BAND FILLING AND SUPERCONDUCTIVITY IN ZR2M COMPOUNDS

The observed variation in superconducting transition temperature (T(c) ) in Zr2M (M = Fe, Co, Ni, Rh) compounds is explained on the basis of band filling with increasing electron to atom ratio. The relatively la rge T(c) in Zr2Co and Zr2Rh arises due to the Fermi level (E(F)) lying at the peak of the density of states (DOS), while in case of both Zr2 Fe and Zr2Ni, E(F) lies in the valley of DOS. The values of DOS at the Fermi level rho(E(F)), as estimated from measured specific heat data are compared with those from the calculated electronic structure. Also estimated are the electron-phonon coupling constant (lambda), the Deb ye temperature (THETA(D)) and the electronic specific heat coefficient (gamma).