogical analysis performed on three samples of peridotite tubes Udachnaya, Yubileynaya and Mir and two samples of eclogite tubes Udachnaya and Komsomolskaya, showed that at temperatures below room temperature magnetic properties of peridotites due ferrishpineles with high content of chromium, titanium and aluminum; eclogitic rocks - due hemoilmenites. Among the studied xenoliths, peridotites from the tubes with high diamond productivity (Udachnaya, Mir, Yubileynaya) are characterized by low values of NRM, k0, SM and high paramagnetic contribution. We conclude that the concentration of magnetite in them is very small, and the magnetic properties peridotite above room temperature are determined mainly paramagnetic minerals. This work was supported by RFBR grant No. 11-05-00740. Literature: 1. V.I. Truhin, V.A. Zhilyaeva, N.N. Zinchuk, N.N. Romanov. Kimberlites and traps magnetism. M.MGU. 1989. p. 165 (Russian) 2. V.I. Maksimochkin, V.I. Truhin, Y.A. Minina. Magnetic properties and mineralogy of Botswana kimberlites. Physics of the Earth, 2013, No. 2, p. 143-160 (Russian)

  8. Wide-band complex magnetic susceptibility measurements of magnetic fluids as a function of temperature

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Kinsella, L.; Charles, S. W.

    1999-07-01

    Measurements of the complex magnetic susceptibility over the frequency and temperature ranges of 2 MHz-6 GHz and 20 to -100°C, respectively, are reported for the first time for a magnetic fluid. The fluid used was a colloidal suspension of magnetite particles of median diameter 9 nm in a hydrocarbon oil (isopar m). Resonance was observed and found to increase from approx 1.5 GHz to 3.3 GHz in the temperature range 20 to -50°C. The increase in resonant frequency is attributed to a decrease in thermal fluctuations with decrease in temperature. At frequencies below approximately 19 MHz, a significant drop in ?'( ?) with decrease in temperature over the temperature range 20 to -100°C, is observed and is attributed to the changes in the Néel and Brownian relaxation processes. Below -60°C, the temperature at which the suspension becomes solid, Brownian relaxation ceases to exist.

  9. Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders

    NASA Astrophysics Data System (ADS)

    Zamanpour, Mehdi; Bennett, Steven; Taheri, Parisa; Chen, Yajie; Harris, Vincent G.

    2014-05-01

    CoxC magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co2C and Co3C phases possessing magnetization values exceeding 45 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of CoxC, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co2C and Co3C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the CoxC nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

  10. Magnetic properties and scale-up of nanostructured cobalt carbide permanent magnetic powders

    SciTech Connect

    Zamanpour, Mehdi, E-mail: zamanpour.m@husky.neu.edu; Bennett, Steven; Taheri, Parisa; Chen, Yajie [Center for Microwave Magnetic Materials and Integrated Circuits, Northeastern University, Boston, Massachusetts 02115 (United States); Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, Northeastern University, Boston, Massachusetts 02115 (United States); Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2014-05-07

    Co{sub x}C magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co{sub 2}C and Co{sub 3}C phases possessing magnetization values exceeding 45?emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of surfactants, reaction temperature, and reaction duration on the crystallographic structure and magnetic properties of Co{sub x}C, while tetraethylene glycol was employed as a reducing agent. The role of the ratios of Co{sub 2}C and Co{sub 3}C phases in the admixture magnetic properties is discussed. The crystallographic structure and particle size of the Co{sub x}C nanoparticles were characterized by X-ray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 g per batch was demonstrated with no significant degradation of magnetic properties.

  11. Magnetic properties of Co nanopillar arrays prepared from alumina templates.

    PubMed

    Vivas, L G; Ivanov, Yu P; Trabada, D G; Proenca, M P; Chubykalo-Fesenko, O; Vázquez, M

    2013-03-15

    The preparation of magnetic nanopillars from anodic alumina templates represents a cheap way to obtain extensive ordered arrays, and thus is very appealing for nanotechnology applications. In this paper we report the preparation of arrays of Co nanopillars with 120 nm height and varying diameter. The high anisotropy of Co offers an additional possibility to control their magnetic properties. The magnetic properties of arrays of Co nanopillars are studied both experimentally and by micromagnetic simulations. Experiment and modeling show crucial changes of hysteresis loops when the diameter is increased. Magnetic data are interpreted considering the change of crystalline structure as well as the influence of geometry. The micromagnetic simulations explain the measured magnetic properties by the role of magnetocrystalline anisotropy and the combined influence of the shape anisotropy and the interactions. They also show the change in the reversal mode with the increased diameter from vortex propagation to curling when the field is applied parallel to the nanopillar axis, and from coherent rotation to curling when it is applied perpendicular. PMID:23416958

  12. 1H NMR study of the magnetic properties and electronic structure of the hydroxide complex of substrate-bound heme oxygenase from Neisseria meningitidis; Influence of the axial water deprotonation on the distal H-bond network

    PubMed Central

    Ma, Li-Hua; Liu, Yangzhong; Zhang, Xuhang; Yoshida, Tadashi; La Mar, Gerd N.

    2008-01-01

    The substrate and active site residues of the low-spin hydroxide complex of the protohemin complex Neisseria meningitidis heme oxygenase, HO, NmHO, have been assigned by saturation transfer between the hydroxide and previously characterized aquo complex. The available dipolar shifts allowed the quantitation of both the orientation and anisotropy of the paramagnetic susceptibility tensor. The resulting positive sign, and reduced magnitude of the axial anisotropy relative to the cyanide complex, dictate that the orbital ground state is the conventional ‘d?’ (dxy 2(dxz, dyz)3); and not the unusual ‘dxy’ (dxz 2dyz 2dxy) orbital ground state reported for the hydroxide complex of the homologous heme oxygenase from Pseudomonas aeruginosa, (Caignan, G., Deshmukh, R., Zeng, Y., Wilks, A., Bunce, R.A., Rivera, M.; J. Am. Chem. Soc. 125, 11842-11852) and proposed as a signature of the HO distal cavity. The conservation of slow labile proton exchange with solvent from pH 7.0 to 10.8 confirms the extraordinary dynamic stability of NmHO complexes. Comparison of the diamagnetic contribution to the labile proton chemical shifts in the aquo and hydroxide complexes reveals strongly conserved bond strengths in the distal H-bond network, with the exception of the distal His53 N?1H. The iron-ligated water is linked to His53 primarily by a pair of non-ligated, ordered water molecules which transmit the conversion of the ligated H-bond donor (H2O) to a H-bond acceptor (OH-), thereby increasing the H-bond donor strength of the His53 side chain. PMID:16704267

  13. GEMAS: Mineral magnetic properties of European agricultural soils

    NASA Astrophysics Data System (ADS)

    Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Fabian, Karl; Nourgaliev, Danis; Reimann, Clemens

    2015-04-01

    The GEMAS survey of European agricultural soil provides a unique opportunity to create the first comprehensive overview of mineral magnetic properties in agricultural soil on a continental scale. Samples from the upper 20 cm were taken in large agricultural fields (Ap-sample) at a density of 1 site/2500 km2. After air drying and sieving to < 2 mm, low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k was measured on 2500 samples using a Bartington MS2B sensor to obtain frequency dependence of magnetic susceptibility kfd. Hysteresis properties are determined using a J coercivity spectrometer, built in the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T, taking approximately 15 minutes. This allows to measure a wide range of magnetic parameters for large sample collections. Because the GEMAS geochemical atlas provides a comprehensive set of geochemical measurements characterizing the individual soil samples, the new data allow to study magnetic parameters in relation to chemical and geological parameters. The results show a clear large scale spatial distribution with e.g. broad distinct lows of k over sandy sediments of the last glaciation in central northern Europe and other sedimentary basins. More localized positive k anomalies occur near young volcanism, or old basalts exposed on the surface. On the other hand, frequency dependence of k displays a much more scattered behavior, indicating either high noise level, or large local variability. Clearly distinguishable, small-scale patterns in the randomized data set indicate that the latter is more likely. This indicates that local influences on soil magnetic properties, including anthropogenic effects, may be easier detected by frequency dependence than by k itself, which is largely controlled by geological and climatic background variability. Mapping the isothermal mineral magnetic properties shows again a clear relation to large scale European geology. Thereby, the GEMAS data set of magnetic parameters provides a continent wide reference of the natural background in Ap soil. For the first time the geological background variability of magnetic minerals for national and local soil studies is defined at the European scale.

  14. Magnetism in Complex Oxides Probed by Magnetocaloric Effect and Transverse Susceptibility

    NASA Astrophysics Data System (ADS)

    Bingham, Nicholas S.

    Magnetic oxides exhibit rich complexity in their fundamental physical properties determined by the intricate interplay between structural, electronic and magnetic degrees of freedom. The common themes that are often present in these systems are the phase coexistence, strong magnetostructural coupling, and possible spin frustration induced by lattice geometry. While a complete understanding of the ground state magnetic properties and cooperative phenomena in this class of compounds is key to manipulating their functionality for applications, it remains among the most challenging problems facing condensed-matter physics today. To address these outstanding issues, it is essential to employ experimental methods that allow for detailed investigations of the temperature and magnetic field response of the different phases. In this PhD dissertation, I will demonstrate the relatively unconventional experimental methods of magnetocaloric effect (MCE) and radio-frequency transverse susceptibility (TS) as powerful probes of multiple magnetic transitions, glassy phenomena, and ground state magnetic properties in a large class of complex magnetic oxides, including La0.7Ca0.3- xSrxMnO3 (x = 0, 0.05, 0.1, 0.2 and 0.25), Pr0.5Sr0.5MnO3, Pr1-xSrxCoO 3 (x = 0.3, 0.35, 0.4 and 0.5), La5/8- xPrxCa3/8MnO3 (x = 0.275 and 0.375), and Ca3Co2O 6. First, the influences of strain and grain boundaries, via chemical substitution and reduced dimensionality, were studied via MCE in La0.7Ca 0.3-xSrxMnO 3. Polycrystalline, single crystalline, and thin-film La0.7Ca 0.3-xSrxMnO 3 samples show a paramagnetic to ferromagnetic transition at a wide variety of temperatures as well as an observed change in the fundamental nature of the transition (i.e. first-order magnetic transition to second order magnetic transition) that is dependent on the chemical concentration and dimensionality. Systematic TS and MCE experiments on Pr0.5Sr0.5MnO 3 and Pr0.5Sr0.5CoO3 have uncovered the different nature of low-temperature magnetic phases and demonstrate the importance of coupled structural/magnetocrystalline anisotropy in these half-doped perovskite systems. These findings point to the existence of a distinct class of phenomena in transition-metal oxide materials due to the unique interplay between structure and magnetic anisotropy, and provide evidence for the interplay of spin and orbital order as the origin of intrinsic phase separation in manganites. While Pr0.5Sr0.5MnO3 provides important insights into the influence of first- and second-order transitions on the MCE and refrigerant capacity (RC) in a single material, giving a good guidance on the development of magnetocaloric materials for active magnetic refrigeration, Pr1-xSrxCoO 3 provides an excellent system for determining the structural entropy change and its contribution to the MCE in magnetocaloric materials. We have demonstrated that the structural entropy contributes significantly to the total entropy change and the structurally coupled magnetocrystalline anisotropy plays a crucial role in tailoring the magnetocaloric properties for active magnetic refrigeration technology. In the case of La5/8-xPr xCa3/8MnO3, whose bulk form is comprised of micron-sized regions of ferromagnetic (FM), paramagnetic (PM), and charge-ordered (CO) phases, TS and MCE experiments have evidenced the dominance of low-temperature FM and high-temperature CO phases. The "dynamic" strain liquid state is strongly dependent on magnetic field, while the "frozen" strain-glass state is almost magnetic field independent. The sharp changes in the magnetization, electrical resistivity, and magnetic entropy just below the Curie temperature occur via the growth of FM domains already present in the material, even in zero magnetic field. The subtle balance of coexisting phases and kinetic arrest are also probed by MCE and TS experiments, leading to a new and more comprehensive magnetic phase diagram. A geometrically frustrated spin chain compound Ca3Co 2O6 provides an interesting case study for understanding the cooperative pheno

  15. Peculiarities in the magnetic, magnetoelectric, and magnetoelastic properties of SmFe 3 (BO 3 ) 4 multiferroic

    Microsoft Academic Search

    Yu. F. Popov; A. P. Pyatakov; A. M. Kadomtseva; G. P. Vorob’ev; A. K. Zvezdin; A. A. Mukhin; V. Yu. Ivanov; I. A. Gudim

    2010-01-01

    Results of a complex investigation of the magnetic, magnetoelectric, and magnetoelastic properties of a SmFe3(BO3)4 single crystal are presented. Samarium iron borate is similar to another easy-plane iron borate, NdFe3(BO3)4, in that it possesses a large value of the magnetic-field-induced polarization (about 500 ?C\\/m2), the sign of which changes when the field direction is changed between axes a and b

  16. Magnetic Magnetoelectric and Magnetoelastic Properties of new multiferroic material NdFe3(BO3)4

    Microsoft Academic Search

    A. M. Kadomtseva; A. V. Kuvardin; A. P. Pyatakov; A. K. Zvezdin; G. P. Vorob'ev; Yu. F. Popov; L. N. Bezmaternykh

    2006-01-01

    Complex experimental and theoretical study of the magnetic, magnetoelectric, and magnetoelastic properties of neodymium iron borate NdFe3(BO3)4 along various crystallographic directions have been carried out in strong pulsed magnetic fields up to 230 kOe in a temperature range of 4.2-50 K. It has been found that neodymium iron borate, as well as gadolinium iron borate, is a multiferroic. It has

  17. Peculiarities in the magnetic, magnetoelectric, and magnetoelastic properties of SmFe3(BO3)4 multiferroic

    Microsoft Academic Search

    Yu. F. Popov; A. P. Pyatakov; A. M. Kadomtseva; G. P. Vorob'ev; A. K. Zvezdin; A. A. Mukhin; V. Yu. Ivanov; I. A. Gudim

    2010-01-01

    Results of a complex investigation of the magnetic, magnetoelectric, and magnetoelastic properties of a SmFe3(BO3)4 single crystal are presented. Samarium iron borate is similar to another easy-plane iron borate, NdFe3(BO3)4, in that it possesses a large value of the magnetic-field-induced polarization (about 500 muC\\/m2), the sign of which changes when the field direction is changed between axes a and b

  18. Growth, characterization and properties of ultrathin magnetic films and multilayers

    Microsoft Academic Search

    B. T. Jonker; J. P. Heremans; E. E. Marinero

    1989-01-01

    This book is a collection of invited and contributed papers presented at the Symposium on Growth, Characterization and Properties of Ultrathin Magnetic Films and Multilayers, held during the Spring Meeting of the Materials Research Society in San Diego, April 25-29, 1989. This symposium comprised 11 invited talks and 42 contributed papers, ran over 3 1\\/2 days, and provided a unique

  19. Characterization, electrical and magnetic properties of polyaniline\\/maghemite nanocomposites

    Microsoft Academic Search

    Panagiotis Dallas; Nikolaos Moutis; Eamonn Devlin; Dimitrios Niarchos; Dimitrios Petridis

    2006-01-01

    Composites of polyaniline with nanocrystalline maghemite capped with oleic acid were synthesized at various maghemite loadings and their electrical and magnetic properties were studied from 5 to 300 K. Chemisorption of oleic acid by the surface iron atoms provided excellent dispersion of maghemite in organic solvents and thus enabled their homogenous dispersion in the polymer matrix. The resulting nanocomposite materials

  20. Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications

    Microsoft Academic Search

    Matthew John Banholzer

    2010-01-01

    As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced

  1. Thursday, March 9 85 Magnetic Properties of Carbon Nanofoam PTh

    E-print Network

    Maruyama, Shigeo

    Thursday, March 9 85 Magnetic Properties of Carbon Nanofoam PTh 7D. Ar`eon, P. Cevc, Z. Jagli have been observed. NOVEL ROUTE TO (BIO)-POLYMER NANOTUBE COMPOSITES PTh 8A.I. Minett1 , J.N. Coleman2 OF VARIOUS (N, M) NANOTUBES BY CROSS- PTh 9POLARIZED ABSORPTION Yuhei Miyauchi, Mototeru Oba, and Shigeo

  2. Magnetic Properties of Single-Crystalline CoSi Nanowires

    E-print Network

    Kim, Bongsoo

    magnitude gets larger at lower temperatures. Transition metal monosilicides of Cr, Mn, Fe, and Co and solid and electrical transport properties.1 While MnSi shows low- temperature helimagnetic order,2 FeSi is a small solution alloys among them have a simple cubic B20 crystal structure and show a broad spectrum of magnetic

  3. Transport and magnetic properties of CMR manganites with antidot arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Du, Kai; Niu, Jiebin; Wei, Wengang; Chen, Jinjie; Yin, Lifeng; Shen, Jian

    2014-03-01

    We fabricated and characterized a series of manganites thin film samples with different densities of antidots. With increasing antidot density, the samples show higher MIT temperature and lower resistivity under zero and low magnetic fields. These differences become smaller and finally vanished when the magnetic field is large enough to melt the charge ordered phase in the system, which is expected in our theoretical explanations. We believe that emerging edge states at the ring of antidotes play a significant role for observed metal-insulator transition and electrical transport properties, which are of great importance of real storage and sensor device design. Magnetic property measurements and theoretical simulation also support the conclusion. These results open up new ways to control and tune the strongly correlated oxides without introduce any new material or field.

  4. Transport properties of graphene under periodic and quasiperiodic magnetic superlattices

    NASA Astrophysics Data System (ADS)

    Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen

    2013-08-01

    We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.

  5. Mechanical and hyperthermic properties of magnetic nanocomposites for biomedical applications.

    PubMed

    Kan-Dapaah, Kwabena; Rahbar, Nima; Tahlil, Abdullahi; Crosson, David; Yao, Nan; Soboyejo, Wole

    2015-09-01

    An understanding of the properties of multifunctional materials is important for the design of devices for biomedical applications. In this paper, a combination of experiments and models was used to study the mechanical and hyperthermic properties of magnetic nanoparticles (MNP)-filled PDMS composites for biomedical applications. These are studied as a function of the weight of MNP, ?-Fe2O3. The results showed the effects on mechanical behavior, and specific losses in a magnetic field. The measured Young's moduli are in good agreement with the moduli predicted from the Bergström-Boybce model. Specific losses calculated from magnetic measurements are used to predict the thermal dose under in-vivo conditions. The implications of the results were discussed for potential applications in biomedical devices. PMID:26005843

  6. Magnetic property improvement of niobium doped with rare earth elements

    NASA Astrophysics Data System (ADS)

    Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin

    2014-05-01

    A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

  7. Stable and color tunable emission properties based on non-cyclometalated gold(iii) complexes.

    PubMed

    Bachmann, Michael; Blacque, Olivier; Venkatesan, Koushik

    2015-05-19

    Stable and emission tunable non-cyclometalated gold(iii) triaryl complexes of the type [(L)Au(C6F5)3] [L = 2-(2,4-difluorophenylpyridine) (), 4-phenylpyridine (), 2-phenylpyridine (), 2-phenylisoquinoline (), 2-thienylpyridine ()] were synthesized starting from a common precursor complex [(THT)Au(C6F5)3] [THT = tetrahydrothiophene] in good to modest yields. Extensive characterization of the complexes by various nuclear magnetic resonance spectroscopy techniques and elemental analysis further corroborated the single-crystal X-ray diffraction studies. The complexes displayed room temperature phosphorescence in the neat solid and in 2-MeTHF at 77 K. Detailed photophysical investigations of the complexes in the neat solid and at 77 K revealed the successful tuning of the emission maxima with modest quantum yields across the visible part of the electromagnetic spectrum depending on the electronic properties of the heterocyclic ligands. DFT (Density Functional Theory) and TDDFT (Time Dependent Density Functional Theory) calculations were performed to discern the composition of the excited state as well as confirm the obtained relative emission energies upon substitution with electronically different ligands. The obtained diverse emissive behavior of the complexes combined with the ease of synthesis illustrate the generality and applicability of the design approach to obtain emissive gold(iii) complexes devoid of cyclometalation. PMID:25947068

  8. Magnetic properties of pulsed laser deposition-fabricated isotropic Fe-Pt film magnets

    SciTech Connect

    Nakano, M.; Oniki, W.; Yanai, T.; Fukunaga, H. [Faculty of Engineering, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521 (Japan)

    2011-04-01

    A high-speed pulsed laser deposition method with the deposition rate of several tens of microns per 1 h enabled us to obtain isotropic Fe-Pt thick film magnets. Increase in the laser power enabled us to obtain as-deposited films with L1{sub 0} ordered phase due to the heat radiation from a target, which means that a substrate heating system and a post-annealing process are not required to achieve hard magnetic properties in the process. Use of an Fe-rich target enhanced the magnetic properties, and as a result (BH){sub max} value exceeded 100 kJ/m{sup 3} in an isotropic Fe-Pt film fabricated at the power of 3 W, which was comparable to those of isotropic Fe-Pt thick film magnets prepared by a sputtering method.

