Physica B-Condensed Matter
The temperature dependence of EPR g factor for MgO:V2+ crystal has been studied theoretically by considering both the static contribution due to the thermal expansion of crystal and the vibrational contributions due to the electron-phonon interaction of the acoustic and optical branches. The static contribution is calculated from the high-order perturbation formula of g factor and the thermal expansion coefficients alpha(T) at various temperatures. The vibrational contribution of acoustic phonons is obtained by using a Debye model for the lattice vibrations and that of optical phonons is calculated by use of a single frequency model. The calculated results show that for the g factor at various temperatures, the static contribution is dominant, but for the temperature dependence of g factor, i.e., (dg/dT)(p) or Delta g(T) = g(T) - g(0), the vibrational contributions from the acoustic and optical phonons are comparable with the static contribution due to thermal expansion. It appears that a reasonable theoretical explanation for the temperature dependence of g factor should take all of these contributions into account.
关键词:
impurities
Semiconductor Science and Technology
A two spin-orbit coupling parameter model based on a cluster approach is presented in this paper for the calculations of the g factor for V3+ ions in the cation sites of GaP, InP and GaAs crystals. In this model, differing from the conventional one spin-orbit coupling parameter model, both the contributions from the spin-orbit coupling of the central 3d(2) ion and those of ligand ions are included. By using the parameters obtained from the optical spectra of the studied crystals, the calculated g shifts (g - 2.0023) are in good agreement with the observed values. Various contributions to the g shift are discussed.
关键词:
electron-paramagnetic-resonance;transition-metal impurities;vanadium;gaas;crystal;epr;spectra;cr2+;gap;inp
Physica B-Condensed Matter
In this paper, by using only one adjustable parameter V' (the trigonal-field parameter), the zero-held splitting D, the g factors g(parallel to) and Delta g (= g(parallel to) -g(perpendicular to)) for CsMgCl3:V2+ crystal have been calculated from the high-order perturbation formulas based on the two spin-orbit coupling parameter model. The calculated results show good agreement with the observed values. A comparison between the calculated results from various crystal field theories are also made. It is found that the difference between signs D and Delta g for CsMgCl3:V2+ crystal is caused by the contributions from the excited multiplets, particularly those arising from the free ionic term (2)G. (C) 1998 Elsevier Science B.V. All rights reserved.
关键词:
crystal and ligand field theory;electron paramagnetic resonance;spin-orbit coupling;V2+ ion;CsMgCl3;crystal;spectra;ions
Journal of Physics and Chemistry of Solids
The zero-field splitting D and g factors g(parallel to),g(perpendicular to) for V3+ ions substituting for Cu+-site and Al3+-site in CuAlS2 ternary semiconductor was calculated by using the high-order perturbation formulas based on the two spin-orbit coupling parameter model where the contributions to EPR parameters from both the spin-orbit coupling of the central 3d(2) ion and that of the ligands are considered. The calculated D, g(parallel to) and g(perpendicular to) for V3+ replacing Cu+-site are in good agreement with the observed values, whereas the calculated D value for V3+ replacing Al3+-site is not. These results show that V3+ substitutes for Cu+-site in CuAlS2 crystal. (C) 1999 Elsevier Science Ltd. All rights reserved.
关键词:
semiconductors;crystal fields;defects;electronic paramagnetic;resonance (EPR);superposition model;semiconductors;resonance;spectra
Communications in Theoretical Physics
The calculations of the whole energy spectrum and the g factors of the ground state and t(2)(3) E-2 excited state for MgO:V2+ at normal pressure as well as their pressure-induced shifts have been carried out on the basis of the theory of pressure-induced shifts and the diagonalization of the complete d(3) energy matrix in a regular octahedral field. The calculated results are in very good agreement with experimental data. It is found that in the range of 1 bar similar to 100 kbar, the g value of the ground state increases monotonously with pressure, but the g value of t(2)(3) E-2 excited state for MgO:V2+ decreases at first, and then increases. For the first time, the physical essentials of the pressure-induced shifts of g values for the ground state and t(2)(3) E-2 excited state have been thoroughly analyzed and revealed by taking into account the wavefunctions, energy spectra and orbital-angular-momentum reduction factors at various pressures.
关键词:
high pressure effect;ligand field;optical spectra;line shift;electronic spin resonance;3d transition-metal ions;theoretical calculations;ruby;mgo-cr3+;cr3+;mgo
谢林华
量子电子学报
doi:10.3969/j.issn.1007-5461.2008.04.002
掺V3+离子的ZnS晶体局部结构与光谱和顺磁共振(EPR)参量有关联.根据Sugano-Tanabe方案建立了d2/8电子强场45×45阶完全能量矩阵,由自旋哈密顿理论推导了EPR参量的计算公式,通过点荷-偶极子模型得到了离子簇局部Td对称结构与晶场参量的关系,基于半自洽场d轨道和完全对角化方法,从局部结构统一解释了ZnS:V3+的光谱和顺磁g因子,计算结果与实验符合.计算结果表明,ZnS:V3+的光谱和EPR谱可以在晶体场理论框架内得到理解.
关键词:
光谱学
,
光学和磁学性质
,
晶体场
,
顺磁g因子
,
ZnS
European Physical Journal-Applied Physics
The local structures and the EPR g factors g(parallel to) and g(perpendicular to) are theoretically studied for the tetragonal Ti(3+)-V(O) centers in BaTiO(3) bulks and thin films using the perturbation formulas of the g factors for a 3d(1) ion in tetragonally elongated octahedra and compressed tetrahedra, respectively, based on the cluster approach. For the Ti(3+)-V(O) center in BaTiO(3) bulks, the impurity Ti(3+) suffers the displacement away from the oxygen vacancy V(O) by about 0.15 angstrom along the C(4) axis due to the electrostatic repulsion of the V(O). Nevertheless, the Ti(3+)-V(O) center in BaTiO(3) thin films may exhibit the tetragonally compressed tetrahedron, characterized by the bond angle 55.88 degrees larger than that (approximate to 54.74 degrees) of an ideal tetrahedron. The quite different g factors (especially g anisotropies Delta g = g(parallel to) - g(perpendicular to)) for the two kinds of samples are discussed, in view of the dissimilar bonding or coordination environments (i.e., incomplete bonding in the thin films may lead to the lower coordination number).
关键词:
electron-paramagnetic resonance;atomic screening constants;superposition model;spin-resonance;scf functions;crystals;epr
Journal of Magnetism and Magnetic Materials
The electron paramagnetic resonance g factors g(parallel to) and g(perpendicular to) for the trigonal Er3+-V-K centers (where V-K denotes K+ vacancy) in KMF3 (M = Mg and Zn) are theoretically investigated from the perturbation formulas of the g factors for a 4f(11) ion in trigonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixture of various energy levels are taken into account. In the above trigonal centers, the impurity Er3+ resides in the octahedral M2+ site of both crystals, associated with one V-K in the C-3-axis due to charge compensation. By analyzing their g factors, we find that the impurity Er3+ in both centers would move towards the V-K by an amount DeltaZ along the C-3-axis due to electrostatic attraction. The calculated g factors for the Er3+ centers based on the above displacements DeltaZ show good agreement with the observed values. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
electron paramagnetic resonance (EPR);defects and impurities;crystal-field and spin hamiltonians;Er3+;KMF3;(M = Mg and Zn);crystal-field;superposition-model;perovskite kmgf3;conversion;parameters;fluorides;kznf3
