Magnetization and Temperature Dependence of the Mössbauer Spectrum Shift for an Insulator

The results of a Mössbauer-effect study of HoFe${\mathrm{O}}_3$ in the temperature range 99-875°K are presented. Special attention is paid to the shift of the center of the spectrum and its temperature dependence both above and below the Néel point $T_N$. Although no discontinuity is found at the Néel temperature, the total shift has a different temperature dependence for $T<\mathrm{}{T}_N$ and for $T>\mathrm{}{T}_N$. The experimental results are compared with theoretical predictions based on a magnetization-dependent Debye model. Also, a theoretical model based on the supertransferred process is presented which gives rise to a magnetization-dependent isomer shift, although the calculated effect is almost two orders of magnitude too small.