Spin-Hamiltonian parameters, defect model and defect structure for the tetragonal Mo5+ center in x-ray-irradiated α-ZnMoO4 crystals

Abstract

ABSTRACTThe spin-Hamiltonian parameters (g factors gi, hyperfine structure constants Ai (95Mo5+) and Ai (97Mo5+), i = // and ⊥) assigned to the tetragonal Mo5+ (4d1) tetrahedral center in α-ZnMoO4 crystal caused by a Mo6+(1) ion trapping an electron after x-ray irradiation are calculated from the high-order perturbation formulas resting on the two-mechanism model. The model takes account of both the effects of crystal-field (CF) mechanism concerning the CF excited states in the CF theory and that of the charge-transfer (CT) mechanism related to CT excited states. The calculated results are reasonably consistent with the experimental values, confirming this assignment (or defect model). The calculations also indicate that the effect of CT mechanism cannot be neglected. The defect structure (particularly, the angular distortion) and signs of constants Ai (95Mo5+) and Ai (97Mo5+) of this Mo5+ defect center are also decided from the calculations. The outcomes are discussed.