  9. Magnetic properties prediction of NdFeB magnets by using support vector regression

    NASA Astrophysics Data System (ADS)

    Cheng, Wende

    2014-09-01

    A novel model using support vector regression (SVR) combined with particle swarm optimization (PSO) was employed to construct mathematical model for prediction of the magnetic properties of the NdFeB magnets. The leave-one-out cross-validation (LOOCV) test results strongly supports that the generalization ability of SVR is high enough. Predicted results show that the mean absolute percentage error for magnetic remanence Br, coercivity Hcj and maximum magnetic energy product (BH)max are 0.53%, 3.90%, 1.73%, and the correlation coefficient (R2) is as high as 0.839, 0.967 and 0.940, respectively. This investigation suggests that the PSO-SVR is not only an effective and practical method to simulate the properties of NdFeB, but also a powerful tool to optimatize designing or controlling the experimental process.

  10. Direct production of hard magnetic ribbons with enhanced magnetic properties by controlling cooling rate of melt

    NASA Astrophysics Data System (ADS)

    Zhou, Weifei; Chang, Chuntao; Inoue, Akihisa; Wang, Xinmin; Li, Fushan; Huo, Juntao

    2015-03-01

    We produced a high-quality hard magnetic Fe81Co2Nb1Nd10B6 alloy by melt spinning without additional treatment. The as-spun ribbons produced at a wheel speed of ˜25 m/s had the best hard magnetic properties: a remanence Br, coercive force Hc, and maximum energy product (BH)max of 0.97 T, 676 kA/m, and 140 kJ/m3, respectively. The Nd2Fe14B/?-Fe nanocomposite phases had grain sizes of ˜10-30 nm. We investigated how the magnetic properties changed with wheel speed, finding that they depended on the as-spun structure and magnetic structure, which changed upon over- and under-quenching from the melt.

  11. Micromagnetic modeling of the effects of stress on magnetic properties

    SciTech Connect

    Zhu, B.; Lo, C. C. H.; Lee, S. J.; Jiles, D. C.

    2001-06-01

    A micromagnetic model has been developed for investigating the effect of stress on the magnetic properties of thin films. This effect has been implemented by including the magnetoelastic energy term into the Landau{endash}Lifshitz{endash}Gilbert equation. Magnetization curves of a nickel film were calculated under both tensile and compressive stresses of various magnitudes applied along the field direction. The modeling results show that coercivity increased with increasing compressive stress while remanence decreased with increasing tensile stress. The results are in agreement with the experimental data in the literature and can be interpreted in terms of the effects of the applied stress on the irreversible rotation of magnetic moments during magnetization reversal under an applied field. {copyright} 2001 American Institute of Physics.

  12. Magnetic properties of a family of quinternary oxalates

    NASA Astrophysics Data System (ADS)

    Lhotel, E.; Simonet, V.; Ortloff, J.; Canals, B.; Paulsen, C.; Suard, E.; Hansen, T.; Price, D. J.; Wood, P. T.; Powell, A. K.; Ballou, R.

    2013-06-01

    We report on the magnetic properties of four isomorphous compounds of a family of quinternary oxalates down to 60 mK. In all these materials, the magnetic FeII ions with a strong magneto-crystalline anisotropy form a distorted kagome lattice, topologically equivalent to a perfect kagome one if nearest-neighbor interactions only are considered. All the compounds order at low temperature in an antiferromagnetic arrangement with magnetic moments at 120°. A remarkable magnetic behavior emerges below the Néel temperature in three compounds (with inter-kagome-layer Zr, Sn, Fe but not with Al): the spin anisotropy combined with a low exchange path network connectivity lead to domain walls intersecting the kagome planes through strings of free spins. These produce an unfamiliar slow spin dynamics in the ordered phase observed by AC susceptibility, evolving from exchange-released spin-flips towards a cooperative behavior on decreasing the temperature.

  13. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

    Gianakon, T.A.; Callen, J.D.; Hegna, C.C.

    1993-10-01

    This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.

  14. Small World Property of a Rock Joint(Complexity of Frictional Interfaces: A Complex Network Perspective)

    Microsoft Academic Search

    Hamed O. Ghaffari; M. Sharifzadeh; E. Evgin

    2010-01-01

    The shear strength and stick-slip behavior of a rough rock joint are analyzed using the complex network approach. We develop a network approach on correlation patterns of void spaces of an evolvable rough fracture (crack type II). Correlation among networks properties with the hydro -mechanical attributes (obtained from experimental tests) of fracture before and after slip is the direct result

  15. Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Zhang, Xue-Mei; Cui, Long; Deng, Ke; Zeng, Qing-Dao; Zuo, Jing-Lin

    2014-08-01

    Self-assembly of functional compounds into a prerequisite nanostructure with desirable dimension and morphology by controlling and optimizing intermolecular interaction attracts an extensive research interest for chemists and material scientist. In this work, a new triple-decker sandwich-type lanthanide complex with phthalocyanine and redox-active Schiff base ligand including tetrathiafulvalene (TTF) units has been synthesized, and characterized by single crystal X-ray diffraction analysis, absorption spectra, electrochemical and magnetic measurements. Interestingly, the non-centrosymmetric target complex displays a bias dependent selective adsorption on a solid surface, as observed by scanning tunneling microscopy (STM) at the single molecule level. Density function theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular assemblies, and show that such electrical field dependent selective adsorption is regulated by the interaction between the external electric field and intrinsic molecular properties. Our results suggest that this type of multi-decker complex involving TTF units shows intriguing multifunctional properties from the viewpoint of structure, electric and magnetic behaviors, and fabrication through self-assembly.

  16. Three-dimensional Magnetostriction and Vector Magnetic Properties under Alternating Magnetic Flux Conditions in Arbitrary Direction

    NASA Astrophysics Data System (ADS)

    Wakabayashi, Daisuke; Todaka, Takashi; Enokizono, Masato

    This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional magnetostriction in non-oriented and grain-oriented silicon steel sheets are compared.

  17. Three-dimensional Magnetostriction and Vector Magnetic Properties under Alternating Magnetic Flux Conditions in Arbitrary Direction

    Microsoft Academic Search

    Daisuke Wakabayashi; Takashi Todaka; Masato Enokizono

    2010-01-01

    This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional

  18. Magnetic nanoparticles with dual functional properties: Drug delivery and magnetic resonance imaging

    Microsoft Academic Search

    Tapan K. Jain; John Richey; Michelle Strand; Diandra L. Leslie-Pelecky; Chris A. Flask; Vinod Labhasetwar

    2008-01-01

    There is significant interest in recent years in developing magnetic nanoparticles (MNPs) having multifunctional characteristics with complimentary roles. In this study, we investigated the drug delivery and magnetic resonance imaging (MRI) properties of our novel oleic acid-coated iron-oxide and pluronic-stabilized MNPs. The drug incorporation efficiency of doxorubicin and paclitaxel (alone or in combination) in MNPs was 74–95%; the drug release

  19. Structural and Magnetic Properties of Codoped ZnO based Diluted Magnetic Semiconductors

    Microsoft Academic Search

    Bin-Bin Li; Hong-Lie Shen; Rong Zhang; Xiang-Qiang Xiu; Zhi Xie

    2007-01-01

    Zn1-xCoxO (x = 0.01, 0.02, 0.05, 0.10 and 0.20) diluted magnetic semiconductors are prepared by the sol-gel method. The structural and magnetic properties of the samples are studied using x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS) and superconducting quantum interference device (SQUID). The XRD patterns does not show any signal of precipitates that are different from wurtzite type

  20. Crystal growth and magnetic properties of equiatomic CeAl

    NASA Astrophysics Data System (ADS)

    Das, Pranab Kumar; Thamizhavel, A.

    2015-03-01

    Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 ?B/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

  1. Magnetic properties of textured CoPd nanocrystalline thin films.

    PubMed

    Vlachos, A; Pappas, S D; Kapaklis, V; Karoutsos, V; Kordatos, A; Wilhelm, F; Rogalev, A; Fumagalli, P; Poulopoulos, P; Velgakis, M J; Politis, C

    2012-08-01

    CoPd is an important nanomaterial for magnetic and magneto-optic storage of information. In this work, CoPd alloyed thin films are grown via radio frequency magnetron sputtering on silicon, glass and polyimide substrates in a vacuum chamber with base pressure of 5 x 10(-8) mbar. The films are nanocrystalline with grain size between 4 and 80 nm. The magnetic properties of thoroughly textured CoPd alloyed thin films are compared to random polycrystalline ones. Magnetization hysteresis loops recorded under fields up to 12 kOe via a home-made magneto-optic Kerr-effect magnetometer reveal strong tendency for perpendicular magnetic anisotropy for the textured film. This anisotropy leads to the formation of well-defined stripe or labyrinthine ferromagnetic domains with the local spins oriented perpendicular to the film plane. The domain patterns and the hysteresis loops are simulated with micromagnetic calculations. Finally, an induced magnetic moment of 0.44 microB/atom is measured for Pd via X-ray magnetic circular dichroism and it is separated into spin and orbital magnetic moment contributions. PMID:22962731

  2. Magnetic properties of d - atomic systems with unquenched orbital moments

    NASA Astrophysics Data System (ADS)

    Antonov, Victor; Ke, Liqin; Jesche, Anton; Antropov, Vladimir

    2013-03-01

    Many systems of d-atoms with unquenched orbital moments demonstrate unusually large values of atomic magnetic moments, high magnetic anisotropy and small magnetic ordering temperatures. Using electronic structure analysis, we study a mechanism of the formation of strong on-site electronic correlations that lead to a strong orbital polarization, and in turn, generate a highly orbitally polarized hybridization with non-magnetic host atoms. In this case, even a small spin orbital coupling of 3 d -atoms can create a significant effect. We introduce a consistent model of the formation of large orbital moments and magnetic anisotropy both in the metallic and insulating cases, and apply it to several realistic systems. Detailed calculations of magnetic properties, including magneto-optical studies of the Kerr angle rotation, are performed for several nitrometalates of Mn, Fe and Co where a rather large (3-5 degrees) Kerr angle rotation is predicted for the first time. We further discuss the nature of critical temperature in magnetic phase transition in such systems and the opportunity to increase it.

  3. Superconducting and magnetic properties of Sr?Ir?Sn??

    DOE PAGESBeta

    Biswas, P. K.; Wang, Kefeng; Amato, A.; Khasanov, R.; Luetkens, H.; Petrovic, C.; Cook, R. M.; Lees, M. R.; Morenzoni, E.

    2014-10-01

    Magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr?Ir?Sn??. From magnetization measurements the lower and upper critical fields of Sr?Ir?Sn?? are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr?Ir?Sn??. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth ?. The dependence of ??² with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr?Ir?Sn?? with a gap valuemore »of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature ?(0) is 291(3) nm. The ratio ?(0)/kBTc = 2.1(1) indicates that Sr?Ir?Sn?? should be considered as a strong-coupling superconductor.« less

  4. Superconducting and magnetic properties of Sr?Ir?Sn??

    SciTech Connect

    Biswas, P. K. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Wang, Kefeng [Brookhaven National Lab. (BNL), Upton, NY (United States); Amato, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Khasanov, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Luetkens, H. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Petrovic, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cook, R. M. [Univ. of Warwick, Coventry (United Kingdom); Lees, M. R. [Univ. of Warwick, Coventry (United Kingdom); Morenzoni, E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    2014-10-01

    Magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr?Ir?Sn??. From magnetization measurements the lower and upper critical fields of Sr?Ir?Sn?? are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr?Ir?Sn??. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth ?. The dependence of ??² with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr?Ir?Sn?? with a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature ?(0) is 291(3) nm. The ratio ?(0)/kBTc = 2.1(1) indicates that Sr?Ir?Sn?? should be considered as a strong-coupling superconductor.

  5. Superconducting and magnetic properties of Sr?Ir?Sn??

    DOE PAGESBeta

    Biswas, P. K. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Wang, Kefeng [Brookhaven National Lab. (BNL), Upton, NY (United States); Amato, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Khasanov, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Luetkens, H. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Petrovic, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cook, R. M. [Univ. of Warwick, Coventry (United Kingdom); Lees, M. R. [Univ. of Warwick, Coventry (United Kingdom); Morenzoni, E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    2014-10-01

    Magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr?Ir?Sn??. From magnetization measurements the lower and upper critical fields of Sr?Ir?Sn?? are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr?Ir?Sn??. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth ?. The dependence of ??² with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr?Ir?Sn?? with a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature ?(0) is 291(3) nm. The ratio ?(0)/kBTc = 2.1(1) indicates that Sr?Ir?Sn?? should be considered as a strong-coupling superconductor.

  6. Magnetorheological properties of a magnetic nanofluid with dispersed carbon nanotubes.

    PubMed

    Felicia, Leona J; Philip, John

    2014-02-01

    We investigate the effect of multiwalled carbon nanotubes (MWCNTs) on the magnetorheological properties of an oil based magnetic nanofluid (ferrofluid). The shear resistant plateau observed in a pure ferrofluid disappears when 0.5 wt% of MWCNT is incorporated. The yield stress values of the composite system are slightly smaller than that of the pure system. This shows that the presence of carbon nanotubes (CNTs) weakens the magnetic field induced microstructure of the ferrofluid due to their interaction that affects the hydrodynamic and magnetic interactions between the dispersed nanoparticles. Interestingly, the Mason number plots for both the pure and composite system show scaling of the viscosity curves onto a single master curve for magnetic fields of 80 mT and above while deviations are observed for lower magnetic fields. The weakening of the ferrofluid microstructure in the presence of CNTs is further evident in the amplitude sweep measurements where the linear viscoelastic region develops only at a higher magnetic field strength compared to lower magnetic fields in pure ferrofluids. These results are useful for tailoring ferrofluids with a faster response for various applications. PMID:25353475

  7. Measurement of bidirectional optical properties of complex shading devices

    SciTech Connect

    Klems, J.H.; Warner, J.L.

    1995-01-01

    A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This paper describes the method of measuring the spatially averaged bidirectional optical properties using an automated, large-sample gonioradiometer/photometer, termed a ``Scanning Radiometer.`` Property measurements are presented for one of the most optically complex systems in common use, a venetian blind. These measurements will form the basis for optical system calculations used to test the method of determining performance.

  8. Magnetic properties of the anisotropic MnBi/Sm2Fe17Nx hybrid magnet

    NASA Astrophysics Data System (ADS)

    Yang, Y. B.; Wei, J. Z.; Peng, X. L.; Xia, Y. H.; Chen, X. G.; Wu, R.; Du, H. L.; Han, J. Z.; Wang, C. S.; Yang, Y. C.; Yang, J. B.

    2014-05-01

    In order to improve the magnetic properties of MnBi compound, anisotropic MnBi/Sm2Fe17Nx hybrid magnet was prepared by grinding of high purity MnBi ribbons and Sm2Fe17Nx particles together. The smooth hysteresis loops of the hybrid magnets indicated that the mixture of the hard/hard phase magnetic components was well exchange coupled. As compared to the single MnBi phase magnet, the remanent magnetization and maximum energy product (BH)max of the composited magnets were improved. As an optimized result, the exchange coupled magnet of MnBi/Sm2Fe17Nx = 3/7 yielded both high remanence and coercivity from 250 K to 380 K. A maximum energy product (BH)max of 18 MGOe was achieved at 300 K, and remained 10 MGOe at 380 K, implying the MnBi/Sm2Fe17Nx magnets can be specially utilized in the high temperature environment.

  9. Magnetic properties and magnetization of a freshly fallen LL ordinaty chondrite

    NASA Astrophysics Data System (ADS)

    Gattacceca, J.; Rochette, P.

    2003-04-01

    A comprehensive rock magnetic, magnetic anisotropy and paleomagnetic study has been undertaken in the brecciated LL6 Bensour meteorite, a few months after its fall on Earth. Magnetic properties, in particular hysteresis loops before and after heating, as well as high field anisotropy indicate that tetrataenite is the major magnetic mineral. A very strong coherent susceptibility and remanence anisotropy is evidenced and interpreted as due to the last large impact responsible for the post-metamorphic and post-brecciation compaction of this material. Demagnetization of mutually oriented sub-samples evidences three components of magnetization. Medium and high coercivity components carried by tetrataenite are randomly distributed down to a scale of 125 mm3. They represent the magnetization acquired by tetrataenite during its formation by low-temperature atomic ordering of taenite, but the link with the original magnetization of taenite and kamacite grains, acquired during cooling of the parent body after metamorphism, is unknown. Alternatively this randomness may be due to a post-metamorphic thermoremanent magnetization subsequently randomized by brecciation. A non random low-coercivity component is also evidenced. Its origin clearly predates the fall of the meteorite on Earth and postdates the last major impact on the meteorite parent body. The coercivity spectrum of this component as well as the strong relation with the impact-related petrofabric indicate that the low coercivity component is likely related to this major impact, possibly in quasi-absence of ambient magnetic field.

  10. Guadiana fault: magnetic and gravity constraints related with the Monchique Alkaline Complex structure (Betic Cordillera foreland)

    NASA Astrophysics Data System (ADS)

    González-Castillo, Lourdes; Galindo-Zaldívar, Jesús; Ruiz-Constán, Ana; Pedrera, Antonio

    2014-05-01

    Geophysical data are essential to reveal the main crustal deep structures in areas where geological surface observations do not provide enough detailed data. Magnetic anomalies studies help us to constrain the structure of intermediate and basic igneous rocks. Magnetic and gravity surveys have been combined to determine the geometry, position and properties of intermediate igneous intrusive bodies responsible of the magnetic anomalies in the western area of the Betic Cordillera foreland. Furthermore, crustal structure has been characterized revealing the presence of a blind fault: The Guadiana fault. The aeromagnetic data reveal that the southwestern Iberian Peninsula is characterized by an elongated E-W dipole extending 200 km towards the Betic Cordillera external zones. The anomaly is related to the outcropping Monchique Alkaline Complex, characterized by rocks of moderate magnetic susceptibility (0.029 SI) intruding into the metapelitic host rock of the South Portuguese Zone. In this region, new total field magnetic data has been acquired with a GSM 8 proton precession magnetometer with an accuracy of 1 nT at a mean height of 2 m above the topography. Susceptibility measurements were done with an Exploranium KT-9 kappameter. Combined analysis of aeromagnetic and field magnetic anomalies serves to constrain the depth and geometry of this laccolith. Toward the east, the magnetic dipole has a 60 km long N-S sharp step that coincides with the southern part of the Guadiana River (Spain-Portugal southernmost border). In addition, gravity measurements were performed simultaneously with the magnetic data acquisition using a Scintrex Autograv CG-5 gravity meter whose maximum accuracy is 0.001 mGal. This data support the presence of this major discontinuity in the elongated anomalous body, with an E downthrown block, interpreted as the offset produced by a deep N-S crustal fault - The Guadiana Fault. Therefore, the Guadiana River has three long linear segments near its mouth, locally coinciding with a N-S trending joint set, that support the presence of this structure. To date, no evidence of this tectonic discontinuity, coinciding with the Spanish-Portuguese border, has been reported. Magnetic research is essential for understanding the structure of wide regions intruded by intermediate and/or basic igneous rocks.

  11. Chemical tuning of the magnetic relaxation in dysprosium(iii) mononuclear complexes.

    PubMed

    Batchelor, Luke J; Cimatti, Irene; Guillot, Régis; Tuna, Floriana; Wernsdorfer, Wolfgang; Ungur, Liviu; Chibotaru, Liviu F; Campbell, Victoria E; Mallah, Talal

    2014-08-28

    A dysprosium(iii) complex, exhibiting slow relaxation of magnetization, was prepared. Crystallographic studies showed a perturbation of local symmetry upon deprotonation of the ligand, with concomitant faster relaxation of magnetization. This was attributed to a large shift in the direction of the main magnetic axis, as indicated by ab initio calculations. PMID:24827003

  12. Magnetic properties of Co/Rh ,,001... multilayers studied by x-ray magnetic-circular dichroism M. A. Tomaz

    E-print Network

    Lederman, David

    /Rh 001 multilayer thin films using the x-ray magnetic circular dichroism. The Rh moments were measuredMagnetic properties of Co/Rh ,,001... multilayers studied by x-ray magnetic-circular dichroism M. A the magnetic behavior of the Co/Rh 001 and Fe/Rh 001 multilayer systems. S0163-1829 98 07641-3 I. INTRODUCTION

  13. Effect of external magnetic field on magnetic properties of Co-Pt nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Liu, H. R.; Ahmad, N.; Li, Y. L.; Chen, Z. Y.; Zhou, W. P.; Han, X. F.

