Angular dependence of critical currents in Bi 2Sr 2CaCu 2O 8 thin films predominant role of the transverse magnetic field component

Abstract

We have studied the critical of c-axis oriented Bi 2Sr 2CaCu 2O 8 thin films measured at various temperatures as a function of magnitude ( H ≤ 20 T) and orientation θ (with respect to the c-axis) of the applied magnetic field. The curves J c (θ) at a giv en field H show a strong maximum when H is parallel to the CuO 2 planes ( θ=90°). For θ≠90°, we show that J c depends o 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, θ) behaves as | Hcos θ| -α with 0.44 ≤ α≤0.5. These results agree with the recent scaling theory proposed by Blatter et al. describi the behaviour of anisotropic superconductors for an arbitrary angle between the magnetic field and the anisotropic crystallographic axis.