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

The EPR g factors, g(parallel to) and g(perpendicular to), for the isoelectronic 3d(9) ions Ni+ and Cu2+ at the tetragonal Cu+ site of the CuGaSe2 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 theta - theta(0), where theta is the angle between the metal-ligand bond and C-4 axis, and theta(0)approximate to E54.74 degrees is the same angle in cubic symmetry) of Ni+ and Cu2+ centers, which are different from the corresponding angle in the host CuGaSe2 crystal and from impurity to impurity, are obtained from the calculations. The difference of the sign of g(parallel to) - g(perpendicular to) between the isoelectronic Ni+ and Cu2+ centers is found to be due to the different tetragonal distortions of both centers in the CuGaSe2 crystal. (C) 2010 Elsevier B.V. All rights reserved.