2-DIMENSIONAL BEHAVIOR AND CRITICAL-CURRENT ANISOTROPY IN EPITAXIAL BI2SR2CACU2O8+X THIN-FILMS

The critical-current anisotropy j(c)(B, T, THETA) of epitaxial Bi2Sr2CaCu2O8+x films has been measured in detail. Below 70 K, the measured j(c) (B, T, THETA)) can be fully accounted for by the assumption that only the field component B parallel-to = B cos-THETA influences j(c), as has been proposed by Kes et al. Above this temperature, a 2D-to-3D dimensional crossover results in additional dissipation. By comparison with results on polycrystalline samples, evidence is given for the absence of any influence of the grain boundaries on j(c)(THETA)).