    2011-04-01

    Well-ordered Co90Pt10 nanotubes and nanowires have been fabricated into anodic aluminum oxide (AAO) templates by using a dc electrodeposition method. The effects of an external magnetic field on the magnetic properties of Co90Pt10 nanotubes and nanowires are investigated. The results show that the external magnetic field during electrodeposition has a significant effect on Co90Pt10 nanowires, as well as nanotubes. The external magnetic field induces good texture and large grain size in Co90Pt10 nanowires, causing a reduction of coercivity. An obvious uniaxial anisotropy is induced in Co90Pt10 nanotubes, causing the crossover of the easy axis along the directions of an external magnetic field.

  14. The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement.

    PubMed

    Chiang, Yuan-Ching; Chieh, Jen-Jie; Ho, Chia-Che

    2012-01-01

    This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200?Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60?W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system. PMID:22716909

  15. Determination of Complex Magnetic Structures From Polarized Neutron Reflectivity Data by Flexible Modeling of Depth-Dependent Vector Magnetization

    Microsoft Academic Search

    A. D. Mont; P. A. Kienzle; S. M. Watson; J. A. Borchers; J. Eckert; P. Sparks; S. Moyerman; M. J. Carey

    2007-01-01

    In multilayer systems with exchange-coupled layers such as exchange-spring magnets, interfacial pinning can give rise to spiral domain walls and other complex magnetic structures that are sensitive to temperature, relative layer thicknesses, etc. Though these spin structures develop in subsurface layers, the depth-dependent magnetic profile can be fully characterized using polarized neutron reflectivity (PNR). In order to obtain the profile

  16. Experimental econophysics: Complexity, self-organization, and emergent properties

    NASA Astrophysics Data System (ADS)

    Huang, J. P.

    2015-03-01

    Experimental econophysics is concerned with statistical physics of humans in the laboratory, and it is based on controlled human experiments developed by physicists to study some problems related to economics or finance. It relies on controlled human experiments in the laboratory together with agent-based modeling (for computer simulations and/or analytical theory), with an attempt to reveal the general cause-effect relationship between specific conditions and emergent properties of real economic/financial markets (a kind of complex adaptive systems). Here I review the latest progress in the field, namely, stylized facts, herd behavior, contrarian behavior, spontaneous cooperation, partial information, and risk management. Also, I highlight the connections between such progress and other topics of traditional statistical physics. The main theme of the review is to show diverse emergent properties of the laboratory markets, originating from self-organization due to the nonlinear interactions among heterogeneous humans or agents (complexity).

  17. Simulation of energy levels schemes and of some magnetic properties of divalent copper in tetragonal or pseudo tetragonal symmetries

    Microsoft Academic Search

    Stéphane Bailleul; Pierre Porcher

    1989-01-01

    The optical and magnetic properties of 20 complexes of divalent copper are re-analysed. The aim of the work is to simulate simultaneously the data by using a unique set of phenomenological parameters, those introduced by the crystal-ligand field theory, when the vectorial space basis is described on the |alphaSLJM> kets.

  18. Radiative properties of rare earth complexes\\/silver nanoparticles nanocomposite

    Microsoft Academic Search

    Si Wu; Youyi Sun; Xin Wang; Wenxuan Wu; Xiujie Tian; Qing Yan; Yanhua Luo; Qijin Zhang

    2007-01-01

    Rare earth complexes\\/silver nanoparticles nanocomposite was prepared by introducing Tb(TTA)3Bipy as stabilizer. The radiative properties of the nanocomposite were studied by experiments and spectra calculation. The transmission electron microscope image of the composite indicates that the silver nanoparticles are spherical, monodispersed and with an average size of 18nm. Fluorescence study shows silver nanoparticles have both enhancement effect and quenching effect

  19. Rational synthesis and magnetic properties of a family of low-dimensional heterometallic Cr-Mn complexes based on the versatile building block [Cr(2,2'-bipyridine)(CN)4]-.

    PubMed

    Zhang, Yuan-Zhu; Gao, Song; Wang, Zhe-Ming; Su, Gang; Sun, Hao-Ling; Pan, Feng

    2005-06-27

    Six heterometallic compounds based on the building block [Cr(bpy)(CN)4]- (bpy = 2,2'-bipyridine) with secondary and/or tertiary coligands as modulators, {Mn(H2O)2[Cr(bpy)(CN)4]2}n (1), {Mn(bpy)(H2O)[Cr(bpy)(CN)4]2 x H2O}n (2), [Mn(bpy)2][Cr(bpy)(CN)4]2 x 5H2O (3), {[Mn(dca)(bpy)(H2O)][Cr(bpy)(CN)4] x H2O}n (4) (dca = N(CN)2(-)), {Mn(N3)(CH3OH)[Cr(bpy)(CN)4] x 2H2O}n (5), and {Mn(bpy)(N3)(H2O)[Cr(bpy)(CN)4] x H2O}2 (6), have been prepared and characterized structurally and magnetically. X-ray crystallography reveals that the compounds 1, 2, 4, and 5 consist of one-dimensional (1D) chains with different structures: a 4,2-ribbon-like chain, a branched zigzag chain, a 2,2-CC zigzag chain, and a 3,3-ladder-like chain, respectively. It also reveals that compound 3 has a trinuclear [MnCr2] structure, and compound 6 has a tetranuclear [Mn2Cr2] square structure. Magnetic studies show antiferromagnetic interaction between Cr(III) and Mn(II) ions in all compounds. All of the chain compounds exhibit metamagnetic behaviors with different critical temperatures (Tc) and critical fields (Hc; at 1.8 K): 3.2 K and 3.0 kOe for 1; 2.3 K and 4.0 kOe for 2; 2.1 K and 1.0 kOe for 4; and 4.7 K and 5.0 kOe for 5, respectively. The noncentrosymmetric compound 2 is also a weak ferromagnet at low temperature because of spin canting. The magnetic analyses reveal Cr-Mn intermetallic magnetic exchange constants, J, of -4.7 to -9.4 cm(-1) (H = -JS(Cr) x S(Mn)). It is observed that the antiferromagnetic interaction through the Mn-N-C-Cr bridge increases as the Mn-N-C angle (theta) decreases to the range of 155-180 degrees, obeying an empirical relationship: J = -40 + 0.2theta. This result suggests that the best overlap between t(2g) (high-spin Mn(II)) and t(2g) (low-spin Cr(III)) occurs at an angle of approximately 155 degrees. PMID:15962960

  20. Broadband complex permeability characterization of magnetic thin films using shorted microstrip transmission-line perturbation

    Microsoft Academic Search

    Yan Liu; Linfeng Chen; C. Y. Tan; H. J. Liu; C. K. Ong

    2005-01-01

    A brief review of the methods used for broadband complex permeability measurement of magnetic thin films up to microwave frequencies is given. In particular, the working principles of the transmission-line perturbation methods for the characterization of magnetic thin films are discussed, with emphasis on short-circuited planar transmission-line perturbation methods. The algorithms for calculating the complex permeability of magnetic thin films

  1. Hydrothermal syntheses, structures and magnetic properties of two transition metal coordination polymers with a square

    E-print Network

    Gao, Song

    bonding, resulting in a 3-D supramolecular architecture. Magnetic susceptibility studies reveal reserved. Keywords: Hydrothermal synthesis; Coordination polymer; Magnetic property; Transition metal analysis was performed with a ZRY-2P Thermal Analyzer. The magnetic susceptibility measurements were

  2. Magnetic antenna excitation of whistler modes. I. Basic properties

    NASA Astrophysics Data System (ADS)

    Urrutia, J. M.; Stenzel, R. L.

    2014-12-01

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  3. Magnetic properties of bio-synthesized zinc ferrite nanoparticles

    SciTech Connect

    Yeary, Lucas W [ORNL; Moon, Ji Won [ORNL; Rawn, Claudia J [ORNL; Love, Lonnie J [ORNL; Rondinone, Adam Justin [ORNL; Thompson, James R [ORNL; Chakoumakos, Bryan C [ORNL; Phelps, Tommy Joe [ORNL

    2011-01-01

    The magnetic properties of zinc ferrite (Zn-substituted magnetite, Zn{sub y}Fe{sub 1-y}Fe{sub 2}O{sub 4}) formed by a microbial process compared favorably with chemically synthesized materials. A metal reducing bacterium, Thermoanaerobacter, strain TOR-39 was incubated with Zn{sub x}Fe{sub 1-x}OOH (x=0.01, 0.1, and 0.15) precursors and produced nanoparticulate zinc ferrites. Composition and crystalline structure of the resulting zinc ferrites were verified using X-ray fluorescence, X-ray diffraction, transmission electron microscopy, and neutron diffraction. The average composition from triplicates gave a value for y of 0.02, 0.23, and 0.30 with the greatest standard deviation of 0.02. Average crystallite sizes were determined to be 67, 49, and 25 nm, respectively. While crystallite size decreased with more Zn substitution, the lattice parameter and the unit cell volume showed a gradual increase in agreement with previous literature values. The magnetic properties were characterized using a superconducting quantum interference device magnetometer and were compared with values for the saturation magnetization (M{sub s}) reported in the literature. The averaged M{sub s} values for the triplicates with the largest amount of zinc (y=0.30) gave values of 100.1, 96.5, and 69.7 emu/g at temperatures of 5, 80, and 300 K, respectively indicating increased magnetic properties of the bacterially synthesized zinc ferrites.

  4. Unified theoretical description of the thermodynamical properties of spin crossover with magnetic interactions

    NASA Astrophysics Data System (ADS)

    Boukheddaden, Kamel; Nishino, Masamichi; Miyashita, Seiji; Varret, François

    2005-07-01

    After the discovery of the phenomena of light-induced excited spin-state trapping (LIESST), the functional properties of metal complexes have been studied intensively. Among them, cooperative phenomena involving low spin-high spin (spin-crossover) transition and magnetic ordering have attracted interests, and it has become necessary to formulate a unified description of both phenomena. In this work, we propose a model in which they can be treated simultaneously by extending the Wajnflasz-Pick model to include a magnetic interaction. We found that this model is equivalent to Blume-Emery-Griffiths (BEG) Hamiltonian with degenerate levels. It provides a unified description of the thermodynamic properties associated with various types of systems, such as spin-crossover (SC) solids and Prussian blue analog. Here, the high spin fraction and the magnetization are the order parameters describing the cooperative phenomena of the model. We present several typical temperature dependences of the order parameters and determine the phase diagram of the system using the mean-field theory and Monte Carlo simulations. We found that the magnetic interaction drives the SC transition leading to reentrant magnetic and first-order SC transitions.

  5. Magnetic dipole properties in deformed nuclei

    NASA Astrophysics Data System (ADS)

    Faessler, A.

    The magnetic dipole response in deformed nuclei is investigated. Spurious states due to the rotation of the whole nucleus are removed by restricting the residual interaction in such a way that it commutes with the total angular momentum as a ground state expectation value in the quasi-particle random phase approximation. By this one guarantees that the spurious state due to rotations lies at energy zero and that it is a solution of the quasi-particle random phase equation (QRPA) and can easily be removed. The Hamiltonian is chosen to be a deformed Saxon Woods potential with a pairing force and an isoscalar and isovector generalized quadrupole-quadrupole and spin-spin interaction. The generalized isoscalar quadrupole operator is defined as the commutator of the independent quasi-particle Hamiltonian with the total angular momentum. The restoration of rotational symmetry mentioned above determines the isoscalar coupling constant. The generalized isovector quadrupole-quadrupole force does not commute with the total angular momentum. But one can find a linear “isovector” combination of the proton and the neutron total angular momentum which produces by a commutator with the independent quasiparticle Hamiltonian an “isovector” quadrupole operator which yields an isovector quadrupole-quadrupole force which always commutes with the total angular momentum. Thus one gets no restriction of the isovector quadrupole-quadrupole force constant. We fit it to the isovector giant quadrupole resonance ( E(E2) = {130}/{A {1}/{3}}MeV). The Hamiltonian contains in addition a spin-spin force, which always commutes with the total angular momentum and therefore does not spoil the restoration of rotational symmetry. The proton-proton, neutron-neutron and proton-neutron spin force constant is determined by solving the nuclear matter problem with the Reid soft core interaction within the Brückner theory and translating the result with the help of the Migdal force into finite nuclei. This yields an almost pure repulsive isovector spin-spin force. This Hamiltonian predicts a high lying ?N = 2 scissors mode which lies between 17 and 26 MeV. It is spread over very many 1 + states with an average spacing of 15 keV. This highlying scissors mode consists of several hundred states and the overlap with an artificially constructed scissors mode is of the order of 38%, while the low lying scissors mode which shows up as 1 + states around 3 MeV has an overlap with the scissors mode of more than 50 %. In the same energy range as the high lying scissors mode lies also the isovector giant quadrupole resonance. Even at 180°, that means at completely backward angles, the E2 is comparable with the M1 excitation. This is due to the transversal quadrupole transition probability which is not disappearing in electron scattering at 180°. The same Hamiltonian is nicely describing the low lying scissors mode around 3 MeV in the rare earth and the transuranic nuclei. It gives the energies and the reduced magnetic dipole transition probabilities. It also can reproduce the formfactors measured by inelastic electron scattering. The Hamiltonian also reproduces the spin-flip states between 5 and 9 MeV excitation energy, which can be measured by inelastic proton scattering. One obtains in this region two maxima. The lowest one around 6 MeV is mainly of isoscalar nature and is weaker than the spin flip maximum at 7 to 8 MeV, which is mainly of isovector nature. The detailed form of this two-spin flip maxima depend very sensitively on the ratio of the isoscalar and isovector strength of the spin-spin force. In conclusion one can say: There exist a high lying scissors mode, but it is strongly fragmented over several hundred 1 + states between 17 and 26 MeV and even in electron scattering at backward angles the cross section for the excitation of the isovector giant quadrupole resonance is of comparable size. Thus it will be difficult to establish experimentally the existence of this high lying scissors mode.

  6. Properties of the manganese(II) binding site in ternary complexes of Mnter dot ADP and Mnter dot ATP with chloroplast coupling factor 1: Magnetic field dependence of solvent sup 1 H and sup 2 H NMR relaxation rates

    SciTech Connect

    Haddy, A.E.; Frasch, W.D.; Sharp, R.R. (Univ. of Michigan, Ann Arbor (USA))

    1989-05-02

    The influence of the binding of ADP and ATP on the high-affinity Mn(II) binding site of chloroplast coupling factor 1 (CF{sub 1}) was studied by analysis of field-dependent solvent proton and deuteron spin-lattice relaxation data. In order to characterize metal-nucleotide complexes of CF{sub 1} under conditions similar to those of the NMR experiments, the enzyme was analyzed for bound nucleotides and Mn(II) after incubation with AdN and MnCl{sub 2} and removal of labile ligands by extensive gel filtration chromatography. In the field-dependent NMR experiments, the Mn(II) binding site of CF{sub 1} was studied for three mole ratios of added Mn(II) to CF{sub 1}, 0.5, 1.0, and 1.5, in the presence of an excess of either ADP or ATP. The results were extrapolated to zero Mn(II) concentration to characterize the environment of the first Mn(II) binding site of Cf{sub 1}. In the presence of both adenine nucleotides, pronounced changes in the Mn(II) environment relative to that in Mn(II)-CF{sub 1} were evident; the local relaxation rate maxima were more pronounced and shifted to higher field strengths, and the relaxation rate per bound Mn(II) increased at all field strengths. Analysis of the data revealed that the number of exchangeable water molecules liganded to bound Mn(II) increased from one in the binary Mn(II)-CF{sub 1} complex to three and two in the ternary Mn(II)-ADP-CF{sub 1} and Mn(II)-ATP-CF{sub 1} complexes, respectively; these results suggest that a water ligand to bound Mn(II) in the Mn(II)-ADP-CF{sub 1} complex is replaced by the {gamma}-phosphate of ATP in the Mn(II)-ATP-CF{sub 1} complex. A binding model is presented to account for these observations.

  7. A reentrant phenomenon in magnetic and dielectric properties of Dy2BaNiO5 and an intriguing influence of external magnetic field.

    PubMed

    Basu, Tathamay; Paulose, P L; Iyer, K K; Singh, K; Mohapatra, N; Chowki, S; Gonde, B; Sampathkumaran, E V

    2014-04-30

    We report that the spin-chain compound Dy2BaNiO5, recently proven by us to exhibit magnetoelectric coupling below its Néel temperature (TN) of 58 K, exhibits strong frequency-dependent behavior in ac magnetic susceptibility and complex dielectric properties at low temperatures (<10?K), mimicking the 'reentrant' multiglass phenomenon. Such a behavior is not known among undoped compounds. A new finding in the field of multiferroics is that the characteristic magnetic feature at low temperatures moves towards higher temperatures in the presence of a magnetic field (H), whereas the corresponding dielectric feature shifts towards lower temperatures with H, unlike the situation near TN. This observation indicates that the alignment of spins by external magnetic fields tends to inhibit glassy-like slow electric-dipole dynamics, at least in this system, possibly arising from peculiarities in the magnetic structure. PMID:24722401

  8. Magnetic Properties of MnFe2Ga Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Elgendy, Ahmed A.; Salehi-Fashami, Mohammad; Sellmyer, David; Hadjipanayis, George

    2015-03-01

    Recently, MnFe2Ga Heusler alloys have attracted significant attention due to their interesting physical properties such as large magnetic-field-induced strain, giant magnetocaloric effects,large magnetoresistance, and exchange bias behavior. These properties make them promising candidates for various practical applications in the field of smart materials, magnetic refrigeration and spintronics. In this work, we prepared MnFe2Ga alloys by melt-spinning and sputtering and studied the structural and magnetic properties. The melt-spun ribbons were prepared with a wheel speed of 30 m/s. The ribbons were annealed at different temperatures for 1 hour and grinded to make fine powders. The grinded powders were also used to make the target that is used in the cluster gun for the fabrication of MnFe2Ga nanoparticles. The structure of the as made, annealed ribbons, and powders displayed a face-centered-cubic structure. The microstructure of the as-made ribbons showed equiaxed grains with an average size of 3-5 ?m while the annealed ribbons showed bigger grains with small particles covering homogeneously their surface. The magnetic properties show an enhancement of magnetization while coercivity remains the same with values M(3T) and HC of 85 emu/g and 150 Oe, respectively Transmission electron microscopy with elemental mapping is currently underway to determine the structure and composition of the surface nanoparticles. The work was supported by DOE-BES-DMSE (Grant No. DE-FG02-04ER4612).

  9. Magnetic and magnetostrictive properties of manganese substituted cobalt ferrite

    Microsoft Academic Search

    S. D. Bhame; P. A. Joy

    2007-01-01

    The magnetic and magnetostrictive properties of polycrystalline\\u000a Co1-xMnxFe2O4 ( 0 = x = 0.4) have been studied. Although the Curie\\u000a temperature decreases continuously with increasing concentration of Mn,\\u000a the magnetization remains high up to x = 0.3 and unexpectedly low\\u000a coercivity is observed for this composition showing an unusual\\u000a magnetostrictive behaviour. This composition shows a relatively larger\\u000a magnetostriction at low

  10. Aging of magnetic properties in MgO films

    SciTech Connect

    Balcells, Ll.; Konstantinovic, Z.; Martinez, B. [Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain); Beltran, J. I. [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Martinez-Boubeta, C. [Departament d'Electronica and IN2UB, Universitat de Barcelona, Barcelona 08028 (Spain); Arbiol, J. [Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain); Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona 08010 (Spain)

    2010-12-20

    In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role played by defects in stabilizing ferromagnetism in MgO films and is likely to be closely related to the hydrogen-driven instability of V-type centers in this material.

  11. Tuning electronic and magnetic properties of graphene by surface modification

    NASA Astrophysics Data System (ADS)

    Zhou, Jian; Wu, Miao Miao; Zhou, Xiao; Sun, Qiang

    2009-09-01

    We have demonstrated that the electronic and magnetic properties of graphene sheet can be delicately tuned by surface modification. Applying an external electric field to a fully hydrogenated graphene sheet can unload hydrogen atoms on one side, while keeping the hydrogen atoms on the other side, thus forming a half-hydrogenated graphene sheet, where the unpaired electrons in the unsaturated C sites give rise to magnetic moments, coupled through extended p-p interactions. Furthermore, the electronic structure of the resulting half-hydrogenated graphene sheet can be further tuned by introducing F atoms on the other side, making a nonmagnetic semiconductor with a direct band gap.

