Magnetic, Thermal and Transport Properties of Ce(Ni_1−xCu_x)₂Al₃: The Dominant Role of Electronic Change

Abstract

The Ni sites of an intermediate-valence compound CeNi₂Al₃ can be partially substituted with Cu atoms up to 40%. Both the unit-cell volume and the number of conduction electrons increase with the substitution. The magnetic susceptibility χ(T), specific heat C(T), electrical resistivity ρ(T) and thermoelectric power S(T) were measured for the Ce(Ni_1−xCu_x)₂Al₃ system. With increasing x, the χ(T) curve changes from that of a Pauli paramagnet to a Curie–Weiss type showing Ce³⁺ local moments above T=50 K. Huge thermoelectric power is observed in all the samples of our study. The great peak over 50 μV/K in S(T) curve and the broad hump in ρ(T) curve shift down to lower temperatures, meanwhile, a ten-fold enhancement of both the electronic specific-heat coefficient γ and the linear coefficient α of S(T) takes place simultaneously, with increasing x. These results reveal that the hybridization between 4f and conduction electrons is weakened by introducing the Cu atoms into the Ni sites. The effects arising from the electronic change in conduction band as well as the unit-cell volume expansion are discussed, of which the former is found to dominate the evolution of the properties in Ce(Ni_1−xCu_x)₂Al₃.