STUDIES ON THE LOCAL STRUCTURE AND THE SPIN HAMILTONIAN PARAMETERS FOR THE TRIGONALMn2+CENTER INBi4Ge3O12

Abstract

The local structure and the spin Hamiltonian parameters (the zero-field splitting D, the g factors g//, g⊥and the hyperfine structure constants A//and A⊥) for the trigonal Mn2+center in Bi4Ge3O12are theoretically studied from the perturbation formulas of these parameters for a 3d5ion in trigonal symmetry. The impurity Mn2+replacing host Bi3+is not found to occupy the exact Bi3+site but to suffer a large off-center displacement by about 0.36 Å towards the center of the oxygen octahedron along the C3-axis due to the size and charge mismatching substitution. The calculated spin Hamiltonian parameters based on the above displacement show good agreement with the observed values. The results and the mechanism of the impurity displacement are discussed.