材料期刊网

MAGNETIC PROPERTIES AND STRUCTURES OF NANO-CRYSTALLINE Fe-P-C-Mo-Cu-Si ALLOYS

Y.F. Gao , J.Tan , G.D. Liu , C.L.Zhang , T.Liuand R.Z Ma (Rapidly Quenched Materials Research and Development Centre , Central Iron & Steel Research Institute , Beijing 100081 , China)(Metal Physics Department , University of Science and Technology Beijing , Beijing 100083 , China)

金属学报(英文版)

A mostly single bcc phase with grain sizes of 15-20 nm was prepared by crystallization of amorphous Fe-P-C-Mo-Cu-Si alloys.The Bs value (H=10000 Oe) reaches 1.595 T for Fe(79.5) P(12)C6Cu(0.5)Mo(0.5)Si(1.5) alloys. The low core loss of 0.14 w/kg at 1.3 T and 50 Hz was confirmed for the bcc Fe(79.5)P(12)C6Cu(0.5)Mo(0.5)Si(1.5) alloy.The structures of the alloy annealed at different temperatures have been investigated by means of Xray diffraction and transmission electron microscope. The relationship between the structure and magnetic properties of the alloy is discussed.

关键词: : amorphous alloy , null , null

SPIN-LATTICE COUPLING-COEFFICIENTS G(11) AND G(44) FOR 3D(5) IONS IN 12-FOLD CUBIC COORDINATION

Physica B-Condensed Matter

Similar to the cases of 3d(n) ions in 4-fold (or 8-fold) and 6-fold cubic coordinations, a simple and uniform method that calculates the spin-lattice coupling coefficients G11 and G44 for those ions in the more complex 12-fold cubic coordination from the derivatives of zero-field splittings in low symmetries with respect to the distinct structural parameters has been established. Through this method, the analytic expressions of G11 and G44 for 3d5 ions in this cubic coordination based on various mechanisms and models have been given. The results are rather different from those in 4-fold (or 8-fold) and 6-fold cubic coordinations. As an example, the coefficients G11 and G44 for Fe3+ in K+ site ( 12-fold cubic coordination) as well as Ta5+ site (6-fold cubic coordination) of KTaO3 crystal are studied from the important spin-orbit coupling mechanism. When we compare these results with the experimental findings, it appears that the Fe3+ ion is in a Ta5+ site, and not in a K+ site as shown by some researchers.

关键词: s-6-state ions;symmetry;formulas

Theoretical investigations of the local structures and the g factors for 3d(9) ions in CdS

Physics and Chemistry of Minerals

The local structures and the g factors g (//) and g (aSyen) for the isoelectronic 3d(9) ions Cu(2+) and Ni(+) in CdS are theoretically investigated from the perturbation formulas of these parameters for a 3d(9) ion under trigonally distorted tetrahedral environments. In consideration of significant covalency of the [MS(4)] combinations (M = Cu and Ni), the ligand orbital and spin-orbit coupling contributions are taken into account using the cluster approach. Based on the studies, the substitutional impurity Cu(2+) (or Ni(+)) on Cd(2+) site is found to undergo a small inward displacement 0.026 (or a slight outward shift 0.017 ) towards (or away from) the ligand triangle along C (3) axis. The theoretical g factors for both ions based on the above impurity displacements are in good agreement with the experimental data.

关键词: Electron paramagnetic resonance;Defect structures;Crystal-fields and;spin Hamiltonians;Cu(2+);Ni(+);CdS;electron-paramagnetic-resonance;atomic screening constants;defect;structures;crystal-field;3d impurities;scf functions;semiconductors;parameters;epr;spectra

Zero-field splitting and g factors for d(2) ions in trigonally distorted cubic crystal fields

Communications in Theoretical Physics

By successively taking into account various interactions for d(2) ions in trigonally distorted cubic crystal fields, detailed analyses, derivations and calculations of the zero-field splitting (ZFS) and g factors of the ground state have been carried out; and their physical essentials and origins have been clearly revealed. The mistakes and shortcomings in some references have been corrected and improved. The calculated results are in excellent agreement with experimental data and much better than those of previous work. It is found that both the combined action of the trigonal field and spin-orbit interaction and the interaction between the ground state and excited states are quite necessary for causing ZFS of the ground state, and both the spin-orbit interaction and the admixture between the ground state and excited states are necessary for causing the deviation of g factors of the ground state from spin-only values.

