Low-Temperature Heat Capacity of LaRu2, CeRu2, and CeRu2−xPtx

Abstract

The heat capacity of two samples of Ce${\mathrm{Ru}}_2$ and one sample each of Ce${\mathrm{Ru}}_{1.9}$ ${\mathrm{Pt}}_{0.1}$, Ce${\mathrm{Ru}}_{1.8}$ ${\mathrm{Pt}}_{0.2}$, and La${\mathrm{Ru}}_2$ were measured from 1.3 to 9°K (to 20°K for La${\mathrm{Ru}}_2$). All samples are superconducting, have high $\gamma$ values (10-14 mJ/g atom°${\mathrm{K}}^2$) and moderately low Debye temperatures (144-158°K). None of these materials behaves as a BCS-type superconductor. All of these materials exhibit a departure from the normal $T^3$ behavior at a temperature $\frac{1}{3}$ to ½ of that which might be expected from the Debye theory. The departure is unusual in that the Debye temperature increases with increasing temperature, while other Laves-phase compounds that we have recently examined show the opposite and more normal (?) behavior. These different behaviors are explained on the basis of the structural nature of the Laves phase.