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

The results of a M\"ossbauer-effect study of HoFeO₃ 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 N\'eel point TN. Although no discontinuity is found at the N\'eel temperature, the total shift has a different temperature dependence for T<TN and for T>TN. 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.