Experimental and theoretical reasons for inclusion of fourth-order terms into spin Hamiltonian of glasses doped by d5 impurities with 6A1 ground states

Abstract

Abstract Isofrequency curves (of magnitude of the magnetic resonance field as a function of its spherical angles θ and Φ were calculated for a number of sets of spin Hamiltonian parameters a, F, D and E. Lowest possible values of the a and D parameters that both fulfil the so-called ‘tetragonal conditions’ and correspond to d5 centres with isotropic resonances of geff ≊4·3 and geff ≊3· 3 were assessed. Model calculations, based on the Boltzmann distribution of energy population, of the temperature dependence of resonance intensities were performed. Their comparison with experiment made it possible to decide which of the two spin Hamiltonians commonly used for the interpretation of the electron paramagnetic resonance (EPR) spectra of d5 centres were more plausible in the case of halide glasses doped by Mn2+. Objections to the interpretation of the geff ≊4· 3 resonance on the basis of the fourth-order spin Hamiltonian were reexamined from the point of view of ligand field theory and reasons for support of t...