关键词: zero-field splitting;g factors;d(2) ions;crystal field;combined;action;admixture of wavefunction

Studies of EPR g factors of the isoelectronic 3d(3) series Cr3+Mn4+ and Fe5+ in SrTiO3 crystals

Journal of Physics and Chemistry of Solids

The g-shifts Ag( = g-g(s), where g(s) approximate to 2.0023 is the free-ion value) of the isoelectronic 3d(3) series Cr3+. Mn4+ and Fe5+ in SrTiO3 crystals are calculated from the high-order perturbation formula based on the cluster approach for 3d3 ion in cubic octahedral site. The formula includes not only the contribution from the crystal-field (CF) mechanism, but also that from the charge-transfer (CT) mechanism (which is omitted in the CF theory). From the calculations, it is found that the contribution Delta g(CT) from the CT mechanism in sign is contrary to the corresponding Delta g(CF) from the CF mechanism and the relative importance of CT mechanism (characterized by vertical bar Delta g(CT)/Delta g(CF)vertical bar) increases with the increasing valence state (and hence the atomic number) of 3d(3) ion. The positive g-shift Delta g of SrTiO3:Fe5+ is due mainly to the contribution of CT mechanism. So, for the explanations of g factors of the high valence state 3d" ions (e.g. Mn4+ and Fe5+) in crystals, the contributions from both CF and CT mechanisms should be taken into account. (c) 2005 Elsevier Ltd. All rights reserved.

关键词: oxides;crystal fields;electronic paramagnetic resonance;optical;properties;electron-paramagnetic-resonance;atomic screening constants;scf;functions;luminescence;parameters;spectra;temperature;manganese;lattices;csmgbr3

CALCULATION OF THE SPIN-LATTICE COUPLING-COEFFICIENTS G11 AND G44 FOR GAP-FE(3+) CRYSTAL

Nuovo Cimento Della Societa Italiana Di Fisica D-Condensed Matter Atomic Molecular and Chemical Physics Fluids Plasmas Biophysics

A uniform und simple method suitable to all d(n) ions is established for the calculation of spin-lattice coupling coefficients G11 and G44 in T(d) symmetry. According to the method, the coefficients G11 and G44 for Fe3+ ion in GaP crystal have been obtained from the high-order perturbation formulae of zero-field splitting in tetragonal and trigonal fields based on the spin-orbit coupling mechanism. The calculated results show good agreement with the experimental findings.

关键词: level splitting and interaction;electron paramagnetic resonance and;relaxation;crystal and ligand fields;d-orbital theory;ions

Investigations of the g factors for Co2+ in fluoroperovskites

Physica B-Condensed Matter

The perturbation formula of g factor for 3d(7) ion in cubic octahedral crystals has been obtained from a cluster approach. In the formula, the parameters related to the configuration interaction and the covalency reduction effect can be obtained from the optical spectra of the crystal under study and so no adjustable parameters are applied. From the formula, the g factors for Co2+ in fluoroperovskites LiBaF3, KMBF3, KZnF3 and CsCdF3 are calculated. The calculated results are in agreement with the observed values. The g factor following the order of LiBaF3 : Co2+ < KMgF3 : Co2+ < KZnF3: Co2+ < CsCdF3 : Co2+ is also explained. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Co2+;LiBaF3;KMgF3;KZnF3;CsCdF3;perovskite;transition;impurities;crystals

Investigations of the EPR g factors of NaCrS2 and NaCrSe2

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The EPR g factors of Cr3+ in NaCrS2 and NaCrSe2 crystals are calculated from the high-order perturbation formulas based on the one-spin-orbit (SO)-coupling-parameter (i.e., the SO-coupling-parameter of the central 3d(n) ion) as well as the two-SO-coupling-parameter (i.e., the SO-coupling-parameter of the 3d(n) ion and that of ligands) models for 3d(n) ions in cubic octahedral sites. The calculated results (in particular for NaCrSe2) based on the two-SO-coupling-parameter model are closer to the observed values than those based on the one-SO-coupling-parameter model, suggesting that for calculations of the g factor of 3d(n) ions in covalent crystals the two-SO-coupling-parameter model is preferable to the one-SO-coupling-parameter model. The reasonableness of the calculated results from the two-SO-coupling-parameter model is discussed.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;spin-orbit coupling;Cr3+;NaCrS2;NaCrSe2;atomic screening constants;chromium(iii) sulfides;scf functions;crystals;selenides;resonance;spectra

Theoretical studies of the g factors for Co2+ in MgO and CaO crystals

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

This paper presents a cluster approach to the calculation of the g factors for 3d(7) ions in cubic octahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are calculated. The calculated results show good agreement with the observed values. The experimental values of g < 4.333 (the first order value in absence of configuration and covalency interactions) for MgO:Co2+ and g > 4.333 for CaO:Co2+ are also explained.

关键词: electron paramagnetic resonance (EPR);crystal-field theory;Co2+ ion;MgO;CaO

Explanations of the optical spectra and g factor for V3+ ions in ZnX (X = S, Se, Te) crystals

Physica B-Condensed Matter

This paper presents a cluster approach for the calculations of the absorption band positions and the g factor of d(2) tetrahedral cluster. In the approach, the different modifications of e and t(2) orbitals of d electrons and the contribution from the spin-orbit coupling of ligands to the EPR g factor due to the mixing of d(2) ions with the ligands are considered. The calculated band positions and g factor for ZnX : V3+ (X = S, Se, Te) crystals show good agreement with the observed values by using only two adjustable parameters. The contribution from the spin-orbit coupling of ligands to the g factor is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

关键词: crystal- and ligand-field theory;optical spectra;electron paramagnetic;resonance;spin-orbit coupling;V3+ ZnX (X = S, Se, Te);vanadium centers;znte crystals