  12. Effects of coating on magnetic properties in iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Bittova, B.; Poltierova-Vejpravova, J.; Roca, A. G.; Morales, M. P.; Tyrpekl, V.

    2010-01-01

    We have studied influence of surface modification on physical properties of iron oxide nanoparticles. We compared samples prepared by thermal decomposition of organic precursor in the presence of oleic acid, and the particles prepared by coprecipitation and partially coated by SiO2 or modified by citric acid and subsequently covered by photoactive TiO2 layer, respectively. Samples were characterised using TEM and XRD, further magnetic studies such as temperature dependence of magnetization and a.c. susceptibility show superparamagnetic behavior for all samples at room temperature. The effects of coating on dipolar inter particle interactions are discussed.

  13. Hydrothermal synthesized bismuth ferrites particles: thermodynamic, structural, and magnetic properties.

    PubMed

    Du, Yi; Cheng, Zhenxiang; Yu, Zhenwei; Dou, Shi Xue; Wang, Xiaolin; Liu, L Q

    2012-02-01

    A family of bismuth ferrites (BFO), including Bi2Fe4O9, BiFeO3, and Bi25FeO39 with different morphologies, has been prepared by the hydrothermal method assisted by different alkaline mineralizers. X-ray diffraction refinement calculations are carried out to study the crystal structures of bismuth ferrites. A thermodynamic calculation based on the dissolution-precipitation model was carried out to analyze the hydrothermal synthesis of BFO powders. Magnetic measurements of the obtained bismuth ferrites show different magnetic properties from 5 K to 350 K. PMID:22630029

  14. Synthesized some 4-(2-thiazolylazo)resorcinol complexes: characterization, thermal and optical properties.

    PubMed

    Karipcin, Fatma; Kabalcilar, Eser; Ilican, Saliha; Caglar, Yasemin; Caglar, Mujdat

    2009-07-01

    Some transition metal complexes of the type [ML2].nH2O (n=0 or 2) of the title ligand, 4-(2-thiazolylazo)resorcinol, HL (TAR) have been synthesized and characterized by various analytical and physicochemical (elemental, thermal analyses, AAS, electrolytic conductance and magnetic susceptibility measurements) and spectral (UV-vis and IR) techniques for structure determination and optical properties. The complexes have the formulae [ML2] for M=Fe(II), Cu(II) and Zn(II); [CdL2].2H2O. An octahedral structure is proposed for all complexes. IR spectra show that the ligand is coordinated to the metal ions in a tridentate manner with ONN donor sites of the resorcinol OH, azo N and thiazole N. The effect of varying pH and solvent on the absorption behavior of the ligand and complexes has been investigated. The optical constants such as, refractive index, extinction coefficient, dielectric constant were determined for the ligand and its complexes. These parameters changed with different metal complexes. The optical absorption data revealed that the band gap of the films was direct transitions. The optical band gap and Urbach energy of the films were determined using the known theory. The optical dispersion parameters were determined according to Wemple and DiDomenico method. PMID:19297240

  15. Synthesized some 4-(2-thiazolylazo)resorcinol complexes: Characterization, thermal and optical properties

    NASA Astrophysics Data System (ADS)

    Karipcin, Fatma; Kabalcilar, Eser; Ilican, Saliha; Caglar, Yasemin; Caglar, Mujdat

    2009-07-01

    Some transition metal complexes of the type [ML 2]· nH 2O ( n = 0 or 2) of the title ligand, 4-(2-thiazolylazo)resorcinol, HL (TAR) have been synthesized and characterized by various analytical and physicochemical (elemental, thermal analyses, AAS, electrolytic conductance and magnetic susceptibility measurements) and spectral (UV-vis and IR) techniques for structure determination and optical properties. The complexes have the formulae [ML 2] for M = Fe(II), Cu(II) and Zn(II); [CdL 2]·2H 2O. An octahedral structure is proposed for all complexes. IR spectra show that the ligand is coordinated to the metal ions in a tridentate manner with ONN donor sites of the resorcinol OH, azo N and thiazole N. The effect of varying pH and solvent on the absorption behavior of the ligand and complexes has been investigated. The optical constants such as, refractive index, extinction coefficient, dielectric constant were determined for the ligand and its complexes. These parameters changed with different metal complexes. The optical absorption data revealed that the band gap of the films was direct transitions. The optical band gap and Urbach energy of the films were determined using the known theory. The optical dispersion parameters were determined according to Wemple and DiDomenico method.

  16. Synthesis, crystal structure and study of magnetocaloric effect and single molecular magnetic behaviour in discrete lanthanide complexes.

    PubMed

    Adhikary, Amit; Sheikh, Javeed Ahmad; Biswas, Soumava; Konar, Sanjit

    2014-06-28

    The synthesis, crystal structure and magnetic properties of four polynuclear lanthanide coordination complexes having molecular formulae, [Gd3(2)(1)L(H2O)8(Cl)](Cl)4·10H2O (1), [Dy3L(2)(1)(H2O)9](Cl)5·6H2O (2) [Gd6L(2)(2)(HCO2)4(?3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (3) and [Dy6L(2)(2)(HCO2)4(?3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (4) (where H2L(1) = bis[(2-pyridyl)methylene]pyridine-2,6-dicarbohydrazide and H4L(2) = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by X-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shapes of the molecules. Non-covalent interactions between the molecules create double helical arrangements for both molecules. Complexes 3 and 4 are isostructural and the core structures feature four distorted hemi-cubanes connected by vertex sharing. Magnetic studies unveil significant magnetic entropy changes for complexes 1, 3 and slow relaxation of magnetization for both dysprosium analogues 2 and 4. PMID:24818564

  17. Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

    2013-04-01

    In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

  18. Fe-nanoparticle coated anisotropic magnet powders for composite permanent magnets with enhanced properties

    NASA Astrophysics Data System (ADS)

    Marinescu, M.; Liu, J. F.; Bonder, M. J.; Hadjipanayis, G. C.

    2008-04-01

    Utilizing the chemical reduction of FeCl2 with NaBH4 in the presence of 2:17 Sm-Co powders, we synthesized composite Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4/nano-Fe anisotropic hard magnetic powders. The average particle size of the hard magnetic core powder was 21?m while the soft magnetic Fe nanoparticles deposited uniformly on the core powder had a particle size smaller than 100nm. Different reaction protocols, such as immersion of the hard magnetic core powder in each reagent, the use of microemulsion (micelle) technique, or doubling the weight ratio of FeCl2 to core powder, led to different degrees of magnetic coupling of the hard and soft magnetic components of the composite powder. A reaction time of 180s led to deposition of 3.5wt% Fe nanoparticles and improved magnetic properties of the composite powder compared to the uncoated Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4 powder. The respective magnetic hysteresis parameters were 4?M18kOe=11.3kG, 4?Mr=11kG, and Hci>20kOe with a smooth demagnetization curve.

  19. Using Solution Phase Self-Assembly to Control the Properties of Magnetic and Magnetoelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Schelhas, Laura Theresa

    Nanostrutured magnetic materials have gained much recent interest because of their application in various electronic systems. These materials, however, often require complex lithography and epitaxy to control the magnetic properties. In this work, solution-phase self-assembly is used to create magnetic and magnetoelectric materials with a variety of nanoscale structures. By engineering the architecture of the system, control over a range of magnetic properties can be realized. The first part of this work focuses on nano-magnetic materials. Here, the organization of nanoscale magnets into different geometries is controlled, and the properties of the systems are studied. In the first chapter, Ni-Cu nanowire stacks are examined to explore the effect of shape anisotropy on the coupling between different elements. This work provides insight into how to design new elements for spin-torque devices. In the next chapter, directed self-assembly of block copolymers is used to create coupled 1D chains of ferromagnetic and superparamagnetic FePt nanoparticles. These nano-patterned are globally aligned on the wafer length-scale using micron-sized lithographic grooves. This system is ideal for studying dipolar coupling between magnetic nanocrystals. Additionally, the processing methods developed here provide a platform for organizing other types of nanomaterials. The second sections explore magnetoelectric materials. These are materials that combine ferromagnetism and ferroelectricity in a coupled manner. One material that does this intrinsically is bismuth ferrite. The first chapter of this section explores ordered nanoporous bismuth ferrite produced by block copolymer templating. It is shown that the ordered porosity of the system creates a unique strain state in the bismuth ferrite, which in turn produces a large change in magnetization upon application of an electric field. Finally, in the last chapter, a nanostructured composite magnetoelectric system is studied. Here, magnetostrictive Ni nanocrystals are coupled to a single-crystalline piezoelectric substrate. The nanocrystals are superparamagnetic and show no net magnetization. Upon application of an electric field, however, strain induced in the piezoelectric substrate strains the lattice of the nanocrystals, creating a preferred magnetic axis along the high strained direction. This locks the magnetization along the strain axis and switches the nanocrystals from a superparamagnetic to a ferromagnetic state.

  20. Nanostructure and magnetic properties of Ni-substituted finemet ribbons

    NASA Astrophysics Data System (ADS)

    Iturriza, N.; Fernández, L.; Ipatov, M.; Vara, G.; Pierna, A. R.; del Val, J. J.; Chizhik, A.; González, J.

    2007-09-01

    Magnetic anisotropy has been induced during the nanocrystallization process of Ni-rich amorphous ferromagnetic ( Finemet) ribbons by means of the application of a constant stress during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work was the analysis of the treated ribbons using X-ray Diffraction (XRD), Transmission Electronic Microscopy (TEM) and Atomic Force Microscopy (AFM). AFM measurements revealed in all the cases a strong nanocrystallisation of the surface without evidences of amorphous matrix, which contrast with XRD and TEM measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements show much higher coercive field values than in the bulk, indicating a complex magnetic behavior for the surface of the ribbons.

  1. Stochastic Modeling of Soft Magnetic Properties of Electrical Steels: Application to Stators of Electrical Machines

    E-print Network

    Paris-Sud XI, Université de

    1 Stochastic Modeling of Soft Magnetic Properties of Electrical Steels: Application to Stators magnetic materials properties (magnetic behavior law, iron losses) during the manufacturing process an impact on the magnetic behavior law and iron losses of the considered material [30-33]. Therefore

  2. Investigation of the Properties of Magnetic Films Deposited on Carbon Nitride

    E-print Network

    Reilly, Anne

    /R) seen in ferromagnetic/non-magnetic multilayer thin films when a magnetic field is applied1 Investigation of the Properties of Magnetic Films Deposited on Carbon Nitride A thesis submitted C. Vibrating Sample Magnetometry IV. Results A. Roughness of Films B. Magnetic Properties V

  3. Electronic and magnetic properties of small rhodium clusters

    NASA Astrophysics Data System (ADS)

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-01

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh4 and Rh6 are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

  4. Effect of Cu Layer on FeMn Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Kaya, Dogan; Jayathilaka, Priyanga; Miller, Casey W.; Roshchin, Igor V.

    2011-10-01

    Growing demand for high-density memories requires new materials for magnetoresistive sensors in the read heads. FeMn has a great potential to be used for exchange-biasing the reference layer in the read heads. One of the crucial puzzles is the origin of the uncompensated magnetization in the antiferromagnetic FeMn. To study that, we use Cu layer to affect the magnetic properties of FeMn and its uncompensated magnetization. The multilayers of Ta(50 å)/[FeMn(50 å -- 150 å)/Cu(50 å)]10/Ta(50 å) are deposited by UHV DC magnetron sputtering on top of Si/SiOx 3 mm x5 mm substrates. Samples with a single layer of FeMn of the same thickness, Ta(50 å)/FeMn(50 å -- 150 å)/Ta(50 å) are used as control samples. The samples are cooled in a field of 7 T and their magnetization is measured using a SQUID magnetometer. All the samples have uncompensated magnetization that exhibits a hysteresis at 10 K. It is found that for the FeMn/Cu multilayers, the hysteresis loops are exchange bias shifted, while FeMn without Cu exhibits no exchange bias. Dependence of coercive field (Hc), exchange bias (He), and saturated magnetization (Ms) on the FeMn thickness and on temperature will be discussed. Work is supported by Texas A&M University, TAMU-CONACYT Collaborative Research Program, and by NSF-CAREER.

  5. Electronic and magnetic properties of DUT-8(Ni).

    PubMed

    Trepte, Kai; Schwalbe, Sebastian; Seifert, Gotthard

    2015-06-24

    First principles calculations using density functional theory (DFT) have been performed to investigate the electronic and magnetic properties of DUT-8(Ni) (DUT - Dresden University of Technology). This flexible metal-organic framework (MOF) exists in two crystalline forms: DUT-8(Ni)open and DUT-8(Ni)closed. To identify the energetically favoured magnetic ordering, the density of states (DOS) and the energy difference between a low-spin (LS) and a high-spin (HS) coupling ?ELS-HS for those crystalline structures have been computed. Calculations on supercells have been carried out to include a variety of different magnetic couplings beyond a single unit cell. Several molecular model systems have been employed to further investigate the magnetic behaviour by introducing a diversity of chemical environments to the magnetic centers. The magnetic ground state of both crystalline structures has been found to be the low-spin state (S = 0). This low-spin ordering can be seen in the DOS as well as from ?ELS-HS calculations. Additionally, the calculations on the supercells confirm that the local character of the ordering (i.e. within the Ni dimers) is the most favoured one. However, the model systems indicate a change from the low-spin (S = 0) to a high-spin (S ? 0) ordering by introducing certain alterations into the chemical environment. Such alterations could be incorporated into the crystalline systems which should lead to similar results. PMID:26067446

  6. A Study of the Magnetic and Thermal Properties of Ln

    SciTech Connect

    Harada, Daijitsu; Hinatsu, Yukio

    2001-05-01

    Crystal structures, and magnetic, electric, and thermal properties of fluorite related compounds Ln{sub 3}RuO{sub 7} (Ln=Sm, Eu) have been investigated. For Eu{sub 3}RuO{sub 7}, a magnetic transition due to Ru{sup 5+} ions is found at T{sub N}=22.5 K on the susceptibility-temperature curve. Specific heat measurements also exhibit a {lambda}-type anomaly at the same temperature. The Moessbauer spectrum measured at 10 K shows broadening of the line corresponding to magnetic splitting. For Sm{sub 3}RuO{sub 7}, two magnetic anomalies have been observed at 10.5 and 22.5 K from its magnetic susceptibility measurements. Below 22.5 K Ru{sup 5+} ions are antiferromagnetically coupled, and when the temperature is decreased through 10.5 K the ordering of Sm{sup 3+} ions occurs rapidly. Specific heat measurements show first-order transition peaks at T=280 and 190 K for Eu{sub 3}RuO{sub 7} and Sm{sub 3}RuO{sub 7}, respectively. T he results of magnetic susceptibility and electric resistivity measurements indicate that these transitions are structural phase transitions.

  7. The Stardalur magnetic anomaly revisited—New insights into a complex cooling and alteration history

    Microsoft Academic Search

    C. Vahle; A. Kontny; H. P. Gunnlaugsson; L. Kristjansson

    2007-01-01

    This study provides new rock magnetic and magneto-mineralogical data including Mössbauer spectroscopy of basaltic drill cores from the Stardalur volcanic complex, Iceland, in order to better understand the strong magnetic anomaly, which is caused by an extraordinary high natural remanent magnetization (NRM). NRM and magnetic susceptibility (?) display a positive linear correlation (R2=0.81) and reach very high values up to

  8. Spectroscopic and Interfacial Properties of Myoglobin/Surfactant Complexes

    PubMed Central

    Tofani, Luca; Feis, Alessandro; Snoke, Roy E.; Berti, Debora; Baglioni, Piero; Smulevich, Giulietta

    2004-01-01

    The complexes of horse myoglobin (Mb) with the anionic surfactant sodium dodecyl sulfate (SDS), and with the cationic surfactants cetyltrimethylammonium chloride (CTAC) and decyltrimethylammonium bromide (DeTAB), have been studied by a combination of surface tension measurements and optical spectroscopy, including heme absorption and aromatic amino acid fluorescence. SDS interacts in a monomeric form with Mb, which suggests the existence of a specific binding site for SDS, and induces the formation of a hexacoordinated Mb heme, possibly involving the distal histidine. Fluorescence spectra display an increase of tryptophan emission. Both effects point to an increased protein flexibility. SDS micelles induce both the appearance of two more heme species, one of which has the features of free heme, and protein unfolding. Mb/CTAC complexes display a very different behavior. CTAC monomers have no effect on the absorption spectra, and only a slight effect on the fluorescence spectra, whereas the formation of CTAC aggregates on the protein strongly affects both absorption and fluorescence. Mb/DeTAB complexes behave in a very similar way as Mb/CTAC complexes. The surface activity of the different Mb/surfactant complexes, as well as the interactions between the surfactants and Mb, are discussed on the basis of their structural properties. PMID:15298921

  9. Structural magnetism: Experimental studies of the relations between structures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Lin, Tao

    The magnetic properties of transition metals are known to depend strongly upon their crystal structure. One way to artificially control the structure is through the preparation of superlattices, where a metastable phase of one element may be stabilized through epitaxial growth. Many metastable systems achieved exhibit unusual properties. Some newly developed technologies make this study possible. Epitaxial sputtering was established within this decade and it is our primary growth method. X-ray diffraction is still the most important technique in determining crystal structure. Magnetic optical Kerr effect (MOKE) can give lots of important information on magnetic properties such as the coercivity and the saturation Kerr effect. The theory of the X-ray magnetic circular dichroism (XMCD) is quite similar to MOKE except that it uses X-rays instead of visible light. This feature enables XMCD to detect the element specific magnetic properties which play a central role in this study. The studies on Fe/Ni and Fe/Ru multilayers discovered many extraordinary behaviors of Ni and Ru. in their metastable phase. For example, as an important ferromagnetic metal, Ni is found enhanced magnetic moment in bct structure for the first time. The study on the Slater-Pauling curve for the 4d elements is to continue a 70-year construction of Slater-Pauling curve. Benefited from those new techniques, the construction of the Slater- Pauling curve for the 4d elements was accomplished. Metastable phase fct-Fe is of particular interesting because it displays a large variety of structural magnetic properties. It was found in this project that Fe magnetic moment in the [4d alloy/Fe/4d alloy] structure has a strong dependence on the electron interaction between Fe and 4d element. Although there is no solid evidence indicating that the resistance of tunneling junctions with GdN barrier have dependence on external magnetic field, lots of interesting results were still found, such as the relation between exchange biasing field and the thickness of FeMn layer.

  10. Soft Magnetic Properties of Obliquely Deposited Co-Zr-O Films

    E-print Network

    , multilayer, nano-composite films, oblique deposition, shadowing effect, soft magnetic properties, stripeSoft Magnetic Properties of Obliquely Deposited Co-Zr-O Films Yuqin Sun C. R. Sullivan Weidong Li D Magnetic Properties of Obliquely Deposited Co­Zr­O Films Yuqin Sun1, Charles R. Sullivan1, Weidong Li1

  11. CocoreAushell nanoparticles: evolution of magnetic properties in the displacement reaction

    E-print Network

    Krishnan, Kannan M.

    CocoreAushell nanoparticles: evolution of magnetic properties in the displacement reaction Saikat for the gold metal deposition on its surface. Hysteretic magnetic properties of nanoparticles depend critically­shell morphology allow modification and tailoring of the particle properties (e.g., optical, magnetic, catalytic

  12. MAGNETIC PROPERTIES OF SEDIMENTARY GREIGITE (Fe3S4): AN UPDATE

    E-print Network

    Utrecht, Universiteit

    MAGNETIC PROPERTIES OF SEDIMENTARY GREIGITE (Fe3S4): AN UPDATE Andrew P. Roberts,1,2 Liao Chang,1. Much recent progress has been made in understanding its magnetic properties. Greigite is an inverse magnetic properties of greigite (at high, ambient, and low temperatures and with alternating and direct

  13. Author's personal copy Magnetic properties of stainless steels at room and cryogenic temperatures

    E-print Network

    Oxley, Paul

    Author's personal copy Magnetic properties of stainless steels at room and cryogenic temperatures: Magnetic measurement Ferromagnetic property Stainless steel Martensitic Ferritic a b s t r a c t The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room

  14. Magnetic properties of nanomagnetic and biomagnetic systems analyzed using cantilever magnetometry

    E-print Network

    Aste, Andreas

    Magnetic properties of nanomagnetic and biomagnetic systems analyzed using cantilever magnetometry.1088/0957-4484/22/28/285715 Magnetic properties of nanomagnetic and biomagnetic systems analyzed using cantilever magnetometry Urs at stacks.iop.org/Nano/22/285715 Abstract Magnetic properties of nanomagnetic and biomagnetic systems

  15. Magnetic structure and Magnetic transport Properties of Graphene Nanoribbons With Sawtooth Zigzag Edges

    NASA Astrophysics Data System (ADS)

    Wang, D.; Zhang, Z.; Zhu, Z.; Liang, B.

