Mechanisms of limitation and nature of field dependence of critical current in HTS epitaxial YBaCuO films

Magnetic field and temperature dependencies of the critical current density, J/sub c/(H||c, T) were measured by SQUID-magnetometry, ac magnetic susceptibility, and dc transport current techniques in the single-crystalline epitaxiallygrown by off-axis dc magnetron sputtering YBa/sub 2/Cu/sub 3/O/sub 7-(delta)/ (YBCO) films with J/sub c/(H||c, 77 K) >=2.10/sup 6/ A/cm/sup 2/. The mechanism of vortex depinning from growth-induced linear defects, i.e., out-of-plane edge dislocations in low-angle tilt domain boundaries, is shown to describe quantitatively measured J/sub c/(H||c, T). The developed model takes into account a statistical distribution of the dislocation domain boundaries ordered in a network as well as the interdislocation spacing within boundaries. Actual structural features of YBCO film known from HREM data turn out to be extracted from J/sub c/(H||c, T)-curves by a fitting procedure within the proposed model.