Temperature Dependence of the Crystal-Field-Induced Anisotropy in SmFe2

For the compound Sm${\mathrm{Fe}}_2$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ Mössbauer spectra were obtained at various temperatures between 5 and 300 K. We observed that the axis of easy magnetization changes from [011] below about 175 K to [111] above this temperature. We have calculated the single-ion crystal-field magnetic anisotropy of ${\mathrm{Sm}}^{3+}$, with the inclusion of effects of exchange, and have found this model to account well for the transition in the direction of easy magnetization.