Low-temperature specific heat of Zr 2(Co 1− xNi x) under magnetic fields

Abstract

We measured the low-temperature specific heat in pseudo-binary alloyed compounds Zr 2( Co 1−x Ni x) (0⩽x⩽0.3) in the temperature range from 1.5 to 8 K under various magnetic fields. In this system, T c has one maximum (≈6 K) near x=0.1. Corresponding to the maximum of T c, the electronic specific heat coefficient γ and energy gap 2 Δ(0)/ k B T c are maximum near x=0.1, that is, higher density of states N(0) at the Fermi level near x=0.1 results in higher T c. Furthermore, the upper critical field, H c2(0), is maximum near x=0.1.