    2014-12-01

    The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices.

  16. Magnetic and structural properties of ion nitrided stainless steel

    NASA Astrophysics Data System (ADS)

    Basso, R. L. O.; Pimentel, V. L.; Weber, S.; Marcos, G.; Czerwiec, T.; Baumvol, I. J. R.; Figueroa, C. A.

    2009-06-01

    The magnetic properties and crystalline structure of expanded austenite obtained by ion beam nitriding of AISI 316 steel are investigated. Magnetic force microscopy reveals that the nitrogen expanded austenite has two different layers, an outermost ferromagnetic layer and a paramagnetic layer beneath it. Superimposing the nitrogen concentration profile determined by secondary neutral mass spectrometry and the magnetic force microscopy image, one can see that the paramagnetic-ferromagnetic transition takes place at the inflection point of the nitrogen concentration profile at about 14±2 N at. %. Conventional and glancing angle x-ray diffraction suggests that nitrogen could occupy first tetrahedral interstitial positions (nitrogen-poor paramagnetic phase) and then, after saturation of Cr traps, octahedral interstitial positions (nitrogen-rich ferromagnetic phase). The ferromagnetic-paramagnetic transition is seen to be governed by Cr (traps)-N interactions.

  17. Ferromagnetism of dense matter and magnetic properties of neutron stars

    E-print Network

    P. Haensel; S. Bonazzola

    1996-05-24

    Possible consequences of ferromagnetic transition in dense matter suggested recently by Kutschera and W{\\'o}jcik, for the magnetic properties of neutron stars, are studied. Specific model of dense matter, in which a small admixture of protons is completely polarized due to their interaction with neutrons, is considered. Magnetic field of neutron stars with a ferromagnetic core is calculated within the framework of general relativity. Two types of boundary conditions at the ferromagnetic core edge are considered, corresponding to normal and superconducting liquid envelope, respectively. Numerical results for the neutron star magnetic dipole moment are confronted with pulsar timing. To be consistent with observations, ferromagnetic cores surrounded by a non-superconducting envelope, should consist of weakly ordered ferromagnetic domains. If domains are highly ordered, ferromagnetic core should be screened by a superconducting envelope.

  18. Artificial multiferroic heterostructures for an electric control of magnetic properties

    NASA Astrophysics Data System (ADS)

    Garcia, Vincent; Bibes, Manuel; Barthélémy, Agnès

    2015-03-01

    The control of magnetism by electric fields is an important goal for future low-power spintronics devices. This partly explains the intensified recent interest for magnetoelectric multiferroic materials and heterostructures. The lack of ferro- or ferrimagnetic-ferroelectric materials with large magnetoelectric coupling between the two orders has spurred intensive research on artificial multiferroics combining ferroelectric or piezoelectric materials and ferromagnets. In this paper we review synthetically the potential of thin-film-based heterostructures in which a magnetic film is in contact with a ferroelectric or piezoelectric one to obtain an electric control of magnetic properties. This electric control either results from a strain-induced magnetoelectric coupling, a charge-driven one, or from the modulation of an interfacial exchange-bias interaction.

  19. Magnetic properties of X-ray bright points. [in sun

    NASA Technical Reports Server (NTRS)

    Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S.

    1977-01-01

    Using high-resolution Kitt Peak National Observatory magnetograms and sequences of simultaneous S-054 soft X-ray solar images, the properties of X-ray bright points (XBP) and ephemeral active regions (ER) are compared. All XBP appear on the magnetograms as bipolar features, except for very recently emerged or old and decayed XBP. The separation of the magnetic bipoles is found to increase with the age of the XBP, with an average emergence growth rate of 2.2 plus or minus 0.4 km per sec. The total magnetic flux in a typical XBP living about 8 hr is found to be about two times ten to the nineteenth power Mx. A proportionality is found between XBP lifetime and total magnetic flux, equivalent to about ten to the twentieth power Mx per day of lifetime.

  20. Enhancement of the magnetic properties of Al/La multiferroic

    NASA Astrophysics Data System (ADS)

    Ahmed, M. A.; Okasha, N.; Hussein, B.

    2012-08-01

    Nanosized multiferroic La1-xAlxFeO3 (0.00?x?0.20) samples were successfully synthesized by the citrate technique without subsequent heat treatment. All the prepared samples revealed single phase orthorhombic structure of space group Pbnm. XRD data revealed that the lattice parameters (a) decrease with increasing Al content. The magnetic susceptibility (?M) was enhanced significantly from 0.36 to 0.68 emu/g mole from LaFeO3 to La0.8Al0.2FeO3 respectively. The values of magnetization (M) and effective magnetic moment (?eff) were found to increase with increasing Al content. The enhancement of the physical and structural properties of the investigated multiferroic is possibly due to the changes in the lattice parameters, tolerance factor as well as crystallite size caused by aluminum substitution.

  1. Discontinuous properties of current-induced magnetic domain wall depinning

    PubMed Central

    Hu, X. F.; Wu, J.; Niu, D. X.; Chen, L.; Morton, S. A.; Scholl, A.; Huang, Z. C.; Zhai, Y.; Zhang, W.; Will, I.; Xu, Y. B.; Zhang, R.; van der Laan, G.

    2013-01-01

    The current-induced motion of magnetic domain walls (DWs) confined to nanostructures is of great interest for fundamental studies as well as for technological applications in spintronic devices. Here, we present magnetic images showing the depinning properties of pulse-current-driven domain walls in well-shaped Permalloy nanowires obtained using photoemission electron microscopy combined with x-ray magnetic circular dichroism. In the vicinity of the threshold current density (Jth = 4.2 × 1011?A.m?2) for the DW motion, discontinuous DW depinning and motion have been observed as a sequence of “Barkhausen jumps”. A one-dimensional analytical model with a piecewise parabolic pinning potential has been introduced to reproduce the DW hopping between two nearest neighbour sites, which reveals the dynamical nature of the current-driven DW motion in the depinning regime. PMID:24170087

  2. Transport and magnetic properties of BaVSe3

    NASA Astrophysics Data System (ADS)

    Akrap, Ana; Stevanovi?, Vladan; Herak, Mirta; Miljak, Marko; Bariši?, Neven; Berger, Helmuth; Forró, László

    2008-12-01

    We report a comprehensive study of transport, magnetotransport, and magnetic properties of single crystals of BaVSe3 . The paramagnetic metal-ferromagnetic metal transition at 43 K was followed as a function of pressure by measuring the electrical resistivity and the thermoelectric power. The exponent of the low-temperature power-law dependence of the resistivity increases with pressure. The effective magnetic moment obtained from magnetic susceptibility in the paramagnetic regime is ?eff=1.40?B . The study was completed by band-structure calculations based on density-functional theory both at ambient and high pressures. Transport coefficients of BaVSe3 resemble the high-pressure phase of BaVS3 , which suggest that the replacement of sulfur with selenium can be viewed as chemical pressure.

  3. Magnetic properties of CdSb doped with Ni

    NASA Astrophysics Data System (ADS)

    Laiho, R.; Lashkul, A. V.; Lähderanta, E.; Lisunov, K. G.; Ojala, I.; Zakhvalinskii, V. S.

    2006-05-01

    Magnetic properties of the group II-V semiconductor CdSb single crystals doped with Ni (2 at%) are investigated. Deviation of the zero-field-cooled susceptibility, ? ZFC, from the field-cooled susceptibility is observed below 300 K, along with a broad maximum of ? ZFC ( T) at Tb in fields below the anisotropy field BK˜4 kG. Tb( B) obeys the law [ Tb( B)/ Tb(0)] 1/2=1- B/ BK with Tb(0)˜100 K. The magnetization exhibits saturation above ˜20-30 kG, a weak temperature dependence and anisotropy of the saturation value Ms. The coercive field is much smaller then BK and displays anisotropy inverted with respect to that of Ms. Such magnetic behavior is expected for spheroidal Ni-rich Ni 1-xSb x nanoparticles with high aspect ratio, broad distribution of the sizes and with orientations of the major axis distributed around a preferred direction.

  4. Magnetic Properties of Bio-Synthesized Magnetite Nanoparticles

    SciTech Connect

    Rawn, Claudia J [ORNL; Yeary, Lucas W [ORNL; Moon, Ji Won [ORNL; Love, Lonnie J [ORNL; Thompson, James R [ORNL; Phelps, Tommy Joe [ORNL

    2005-01-01

    Magnetic nanoparticles, which are unique because of both structural and functional elements, have various novel applications. The popularity and practicality of nanoparticle materials create a need for a synthesis method that produces quality particles in sizable quantities. This paper describes such a method, one that uses bacterial synthesis to create nanoparticles of magnetite. The thermophilic bacterial strain Thermoanaerobacter ethanolicus TOR-39 was incubated under anaerobic conditions at 65 C for two weeks in aqueous solution containing Fe ions from a magnetite precursor (akaganeite). Magnetite particles formed outside of bacterial cells. We verified particle size and morphology by using dynamic light scattering, X-ray diffraction, and transmission electron microscopy. Average crystallite size was 45 nm. We characterized the magnetic properties by using a superconducting quantum interference device magnetometer; a saturation magnetization of 77 emu/g was observed at 5 K. These results are comparable to those for chemically synthesized magnetite nanoparticles.

  5. Intraband magneto-optical properties of magnetic quantum dots

    NASA Astrophysics Data System (ADS)

    Savi?, Ivana; Vukmirovi?, Nenad

    2007-12-01

    The intraband optical properties of quantum dots comprising one electron and up to two Mn ions, subjected to an axial magnetic field, have been investigated theoretically using the configuration-interaction method. We have shown that the electron-Mn and the Mn-Mn exchange interaction mechanisms induce splitting of the energy levels for zero magnetic field, and lead to ground-state transitions and anticrossing of the states for finite magnetic fields. This results in the presence of interesting effects in the intraband absorption spectrum, such as the appearance of new absorption lines and anticrossing features, absent in the single-particle spectrum. Our analysis predicts that both the electron Mn ion and the Mn-Mn exchange interactions may be probed by means of intraband magneto-optical spectroscopy.

  6. Magnetic Properties of Nanocrystalline Nickel-Cobalt Ferrites

    NASA Astrophysics Data System (ADS)

    Tiwari, D. K.; Villaseñor-Cendejas, L. M.; Thakur, A. K.

    2013-09-01

    In this study, the nanocrystalline nickel-cobalt ferrites were prepared via the citrate route method at . The samples were calcined at for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of and the behavior of a hard magnet.

  7. Magnetic Properties and Hyperfine Interactions in Iron Containing Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Unruh, Karl Marlin

    Amorphous samples of Fe(,x)B(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 90), Fe(,x)Ag(,100-x) (40 (LESSTHEQ) x (LESSTHEQ) 50), and Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93) have been prepared, and their magnetic properties and hyperfine interactions studied by ('57)Fe Mossbauer spectroscopy. Each system is representative of either Fe-metalloid (Fe-B), Fe-noble metal (Fe-Ag), or Fe-early transition metal (Fe -Zr) amorphous alloys. Therefore, by studying these three amorphous solids an overview is obtained, not only of the properties of the individual alloys, but also of the wider class of alloys of which they are representative. The amorphous Fe-B and Fe-Zr systems have been successfully fabricated over very wide ranges in composition, allowing the evolution of the magnetic properties and hyperfine interactions to be systematically studied. As a result it has been possible to determine the critical concentration for magnetic order (x(,c)). It has been shown that the loss of magnetic order below x(,c) is the result of the reduction and eventual disappearance of the Fe moment. The isomer shifts (IS) and quadrupole splittings (QS) have also been determined over wide composition ranges. This has led to the observation of a maximum in IS with decreasing Fe concentration in amorphous alloys of Fe and B. On the other hand, IS in the amorphous Fe-Zr alloys has been found to decrease monotonically over the same concentration range. In the paramagnetic region all the samples display quadrupole split doublets characteristic of site symmetries lower than cubic. It has been found that the observed asymmetry in the quadrupole spectra can be correlated with the relative changes in IS and QS as a function of composition. Amorphous alloys of Fe and Ag have been prepared for the first time and have been found to be stable at room temperature. The somewhat unusual magnetic properties of these alloys suggests that they may be simpler magnetically than previously studied magnetic amorphous solids. The very existence of this kind of amorphous alloy raises a number of interesting questions on the nature of the amorphous state. Two tests of the quasi-crystalline model have also been undertaken. In the first instance crystalline and amorphous FeB have been directly compared. The quasi -crystalline model cannot account for the significant differences that exist between the amorphous alloy and the crystalline compound. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.

  8. Physical properties of Moving Magnetic Features observed around a pore

    NASA Astrophysics Data System (ADS)

    Criscuoli, S.; Del Moro, D.; Giannattasio, F.; Viticchié, B.; Giorgi, F.; Ermolli, I.; Zuccarello, F.; Berrilli, F.

    2012-06-01

    Movies of magnetograms of sunspots often show small-size magnetic patches that move radially away and seem to be expelled from the field of the spot. These patches are named Moving Magnetic Features (MMFs). They have been mostly observed around spots and have been interpreted as manifestations of penumbral filaments. Nevertheless, few observations of MMFS streaming out from spots without penumbra have been reported. He we investigate the physical properties of MMFs observed around the field of a pore derived by the analyses of high spectral, spatial and temporal resolution data acquired at the Dunn Solar Telescope with IBIS. We find that the main properties of the investigated features agree with those reported for MMFs observed around regular spots. These results indicate that an improvement of current numerical simulations is required to understand the generation of MMFs in the lack of penumbrae.

  9. Magnetic properties and transformation of crystal structure in the ErFe2-ErAl2 system

    NASA Astrophysics Data System (ADS)

    ?wik, J.; Koshkid'ko, Y.; Mikhailova, A.; Kolchugina, N.; Nenkov, K.; Hackamer, A.; Miller, M.

    2015-03-01

    The modification of structural properties and magnetic behaviour of the ErFe2-xAlx Laves phase intermetallic compounds have been studied while changing the Al content in the range 0.36 ? x ? 1.5. Powder X-ray diffraction study at room temperature showed the formation of the cubic C15 structure, in the samples with Al content of 0.36 ? x < 0.75 and 1.4 ? x ? 2.0. For the intermediate compositions with 0.75 ? x ? 1.4, the hexagonal C14 structure is observed. Magnetic and magnetocaloric properties of polycrystalline ErFe2-xAlx intermetallic compounds were investigated experimentally using magnetic and heat capacity measurements. The Curie temperature TC decreases from 275 to 28 K as the Al content increases from x = 0.36 to x = 1.5, respectively. Magnetization measurements in strong magnetic fields showed the complex mechanism of magnetic saturation in the studied compounds. Under an external field change from 0 to 2 T, the maximum entropy change is 6 J/kg K at T = 28 K for the composition with x = 1.5. The minimum in the concentration dependence of the magnetic entropy change is observed in the vicinity of x equal to 1.25. Regularities of variations of magnetocaloric properties of ErFe2-xAlx intermetallic compounds with increasing Al content are discussed from the point of view of their both structural and magnetic states.

  10. Synthesis and Magnetic Properties of Fe7C3 Particles with High Saturation Magnetization

    NASA Astrophysics Data System (ADS)

    Tajima, Shin; Hirano, Shin-ichi

    1990-04-01

    The formation behavior and magnetic properties of Fe7C3 particles were investigated under atmospheric pressure. The starting material of barium-containing iron oxide was carbureted with CO by heat treatment. Fe7C3 particles were formed in the reaction temperature range of 300-375°C along with a small amount of Fe5C2 particles. Fe7C3 content in the product increased with the increase in the partial pressure of CO and the decrease in the reaction temperature. DTA-TG analysis revealed that the product contained about 5-10 wt% free carbon. The saturation magnetization of the product was about 110 emu/g regardless of the reaction conditions. The coercivity and the ratio of the residual magnetization to the saturation magnetization increased with the increase of the Fe7C3 content in the product.

  11. A comparative study of magnetic anisotropy measurement techniques in relation to rock-magnetic properties

    NASA Astrophysics Data System (ADS)

    Bilardello, Dario; Jackson, Michael J.

    2014-08-01

    Magnetic anisotropy measurements are becoming increasingly common to many studies within the different disciplines of geology, involving sedimentary, igneous and metamorphic rocks. A plethora of techniques exists for measuring magnetic anisotropy of rocks. Some are rapid and non-destructive while others are more labor-intensive or may result in alteration of the magnetic minerals. All, however, have the potential of revealing a wealth of information when measured and interpreted correctly. In broad terms, anisotropy techniques subdivide into measurements of susceptibility, remanence and torque; here we consider the first two of these. Anisotropy of magnetic susceptibility (AMS) is by far the most utilized, and measures composite fabrics. Magnetic susceptibilities in high fields and low temperatures, however, are being increasingly used to isolate the paramagnetic contribution to the fabrics. When distinguishing between fabrics carried by different ferromagnetic phases, or to separate these from the diamagnetic and paramagnetic contributions to the fabric, then remanence anisotropy techniques become necessary. Anisotropies of thermal remanence (ATRMs), of anhysteretic remanence (AARM) and of isothermal remanence (AIRM) are the most common examples. Remanence anisotropy may be measured over the full spectrum of magnetic coercivities or over a targeted range (e.g. partial or ApARM). Moreover, anisotropies may be calculated using only the resolved field-parallel component of the vector, in which case a minimum of six different orientations is necessary to obtain a complete symmetric tensor, or using the three components (full vector) of the measured magnetic vectors (e.g. AvARM), in which case three orthogonal applied magnetizations are the minimum requirement. In this study we utilize a variety of magnetic remanence room temperature techniques to measure remanence anisotropy of selected coarse and finer grained gneiss-granulitic specimens with well-pronounced fabrics. Results are compared to room temperature AMS and are interpreted in terms of the applicability of instrumentation/technique to specific rock-magnetic properties.

  12. Structural, dielectric and magnetic properties of Ni substituted zinc ferrite

    NASA Astrophysics Data System (ADS)

    Kumbhar, S. S.; Mahadik, M. A.; Mohite, V. S.; Rajpure, K. Y.; Kim, J. H.; Moholkar, A. V.; Bhosale, C. H.

    2014-08-01

    NixZn1-xFe2O4 ferrite has been synthesized by the ceramic method using Ni CO3, ZnO, Fe2O3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of NixZn1-xFe2O4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of NixZn1-xFe2O4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of NixZn1-xFe2O4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x=0.8, is attributed to magnetic moment of Fe3+ ions.

  13. Magnetic complexity as an explanation for bimodal rotation populations among young stars

    E-print Network

    Garraffo, Cecilia; Cohen, Ofer

    2015-01-01

    Observations of young open clusters have revealed a bimodal distribution of fast and slower rotation rates that has proven difficult to explain with predictive models of spin down that depend on rotation rates alone. The Metastable Dynamo Model proposed recently by Brown, employing a stochastic transition probability from slow to more rapid spin down regimes, appears to be more successful but lacks a physical basis for such duality. Using detailed 3D MHD wind models computed for idealized multipole magnetic fields, we show that surface magnetic field complexity can provide this basis. Both mass and angular momentum losses decline sharply with increasing field complexity. Combined with observation evidence for complex field morphologies in magnetically active stars, our results support a picture in which young, rapid rotators lose angular momentum in an inefficient way because of field complexity. During this slow spin-down phase, magnetic complexity is eroded, precipitating a rapid transition from weak to str...

  14. Magnetic Complexity as an Explanation for Bimodal Rotation Populations among Young Stars

    NASA Astrophysics Data System (ADS)

    Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer

    2015-07-01

    Observations of young open clusters have revealed a bimodal distribution of fast and slower rotation rates that has proven difficult to explain with predictive models of spin down that depend on rotation rates alone. The Metastable Dynamo Model proposed recently by Brown, employing a stochastic transition probability from slow to more rapid spin down regimes, appears to be more successful but lacks a physical basis for such duality. Using detailed 3D MHD wind models computed for idealized multipole magnetic fields, we show that surface magnetic field complexity can provide this basis. Both mass and angular momentum losses decline sharply with increasing field complexity. Combined with observation evidence for complex field morphologies in magnetically active stars, our results support a picture in which young, rapid rotators lose angular momentum in an inefficient way because of field complexity. During this slow spin-down phase, magnetic complexity is eroded, precipitating a rapid transition from weak to strong wind coupling.

