The Mössbauer technique was employed to study the paramagnetic hfs of ${\mathrm{Fe}}^{57}$-doped corundum ($\alpha -{\mathrm{Al}}_2{\mathrm{O}}_3$) in the presence of an external magnetic field. Experiments were performed with an oriented single crystal and with external field strengths to 41 kOe parallel to the trigonal axis of the crystal field at the iron site. The results showed noticeable field-dependent features. Several of these effects were analyzed by detailed calculations of theoretical hfs from the ground-term electronic levels of ${\mathrm{Fe}}^{3+}$. Effects of small local fields and of mixing of electronic states by crystal-field terms and by the hyperfine interaction are shown to produce gross changes in the Mössbauer spectra. Some of these features were observed; others which require a more homogeneous magnetic field were not observed because major changes in the Mössbauer spectra occur over relatively small ranges of external field strengths.

• Received 16 February 1966

DOI:https://doi.org/10.1103/PhysRev.148.211