Heat Capacity of Aluminum between 0.1°K and 4.0°K

Measurements of the heat capacity of aluminum have been made between 0.11 and 4.0^∘{}K in the normal state and between 0.17 and 4.0^∘{}K in the superconducting state. Within the experimental error the normal state heat capacity, Cₙ, can be represented by Cₙ=γT+βT³ with γ=1.35×10^-3 Joules/mole deg² and a value of β corresponding to a Debye temperature of 427.7^∘{} in agreement with calculations based on elastic constants. For reduced temperatures between 0.5 and 0.25 the electronic heat capacity in the superconducting state, Cₑₛ, is approximated by CₑₛγTc=7.1exp(-1.34TcT), in which Tc is the transition temperature, 1.163^∘{}K. At reduced temperatures less than about 0.25, Cₑₛ is greater than an extrapolation of the exponential, the difference amounting to a factor of 4 at the lowest temperature. The departure of Cₑₛ from an exponential temperature dependence, which is believed to be outside the experimental error, is not consistent with the existence of a constant energy gap at low reduced temperatures. The calculated critical field is 103.0 gauss at 0^∘{}K and shows a maximum negative deviation of 4% from the parabolic law. The results are compared with other measurements and with theory.