Specific heat measurements of PdHx over wide temperature range

Quantum effects of atomic hydrogen may be expected in palladium hydride at some low temperature. The present paper describes specific-heat measurements of PdHx (x = 0.13, 0.33, 0.71) over a wide temperature range from 0.3 to 200 K in magnetic fields up to 1 T. From the low-temperature part of the results the specific-heat coefficients gamma for electrons and beta for lattice have been evaluated and found to be consistent with earlier reports. However, the specific-heat anomaly, found around 55 K in earlier measurements, could not be detected. Below 2 K the specific heat was observed to depend on magnetic field, which indicates a nuclear contribution. Based on the electronic and nuclear specific heats, the electronic state of the matrix and of the hydrogen will be discussed. The origin of the 55 K anomaly will also be discussed. (C) 2000 Elsevier Science B.V. All rights reserved.