Low-temperature specific heat measurements for Er and α-ErH_x

Abstract

The heat capacity of polycrystalline Er and alpha -ErHx solid solutions (0<or=x<or=0.03) has been measured between 1.5 and 70 K. The authors report a detailed analysis of the specific heat of pure Er, including a comparison with the literature data, which conflict widely. They observe that the antiferromagnetic (TN) and helicoidal (TH) transition temperatures decrease while the Curie temperatures TC and TC1 (for the change to commensurate structure) increase with growing H or D content, in agreement with what is found from magnetic and resistivity measurements. The hydrogenated specimens exhibit an increasing electronic contribution to the heat capacity; from the variation of the Neel temperature, the spin-disorder resistivity and the magnetic contribution to the specific heat they conclude that the exchange interaction reduces with growing H content.