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° [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.