GINZBURG-LANDAU THEORY OF SPECIFIC-HEAT ANOMALY OF HIGH-TC SUPERCONDUCTORS IN MAGNETIC-FIELD

The change in specific heat by the application of magnetic field (B(a) approximately 1 T) in the case of the high-T(c) superconductors is ex amined phenomenologically by the Ginzburg-Landau theory of anisotropic type-II superconductors. The observed large reduction of specific hea t anomaly just below the superconducting transition is explained quant itatively. We have obtained the expression for the change in specific heat in a magnetic field (DELTAC) for any general orientation of B(a) with respect to the crystallographic c-axis. We also present the resul t for a polycrystalline sample. DELTAC is shown to be linear in (B(a)/ T(c)[t/(1 - t)] for temperatures slightly below T(c), where t = T/T(c) . The slope of this linear behaviour is found to be related to the ani sotropy of the effective mass.