TRANSPORT-PROPERTIES OF HIGH-ANGLE GRAIN-BOUNDARY WEAK LINKS IN YBA2CU3O7 THIN-FILMS

By patterning approximately 1-mu-m-wide microbridges in laser ablated YBa2Cu3O7 films containing high-angle tilt boundaries, weak links have been isolated with critical currents low enough to avoid self-screening effects. The current-voltage characteristics of these high-angle tilt-boundary weak links are well described by the resistively shunted junction model, if noise rounding is included. The response of the supercurrent to magnetic field and temperature indicates that the weak links are spatially nonuniform, consisting of relatively small areas of high critical current density, J(c), separated by areas with very low or zero J(c). The response to rf power suggests that the current-phase relation is nonsinusoidal.