Properties of the Ni-Ir Alloy System

Measurements of the lattice parameter, electronic specific heat, magnetic susceptibility, and Debye temperature are presented in the Ni-Ir alloy system from 0 to 100 at.% Ir. This system forms an uninterrupted series of solid solutions over the entire concentration range. No ordering nor decomposition could be observed after annealing for several days at temperatures between 500 and 1100°C. The system develops a sharp peak in the electronic specific heat versus concentration at 85 at.% Ni, a concentration slightly higher than the critical concentration determined magnetically (81 at.% Ni). A weak anomaly was found also in the $T^3$ term of the low-temperature specific heat around the same concentration. Generally, no lowtemperature anomaly, such as was predicted by the early paramagnon theories, was detected down to 1.5°K. The susceptibility was measured on the paramagnetic side only up to 79 at.% Ni, where a spontaneous moment develops at low temperature.