Research on the Spin-Hamiltonian Parameters and Local Structure for the Tetragonal Mo⁵⁺Centers in CaWO₄Crystal

Abstract

The spin-Hamiltonian parameters (g factors g , g ⊥ and hyperne structure constants A (A), A ⊥ (A), A (B) and A ⊥ (B), A(A) and A(B) belonging to isotopes 95 Mo 5+ and 97 Mo 5+ ) of Mo 5+ ion at the tetragonally-compressed tetrahedral W 6+ site in CaWO4 crystal are calculated from the high-order perturbation formulae based on the two-mechanism model, where besides the contributions to spin-Hamiltonian parameters due to the crystal-eld mechanism concerning the crystal-eld excited states in the extensively-applied crystal-eld theory, those due to charge-transfer mechanism concerning charge-transfer excited states (which are omitted in crystal-eld theory) are included. The calculated results are in reasonable agreement with the experimental values. The calculations show that for the high-valence state d n ions (e. g., Mo 5+ considered) in crystals, the contributions due to charge-transfer mechanism should be taken into account in the studies of spin-Hamiltonian parameters. The local structure of Mo 5+ center in CaWO4 crystal due to the impurity-induced local lattice relaxation is estimated from the calculations. The results are discussed.

Studies on the EPR parameters and local angular distortion for the tetragonal Cu2+ center in CaWO4 crystal

“…a ) without the ligand contributions and those (Cal. b ) based on host structure of the Cu 2+ center (56.89 [43] ). Thus, the observed EPR parameters for CaWO 4 :Cu 2+ are satisfactorily interpreted in this work, and the information about the impurity local structure (i.e., the local bond angle distortion δθ) was obtained.…”

“…In order to clarify the contributions of the local bond angle distortion δθ to the EPR parameters, the theoretical results (Cal. b ) based on the host angle θ h (≈56.89 [43] ) of W 6+ site in CaWO 4 are also shown in Table 2.…”