Specific heat and ac susceptibility of Hg0.8Cu0.2Ba2CuO4+delta single crystals with T-c=95 K

We report on the specific heat and magnetic susceptibility of several single crystals of the superconducting compound Hg0.8Cu0.2Ba2CuO4+delta with optimum T-C (around 95 K), and a mass varying between 6 and 18 mu g. We analyze the heat-capacity data with the purpose of extracting the intrinsic behavior of the compound. The accent is put on the shape of the specific-heat anomaly, its height, its symmetry, and its temperature position with respect to the transition in the ac susceptibility. The specific-heat peak in Hg-1201 is seven times less than in YBCO in correlation with the computed density of state at the Fermi level. We define a parameter beta allowing a classification of the sample's quality. The specific-heat anomaly is asymmetric. These considerations allow us to conclude that this compound has a dimensionality intermediate between the three-dimensional YBa2Cu3O7-delta (YBCO) and the two-dimensional Bi2Sr2CaCu2O8 (BSCCO). [S0163-1829(97)00842-4].