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 twinned single crystal of YBa2Cu3O7 have been measured using a high-resolution differential-thermal-analysis calorimeter and superconducting quantum interference device magnetometry, in magnetic fields up to 7 T. An apparently reasonable scaling of the data may be obtained using either the three-dimensional (3D) XY model or the lowest-landau-level approximation. The high relative accuracy of the data allows a direct evaluation of the critical temperature T-c and the critical exponent nu of the 3D XY model. This analysis indicates that the data do not obey 3D XY scaling in fields above approximate to 0.5 T.