ANGULAR-DEPENDENCE OF CRITICAL CURRENTS IN BI2SR2CACU2O8 THIN-FILMS - PREDOMINANT ROLE OF THE TRANSVERSE MAGNETIC-FIELD COMPONENT

We have studied the critical current of c-axis oriented Bi2Sr2CaCu2O8 thin films measured at various temperatures as a function of magnitude (H less-than-or-equal-to 20 T) and orientation-theta (with respect to the c-axis) of the applied magnetic field. The curves J(c)(theta) at a given field H show a strong maximum when H is parallel to the CuO2 planes (theta = 90-degrees). For theta not-equal 90-degrees, we show that J(c) depends only on the component of the magnetic field along the c direction in the whole temperature range. In particular, at 4.2 K, J(c)(H, theta) behaves as \Hcos-theta\-alpha with 0.44 less-than-or-equal-to alpha less-than-or-equal-to 0.5. These results agree with the recent scaling theory proposed by Blatter et al. describing the behaviour of anisotropic superconductors for an arbitrary angle between the magnetic field and the anisotropic crystallographic axis.