ANISOTROPIC SPECIFIC-HEAT OF A BI2SR2CACU2O8 SINGLE-CRYSTAL IN MAGNETIC-FIELDS UP TO 14-T

A 0.25 g single crystal of Bi2Sr2CaCu2O8 with a sharp superconducting transition at 85 K was characterized by AC susceptibility, X-ray diffr action, Meissner effect, normal-state susceptibility, magnetization in the mixed state, and specific heat from 1 to 300K. Many unconventiona l features are found in the specific heat which may be intrinsic featu res of a 2D superconductor, e.g. a field-independent linear term gamma T at low T, the absence of a specific heat jump at T-c, a symmetrical logarithmic anomaly at T-c, an almost field-independent transition te mperature which coincides with the crossing point of the magnetization , a new crossing paint of the specific heat, etc. The accurate data ne ar T-c (<0.02%) allow an expression of partial derivative(C/T)/partial derivative H by an empirical formula that describes the variation of the specific heat and magnetization over a wide temperature and field range about T-c.