  15. Magnetic and transport properties of MnBi\\/Bi nanocomposites

    Microsoft Academic Search

    Kyongha Kang; L. H. Lewis; Y. F. Hu; Qiang Li; A. R. Moodenbaugh; Young-Suk Choi

    2006-01-01

    The magnetic and transport properties of a nanostructured Mn-Bi eutectic composition (~Mn5Bi95) produced by melt spinning and low-temperature\\/short time vacuum annealing were studied. A hysteretic magnetostructural transformation from low-temperature phase to high-temperature phase MnBi is confirmed at 520 K. The fact that the transition temperature is lower than that reported for bulk MnBi (633 K), is tentatively attributed to interfacial

  16. Dielectric, ferroelectric, magnetic, and magnetoelectric properties of multiferroic laminated composites

    Microsoft Academic Search

    N. Cai; J. Zhai; C.-W. Nan; Y. Lin; Z. Shi

    2003-01-01

    Multiferroic laminated composites consisting of lead-zirconate titanate (PZT)\\/polyvinylidene-fluoride (PVDF) particulate composite layers and Tb-Dy-Fe alloy (Terfenol-D)\\/PVDF particulate composite layers, prepared by a simple hot-molding technique, were reported. In the laminated composites, the polymer PVDF is inert and used just as a binder. The measured dielectric, ferroelectric, magnetic, and magnetoelectric properties demonstrate strong dependence on volume fraction f of the PVDF

  17. Photometric properties of magnetic elements: resolved and unresolved features

    E-print Network

    Serena Criscuoli

    2007-12-19

    We investigate, by numerical simulations, the photometric signature of magnetic flux tubes in the solar photosphere. We show that the observed contrast profiles are determined not only by the physical properties of the tube and its surroundings, but also by the peculiarities of the observations, including the line/continuum formation height and the spatial and spectral resolution. The aim is to understand these contributions well enough so that multi-wavelength observations can begin to disentangle them.

  18. Microstructure and magnetic properties of sputtered spin valve systems

    Microsoft Academic Search

    J. Langer; R. Mattheis; B. Ocker; W. Maaß; S. Senz; D. Hesse; J. Kräußlich

    2001-01-01

    Different sputtering methods, viz. rf-diode, rf-magnetron, and dc-magnetron sputtering, have been used to increase the sensitivity of Co\\/Cu\\/Co\\/FeMn top spin valve systems by more than a factor of 2. This improvement is due to an enhanced magnetoresistive effect DeltaR\\/R and a reduced anisotropy field Hk for the best sample. In the present paper the transport and magnetic properties are discussed

  19. Magnetic and magneto-transport properties in nanostructured materials

    Microsoft Academic Search

    Fengyuan Yang

    2001-01-01

    Magneto-transport, magnetic and structural properties of three nanostructured systems: (1) single-crystal bismuth films with and without antidot arrays made by electrodeposition, (2) epitaxial half-metallic CrO2 films made by chemical vapor deposition (CVD), and (3) exchange-coupled Co\\/FeMn\\/permalloy trilayers prepared by magnetron sputtering are presented. Single-crystal Bi thin films have been made by electrodeposition followed by suitable annealing. X-ray diffraction verifies that

  20. Magnetic and structural properties of nanophase Pt\\/Co multilayers

    Microsoft Academic Search

    P. F. Carcia; D. Coulman; R. S. McLean; M. Reilly

    1996-01-01

    We have studied the magnetic and structural properties of Pt\\/Co multilayers grown on Pt nanoparticles with pre-etched thicknesses 10–50 Å. Unexpectedly, the perpendicular anisotropy energy (Keff) and coercivity (Hc) were maximum for multilayers grown on 33 Å Pt. Keff was 1.2 × 107 erg\\/cm3-Co and Hc was 3.5 kOe, both exceptionally large for Ar-sputtered Pt\\/Co multilayers. As revealed by X-ray

  1. Magnetic and structural properties of nanophase Pt\\/Co multilayers

    Microsoft Academic Search

    P. F. Carcia; D. Coulman; R. S. McLean; M. Reilly

    1996-01-01

    We have studied the magnetic and structural properties of Pt\\/Co multilayers grown on Pt nanoparticles with pre-etched thicknesses 10-50 Å. Unexpectedly, the perpendicular anisotropy energy (Keff) and coercivity (Hc) were maximum for multilayers grown on 33 Å Pt. Keff was 1.2 × 107 erg\\/cm3-Co and Hc was 3.5 kOe, both exceptionally large for Ar-sputtered Pt\\/Co multilayers. As revealed by X-ray

  2. Magnetic and structural properties of nanoparticles of nickel oxide

    Microsoft Academic Search

    2006-01-01

    In this dissertation, magnetic properties of NiO nanoparticles (NP) prepared by the sol-gel method in the size range D = 5 nm to 20 nm, with and without oleic acid (OA) coating, are reported. Transmission electron microscopy (TEM) studies show the morphology of the smaller particles to be primarily rod-like, changing over to nearly spherical shapes for D >10 nm.

  3. Magnetic and transport properties of magnetite thin films

    Microsoft Academic Search

    Guomin Zhang; Chongfei Fan; Liqing Pan; Fengping Wang; Ping Wu; Hong Qiu; Yousong Gu; Yue Zhang

    2005-01-01

    Magnetite (Fe3O4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe3O4 films were annealed at 480°C for 80min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR),

  4. Magnetoresistance and magnetic properties of epitaxial magnetite thin films

    Microsoft Academic Search

    G. Q. Gong; A. Gupta; Gang Xiao; W. Qian; V. P. Dravid

    1997-01-01

    The magnetotransport and magnetic properties of epitaxial Fe3O4 thin films grown on (001)-oriented MgO substrates by pulsed-laser deposition have been investigated. The magnetoresistance (MR) exhibits a peak around the Verwey transition (Tnu) as has also been reported previously for single crystals. Additionally, we have observed that the MR increases monotonically below 100 K with decreasing temperature. MR values as high

  5. Structural characterization and magnetic properties of steels subjected to fatigue

    Microsoft Academic Search

    C. C. H. Lo; F. Tang; S. B. Biner; D. C. Jiles

    2000-01-01

    Studies have been made on the effects of residual stress and microstructure on the variations of magnetic properties of steels during fatigue. Strain-controlled fatigue tests have been conducted on 0.2wt% C steel samples which were (1) cold-worked, (2) cold-worked and annealed at 500 °C to relieve residual stress, and (3) annealed at 905 °C to produce a ferrite\\/pearlite structure. The

  6. Magnetic Properties of Ilmenite-Hematite System at Low Temperature

    Microsoft Academic Search

    Yoshikazu Ishikawa

    1962-01-01

    The magnetic properties of FeTiO3 containing less than 50 mole percent of Fe2O3 have been re-examined between 2°K and room temperature by means of a Cioffi-type automatic fluxmeter. It was confirmed that each specimen has a low-temperature transition point, which decreases in temperature with increasing content of Fe2O3. Above the transition temperature the specimens with 8 and 12 mole %

  7. Magnetic properties of transition-metal multilayers studied with x-ray magnetic circular dichroism spectroscopy

    SciTech Connect

    Stoehr, J.; Nakajima, R.

    1998-01-01

    The detailed understanding of the magnetic properties of transition-metal multilayers requires the use of state-of-the-art experimental techniques. Over the last few years, the X-ray magnetic circular dichroism (XMCD) technique has evolved into an important magnetometry tool. This paper is an overview of the principles and unique strengths of the technique. Aspects covered include the quantitative determination of element-specific spin and orbital magnetic moments and their anisotropies through sumrule analyses of experimental spectra. A discussion is presented on how the spin and orbital magnetic moments in transition-metal thin films and sandwiches are modified relative to the bulk. The authors show that a thin film of a nonmagnetic metal such as Cu may become magnetically active when adjacent to a magnetic layer, and a thin film of a ferromagnetic metal such as Fe may become magnetically inactive. The orbital moment is found to become anisotropic in thin films; it can be regarded as the microscopic origin of the magnetocrystalline anisotropy.

  8. A method for analyzing the microwave absorption properties of magnetic materials

    NASA Astrophysics Data System (ADS)

    Pang, Hua; Fan, Mei; He, Zhifu

    2012-08-01

    Based on transmission line theory, a complex thickness is introduced to analyze the electromagnetic wave absorption properties of materials with high magnetic loss and low dielectric loss. At each frequency the real part of the complex thickness denotes the thickness of the absorber to reach maximum absorption, while the absolute value of the imaginary part of the normalized complex thickness represents the degree of impedance mismatch between the material and free space. Using this method, the intensity of the reflection loss and the corresponding material thickness can be well predicted and understood. This method describes well the microwave absorption behaviors of PANI/?-Fe and PANI/CIP/Fe3O4 composites. It is found that the electromagnetic energy loss in the material, as well as the interference cancellation of the reflected waves at the air-material interface, contributes to the global minimum of reflection loss for the two composites.

  9. Magnetic properties of TOAB-capped CuO nanoparticles.

    NASA Astrophysics Data System (ADS)

    Seehra, M.; Punnoose, A.; Mahamuni, S.

    2002-03-01

    Synthesis of CuO nanoparticles (NP) capped with TOAB (tetraoctylammonium bromide) and their structural properties were reported recently [1]. Here we report on the magnetic properties of the TOAB-capped CuO-NP of size 4, 6 and 10 nm and compare these properties with those of uncapped CuO-NP in the size range of 6.6-37 nm described in the above abstract [2] and in a recent publication [3]. Temperature (5 K 350 K) and magnetic field (up to 55 kOe) variations of magnetization M, coercivity H_c, exchange bias He (field-cooled in 55 kOe) and the Neel temperature TN (where He goes to zero) were measured. The TOAB-capped NP have higher magnitudes of Ms (the weak ferromagnetic component of M) and lower He values, confirming the 1/Ms variation of He observed in uncapped CuO-NP for size < 16 nm. The reasons for the larger Ms in the capped vs. uncapped CuO-NP are now under investigation. TN decreases with the decrease in the particle size, as also observed for the uncapped CuO-NP. Supported in part by U.S. DOE (contract DE-FC26-99FT40540). [1]. K. Borgohain et al, Phys. Rev. B61, 11093 (2000). [2]. A. Punnoose and M. S. Seehra, preceding abstract. [3]. Punnoose, Magnone, Seehra & Bonevich, Phys. Rev. B64, 174420 (2001).

  10. Structural and magnetic properties of sonoelectrocrystallized magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Mosivand, S.; Monzon, L. M. A.; Ackland, K.; Kazeminezhad, I.; Coey, J. M. D.

    2014-02-01

    The effect of ultrasound power on the morphology, structure and magnetic properties of magnetite nanoparticles synthesized from iron electrodes by the electro-oxidation method was investigated. Samples made in aqueous solution in the absence or presence of an organic stabilizer (thiourea, tetramethylammonium chloride, sodium butanoate or ?-cyclodextrine) were characterized by x-ray diffraction, transmission and scanning electron microscopy, magnetometry and Mössbauer spectrometry. The iron is almost all in the form of 20-85 nm particles of slightly nonstoichiometric Fe3-?O4, with ? ? 0.10. Formation of a paramagnetic secondary phase in the presence of sodium butanoate or ?-cyclodextrine is supressed by ultrasound. Specific magnetization of the magnetite nanoparticles ranges from 19 to 90 A m2 kg-1 at room temperature, and it increases with particle size in each series. The particles show no sign of superparamagnetism, and the anhysteretic and practically temperature-independent magnetization curves are associated with a stable magnetic vortex state throughout the size range. The spin structure of the particles and the use of magnetization measurements to detect magnetite in unknown mixtures are discussed.

  11. Anisotropic magnetic properties of EuAl2Si2

    NASA Astrophysics Data System (ADS)

    Maurya, Arvind; Kulkarni, Ruta; Thamizhavel, A.; Bonville, P.; Dhar, S. K.

    2015-03-01

    EuAl2Si2 is known to crystallize in the CaAl2Si2-type trigonal structure. We have grown single crystals of EuAl2Si2 by flux method, using Al-Si eutectic (87.8% Al) as self-flux, and investigated their anisotropic magnetic properties by means of magnetization, electrical resistivity and heat capacity in zero and applied magnetic fields, and 151Eu Mössbauer spectroscopy. Magnetic susceptibility data show an antiferromagnetic transition at TN = 33.3 K in agreement with the previously reported value on polycrystalline sample. The isothermal magnetization at 2 K measured along and perpendicular to the c-axis shows anisotropic behaviour, which is rather unexpected as Eu2+ is an S-state ion. The spin flip fields along the two directions are 2.8 and 4.8 T, respectively, while two closely spaced spin-flop transitions in the ab-plane are observed near 1.4 and 1.6 T. The electrical resistivity shows an upturn between TN and 60 K as the temperature is lowered below ~ 60 K, suggesting the presence of antiferromagnetic correlations in the paramagnetic state. Magnetoresistivity at 2 K in 14 T is nearly 1070 % for H // [0001]. The results of heat capacity and 151Eu Mössbauer spectroscopy are in conformity with a bulk transition at 33.3 K.

  12. Magnetic and transport properties of PrRhSi3.

    PubMed

    Anand, V K; Adroja, D T; Hillier, A D

    2013-05-15

    We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility ?(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ?(T,H) and muon spin relaxation (?SR) measurements. At low fields ?(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ?(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ?(T) data indicate a metallic behavior, and ?(H) exhibits a very high positive magnetoresistance, as high as ~300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a ?SR experiment down to 1.2 K. PMID:23604428

  13. Cryogenic properties of dispersion strengthened copper for high magnetic fields

    SciTech Connect

    Toplosky, V. J.; Han, K.; Walsh, R. P. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Swenson, C. A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2014-01-27

    Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

  14. Properties of magnetic nanoparticles prepared by co-precipitation.

    PubMed

    Kim, Jong-Hee; Kim, Sang-Mun; Kim, Yong-Il

    2014-11-01

    Magnetic nanoparticles were synthesized by the addition of ammonium hydroxide to an iron chloride solution by chemical co-precipitation. In order to examine systematically the crystal phase, average size, and magnetic properties of the magnetic nanoparticles, the following were used as experimental parameters: molar ratio of Fe2+/Fe3+, composition of the iron chloride solution, amount of ammonium hydroxide, reaction temperature, and oxidation time of reaction precipitate. In the processing conditions of Fe2+/Fe3+ ratios of 0.5 and 1.0, iron chloride solutions of 0.1-0.8 m, NH4OH molar ratios of 6-14R, reaction temperatures of 25-80 degrees C, and oxidation times of 5-90 min, the co-precipitated nanoparticles were observed to exist as a single phase of Fe3O4. The average size of the particles was approximately 20 nm, and their magnetization was saturated at about 60 emu/g with superparamagnetism. When the iron chloride solution comprised only Fe2+ ions, the oxidation of the reaction precipitates also developed a Fe3O4 phase. However, the particle size reached 78 nm with increasing oxidation times, and the saturation magnetization increased significantly to 82 emu/g while its coercive force was 150 Oe, which indicated that the nanoparticles were paramagnetic. PMID:25958595

  15. Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

    USGS Publications Warehouse

    Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

    2011-01-01

    The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

  16. Preparations, structures and properties of heterobimetallic complexes based on tetrahydrofuran-2,3,4,5-tetracarboxylate

    SciTech Connect

    Jia, Tian-Jing; Li, Shu-Mu; Cao, Wei [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Li, Li-Cun [College of Chemistry, Nankai University, Tianjin 300071 (China); Zheng, Xiang-Jun, E-mail: xjzheng@bnu.edu.cn [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Yuan, Da-Qiang [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

    2013-05-01

    Transition heterobimetallic metal-organic frameworks based on tetrahydrofuran-2,3,4,5-tetracarboxylicate (FTA), namely [M(H?O)?][Cu?M(FTA)?(H?O)?]·4H?O [M=Mn (1), Co (2)], and [CuZn(FTA)(H?O)?]·H?O (3) have been synthesized and characterized. Single-crystal X-ray diffraction indicates that complexes 1 and 2 are isomorphic. In 1 and 2, FTA ligand links the metal ions to a 2-D wave-like negative-charged layer with a topology of (4;6²)?(4;6³;8²)?(6). They possess 1-D channels with [M(H?O)?]²? and lattice water molecules enclathrated. While in the complex 3, Cu²? and Zn²? ions are bridged by FTA to a 2-D neutral layer structure with a (8)?(8?;12²) topology. Magnetic properties of 1–3 were analyzed in connection with their structures, which show that there exist weak antiferromagnetic interactions between metal ions. - Graphical abstract: Three heterobimetallic MOFs were constructed through the size-selectivity of TFA coordination sites for different transition metal ions based on the concept of “Hard and Soft Acids and Bases”. Highlights: • Complexes 1 and 3 contain 2-D wave-like negative-charged layers. • Complex 2 is a 2-D neutral layer structure with a (8)?(8?;12²) topology. • Complexes 1–3 are the first example of heterobimetallic MOFs based on FTA. • The coordination sites of FTA show size-selectivity to metal ions.

  17. Metal nanoparticle fluids with magnetically induced electrical switching properties

    NASA Astrophysics Data System (ADS)

    Kim, Younghoon; Cho, Jinhan

    2013-05-01

    We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media.We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00653k

  18. Magnetic Field Effect on the dielectric properties of the Single Molecule Magnet V15

    NASA Astrophysics Data System (ADS)

    Vasic, Relja; Kaur, Narpinder; Brooks, James; Dalal, Naresh

    2005-11-01

    Single-molecule hysteresis and quantum tunneling of magnetization (QTM) have made single molecule magnets(SMMs) among the most widely studied compounds in the past decade. Best known SMMs are Mn12-acetate and Fe8Br8. Recently a polyoxovanadate compound K6[V15As6O42(H2O)].8H2O, henceforth V15, has been shown to exhibit some of the properties of SMMs despite an S=1/2 ground state, and no evident potential energy barrier to the reorientation of the magnetic moment. In this study we have investigated magnetic field effects on the dielectric properties of V15 using ac impedance technique. In preliminary experiments over the frequency range of 1-100kHz and temperature range of 10-300K, V15 is found to exhibit three independent relaxation mechanisms. On the application of magnetic field, the dielectric relaxation peaks shift towards higher temperatures. The presentation will discuss details of sample preparation, measurement techniques and theoretical interpretation of this newly observed effect.

  19. Shape-tuned dynamic properties of magnetic nanoelements during magnetization reversal

    NASA Astrophysics Data System (ADS)

    Zhang, Guang-fu; Li, Zhi-xiong; Wang, Xi-guang; Nie, Yao-zhuang; Guo, Guang-hua

    2015-07-01

    We study the dynamic properties of magnetic nanoelements with tapered ends by using micromagnetic simulations. It is found that the spin-wave modes can be effectively manipulated by the element shape. With the increase of the end sharpness (described by tapering parameter h), the frequency of the spin-wave edge mode increases rapidly and its oscillation areas in the both ends of element gradually increase and move toward to the central area. Finally, the edge mode completely merges into the fundamental mode. During the magnetization reversal processes, the edge mode experiences one or two softening depending on h?60 nm or 60 nm100 nm, it is the fundamental mode that goes to zero at the switching field. The evolution of the spin-wave modes reflects the change of the micromagnetic structures of the elements during the reversal. It is the softening of the edge mode that triggers the magnetization reversal in elements with h<100 nm. The quasi-uniform reversal in the elements with h>100 nm is induced by the softening of the fundamental mode, where the edge mode is completely suppressed. The results presented in this work demonstrate that the dynamic properties and the magnetization reversal can be effectively tuned by changing the shape of the nanoelements and may be useful for designing the nanoscale magnetic devices.

  20. Magnetic properties of KNaMSi4O10 compounds (M = Mn; Fe; Cu)

    SciTech Connect

    Brandao, Paula [University of Aveiro, Portugal; Rocha, Joao [University of Aveiro, Portugal; Reis, Mario S [University of Aveiro, Portugal; Moreira Dos Santos, Antonio F [ORNL; Jin, Rongying [ORNL

    2009-01-01

    In the present work the synthesis and magnetic properties of three compounds with formula KNaMSi4O10 (M=Mn,Fe,Cu) are described. These compounds are synthetic analogs to natural occurring minerals: fenaksite Fe2+, litidionite Cu2+ and manaksite Mn2+. The crystal structure consists of complex silicate chains interconnected by edge-sharing MO5 square pyramids dimerized in M2O8 units. This charged metal silicate framework is compensated by monovalent alkali metals (K+, Na+). Despite the isostructural nature of these compounds, and the consequent similarity of the M O topology, that rules the magnetic properties, these are quite different. While there are antiferromagnetic (AF) interactions within the Mn and Cu dimers (exchange interaction J=-3.83(1) and View the MathML source, respectively) with no long range order, a ferromagnetic interaction within Fe dimers View the MathML source is observed with a three-dimensional transition at 9 K to an AF ground state. The magnetic behavior is analyzed using the HDVV (Heisenberg Dirac Van Vleck) formalism and discussed in the light of the crystal structure. Magnetic susceptibility times temperature. The antiferromagnetic arrangement within Mn and Cu dimers is evident (due to the positive derivative at lower temperatures). For the Fe-counterpart a three-dimensional transition to an antiferromagnetic (AF) inter-dimer interaction is found upon cooling. Above this transition the drop in T is a signature of ferromagnetic intra-dimer interactions.

