Theoretical investigations of the zero-field splittings and g factors for the ion at the rhombic defect site in the AgCl crystal

Abstract

In this paper we establish the high-order perturbation formulas of zero-field splittings D and E and g factors and for ions in rhombic symmetry by using a two-spin-orbit (SO) coupling parameter model, in which not only the contribution due to the SO coupling of the central ion but also that of the ligands are included. Based on these formulas, all five EPR parameters for the ion at the rhombic defect site in the cubic AgCl crystal are satisfactorily explained by considering suitable defect-induced lattice distortion. The relative importance among the various contributions to the EPR parameters from the SO couplings of the central ion, the ligand ions and the mixed ones is discussed. It can be seen that for the ions in crystals with ligands having large SO coupling parameter, the contribution due to the SO coupling of ligands cannot be neglected and we should apply the two-SO parameter model in studies of EPR parameters.