Critical currents at the grain boundary of Sm1Ba2Cu3O7-delta film under oblique magnetic fields

Abstract

We measured critical current densities (J(cb)) at a [001]-tilt grain boundary (GB) of a bicrystalline Sm1Ba2Cu3O7 film under various magnetic fields (H-a) applied obliquely. The mis-orientation angle, theta, of the [001] tilt GB was 30 degrees. H-a was varied between - 0.65 KOe and + 0.65 KOe. The angle, phi, between the applied fields and the film surface was varied from 0 degrees to 90 degrees. The curves of J(cb) vs. H-a at the different phi s were qualitatively explained by a simple formula suggested in [8]. The formula was expressed by multiplication of the two factors which include the effects of H-perpendicular to and H-parallel to. One fitting parameter, alpha, in this formula was large for the sample of theta = 30 degrees in our previous paper. On the contrast, a for the present sample in this paper is almost zero. The absolute values Of J(cb) for this sample are larger than those for the previous sample by one order of magnitude. These results indicate that the parameter, alpha, closely related to the quality of GB: alpha gets smaller as the film quality at GB become better.