Abstract
The spin-Hamiltonian parameters (g factors g//, g⊥ and zero-field splitting D) of the isoelectronic 3d3 ions Cr3+, Mn4+ and Fe5+ in rhombohedral phase of BaTiO3 are calculated from the high-order perturbation formulas based on the two-mechanism model, where the contributions to spin-Hamiltonian parameters due to both the crystal-field (CF) mechanism concerning the interaction of CF excited states with ground state and the charge-transfer (CT) mechanism concerning that of CT excited states with ground state are contained. The calculated results are in reasonable agreement with the experimental values. The calculations indicate that the relative importance of CT mechanism increases with the increasing valence state of 3d3 ions and that the fact of \(g_{i} (i = {//}, \bot ) > g_{e} ( \approx 2.0023\), the free-electron g value) for Fe5+ in BaTiO3 is due to the contributions of CT mechanism being larger than those of CF mechanism. So, for the high valence state dn ions in crystals, the rational explanations of spin-Hamiltonian parameters should take both CF and CT mechanisms into account. The local trigonal distortions (characterized by the off-center displacements \(\varDelta\)z of 3d3 ions) of 3d3 impurity centers in BaTiO3 crystals are also estimated. These trigonal distortions differ not only from that in the host BaTiO3 crystal, but also from impurity to impurity.
Published Version
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