SPECIFIC-HEAT OF TL2BA2CUO6(2201) 90 K SUPERCONDUCTING CERAMICS IN MAGNETIC-FIELDS UP TO 14-T

The specific heat of Tl2Ba2CuO6 (''2201'') superconducting ceramics wi th T-c approximate to 90 K is measured in magnetic fields of 0, 0.1, 1 , 3, 5, and 14 T. The very small anomaly at the superconducting transi tion can be described in B=0 by 2D fluctuations alone, without any mea surable mean-field component. Its amplitude is found to decrease rapid ly for small fields, and very slowly at large fields while its shape r emains symmetrical. The temperature of the top of the anomaly (''T-c'' ) is field independent. These properties show that the dimensional nat ure of the phase transition in Tl2Ba2CuO6 is more closely related to t hat of Bi2Sr2CaCu2O8 than to that of YBa2Cu3O7. The behavior of the sp ecific-heat anomaly with the field is thermodynamically consistent wit h previous magnetization measurements.