Spin-Hamiltonian parameters and defect structures for the trigonal Yb3+ centers in wurtzite-type ZnS and CdS crystals

A complete diagonalization (of the energy matrix, where the corresponding Hamiltonian consists of free-ion, crystal-field, Zeeman and hyperfine interaction terms) method is applied to calculate the spin-Hamiltonian parameters (g factors g(parallel to), g(perpendicular to) and hyperfine structure constants A(parallel to), A(perpendicular to)) for the trigonal Yb3+ centers in wurtzite-type ZnS and CdS crystals. The calculated results are in reasonable agreement with the experimental values. In the calculations, the crystal-field parameters are obtained from the superposition model, which enables correlation of the spin-Hamiltonian parameters with the defect structure of the studied impurity center. The defect structures of Yb3+ centers (characterized by the local atom-position parameters u(loc), which differ from the corresponding parameter in the host crystal) in both crystals are therefore estimated from the calculations. The results are discussed.