Specific heat of YMn2Hx and HoMn2Hx

Specific heat (SH) measurements of RMn2Hx (R = Y, Ho; x = 0-4.3) powders have been performed by a quasi-adiabatic (in the temperature range of 50-320 K) and relaxation (2-400 K) methods. The hydrogenation causes a large increase of the transition temperature TN with the enhancement of both SH peaks at TN and the specific heat background. Various features of the double specific-heat anomaly were observed close to TN. The possible correlations between the hydrogen vibration modes, hydrogen migration, and the specific heat anomalies have been discussed.