Microscopic characterization of impurities in insulators through EPR

2001

Appl. Magn. Reson.

The displacements of Fei ions and hence the structures of Fei ' -V0 defects in ABO3 oxide perovskites are studied by analyzing their electron paramagnetic resonance data from the high-order perturbation formula of zero-field splitting on the basis of the spin-orbit coupling mechanism. The results suggest that the Fe" ions in the Fei + -V0 defect centers are displaced away from the oxygen vacancy Vo by about 0.035 nm. The reasonableness of the displacement is discussed.

Section: Discussionmentioning

confidence: 99%

Structures of Fe3+-Vo defects in ABO3 perovskite-type crystals

2001

Appl. Magn. Reson.

“…The cubic field parameter Dq G R Àn . The pressure experiment for NiO [11] and the theoretical studies based on molecular orbital calculations for d m ions in many crystals [12,13] show that n % 5, the value obtained from the point-charge model, is approximately valid. So, we use the point-charge model here.…”

Section: Calculationsmentioning

confidence: 91%

Theoretical Studies of EPR Parameters for Cr3+ Ion at an Orthorhombic Defect Site in AgBr Crystal

1998

Phys. Status Solidi B

In this paper, the high-order perturbation formulas of EPR zero-field splittings D, E and g-factors g i i xY yY z for d 3 ions in orthorhombic symmetry are established by using a two-spin±orbit coupling parameter model, in which both contributions from the spin±orbit coupling of the central d 3 ion and that of the ligands are included. Based on these formulas, the EPR parameters for the Cr 3 ion at an orthorhombic defect site in the AgBr crystal are calculated by considering the suitable defect-induced lattice distortion. The calculated parameters D and E show good agreement with the observed values. The reasons for the disparity of the g i -shift Dg i g i À g s between the calculation and the experiment and the importance of the contributions to the EPR parameters from the spin±orbit coupling of ligands are discussed.

“…Since the point-charge model with the expectation values r n of free d n ions can not reproduce the experimental crystal-field parameters, e. g., the cubic field parameter Dq [30,31], we calculate the tetragonal field parameters D s and D t from the empirical superposition model [32]. According to the model, we have…”

Section: Calculationmentioning

confidence: 99%

A Study of Spin-Hamiltonian Parameters and Defect Structure for Co²⁺ Ion in the Tetragonal Zn²⁺ Site of Ba₂ZnF₆ Crystal

Lia

Zeitschrift Für Naturforschung A

Yang

2010

The spin-Hamiltonian (SH) parameters (g factors g , g ⊥ and hyperfine structure constants A , A ⊥ ) for the Co 2+ ion in the tetragonal Zn 2+ site of a Ba 2 ZnF 6 crystal are calculated from the secondorder perturbation formulas based on the cluster approach for the SH parameters of 3d 7 ions in tetragonal symmetry with the effective spin S = 1/2. In the calculations, a reduction factor due to the dynamical Jahn-Teller effect is used. The calculated results are in reasonable agreement with the experimental values, suggesting that the dynamical Jahn-Teller effect should be considered here. The defect structure of the Co 2+ center in Ba 2 ZnF 6 :Co 2+ is also obtained from the calculations. The results are discussed.