Calorimetric investigation of a spin-glass alloy:CuMn

Abstract

In a continuing effort to elucidate the magnetic properties of the spin-glass alloys, the specific heats between 2 and 40 K of two polycrystalline samples, ${\mathrm{Cu}}_{0.988}$ ${\mathrm{Mn}}_{0.012}$ and ${\mathrm{Cu}}_{0.976}$ ${\mathrm{Mn}}_{0.024}$, are reported. The magnetic specific heats show no indication of a cooperative-type peak, discontinuity, or broad anomaly at their respective ordering temperatures of 11.1 and 19 K where the low-field susceptibilities of the same samples display the characteristic sharp cusplike peaks. Instead, the magnetic specific heats essentially increase linearly with temperature and then show rounded maxima centered at 14 and 26 K, respectively. The magnetic entropy changes between absolute zero and the ordering temperature are only 0.33 of $\mathrm{cR}\ln \mathrm{}(2J+1)\mathrm{}$. These calorimetric results on CuMn are in agreement with a prior investigation of AuFe and appear to disagree with the existing spin-glass theories used to explain the susceptibility peak.