Spin-Hamiltonian parameters of Zn 1− xCr xS and Zn 1− xCr xTe

Abstract

The Hamiltonian matrices for the spin-quintet and spin-triplet states of 3d 4 and 3d 6 ions are constructed using a molecular orbital approach, including the electrostatic Coulomb term, tetragonal crystal field as well as the spin-orbit and spin–spin coupling. The spin-Hamiltonian parameters for Cr 2+ ions in ZnS and ZnTe are interpreted using this approach. Correct signs and magnitude of the zero-field splitting parameter b 2 0<0 for ZnS : Cr 2+ and b 2 0>0 for ZnTe : Cr 2+ are obtained including the contributions from the spin–orbit coupling within ligands S or Te. The present values of b 4 0 and b 4 4 in ZnS : Cr 2+ are also improved as compared with the previous results. The good agreement between the calculated and the experimental values shows that the contributions to the zero-field splitting from the spin-triplet states of the central ions Cr 2+ and the spin–orbit coupling of the ligands S (especially) and Te are important.