CRITICAL CURRENT ANISOTROPY OF BISRCACUO THIN-FILMS UNDER MAGNETIC-FIELDS

We report on the strong angular dependence under magnetic field of the critical currents of c-axis oriented Bi2Sr2CaCu2O8 thin films, measured as a function of the angle theta between the c-axis and the applied magnetic field (H less-than-or-equal-to 20 T). The curves J(c)(theta) at a given field H present a peaked maximum occurring when H is parallel to the CuO2 planes (theta = 90-degrees). At theta ]90-degrees, J(c) appears to depend only on the perpendicular field component H perpendicular-to (along the c axis). In particular at 4.2 K and for H perpendicular-to >0.02 T, it is shown that J(c) (H, theta) behaves as \Hcos theta\-alpha with 0.44 less-than-or-equal-to alpha less-than-or-equal-to 0.50.