An all-field-range description of the critical current density in superconducting YBCO films

摘要

A new critical current density (J_c) model for high-quality YBCO (YBa_2Cu_3O_7) thin films has been proposed, combining thermally activated flux creep with a vortex pinning potential for columnar defects. The pinning for thermally activated vortices has been described as strong pinning on chains of individual edge dislocations that form low-angle domain boundaries in high-quality YBCO thin films. The model yields an adequate description of the J_c behaviour over the whole applied field range, as verified by direct measurements of J_c in YBCO thin films grown by pulsed-laser deposition. It also indicates that the effective pinning landscape changes under the influence of the external conditions. Remarkably, the pinning potential obtained from the model is consistent with the values obtained for columnar defects, which confirms the validity of the overall approach.