Investigations of the spin-Hamiltonian parameters and tetragonal compression due to the static Jahn–Teller effect for Cr 5+ center in cubic SrTiO 3 crystal

Abstract

By using the distortion model that the tetragonal site symmetry of Cr 5+ in cubic phase of SrTiO 3 originates from the static Jahn–Teller effect, the spin-Hamiltonian parameters ( g factors g ||, g ⊥ and hyperfine structure constants A ||, A ⊥) of this tetragonally compressed Cr 5+ center in SrTiO 3 are calculated from the high-order perturbation formulas based on a two-mechanism model. In the model, not only the contribution to spin-Hamiltonian parameters due to the crystal-field mechanism, but also that due to the charge-transfer mechanism (which is omitted in the extensively used crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. The tetragonal compression (characterized by Δ R= R ⊥− R ||, where R ⊥ and R || denote the metal–ligand distances perpendicular to and parallel with the C 4 axis) of Cr 5+ center is also obtained from the calculation. The results (including the tetragonal compression and the relative importance of the charge-transfer mechanism) are discussed.