Specific Heat of Lead in the Range from 2 to 8°K

The specific heat of pure lead has been measured in the normal and superconducting states between 2 and 8°K. The electronic contribution in the superconducting state, $C_{\mathrm{es}}$, is derived using $\gamma =3.00\mathrm{}$ mJ/mole${\mathrm{deg}}^2$ taken from other sources. Near $T_c$, $C_{\mathrm{es}}$ is roughly proportional to $T^{3.5}$, but the dependence becomes more marked as the temperature is reduced. Our data do not conform to the $T^4$ dependence deduced from the critical-field curve by Decker, Mapother, and Shaw for $1.2\le T\le 5$°K, although the critical field calculated from the difference $\Delta C=C_n-C_s$ agrees with the measured values to within 0.8%. The Debye temperature $\Theta$ is deduced from the normal-state results, and a plot of $\Theta$ versus $T$ is given. The curve suggests that a maximum in $\Theta$ occurs near 1°K.