Interpretation of Mn²⁺ EPR spectra in disordered Materials

Abstract

It is interesting to be able to estimate the values of the zero-field splitting parametersD andE appearing in the spin Hamiltonian of the Mn²⁺ ion in disordered materials, such as glass and polycrystalline samples. Since the electronic spin of the Mn²⁺ ion is 5/2 (>1/2), it is able to interact with the crystalline electric field of the environment to provide information on its surroundings. The present work attemps to interpret the intensities and positions of both the allowed and hyperfine forbidden EPR lines of the Mn²⁺ ion in disordered materials. First, a discussion is presented of the analytical expressions for the intensities and positions of the EPR lines in a monocrystal, which are then exploited by averaging to describe the expected behavior in disordered materials in order to estimate the values of the parametersD andE. The discussion is thereafter generalized to use computer simulations to generate Mn²⁺ EPR spectra in glassy and polycrystalline media. The effects of distribution ofD andE parameters and expected singularities in Mn²⁺ EPR spectra on the resulting EPR spectra in disordered materials are considered. Some published results are included to illustrate the application of the techniques described in this paper.