  1. Temperature dependent magnetic and microwave absorption properties of doubly substituted nanosized material

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Rana, M. U.; Ashiq, Muhammad Naeem; Ali, Irshad

    2015-07-01

    The sol gel method has been adopted to synthesize a series of X-type hexagonal ferrites with concentration Sr2-x Gdx Ni2 Fe28-yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5). The XRD analysis reveals the single phase of the prepared material and the lattice constants a (Å) and c (Å) varies with additives. The crystallite size of the present investigated ferrite is found in the range of 20-30 nm measured from TEM image. The enhancement in the magnetic properties (saturation magnetization, remanance magnetization and coercivity) can be observed with the increase of dopping concentration and the coercivity lies in the range of (484.22-887.47) G. The saturation and remanance magnetization decreases monotonically with the temperature which is the characteristic of the hexagonal ferrites. The Gd-Cd substituted sample possesses low values of complex relative permittivity and permeability than the pure samples. The material exhibits maximum microwave absorption -23 dB at 11.87 GHz and attenuation peak is in good agreement with the reflection loss value. The microwave absorption properties reflect the applications of this material in super high frequency devices (SHF).

  2. Magnetic and magnetoelectric properties of nickel ferrite–lead iron niobate relaxor composites

    Microsoft Academic Search

    P. Guzdek; M. Sikora; ?. Góra; Cz. Kapusta

    Magnetoelectric effect in bulk ceramic and multilayer (laminated) structures consisting of 6 nickel ferrite and 7 lead iron niobate relaxor (PFN) layers was investigated. This paper describes the synthesis and tape-casting process for ferrimagnetic Ni0.3Zn0.62Cu0.08Fe2O4 ferrite and multiferroic relaxor Pb(Fe0.5Nb0.5)O3. X-ray analysis and studies of the electrical and magnetic properties were performed for bulk and layered composites. Complex impedance and

  3. Transport and optical properties of low-dimensional complex systems

    NASA Astrophysics Data System (ADS)

    Iurov, Andrii

    Over the last five years of my research work, I, my research was mainly concerned with certain crucial tunneling, transport and optical properties of novel low-dimensional graphitic and carbon-based materials as well as topological insulators. Both single-electron and many-body problems were addressed. We investigated the Dirac electrons transmission through a potential barrier in the presence of circularly polarized light. An anomalous photon-assisted enhanced transmission is predicted and explained in a comparison with the well-known Klein paradox. It is demonstrated that the perfect transmission for nearly-head-on collision in an infinite graphene is suppressed in gapped dressed states of electrons, which is further accompanied by shift of peaks as a function of the incident angle away from the head-on collision. We calculate the energy bands for graphene monolayers when electrons move through a periodic electrostatic potential in the presence of a uniform perpendicular magnetic field. We clearly demonstrate the quantum fractal nature of the energy bands at reasonably low magnetic fields. We present results for the energy bands as functions of both wave number and magnetic flux through the unit cells of the resulting moi?e superlattice. This feature is also observed at extremely high magnetic fields. We have discovered a novel feature in the plasmon excitations for a pair of Coulomb-coupled non-concentric spherical two-dimensional electron gases (S2DEGs). Our results show that the plasmon excitations for such pairs depend on the orientation with respect to the external electromagnetic probe field. The origin of this anisotropy of the inter-sphere Coulomb interaction is due to the directional asymmetry of the electrostatic coupling of electrons in excited states which depend on both the angular momentum quantum number L and its projection M on the axis of quantization taken as the probe E-field direction. Such an effect from the plasmon spatial correlation is expected to be experimentally observable by employing circularly-polarized light or a helical light beam for incidence. The S2DEG serves as a simple model for fullerenes as well as metallic dimers, when the energy bands are far apart. Magnetoplasmons in gapped graphene have been investigated and the exchange energy dependence on magnetic field is presented.

  4. Squaring the cube: a family of octametallic lanthanide complexes including a Dy8 single-molecule magnet.

    PubMed

    Fang, Ming; Zhao, Hanhua; Prosvirin, Andrey V; Pinkowicz, Dawid; Zhao, Bin; Cheng, Peng; Wernsdorfer, Wolfgang; Brechin, Euan K; Dunbar, Kim R

    2013-10-01

    A series of isostructural octanuclear lanthanide complexes of general formula [Ln8(sao)4(?3-OH)4(NO3)12(DMF)12] (Ln = Nd (), Sm (), Eu (), Gd (), Tb (), Dy (), Ho (), Er (); DMF = dimethylformamide) have been prepared via reactions of salicylaldoxime (saoH2), tetramethylammonium hydroxide (Me4NOH) with the appropriate lanthanide nitrate salt (Ln(NO3)3·6H2O). The metallic skeletons of the complexes describe [Ln4] tetrahedra encapsulated inside a [Ln4] square with the inner core stabilised through ?3-OH(-) ions and the periphery by ?4-sao(2-) ligands. The magnetic properties of compounds were investigated by dc and ac magnetometry. Temperature dependent ac magnetic susceptibility data reveal that the dysprosium analogue () displays an out-of-phase signal in the absence of an applied magnetic field indicative of slow relaxation of the magnetization typical of a Single-Molecule Magnet (SMM). Micro-SQUID measurements reveal temperature and sweep rate dependent hysteresis below 1.0 K. PMID:23943045

  5. [Synthesis, characterization and luminescence properties of a copper (I) complex].

    PubMed

    Wang, Li-Yuan; Fan, Rui-Qing; Wang, Ping; Yang, Yu-Lin

    2012-09-01

    Binuclear complex [Cu2 (mu-I)2 (phen)2] x CH3CN(1)(phen = 1,10-phenanthroline) was synthesized under solvothermal conditions and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that complex 1 is monoclinic, space group P2(1/n), and the cell parameters are: alpha = 10.505 A, b = 23.628 A, c = 10. 676 A, alpha = 90, beta = 91.40 degrees and gamma = 90 degrees. The authors have studied the luminescence property of 1, Complex 1 has blue-purple luminescence in solutions of DMSO with emission bands at 369, 380 and 460sh nm; and has red luminescence in the solid state at room temperature with a broad emission band at 650-678 nm. These all can be attributed to the pi* --> pi transition based on the ligand. In the solid state, the emission frequencies for complex 1 are red-shifted about 280 nm compared with their emission maximum peaks in solutions of DMSO. This red-shift of emission energy from solution to solid is likely to be caused by the intermolecular pi--pi packing interaction in the solid state which effectively decreases the energy gap. The fluorescence decay curve of complex 1 indicated that the processes of decay consists of two components, whose corresponding lifetimes are tau1 = 1.36 micros and tau2 = 5.98 micros, corresponding factors are 50.21% and 49.79% in DMSO solutions, and tau1 = 1.42 micros, tau2 = 8.85 micros, corresponding factors are 51.15% and 48.85% in the solid state. PMID:23240419

  6. Magnetic and electronic properties of NpCo2: Evidence for long-range magnetic order

    NASA Astrophysics Data System (ADS)

    Sanchez, J. P.; Griveau, J.-C.; Javorsky, P.; Colineau, E.; Eloirdi, R.; Boulet, P.; Rebizant, J.; Wastin, F.; Shick, A. B.; Caciuffo, R.

    2013-04-01

    The magnetic and electronic properties of the cubic Laves phase intermetallic compound NpCo2 have been investigated by magnetization, specific heat, and electrical resistivity measurements. Magnetization data confirm previous results, i.e., an antiferromagneticlike order at 12.5 K and a metamagnetic transition at Bm ˜ 4.3 T at 3 K with a saturation moment of ˜0.6 ?B. Although extensive neutron diffraction studies failed to establish the nature of the antiferromagnetic order, its occurrence is confirmed by specific heat measurements that also highlight the presence of magnetic fluctuations suppressed by the application of an external field larger than Bm. The observed high value of the electronic specific heat, ?0 ˜ 330 mJ/mol K2 as T ? 0, and the minute magnetic entropy, <0.1Rln2, classify NpCo2 as an itinerant, moderately-heavy-fermion antiferromagnet. The electrical resistivity data agree with the presence of an antiferromagnetic order below Bm and suggest a non-Fermi liquid behavior at low temperature. The electronic structure of NpCo2 was examined theoretically and compared to experimental data. Local spin density approximation (LSDA) calculations show that this material is close to a magnetic instability and that ferromagnetic alignment of the Np moments is the most stable. LSDA+U calculations in the fully localized limit with U = 0 give reasonable agreement with the experimental Np moment value and their orbital and spin contributions.

  7. Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field

    E-print Network

    A. Rabhi; M. A. Pérez-García; C. Providência; I. Vidaña

    2015-04-02

    We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

  8. Combined effects of complex magnetic fields and agmatine for contextual fear learning deficits in rats

    E-print Network

    Turner, Ray

    in intensity of the time-varying ambient geomagnetic field) increased during the 3-hr intervals over which. Cumulative evidence indicates that the effectCombined effects of complex magnetic fields and agmatine for contextual fear learning deficits

  9. Transient and Disruption Cavity Dimensions of Complex Terrestrial Impact Structures Derived from Magnetic Data

    NASA Astrophysics Data System (ADS)

    Pilkington, M.; Hildebrand, A. R.

    2003-03-01

    Using published values of crater diameters (D) and values of collapsed disruption cavity diameter, D(CDC) derived from magnetic data for 19 complex terrestrial impact structures, we derive the relationship D(CDC) = 0.49D.

  10. Fractal variability: An emergent property of complex dissipative systems

    NASA Astrophysics Data System (ADS)

    Seely, Andrew J. E.; Macklem, Peter

    2012-03-01

    The patterns of variation of physiologic parameters, such as heart and respiratory rate, and their alteration with age and illness have long been under investigation; however, the origin and significance of scale-invariant fractal temporal structures that characterize healthy biologic variability remain unknown. Quite independently, atmospheric and planetary scientists have led breakthroughs in the science of non-equilibrium thermodynamics. In this paper, we aim to provide two novel hypotheses regarding the origin and etiology of both the degree of variability and its fractal properties. In a complex dissipative system, we hypothesize that the degree of variability reflects the adaptability of the system and is proportional to maximum work output possible divided by resting work output. Reductions in maximal work output (and oxygen consumption) or elevation in resting work output (or oxygen consumption) will thus reduce overall degree of variability. Second, we hypothesize that the fractal nature of variability is a self-organizing emergent property of complex dissipative systems, precisely because it enables the system's ability to optimally dissipate energy gradients and maximize entropy production. In physiologic terms, fractal patterns in space (e.g., fractal vasculature) or time (e.g., cardiopulmonary variability) optimize the ability to deliver oxygen and clear carbon dioxide and waste. Examples of falsifiability are discussed, along with the need to further define necessary boundary conditions. Last, as our focus is bedside utility, potential clinical applications of this understanding are briefly discussed. The hypotheses are clinically relevant and have potential widespread scientific relevance.

  11. Effect of processing parameters on the magnetic properties of strontium ferrite sintered magnets using Taguchi orthogonal array design

    NASA Astrophysics Data System (ADS)

    Sharma, Puneet; Verma, Amitabh; Sidhu, R. K.; Pandey, O. P.

    2006-12-01

    In the present paper, influence of various processing parameters on the magnetic properties of strontium ferrite sintered permanent magnets has been studied. Taguchi L-9 orthogonal array design is used for analyzing the effect of Fe 2O 3/SrO mole ratio, milling time, calcination temperature and sintering temperature on the magnetic properties. The individual effect of each parameter on the magnetic properties in correlation with microstructure and phase formation is discussed. It is found that Taguchi design is adequate to understand the effect of processing parameter in the limited number of experiments.

  12. Magnetic blocking in extended metal atom chains: a pentachromium(II) complex behaving as a single-molecule magnet.

    PubMed

    Cornia, A; Rigamonti, L; Boccedi, S; Clérac, R; Rouzières, M; Sorace, L

    2014-12-14

    Compound [Cr5(tpda)4Cl2] (H2tpda = N(2),N(6)-di(pyridin-2-yl)pyridine-2,6-diamine), an Extended Metal Atom Chain complex featuring two quadruply-bonded {Cr2} units, exhibits field-induced slow relaxation of its magnetization arising from the terminal chromium(II) ion and provides the first example of a chromium(II)-based Single-Molecule Magnet. PMID:25336023

  13. Investigating the anisotropy of magnetic susceptibility and other rock magnetic properties of the Beaver River Diabase in northeastern Minnesota

    NASA Astrophysics Data System (ADS)

    Hariri, Samer H.

    The Beaver River Diabase (BRD) is a series of mafic dikes and sills within the Beaver Bay Complex (BBC) of northern Minnesota, which formed during the development of the ~1.1 Ga Midcontinent Rift (MCR). The BRD is one of the youngest and most extensive intrusive phases of the BBC. The BRD dikes and sills were emplaced into the medial levels of the 6-10 kilometer-thick North Shore Volcanic Group and occur over an arcuate area extending 120 by 20 kilometers. The BRD is composed of fine- to medium-grained ophitic olivine gabbro and does not display obvious foliation or lineation features and rarely displays modal layering. Without obvious magmatic internal structures, it is difficult to determine emplacement properties such as flow direction using standard geologic mapping or petrographic techniques. For this reason, we measured the anisotropy of magnetic susceptibility (AMS), in conjunction with other rock magnetic properties, to better understand the BRD's emplacement and deformation history in the context of the MCR. AMS measures the directional dependence of low-field magnetic susceptibility, and is used to infer a shape-preferred orientation of magnetic minerals within a rock, which can be related to specific emplacement mechanisms (e.g. directional flow or settling). Preliminary analysis of AMS at 20 sites within the southern half of the BRD (with 4-7 samples per site) shows maximum susceptibility values between 4.48 x 10-6 and 2.22 x 10-4 m 3/kg (1165 and 65400 ?SI). Most specimens display nearly isotropic AMS ellipsoids (Pj < 1.15) with minor degrees of prolateness and oblateness. However, about 20% of specimens have higher anisotropies (Pj between 1.15 and 1.67) and higher degrees of oblateness and prolateness. Variations in AMS properties may reflect differences in concentration and composition of magnetic minerals, as well as emplacement mechanisms. Measurements of susceptibility as a function of temperature yield Curie points between 470 and 570 °C, indicating the presence of low-titanium titanomagnetite. Major hysteresis loops show coercivities between 1 and 25 mT, consistent with titanomagnetite as the dominant remanence carrier.

  14. Magnetic and magnetocaloric properties of bulk dysprosium chromite

    SciTech Connect

    McDannald, A. [Material Science and Engineering, University of Connecticut, Storrs, Connecticut 06269 (United States) [Material Science and Engineering, University of Connecticut, Storrs, Connecticut 06269 (United States); Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Kuna, L. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)] [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Jain, M. [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States) [Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

    2013-09-21

    In this work, a polycrystalline bulk DyCrO{sub 3} sample was prepared by a solution route and the structural and magnetic properties were investigated. The phase purity and ionic valence state of the DyCrO{sub 3} sample were determined by x-ray diffraction/Raman spectroscopy and x-ray photoelectron spectroscopy, respectively. The AC and DC magnetization measurements revealed the onset of antiferromagnetic order at 146 K with an effective moment of 8.88 ?{sub B}. Isothermal magnetization measurements of this material are presented for the first time, showing a peak in the coercive field at 80 K that is explained by the competition between the paramagnetic Dy{sup 3+} and Cr{sup 3+} sublattices. DyCrO{sub 3} was found to display a large magnetocaloric effect (8.4 J/kg K) and relative cooling power (217 J/kg) at 4 T applied field, which renders DyCrO{sub 3} useful for magnetic refrigeration between 5 K and 30 K.

  15. Magnetic properties of tunicate blood cells. II. Ascidia ceratodes.

    PubMed

    Kustin, K; Robinson, W E; Frankel, R B; Spartalian, K

    1996-08-15

    The magnetic properties of intact blood cells of the tunicate Ascidia ceratodes have been measured up to 50 kOe with a SQUID susceptometer. Analysis of total metal contents by plasma emission spectroscopy and V(IV) content by epr indicates that approximately 5% of the accumulated vanadium is +4 vanadyl ion. Measured values of the magnetic moment Mp at different values of the applied magnetic field H over the temperature range T = 2-100 K depend on the magnitude of the field indicating magnetic anisotropy of the ground state. The slope of the Mp vs. H/T curve at high temperature is significantly higher than expected from electron spin S = 1 per vanadium(III) ion. The model that fits these data best is a dimer with one V(III) S = 1 ion ferromagnetically coupled to a second V(III) S = 1 ion, with spin-coupling constant J = 3.5 cm-1, and 5% of the total vanadium content in the form of a V(IV) S = 1/2 ion. Since vanadium in A. ceratodes is known to reside in at least three different types of blood cell, the excellent fit indicates that the metal is stored predominantly as a dimer regardless of blood cell type. Ferromagnetic coupling implies that the two vanadium ions in the dimer are connected by an unprotonated mu-oxo bridge. PMID:8758882

  16. Magnetic properties of graphite irradiated with MeV ions

    SciTech Connect

    Ramos, M. A.; Munoz-Martin, A.; Climent-Font, A. [CMAM and Instituto de Ciencia de Materiales 'Nicolas Cabrera', Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Barzola-Quiquia, J.; Esquinazi, P. [Division of Superconductivity and Magnetism, Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

    2010-06-01

    We have studied the change in the magnetic properties produced on highly oriented pyrolytic graphite samples by irradiation of H, C, and N ions in the mega-electron-volt energy range. The use of specially made sample holders for the magnetic measurements provided high reproducibility allowing us to obtain directly the irradiation effects without any corrections or subtractions. Our results show that three magnetic phenomena are triggered by the defects produced by the irradiation, namely, Curie-type paramagnetism, ferromagnetism and an anomalous paramagnetic state that appears as precursor of the magnetic ordered state. Using SRIM simulations to estimate the amount of vacancies produced by the irradiation, the Curie-type paramagnetic response indicates an effective Bohr magneton number per nominally produced vacancy p=0.27+-0.02mu{sub B}. Direct measurements of the surface sample temperature during irradiation and the decrease in the (as-received) paramagnetic as well as ferromagnetic contributions after irradiation indicate that self-heating is one of the causes for small yield of ferromagnetism. Taking into account the hydrogen distribution in the virgin samples, the obtained results indicate that the induced ferromagnetism appears when the average vacancy distance is {approx}2 nm in the near surface region.

  17. Nano-structured magnetic metamaterial with enhanced nonlinear properties

    PubMed Central

    Kobljanskyj, Yuri; Melkov, Gennady; Guslienko, Konstantin; Novosad, Valentyn; Bader, Samuel D.; Kostylev, Michael; Slavin, Andrei

    2012-01-01

    Nano-structuring can significantly modify the properties of materials. We demonstrate that size-dependent modification of the spin-wave spectra in magnetic nano-particles can affect not only linear, but also nonlinear magnetic response. The discretization of the spectrum removes the frequency degeneracy between the main excitation mode of a nano-particle and the higher spin-wave modes, having the lowest magnetic damping, and reduces the strength of multi-magnon relaxation processes. This reduction of magnon-magnon relaxation for the main excitation mode leads to a dramatic increase of its lifetime and amplitude, resulting in the intensification of all the nonlinear processes involving this mode. We demonstrate this experimentally on a two-dimensional array of permalloy nano-dots for the example of parametric generation of a sub-harmonic of an external microwave signal. The characteristic lifetime of this sub-harmonic is increased by two orders of magnitude compared to the case of a continuous magnetic film, where magnon-magnon relaxation limits the lifetime. PMID:22745899

  18. Relationship Between Solar Wind Speed and Coronal Magnetic Field Properties

    E-print Network

    Fujiki, Ken'ichi; Iju, Tomoya; Hakamada, Kazuyuki; Kojima, Masayoshi

    2015-01-01

    We have studied the relationship between the solar-wind speed $[V]$ and the coronal magnetic-field properties (a flux expansion factor [$f$] and photospheric magnetic-field strength [$B_{\\mathrm{S}}$]) at all latitudes using data of interplanetary scintillation and solar magnetic field obtained for 24 years from 1986 to 2009. Using a cross-correlation analyses, we verified that $V$ is inversely proportional to $f$ and found that $V$ tends to increase with $B_{\\mathrm{S}}$ if $f$ is the same. As a consequence, we find that $V$ has extremely good linear correlation with $B_{\\mathrm{S}}/f$. However, this linear relation of $V$ and $B_{\\mathrm{S}}/f$ cannot be used for predicting the solar-wind velocity without information on the solar-wind mass flux. We discuss why the inverse relation between $V$ and $f$ has been successfully used for solar-wind velocity prediction, even though it does not explicitly include the mass flux and magnetic-field strength, which are important physical parameters for solar-wind accele...

