Model calculations for the coordination ofFe3+andMn2+ions in oxide glasses

Abstract

Applying the Newman superposition model to the ligand-field splitting of tetrahedrally and octahedrally coordinated ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Mn}}^{2+}$ ions in glass, we have obtained analytical expressions for the dependence of the spin-Hamiltonian parameters $b_2^m$ ($D$ and $E$) on the distortion from cubic symmetry of the nearest-neighbor oxygen ligands. Quantitative estimates are made of the magnitude of the angular and/or radial distortion required to produce the frequently observed $X$- band $g\simeq 4.3$ ESR signal from these ions. The results of the superposition model are compared with those obtained using a point-charge model for the nuclear quadrupole splitting in the Mössbauer spectra of dilute ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ in oxide glasses.