Electron-Paramagnetic-Resonance Investigation of the Superhyperfine Structure of Iron-Group Impurities in II-VI Compounds

The electron-paramagnetic-resonance spectra of several iron-group impurities in ZnSe, ZnTe, and CdTe are shown to have resolved superhyperfine structure (SHFS) resulting from an interaction with one or two shells of Se or Te nuclei surrounding the impurity. We have observed interaction with the two nearest chalcogenide shells for ZnSe: ${\mathrm{Cr}}^{+}$, ZnSe: ${\mathrm{Mn}}^{2+}$, ZnTe: ${\mathrm{Cr}}^{+}$, ZnTe: ${\mathrm{Mn}}^{2+}$, and ZnTe: ${\mathrm{Fe}}^{+}$, and an interaction with only the nearest chalcogenide shell for ZnSe: ${\mathrm{Fe}}^{3+}$, ZnSe: ${\mathrm{Cr}}^{2+}$, and CdTe: ${\mathrm{Mn}}^{2+}$. Hensel's data on ${\mathrm{Fe}}^{3+}$ in ZnTe were analyzed for the first-shell Te SHFS. None of these data exhibit ${\mathrm{Zn}}^{67}$ SHFS, although the Cd chalcogenides show Cd SHFS. Several other impurities in II-VI compounds were studied to obtain additional information on SHFS. The SHFS results are compared for different impurities and crystals and discussed in relation to the delocalization expected from covalent bonding. The small observed delocalization is surprising in view of the fairly large covalent character of the crystals.