Research of the Spin-Hamiltonian Parameters and Defect Structure for the Trigonal Mn4+ Centers in Y2Ti2O7:Mn4+ Crystal

Resumo

The high-order perturbation formulas founded on the two-mechanism model are applied in this paper to compute the spin-Hamiltonian parameters (g factors g_//, g_⊥ and zero-field splitting D) of the trigonal Mn⁴⁺ centers in Y₂Ti₂O₇:Mn⁴⁺ crystal. In this model, besides the contributions from the traditional crystal-field (CF) mechanism (in the CF theory) related to CF excited states, those from the charge-transfer (CT) mechanism connected with CT excited states are contained. The calculated results are reasonably coincident with the observed values. The calculations show that the contributions of CT mechanism to spin-Hamiltonian parameters (in particular, the g factors) for (MnO₆)⁸⁻ clusters are large and cannot be neglected. The defect structure of trigonal (MnO₆)⁸⁻ clusters in Y₂Ti₂O₇:Mn⁴⁺ crystals is also evaluated. The results are discussed.