Electronic Specific Heats and Superconductivity in the Group-V Transition Metals

Electronic specific heats of Nb-V alloys were measured from 1.5 to 14 °K and on the basis of these measurements superconductivity parameters were calculated. Both the McMillan and the Hopfield theories were used to try to understand the cause of the broad minimum in $T_c$ with alloying composition. The McMillan theory indicates that the cause is due to a weakening of the electron-phonon interaction parameter. The Hopfield theory could not adequately predict the existence of the minimum in these alloys.