Specific heat anomalies in RMn2(H,D)x hydrides

Specific heat (SH) measurements of RMn2(H,D)x (R=Gd, Tb, Er, Nd; x=0 -3.0) powders have been performed in the temperature range of 50-320 K by a quasi-adiabatic technique. The hydrogenation implies a large increase of the Néel temperature (TN), an enormous enhancement of the SH peak at TN, and a large excessive specific heat in the whole temperature range studied. Structured SH anomalies were observed around the temperature of the antiferromagnetic phase transition.