ANGULAR-DEPENDENCE OF THE FLUCTUATION-INDUCED MAGNETIZATION OF SINGLE-CRYSTALLINE BI2SR2CACU2O8 NEAR T(C)

We report a detailed measurement of the magnetization for a high-quality Bi2Sr2CaCu2O8 single crystal as a function of magnetic field (H) and the angle between H and the c-axis, near the transition temperature T(c). The fluctuation magnetization for H parallel to the c-axis was found to be in excellent agreement with the recently developed vortex-fluctuation theory by Bulaevskii et al. and the order-parameter fluctuation theory by Tesanovic et al. However, our fluctuation magnetization data for the fields, applied at a large angle with respect to the c-axis, were found inconsistent with the expectations from the above theories.