Theoretical studies of the g factors and hyperfine structure constants for Ni~+ in AgGaS_2 and AgGaSe_2 crystals

摘要

In this paper, the high-order perturbation formulas based on the two spin-orbit coupling parameter model for the EPR g factors g_(||), g_perpendicular and hyperfine structure constants A_(||), Aperpendicular of 3d~9 ion in tetragonal tetrahedral crystals are established by a molecular orbital approach, In these formulas, the contributions to EPR parameters from both the spin-orbit coupling parameter of central 3d~9 ion and that of ligands are included. By use of these formulas, the EPR parameters #DELTA#G_(||)(= g_s - g_(||)), #DELTA#g_perpendicular(= g_s - g_perpendicular), A_(||) and A_perpendicular for Ni~+ in AgGaS_2 and AgGaSe_2 crystals are calculated. The calculated results show good agreement with the observed values. The importance of the contribution from the spin-orbit coupling of ligands to various EPR parameters is discussed.