FLUX-PINNING IN A SLAB MODEL OF GRAIN AND TWIN BOUNDARIES

The flux pinning potential and critical current of a grain and a twin boundary are evaluated for a S-S'-S junction model and a configuration of parallel magnetic field and junction plane. In the grain boundary model, the S' domain is assumed to be disordered, to mimic oxygen diso rder. Large critical currents almost-equal-to O(10(6) amp/cm2) are est imated for both models. The grain boundary model exhibits a ''nonweak' ' link behavior and moderate critical current dependence on the grain misalignment angle. We briefly dicuss an approach to enhance critical currents based on our grain boundary model.