Temperature-dependent pinning of vortices in low-angle grain boundaries inYBa2Cu3O7−δ

Abstract

Low-angle grain boundaries with misorientation angles $\ensuremath{\theta}<5\ifmmode^\circ\else\textdegree\fi{}$ in optimally doped thin films of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ are investigated by magneto-optical imaging. With a numerical inversion scheme of Biot-Savart's law it is possible to obtain the critical current density across the grain boundary with a spatial resolution of about $5\ensuremath{\mu}\mathrm{m}.$ This technique is now applied to determine the temperature dependence of the critical current density across low-angle grain boundaries. The detailed analysis of the temperature dependence shows a crossover in the pinning properties of Abrikosov-Josephson vortices which are located in the grain boundary.