Vortex Channeling and the V-I Characteristic of YBa2Cu3O7 Low Angle Grain Boundaries

We have performed V-I measurements on a thin film YBa2Cu3O7 4^o [001] tilt low angle grain boundary over an extensive range of temperature and field, 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.