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

Abstract

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.