Electron Paramagnetic Resonance of Photosensitive Iron Transition Group Impurities in ZnS and ZnO

The photosensitive iron transition group impurities Fe, Ni, and V in cubic ZnS and Ni in ZnO have been studied by electron paramagnetic resonance. The charge states ${\mathrm{Fe}}^{3+}$, ${\mathrm{Fe}}^{+}$, ${\mathrm{Ni}}^{3+}$, and ${\mathrm{V}}^{3+}$ were observed after excitation with ultraviolet light, and, in the case of ${\mathrm{Ni}}^{3+}$, after excitation with blue light. The magnetic properties are those to be expected for a $3d^7 \left({\mathrm{Fe}}^{+} \mathrm{and} {\mathrm{Ni}}^{3+}\right)$ and a $3d^2 \left({\mathrm{V}}^{3+}\right)$ configuration in tetrahedral coordination. The quantitative features of the spectra reflect the systematic variations produced by covalency.