LOW-TEMPERATURE SPECIFIC-HEAT AND IR SPECTROSCOPY OF EUD2 AND YBH2

The heat capacities of EuD2 and YbH1.98(1) have been measured in the t emperature range from 4.2 to 250 K. For EuD2 a lambda-type specific he at anomaly due to a magnetic transition was observed at T(c) = 16.3 K. The temperature dependences of the thermodynamic functions S(T)o, (H( T)o-H-0(o))/T and - (G(T)o-H(T)o)/T are calculated. The energy and ent ropy associated with the magnetic transition are E(m)=196 J mol-1 K-1 and S(m) = 17.10 J mol-1 K-1. The isotope effect on the heat capacity is analysed on the basis of frequencies of hydrogen optical modes dete rmined from IR measurements.