Specific heat of ordered CuPt below 30 K

Measurements were made on a sample containing 50.44-at.% Pt. The electronic specific heat $\gamma$ is 248.5 ± 0.5 μcal/${\mathrm{K}}^2$ g-at. (1.040 ± 0.002 mJ/${\mathrm{K}}^2$ g-at.) and the low-temperature limiting value of Debye temperature is 313.6 ± 0.8 K, where the error limits are 95% confidence limits from the statistical analysis. These values correspond to a specific heat nearly double that previously reported for ordered CuPt in the 1-4 K range by Roessler and Rayne. The Debye temperature initially decreases with increasing temperature in the normal way. This behavior is contrasted with that of the ordered equiatomic alloy CuAu I where the Debye temperature initially strongly increases with increasing temperature. Both ordered lattices consist of alternating layers of light and heavy atoms (mass ratio ∼ 3). The layers are in the (111) plane for CuPt and in the (100) plane for CuAu I. It had been suggested that the behavior of CuAu I might be evidence for some two-dimensional character in the low-frequency lattice vibrations.