Magnetic anisotropy and hyperfine interactions in CeFe2, GdFe2, and LuFe2

Abstract

Mössbauer-effect measurements on ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ have been carried out on the cubic Laves compounds Ce${\mathrm{Fe}}_2$, Gd${\mathrm{Fe}}_2$, and Lu${\mathrm{Fe}}_2$ between 80 and 300 K. The analysis of the Mössbauer spectra allowed the determination of the easy axes of magnetization $\overrightarrow{\mathrm{n}}$ in these compounds. In Ce${\mathrm{Fe}}_2$, $\overrightarrow{\mathrm{n}}$ is parallel to the [100] direction up to 150 K; it then becomes of type [$\mathrm{uuw}$] with an angle of inclination with respect to the [100] axis of 20°. Just below the Curie temperature at 230 K, this angle increases to 30°. In Gd${\mathrm{Fe}}_2$, $\overrightarrow{\mathrm{n}}$ is parallel to the [100] direction at 80 and 300 K. In Lu${\mathrm{Fe}}_2$, $\overrightarrow{\mathrm{n}}$ is of [$\mathrm{uuw}$] type at 80 and 300 K. In terms of the phenomenological treatment of the magnetic anisotropy, the presence of an [$\mathrm{uuw}$] type of easy axis of magnetization indicates that the bulk magnetic-anisotropy constant $K_3$ is of the same order of magnitude as $K_1$ and $K_2$. The hyperfine parameters of the three compounds are reported and discussed.