Electronic structure and electron-phonon coupling in the Ni-Zr system

Abstract

The authors present a study of the electronic structure of the Ni-Zr system based on photoemission, susceptibility and specific heat measurements. Their results show that the band structure can be understood in a relatively simple model, which has been partially presented before. For concentrations below 50 at.%Ni the contribution of Ni atoms to the electronic density of states at the Fermi level n(E_F) is small or negligible, while that of Zr atoms is similar to a pure metal. NiZr₂ is a superconductor with T_c=1.62K; it also presents an atypical Debye temperature, which is related to soft modes, and a high electronic specific heat, which is attributable to the occurrence of a strong electron-phonon coupling. For concentrations between about 50 and 27.5% Zr, due to the widening of the Ni d band, the Ni contribution to n(E_F) becomes appreciable and increases moderately with the Ni content. For concentrations higher than 72.5 at.%Ni, this contribution increases rapidly and a large enhancement factor to the susceptibility is noticed. These properties can be related to the atomic structure, in particular the number of Ni neighbours of the Ni atom.