Critical current of YBCO grain boundaries in large magnetic fields

Superconducting electrical transport across single grain boundaries (GBs) in YBCO shows interesting behavior in substantial magnetic fields. Measurements on [001] tilt bicrystal YBCO thin films in strong magnetic fields are consistent with the following: Low-angle GBs (<10/spl deg/) are composed of well-ordered bridges that act as strong superconducting inter-granular links; large-angle GBs exhibit weak coupling behavior that retains a well defined critical current even at high field.