Temperature dependence of the vortex motion along twin planes in YBa2Cu3O7-delta

Using a high resolution magneto-optical technique, flux motion along the tw in planes of a high quality YBa2Cu3O7-delta single crystal was systematical ly studied when an external magnetic field was applied along the c-axis of the crystal. Our results support the concept that whether or not the twin p lanes act as a barrier or a channel for vortex motion depends not only on t he temperature, but also on the direction of vortex motion with respect to the twin plane. At low temperatures, the twin planes, regardless of their d irections, act as easy-flow channels for Vortices to preferentially penetra te, while at high temperatures, the twin planes that are not parallel to th e direction of vortex motion act as barriers to vortex motion. Secondly, at low temperatures, we have also observed a twin barrier that must be overco me before the channelling effect starts. Finally, the results clearly show flux creep along the twin planes at a temperature of 25 K. (C) 2001 Elsevie r Science B.V. All rights reserved.