Electron paramagnetic resonance g-factors, g||, g, and hyperfine structure constants, A||, A, for a tetragonal Co2+ impurity center were calculated by using the perturbation formulae of electron paramagnetic resonance parameters for the 3d7 ion in tetragonal symmetry, as deduced from the cluster approach. Based upon the calculations, the center was suggested to involve a substitutional Co2+ ion which was associated with a nearest-neighbour O2− ion.

Defect Model for a Tetragonal Co2+ Impurity Center in AgCl Crystal. S.Y.Wu, W.C.Zheng: Materials Science and Engineering B, 2001, 86[1], 92-5