EPR g factors and tetragonal distortion for the isoelectronic Ni+ and Cu2+ centers in the CuGaSe2 crystal

Abstract The EPR g factors, g || and g ⊥ , for the isoelectronic 3d 9 ions Ni + and Cu 2+ at the tetragonal Cu + site of the CuGaSe 2 crystal are calculated from the high-order perturbation formulas based on a two-spin–orbit-parameter model. In the model, both the contributions to g factors from the spin–orbit parameter of central 3d 9 ion and that of ligand ion are contained. The calculated results appear to be consistent with the experimental values. The tetragonal distortions (characterized by θ − θ 0 , where θ is the angle between the metal–ligand bond and C 4 axis, and θ 0 ≈54.74° is the same angle in cubic symmetry) of Ni + and Cu 2+ centers, which are different from the corresponding angle in the host CuGaSe 2 crystal and from impurity to impurity, are obtained from the calculations. The difference of the sign of g || − g ⊥ between the isoelectronic Ni + and Cu 2+ centers is found to be due to the different tetragonal distortions of both centers in the CuGaSe 2 crystal.