Temperature dependence of hyperfine magnetic fields in Rh2FeSn and Rh2CoSn metallic ferromagnets

The temperature dependences of the magnetic hyperfine fields for Fe57 and Sn119 in the ordered metallic ferromagnetic substances Rh2FeSn and Rh2CoSn are measured by the Moessbauer γ-spectroscopy technique. It is found that the temperature dependences of the normalized fields h(T)=H(T)/H(77K) for Fe and Sn in Rh2FeSn are significantly different in the range 0.4<T/Tsub(c)<0.8. To explain this temperature anomaly of the hyperfine field a model is proposed in which the temperature dependences of the local magnetization of the Fe and Rh atoms are taken into account. The form of the temperature anomaly h(T) for Sn119 can be completely explained by taking into account that near Tsub(c) the temperature dependences of the magnetic moments of the Fe and Rh atoms are the same whereas in the 0.4 <T/Tsub(c)<0.8 range they are essentially different