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

The gyromagnetic factors g(parallel to), g(perpendicular to) and the hyperfine structure constants A(parallel to) and A(perpendicular to) 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 V-O along the C-4 axis. Due to the electrostatic repulsion of V-O, Cu2+ is displaced away from V-O by Delta Z(approximate to -0.29 angstrom) along the C-4 axis. The theoretical values of the g and A factors based on the above defect structure and the impurity displacement agreee reasonably with the experimental data.