Vortex channeling and the voltage-current characteristics of YBa2Cu3O7 low-angle grain boundaries

We have performed (voltage-current) V-I measurements on a thin film YBa2Cu3O7 4 degrees [001] tilt low-angle grain boundary over an extensive range of temperatures and fields, verifying the presence of a linear characteristic. We report on the occurrence of the linear characteristic in its basic form and on the observation of V-I kinking into several, and in some cases numerous, linear segments. We interpret these findings in terms of a variation in the dissipative width at the grain boundary. Kinking from one linear V-I section to another of different gradient is described in terms of a change in the number of vortex rows being viscously channeled along the boundary. (C) 2001 American Institute of Physics.