Specific Heats of Metals Below One Degree Absolute

The heat capacities of a number of metals have been measured in the region below 1°K, using the technique of adiabatic demagnetization. Copper, silver, platinum, palladium, tungsten, molybdenum, and sodium have been investigated. Apart from sodium, all exhibit a linear dependence of electronic specific heat on temperature. The values of $\gamma$ are in agreement with those obtained in the liquid helium region, except in the case of tungsten, which gives $\gamma =3.5\mathrm{}\pm 0.2\times {10}^{-4\mathrm{}}$ cal/mole ${\mathrm{deg}}^2$ in contrast to the previous value $\gamma =1.8\mathrm{}\pm 0.7\times {10}^{-4\mathrm{}}$ cal/mole ${\mathrm{deg}}^2$ reported in the literature. Sodium exhibits an anomalous peak in its specific heat curve. A low-temperature, martensitic-type transformation is advanced as a likely cause of this behavior.