Evidence for Vortex Pinning by Dislocations inYBa2Cu3O7−δLow-Angle Grain Boundaries

Abstract

The dependence of the critical current density ${j}_{c}$ on the orientation of the magnetic field $\mathbf{H}$ has been measured for a ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ bicrystal film. When the field is rotated in the plane of the grain boundary, ${j}_{c}$ displays a maximum for $\mathbf{H}$ 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.