Critical Currents in [001] Grains and across Their Tilt Boundaries in YBa2Cu3O7 Films

Abstract

The temperature and magnetic field dependences of the critical-current density of superconducting Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ films have been determined from transport measurements across individual [001] tilt boundaries and within single [001] grains. The results provide evidence that the basal-plane $J_f$ is limited by flux creep. In contrast, the $I-V$ characteristics and the temperature magnetic field dependences of the grain-boundary $J_c$ are consistent with a superconductor-normal-superconductor-type weak-link behavior. These results imply that the transport properties of these materials can be treated within a BCS framework.