Theoretical studies of the spin Hamiltonian parameters for the tetragonal Co⁴⁺ and Ir⁴⁺ centers in SrTiO₃

Abstract

The spin Hamiltonian parameters, g factors and the hyperfine structure constants for Co4+ (3d5) and Ir4+ (5d5) in SrTiO3 are theoretically studied from the formulas of these parameters for an n d5 (n = 3 and 5) ion in a tetragonally distorted octahedron with low spin S = 1/2. According to the theoretical analyses, the impurity–ligand bond lengths R ′‖ parallel to the C4 axis are found to be larger than the host values R‖ based on the phase transition rotation angles ϕ of the [TiO6]8– octahedron by the C4 axis at 4.2 and 77 K, respectively. The elongation of the ligand octahedra in the host may be enhanced in the impurity centers by the Jahn–Teller effect of the n d5 ions. The theoretical results based on the above local structures show good agreement with the experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)