THE SPECIFIC-HEAT OF YBA2CU3O7-DELTA SINGLE-CRYSTALS

The specific heat of twinned and detwinned single crystal samples of Y Ba2Cu3O7-delta have been measured with magnetic fields up to 8 tesla a pplied parallel to the c-axes of the crystals. The samples measured ha d transition temperatures around 90 K and transition widths from 0.3 K to 2 K. The data exhibits scaling behaviour characteristic of the 3-d imensional-X-Y model with critical exponents consistent with those obs erved in superfluid He-4. We then compare the scaling properties of th e specific heat in the different samples and look for the 'universal' nature of the scaling function.