Insertion of nanoparticulate artificial pinning centres in YBa₂Cu₃O_7−<i>x</i>films by laser ablation of a Y₂O₃-surface modified target

Abstract

YBa2Cu3O7?x+Y2O3 (YBCO+Y2O3) mixed films were prepared on SrTiO3/MgO substrates by pulsed-laser deposition from a YBCO target with a thin Y2O3 sector on the top. The pinning properties for the mixed YBCO+Y2O3 thin film were strongly enhanced, especially at the temperatures lower than 77?K: the maximum global pinning forces FP for the Y2O3 doped sample are 7.8?GN?m?3 near 2?T at 77?K, 54.5?GN?m?3 near 4?T at 65?K, and 189?GN?m?3 near 9?T at 40?K. In the Y2O3-added samples, except for the plane configuration, the angular dependence of Jc showed a plateau, due to the flux pinning by isotropic pinning centres. Y2O3 nanoparticles randomly dispersed inside the YBCO matrix were consistently observed in the cross-sectional TEM images.