Theoretical studies on the gyromagnetic factors and the hyperfine structure constants for the tetragonal copper center in KTaO3

The gyromagnetic factors g parallel, g perpendicularto and the hyperfine structure constants A parallel and A perpendicularto of the tetragonal Cu2+ center in KTaO3 are theoretically studied in this work. Based on the analyses of the electron paramagnetic resonance results of this center, it is found that the impurity Cu2+ occupies the octahedral Ta5+ site, associated with a nearest-neighbouring oxygen vacancy VO along the C4 axis. Due to the electrostatic repulsion of VO, Cu2+ is displaced away from VO by ΔZ(∼ -0.29 Aa) along the C4 axis. The theoretical values of the g and A factors based on the above defect structure and the impurity displacement agree reasonably with the experimental data. (orig.)