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
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
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
Physica B-Condensed Matter
The zero-field splitting D and g factors g(parallel to) and g(perpendicular to) for Ti2+ ions in CdS and CdSe crystals are calculated from the high-order perturbation formulas of EPR parameters based on the two-spin-orbit (SO) coupling parameter model. In this model, the contributions to EPR parameters from both the SO coupling parameter of the central 3d(2) ion and that of the ligand are considered. The calculated results show good agreement with the observed values. Comparing these results with those calculated from the conventional one-SO-parameter model where the contributions only from the SO coupling parameter of the 3d(2) ion are considered, it suggests that the calculations of EPR parameters D. g(parallel to) and g(perpendicular to) for 3d(2) ions in tetrahedrally coordinated semiconductors should prefer the two-SO-parameter model over the one-SO-parameter model. (C) 1999 Elsevier Science B.V. All rights reserved.
关键词:
crystal- and ligand-field theory;electron paramagnetic resonance;spin-orbit coupling;Ti2+;CdS;CdSe;g-values;ions;spectra;epr
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
Spectroscopy and Spectral Analysis
The complete high-order perturbation formula of g factor for 3d(3) ions in cubic octahedral site was derived. In the formula, both the contribution Delta g(CF) to g-shift Delta g(=g-g(s), where g(s) =2. 002 3) due to crystal-field (CF) mechanism (related to the interactions of CF excited states with the ground state) and that (Delta g(CT)) due to charge-transfer (CT) mechanism (related to the interactions of CT excited states with the ground state, which is omitted in crystal-field theory) are included. By using the formula and the parameters obtained from the optical spectra of CaZrO(3) : Mn(4+) crystal, the g factor of CaZrO(3) : Mn(4+) was calculated. The result is consistent with the experimental value. The calculations show that the contribution is opposite in sign and about 62% in magnitude compared with the contribution Delta g(CF). It appears that both CF and CT mechanisms should be considered in the calculation of g factor for the high valence 3d(3) (e. g., Mn(4+) and Fe(3+)) ions in crystals.
关键词:
electron paramagnetic resonance;g factor;charge transfer mechanism;crystal and ligand field theory;CaZrO(3);Mn(4+);atomic screening constants;scf functions;luminescence;manganese
