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^ in the normal state and between 0. 17 and 4. 0^ in the superconducting state. Within the experimental error the normal state heat capacity, C₍, can be represented by C₍=+T^3 with =1. 3510^-3 Joules/mole deg^2 and a value of 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, C₄ₒ, is approximated by C₄ₒ{T₂}=7. 1exp (-1. 34T₂T), in which T₂ is the transition temperature, 1. 163^. At reduced temperatures less than about 0. 25, C₄ₒ is greater than an extrapolation of the exponential, the difference amounting to a factor of 4 at the lowest temperature. The departure of C₄ₒ 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^ and shows a maximum negative deviation of 4% from the parabolic law. The results are compared with other measurements and with theory.