Electronic density of states in amorphous Zr-Pd and Zr-Ni alloys

We have produced amorphous Zr-Pd and Zr-Ni films by means of rf diode cosputtering techniques. Measurements were made of the superconducting transition temperature Tc, the normal resistivity ρ, and the upper critical field Hc2. From ρ and (dHc2dT)_Tc we determined the dressed density of states at the Fermi level N*=N(1+λ), where λ is the electron-phonon coupling constant and N is the bare density of states. In constrast to amorphous Zr-Cu and Zr-Rh alloys, a direct proportionality between Tc and N* was not observed for these alloys. Thus the composition dependence of N* and Tc is not consistent with the suggestion that N* is the most important factor in determining Tc.