Moessbauer study of magnetic ordering in GdMn2 and YMn2

The magnetic properties of GdMn2 and YMn2 were investigated by means of Moessbauer Spectroscopy at 57Fe nuclei which substituted 0.5% of Mn atoms. Measurements were performed in the temperature range between 4.2 and 300 K. Gadolinium sublattice was monitored by 155Gd(86.5 keV)-resonance at 4.2 K. Results show an evidence for two magnetic transitions at 40 and 100 K for GdMn2, but only one for YMn2, around 100 K. For both compounds Bhf shows thermal hysteresis. A new Yafet-Kittel-type magnetic ground state ordering for GdMn2 is proposed, which came out from the numerical solution of a set of coupled Brillouin equations written in terms of the molecular field approximation. Moessbauer effect results however are too compounded to be explained in details within the frame of this type of ordering. (orig.)