Specific heat up to 14 tesla and magnetization of a Bi2Sr2CaCu2O8 single crystal thermodynamics of a 2D superconductor

A 0.25 g single crystal of Bi 2 Sr 2 CaCu 2 O 8 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 γ ∗ T in the specific heat at low T is small and field independent. High-resolution ( 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 B 1 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 ϑ( C/T )/ϑ H that accounts for C ( H, T ) and M ( H, T ) data over a wide temperature and field range is proposed.