Critical currents at the grain boundary of (Sm0.8Dy0.2)Ba2Cu3O7 film under oblique magnetic fields

Abstract

We measured critical current densities (J(cb)) at the 30 degrees grain boundary of a bicrystalline (Sm0.8Dy0.2)Ba2Cu3O7 film under various magnetic fields ((H) over right arrow (a)), which were applied obliquely. We varied the field from -0.7 kOe to +0.7 kOe while the angles (theta) of the fields were 2 degrees, 22.5 degrees, 45 degrees, 67.5 degrees and 90 degrees with respect to the film surface. The curves of J(cb) vs (H) over right arrow (a) showed the well known butterfly-like hysteretic curves. We separated the two components of field, H-perpendicular to and H-parallel to, which are normal and parallel to the film surface, respectively. Our data indicate that the roles of these two components for the field dependence of J(cb) are different. We combined the effect of H-L deduced from the data for the normal field (theta = 90 degrees) and the effect of H-parallel to deduced from the data for the almost parallel field (theta = 2 degrees). Multiplying the independent reduction factors deduced from these two cases, we found a new formula, which expresses J(cb) vs (H) over right arrow (a) for general theta s. All the experimental data for various theta s fit well to this new formula. (c) 2006 Elsevier B.V. All rights reserved.