Specific Heats below 3°K of Pure Copper, Silver, and Gold, and of Extremely Dilute Gold-Transition-Metal Alloys

The electronic specific-heat coefficient $\gamma$ and the limiting low-temperature Debye temperature (${{\Theta }_0}^c$) are estimated as 165.2±0.8 μcal/°${\mathrm{K}}^2$ (g atom) and 345.8±1.2°K for copper, 153.1±0.9 μcal/°${\mathrm{K}}^2$ (g atom) and 227.3±0.6°K for silver, and 165.1±1.0 μcal/°${\mathrm{K}}^2$ (g atom) and 162.3±0.5°K for gold. The coefficient of the $T^5$ term in the expansion representing the lattice specific heat is -0.23±0.11 μcal/°${\mathrm{K}}^6$ (g atom) for gold, and negligible for copper and silver. The $\gamma$ value for gold is significantly lower than previously reported values. Effective masses of the electrons are: copper, 1.38; silver, 1.01; and gold, 1.09. Two alloys of gold with very small amounts of transition-metal impurity were also measured. For one of these, containing 2.5 ppm by weight Fe and 0.45-ppm Mn, the specific heat is about 5% higher than that of pure gold at 0.4°K and about 1% higher at 1°K.