Theoretical study of anisotropy spin-orbit coupling and local lattice structure for Fe<Superscript>3+</Superscript> ions in MgTiO<Subscript>3</Subscript>:Fe<Superscript>3+</Superscript> system
The anisotropy spin-orbit coupling matrices for a d<Superscript>5</Superscript> configuration ion in a trigonal ligand-field have been established. On basis of the anisotropy spin-orbit coupling matrices, the ground state zero-field splitting of the Fe<Superscript>3+</Superscript> ions in ilmenite-structure MgTiO<Subscript>3</Subscript>:Fe<Superscript>3+</Superscript> system has been studied. The calculated results show that the anisotropy of Fe<Superscript>3+</Superscript> ions in the diamagnetic ilmenite MgTiO<Subscript>3</Subscript> is important and the EPR parameters depend sensitively on the anisotropy divergent parameter. Moreover, the effect of the anisotropy divergent parameter on the second-order parameter D is obviously larger than that on the fourth-order parameter (a-F). Based on this point, the local lattice structure of Fe<Superscript>3+</Superscript> ion in MgTiO<Subscript>3</Subscript>:Fe<Superscript>3+</Superscript> system is determined by diagonalizing the complete energy matrices for a d<Superscript>5</Superscript> configuration ion in a trigonal ligand-field and considering the second-order as well as the fourth-order EPR parameters D and (a-F) simultaneously. Our results are consistent with the experimental proposal that Fe<Superscript>3+</Superscript> ions may locate at both the Mg<Superscript>2+</Superscript> and Ti<Superscript>4+</Superscript> sites. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005