  19. Magnetic Investigations in the J-M Reef Section of the Stillwater Complex, Montana

    NASA Astrophysics Data System (ADS)

    Wnukowski, J. D.; Ferre, E. C.; Butak, K. C.

    2014-12-01

    The Stillwater J-M reef, the only economic platinum deposit in the USA, consists of a 0.5 to 4 m-thick stratiform zone of platinum group element (PGE)-rich sulfides in a layered mafic intrusion. The origin of this reef, purely magmatic or related to late-stage magmatic fluids, remains ambiguous. I propose to test these two genetic hypotheses using rock magnetism. Fractional crystallization trends deduced from petrological models would produce a sharp increase in magnetite and pyrrhotite content near the solidus. In contrast, percolation of sulfur-rich fluids through a crystal mush would produce a gradual increase in magnetite and pyrrhotite up to a fluid permeability barrier. Continuous logging of the magnetic properties of drillcores, combined with petrographic observations, will allow to test these two models. Petrologic similarities between PGE reefs suggest that they share common physico-chemical origins, therefore, understanding the J-M reef genesis would have implications for other deposits such as the Bushveld Complex and the Great Dyke of Zimbabwe. The J-M reef formation has been explained by two alternative models: 1) magmatic model - magma replenishment causes thermal convection at the interface between two magmas, inducing PGE leaching by a sulfur-saturated magma, followed by precipitation of sulfide droplets; 2) fluid fluxing model - a sulfur-rich residual, late magmatic fluid migrates upward through the crystal mush leading to PGE concentration along a magmatic permeability barrier against the hanging wall. Both models account for the majority of geochemical and petrological observations and may not be fundamentally mutually exclusive. However, understanding the origin of PGE reefs would certainly benefit from new approaches. Preliminary data shows systematic inch-scale cycling variations of magnetic susceptibility (Km) in the hanging-wall that supports the magmatic model. The discovery of this magnetic cyclicity matters because this core does not display any macroscopically visible layering. Magnetic measurements (thermomagnetic experiments, magnetic hysteresis and first order reversal curves), in conjunction with detailed petrographic observations on selected specimens, will be performed to evaluate the significance of this cyclic feature.

  20. Transport and Superconducting Properties of Rare Earth Magnetic Superconductors.

    NASA Astrophysics Data System (ADS)

    Zhou, Hu.

    An investigation of transport and magnetic properties of two groups of magnetic superconductors, tetragonal {cal R}Rh_4 B_4 and orthorhombic high -T_{rm c} oxides {cal R}Ba_2 Cu_3O_{7 -delta}, where {cal R} represents rare earth elements and Y, was carried out by means of electrical resistance and magnetic measurements. Single crystals of {cal R} Rh_4B_4 were successfully synthesized using a copper flux method for {cal R} = Y, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. Strong magnetic anisotropy was observed, with the easy magnetization direction along the c-axis for {cal R} = Tb, Dy, and Ho, and along the a-axis for { cal R} = Er and Tm. Theoretical calculations based on the crystalline electric field (CEF) effect gave excellent fits to the experimental data. Significant influence of the magnetic anisotropy on the upper critical magnetic field H_{rm C2} of the superconducting state was observed in { cal R}Rh_4B _4 with {cal R} = Y, Er, and Tm. Lower H_{rm C2} values were observed for these compounds in the easy directions. Electrical resistance and magnetic measurements on polycrystalline {cal R}Ba _2Cu_3O _{7-delta} samples for {cal R} = Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu established almost identical superconducting transition temperatures T_ {rm c} = 90 to 94 K for all these compounds (except for {cal R} = La which has T_{rm c} = 56 K), revealing apparent decoupling of the conduction electrons and the {cal R} magnetic ions. The upper critical magnetic fields H _{rm C2} of these high-T _{rm c} oxides are estimated by the WHHM theory to be of the order of megaoersteds at 0 Kelvin. In the normal state, the susceptibility of these compounds can be fitted to the sum of a Curie-Weiss term and a temperature independent term. The temperature and magnetic field dependences of J_{ rm c} obtained by this model are consistent with those obtained from direct current-voltage measurements. Fine powders of {cal R}Ba _2Cu_3O_ {7-delta} can be aligned in nonmagnetic epoxy by an applied magnetic field at room temperature due to the magnetic anisotropy of these compounds. The directions of the easy axes of {cal R}Ba_2Cu_3 O_{7-delta} are the same as those of {cal R} Rh_4B_4 for the same rare earth {cal R} , and there exists a good correspondence between the sign of the Stevens alpha_{ rm J} factor and the directions of the easy axes of both families of compounds. A preliminary analysis suggests this correlation reflects the similarity of the symmetries of the crystal structure at the rare earth site. (Abstract shortened with permission of author.).

  1. Magnetic Properties of Nonmagnetic Nanostructures: Dangling Bond Magnetic Polaron in CdSe Nanocrystals.

    PubMed

    Rodina, Anna; Efros, Alexander L

    2015-06-10

    We predict theoretically that nonmagnetic CdSe nanocrystals may possess macroscopic magnetic moments due to the formation of dangling-bond magnetic polarons (DBMPs). A DBMP is created in optically pumped nanocrystals by dynamic polarization of dangling bond spins (DBSs) at the nanocrystal surface during radiative recombination of the ground state "dark" exciton assisted by a spin-flip of the DBS. The formation of DBMPs suppresses the radiative recombination of the dark exciton and leads to a temperature-dependent contribution to the Stokes shift of the photoluminescence. This model consistently explains the experimentally observed low-temperature photoluminescence features of nonmagnetic CdSe nanocrystals as manifestations of their spin-related magnetic properties. PMID:25919576

  2. Synthesis, structural characterization, and magnetism of a butterfly-shaped hexanuclear Ni(II) complex

    E-print Network

    Gao, Song

    Synthesis, structural characterization, and magnetism of a butterfly-shaped hexanuclear Ni 2008 Keywords: Hexanuclear Butterfly-shaped Nickel Magnetism a b s t r a c t A new butterfly structure [11] of the title hexanuclear nickel complex is shown in Fig. 1. It exhibits a discrete butterfly

  3. Magnetic properties of sputtered Permalloy/molybdenum multilayers

    SciTech Connect

    Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C. [ISOM and Dpto. Fisica Aplicada, E.T.S.I. Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, Madrid 28040 (Spain); Ranchal, R. [Dpto. Fisica de Materiales, Facultad CC. Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, Madrid 28040 (Spain)

    2011-10-15

    In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni{sub 80}Fe{sub 20})/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

  4. The Magnetic Properties of Zigzag Boron Carbon Carbon Nitride Nanoribbon

    NASA Astrophysics Data System (ADS)

    Rufinus, J.

    2014-03-01

    Recently, substantial theoretical and experimental efforts have been made in the quest to find the candidates for future spintronic devices. Two-dimensional graphene-based structures have attracted much attention in the search for new spintronic materials due to some theoretical predictions that this type of materials show the half-metallic property. Here we present the results of an ab-initio self consistent density functional theory within a generalized gradient approximation of zigzag Boron Carbon Carbon Nitride Nanoribbon (ZBC2NNR). The result of our calculations shows different magnetic orderings. In general, however, we found that narrow ZBC2NNR prefers a magnetic state which depends on the shape and the orientation of the atoms on its edges. Work supported in part by Widener University Faculty Grant.

  5. Magnetic and transport properties of MnBi/Bi nanocomposites

    NASA Astrophysics Data System (ADS)

    Kang, Kyongha; Lewis, L. H.; Hu, Y. F.; Li, Qiang; Moodenbaugh, A. R.; Choi, Young-Suk

    2006-04-01

    The magnetic and transport properties of a nanostructured Mn-Bi eutectic composition (~Mn5Bi95) produced by melt spinning and low-temperature/short time vacuum annealing were studied. A hysteretic magnetostructural transformation from low-temperature phase to high-temperature phase MnBi is confirmed at 520 K. The fact that the transition temperature is lower than that reported for bulk MnBi (633 K), is tentatively attributed to interfacial strain between MnBi and the Bi matrix. A positive temperature coefficient of coercivity is confirmed in the nanocomposites, with a maximum coercivity value of 36 kOe at 500 K. Magnetic field annealing the as-spun composites (525 K at 10 kOe) produces nanoparticle alignment. Annealed MnBi/Bi composites have a very large ordinary magnetoresistance (MR) ratio normal to the ribbon at 5 T, 275% at room temperature and 10 000% at 5 K.

  6. Magnetic properties of permalloy wires in vycor capillaries

    NASA Astrophysics Data System (ADS)

    Lubitz, P.; Ayers, J. D.; Davis, A.

    1991-11-01

    Thin wires of NiFe alloys with compositions near 80% Ni were prepared by melting the alloy in vycor tubes and drawing fibers from the softened glass. The resulting fibers consist of relatively thick-walled vycor capillaries containing permalloy wires filling a few percent of the volume. The wires are continuous over considerable lengths, uniform in circular cross section, nearly free of contact with the walls and can be drawn to have diameters less than 1 ?m. Their magnetic properties are generally similar to bulk permalloy, but show a variety of magnetic switching behaviors for fields along the wire axis, depending on composition, wire diameter, and thermal history. As pulled, the wires can show sharp switching, reversible rotation or mixed behavior. This method can produce NiFe alloy wires suitable for use in applications as sensor, memory or inductive elements; other alloys, such as supermalloy and sendust, also can be fabricated as fine wires by this method.

  7. The Paradox of Scale: Reconciling magnetic anomalies with rock magnetic properties for cost-effective mineral exploration

    NASA Astrophysics Data System (ADS)

    Austin, James R.; Foss, Clive A.

    2014-05-01

    Targeting magnetic anomalies is a common practice in the mineral industry. However, it is uncommon for anomalies to be reconciled with their causative lithologies after a hole has been drilled. Furthermore, the effects of remanent magnetization are seldom considered, even though they are likely to be significant. This study explores how timely rock magnetic property measurements coupled with magnetic field modelling can be used to explain the anomaly whilst drilling is underway, thus saving critical exploration expense.

  8. The magnetic and microstructural properties of Co-Cr thin films with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Grundy, P. J.; Ali, Mubarak

    1983-12-01

    This paper reports measurements of the magnetic properties of dc sputter deposited Co 100- xCr x alloy thin films for 0 ? x ? 30 at %. Properties of interest are those obtained from the in-plane and perpendicular hysteresis loops such as magnetization, saturation fields and coercivities. These properties are correlated with the microstructure, crystal structure and, to some extent, the magnetic domain structure of the films. For particular preparation conditions and within a certain composition range the films are found to have some of the properties suitable for perpendicular magnetic recording applications, i.e., perpendicular magnetization and high coercivity.

  9. A nanoporous molecular magnet with reversible solvent-induced mechanical and magnetic properties

    Microsoft Academic Search

    Daniel Maspoch; Daniel Ruiz-Molina; Klaus Wurst; Neus Domingo; Massimilliano Cavallini; Fabio Biscarini; Javier Tejada; Concepció Rovira; Jaume Veciana

    2003-01-01

    Interest in metal-organic open-framework structures has increased enormously in the past few years because of the potential benefits of using crystal engineering techniques to yield nanoporous materials with predictable structures and interesting properties. Here we report a new efficient methodology for the preparation of metal-organic open-framework magnetic structures based on the use of a persistent organic free radical (PTMTC), functionalized

  10. Electronic and magnetic properties of Co-doped ZnO diluted magnetic semiconductor

    Microsoft Academic Search

    R. K. Singhal; Arvind Samariya; Y. T. Xing; Sudhish Kumar; S. N. Dolia; U. P. Deshpande; T. Shripathi; Elisa B. Saitovitch

    2010-01-01

    The effect of low level Co doping (5%) on polycrystalline ZnO samples has been investigated to correlate the observed changes in their magnetic state vis à vis changes in their electronic properties. Rietveld refinement of the XRD patterns confirms single phase crystallization of the samples in the wurtzite type lattice, with no evidence of any secondary phases. The as-synthesized Co-doped

  11. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: The magnetic and dielectric properties of multiferroic Sr-substituted Zn2-Y hexagonal ferrites

    Microsoft Academic Search

    Fang Xu; Yang Bai; Fen Ai; Li-Jie Qiao

    2008-01-01

    The magnetic and dielectric properties of Sr-substituted Zn2-Y hexagonal ferrites (Ba2-xSrxZn2Fe12O22, 1.0 <= x <= 1.5) are studied in this paper. Sr substitution will lead to the variation of cation occupation, which influences both the magnetic and electric properties. As Sr content x rises from 1.0 to 1.5, magnetic hysteresis loop gets wider gradually and the permeability drops rapidly due

  12. Two-Dimensional Coordination Polymers with One-Dimensional Magnetic Chains: Hydrothermal Synthesis, Crystal Structure, and Magnetic and Thermal Properties of

    E-print Network

    Li, Jing

    , Crystal Structure, and Magnetic and Thermal Properties of 2 [MCl2(4,4-bipyridine)] (M ) Fe, Co, Ni, Co in the field-dependent magnetization measurement for all four compounds. The magnetic properties observed metal species (3.6 Å). Studies on magnetic properties have been reported on a number of compounds

  13. Magnetic and Transport Properties of the Magnetic Polaron: Application to Eu1xLaxB6 System Unjong Yu and B. I. Min

    E-print Network

    Min, Byung Il

    Magnetic and Transport Properties of the Magnetic Polaron: Application to Eu1ÿxLaxB6 System Unjong polaron in magnetic and transport properties of Eu1ÿxLaxB6, we investigate the low carrier density to understand their unusual magnetic and transport properties. This study will shed light on un- derstanding

  14. The effect of mechanical working on the in-plane magnetic properties of Hiperco 50

    E-print Network

    McHenry, Michael E.

    is a premier soft magnetic material. It is often utilized, in laminate form, in rotors for aircraft power of the material as a result of the rolling.3 By connecting the processing and the resulting magnetic properties weThe effect of mechanical working on the in-plane magnetic properties of Hiperco 50 M. L. Storch, A

  15. Biomonitoring of traffic air pollution in Rome using magnetic properties of tree leaves

    Microsoft Academic Search

    Eva Moreno; Leonardo Sagnotti; Jaume Dinarès-Turell; Aldo Winkler; Antonio Cascella

    2003-01-01

    We report a biomonitoring study of air pollution in Rome based on the magnetic properties of tree leaves.In a first step, magnetic properties of leaves from different tree species from the same location were compared. It was observed that leaves of evergreen species, like Quercus ilex, present much higher magnetic intensities than those of deciduous species, like Platanus sp., suggesting

  16. Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz

    E-print Network

    Boyer, Edmond

    Magnetic field properties in a birdcage coil P. Boissoles and G. Caloz March 15, 2006 Abstract Radiofrequency magnetic fields used in MRI experiments have to sat- isfy specific properties. First, they need they generate an adequate homogeneous radiofrequency magnetic field. Since then several studies have used

  17. The dependence of magnetic properties on fatigue in A533B nuclear pressure vessel steels

    Microsoft Academic Search

    Y. Bi; M. R. Govindaraju; D. C. Jiles

    1997-01-01

    Cyclic loading causes cumulative microstructural changes in materials. The magnetic properties of A533B steel are determined by both initial microstructures and microstructural changes induced by fatigue damage. From the results of a series of strain-controlled fatigue tests, the magnetic properties were found to change systematically with fatigue damage throughout the fatigue life. A linear relationship between magnetic remanence and mechanical

  18. Cu{sup II} coordination polymers based on 5-methoxyisophthalate and flexible N-donor ligands: Structures and magnetic properties

    SciTech Connect

    Chang, Xin-Hong; Qin, Jian-Hua [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Ma, Lu-Fang, E-mail: mazhuxp@126.com [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); Wang, Li-Ya, E-mail: wlya@lynu.edu.cn [College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022 (China); College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang 473061 (China)

    2014-04-01

    Three Cu{sup II} coordination polymers, ([Cu{sub 2}(CH{sub 3}O-ip){sub 2}(bmib)]){sub n} (1), ([Cu{sub 2}(CH{sub 3}O-ip){sub 2}(bmib){sub 2}]){sub n} (2) and ([Cu(CH{sub 3}O-ip)(bbip)]?2H{sub 2}O){sub n} (3) (CH{sub 3}O-H{sub 2}ip is 5-methoxyisophthalic acid, bmib is 1,4-bis(2-methylimidazol-1-yl)butane and bbip is 1,3-bis(1H-benzimidazolyl)propane), have been synthesized by hydrothermal methods. Complexes 1–3 were structurally characterized by elemental analysis, infrared (IR) spectra and X-ray single-crystal diffraction. Complex 1 shows a 3D six-connected self-penetrating network based on paddlewheel secondary building units. Complex 2 has a 3-fold interpenetrating 3D diamond framework. Complex 3 possesses a 1D tube-like chain. Thermo-gravimetric and magnetic properties of 1–3 were also investigated. - Graphical abstract: Structures and magnetic properties of copper(II) coordination polymers constructed from 5-methoxyisophthalate linker and two flexible N-donor ancillary ligands. Three copper(II) coordination polymers with 5-methoxyisophthalate and two related flexible N-donor ancillary ligands have been synthesized and structurally characterized. Moreover, thermal behaviors and magnetic properties of these complexes have also been investigated. - Highlights: • Three Cu(II) coordination polymers were synthesized. • The conformations of N-donor ligands and pH value have an effect on the final structures. • The magnetic properties of 1–3 have been investigated.

  19. Corrosion product deposits on boiling-water reactor cladding: Experimental and theoretical investigation of magnetic properties

    NASA Astrophysics Data System (ADS)

    Orlov, A.; Degueldre, C.; Wiese, H.; Ledergerber, G.; Valizadeh, S.

    2011-09-01

    Recent Eddy current investigations on the cladding of nuclear fuel pins have shown that the apparent oxide layers are falsified due to unexpected magnetic properties of corrosion product deposits. Analyses by Scanning Electron Microscopy (SEM) or Electron Probe Micro Analysis (EPMA) demonstrated that the deposit layer consists of complex 3-d element oxides (Ni, Mn, Fe) along with Zn, since the reactor operates with a Zn addition procedure to reduce buildup of radiation fields on the recirculation system surfaces. The oxides crystallise in ferritic spinel structures. These spinels are well-known for their magnetic behaviour. Since non-magnetic zinc ferrite (ZnFe 2O 4) may become magnetic when doped with even small amounts of Ni and/or Mn, their occurrence in the deposit layer has been analyzed. The magnetic permeability of zinc ferrite, trevorite and jacobsite and their solid solutions are estimated by magnetic moment additivity. From the void history examination, the low elevation sample (810 mm) did not face significant boiling during the irradiation cycles suggesting growth of (Mn0.092+Zn0.752+Fe0.293+)[(Fe1.713+Mn0.032+Ni0.132+)O] crystals with theoretical value of the magnetic permeability for the averaged heterogeneous CRUD layer of 9.5 ± 3. Meanwhile, (Mn0.162+Zn0.552+Fe0.293+)[(Fe1.713+Mn0.042+Ni0.252+)O] crystallizes at the mid elevation (1810 mm) with theoretical magnetic permeability for the CRUD layer of 4.2 ± 1.5 at the investigated azimuthal location. These theoretical data are compared with the magnetic permeability of the corrosion product deposited layers gained from reactor pool side Eddy current (EC) analyses (9.0 ± 1.0 for low and 3.5 ± 1.0 for high elevation). The calculated thicknesses and magnetic permeability values of the deposition layers (estimated by MAGNACROX multifrequency EC method) match together with these estimated using an "ion magnetic moment additivity" model.

  20. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-06-01

    The structures and magnetic properties of Co-Zr-B alloys near the composition of Co5Zr with B at. % ?6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the "Co11Zr2" polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the "interruption" sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co5Zr phase and larger than that of the low-temperature Co5.25Zr phase. Our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.