The Specific Heat and Superconductivity of La-Y Alloys

Abstract

The low temperature specific heats of La-Y alloys have been measured in order to investigate the origin of superconductivity in lanthanum. The addition of yttrium to lanthanum was found to result in a large decrease of the electronic specific heat coefficient γ, a decrease in the superconducting transition temperature T c and a gradual increase of the Debye temperature \(\varTheta_{D}\). The rate of increase of \(\varTheta_{D}\) in the yttrium-rich hcp phase was observed to be appreciably larger than in the α-La phase. The effective interaction derived from the BCS formula was found to remain approximately constant in the α-La phase followed by a rapid decrease in the hcp phase. From the general trend of the measured and derived quantities with alloying, it is suggested that the superconductivity of lanthanum may be closely related to mechanism leading to the depression of the Debye temperature and the stabilization of the α-La structure. This implies that phonon processes are of importance in the enhancement of superconductivity.