Magnetism in RFe$_2$Ge$_2$ (R = Y, Lu, Tb) as seen by $^{57}$Fe M\"ossbauer spectroscopy*

Magnetic properties of RFe$_2$Ge$_2$ (R = Y, Lu, Tb) were studied using temperature dependent (4.6 - 300 K) M\"ossbauer spectroscopy and specific heat capacity. In the paramagnetic state all three compounds have similar evolution of the isomer shift and quadrupolar splitting. Magnetic phase transitions can be detected both in LuFe$_2$Ge$_2$ and TbFe$_2$Ge$_2$, with an indication of very small iron magnetic moment in the ordered state for LuFe$_2$Ge$_2$. The Debye temperature evaluated from the temperature-dependent isomer shift for these three compounds is significantly higher that inferred from specific heat capacity measurements, that might indicate presence of magnetic correlations. The results will be compared with the bulk measurements.