Heat capacity of superconducting La/sub 1. 85/Sr/sub 0. 15/CuO/sub 4/

The heat capacity has been obtained for a sample of La/sub 1.85/Sr/sub 0.15/CuO/sub 4/ which is superconducting with a transition temperature T/sub c/ = 31 K. Although the heat capacity is dominated by the lattice in the vicinity of T/sub c/, it has nonetheless been possible to observe the superconducting transition, thus verifying that this is bulk superconductivity. A lower limit is established for the heat-capacity anomaly of ..delta..C/T/sub c/ = (20 +- 5) mJ/mole K/sup 2/. Combined with estimates of the electronic heat capacity ..gamma.., this leads to 2less than or equal to..delta..C/..gamma..T/sub c/less than or equal to10, compared with the Bardeen-Cooper-Schrieffer value of 1.43, which places this material well into the strong-coupling regime.