Evidence for vortex pinning by dislocations in YBa2Cu3O7-δ low-angle grain boundaries

The dependence of the critical current density j(c) on the orientation of the magnetic field H has been measured for a YBa2Cu3O7-delta bicrystal film. When the field is rotated in the plane of the grain boundary, j(c) displays a maximum for H close to the c axis in fields up to 7 tesla. The same experiment performed in the interior of the grain shows no maximum. The pinning force at the maximum varies as H-0.5, consistent with vortex pinning by a dense planar distribution of line pins. These results are a clear demonstration of flux pinning by dislocations in low-angle grain boundaries.