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Highly biaxially oriented YBa 2 Cu 3 O 7-δ (YBCO) films exhibit critical current densities, J c , two orders of magnitude higher than any sort of bulk samples. Out-of-plane edge dislocations (mean 2D density is 10 11 lines/cm 2 in the film area) in low-angle tilt domain boundaries are shown to play a crucial role in J c (H||c, T)-behavior. Measurements of the magnetic field dependence of J c for the pulse-laser deposited YBCO films are carried out by AC magnetic susceptibility technique. Dislocation cores are shown to provide an extremely strong pinning force leading to J c (77 K) ≅ 2 × 10 6 A/ cm 2 . Peculiarities of J c (H||c) are found in the low-field range. A simple model of pinning by dislocation domain boundaries is developed. The model consistently describes the J c (H||c, T)/J c (0, T)-dependencies, accounting for the fraction of vortices pinned by dislocations. |
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