Investigations of EPR parameters and impurity structure for Co2+ in Ca(OH)2 crystal

Abstract

The electron paramagnetic resonance (EPR) parameters (g, and g, factors and hyperfine structure constants A(parallel to) , A(perpendicular to)) for Co2+ in Ca(OH)(2) are studied from the second-order perturbation formulas on the basis of the cluster approach. In these formulas, the contributions to EPR parameters from the state interactions and covalency effects are considered and the parameters related to both effects are obtained from the optical spectra and impurity structure of the studied system. From the study, it is found that the beta angle between the metal-ligand bond and the C-3 axis changes from 61degrees in a pure crystal to 53.68(26)degrees in the impurity center of a Co2+-doped Ca(OH)(2) crystal because of the impurity-induced local lattice relaxation. The reduction of the angle 6 in the impurity center is also supported by the result obtained by analyzing the EPR zero-field splitting for Mn2+ in the same Ca(OH)(2) crystal. The EPR parameters of Ca(OH)(2):Co2+ are also reasonably explained by considering the suitable local lattice relaxation.