SPECIFIC-HEAT UP TO 14 TESLA AND MAGNETIZATION OF A BI2SR2CACU2O8 SINGLE-CRYSTAL THERMODYNAMICS OF A 2D SUPERCONDUCTOR

A 0.25g single crystal of Bi2Sr2CaCu2O8 with a sharp superconducting transition at 85 K is characterized by AC susceptibility, X-ray diffraction, Meissner effect, normal-state susceptibility, magnetization in the mixed state, and specific heat from 1 to 300 K. The residual linear term gamma*T in the specific heat at low T is small and field independent. High-resolution (< 0.02%) adiabatic specific heat experiments performed between 0 and 14 T near T(c) show that: (a) there is no mean-field specific heat jump at T(c); (b) a symmetrical logarithmic 'divergence' occurs at the transition; (c) its amplitude decreases with B(-2/3); (d) its width scales with B1/2; (e) T(c) does not depend on the field, and coincides with the crossing point of the magnetization curves M* (H,T*); (f) a crossing point C(x) (H,T(x) is found in the specific heat 10 K below T(c); (g) the effect of a field along the CuO planes is at least 50 times smaller than that of a field along the c axis; (h) no transition is observed at the irreversibility line. An empirical formula for partial Derivative (C/T)/ Partial DerivativeH that accounts for C(H,T) and M(H,T) data over a wide temperature and field range is proposed.