SCALING OF THE SPECIFIC-HEAT AND MAGNETIZATION OF YBA2CU3O7 IN MAGNETIC-FIELDS UP TO 7 T

The specific heat C-p(T,H) and the magnetization M(T,H) of a large twi nned single crystal of YBa2Cu3O7 have been measured using a high-resol ution differential-thermal-analysis calorimeter and superconducting qu antum interference device magnetometry, in magnetic fields up to 7 T. An apparently reasonable scaling of the data may be obtained using eit her the three-dimensional (3D) XY model or the lowest-landau-level app roximation. The high relative accuracy of the data allows a direct eva luation of the critical temperature T-c and the critical exponent nu o f the 3D XY model. This analysis indicates that the data do not obey 3 D XY scaling in fields above approximate to 0.5 T.