Incorporation of double artificial pinning centers in YBa 2Cu 3O 7−δ films

Abstract

YBa 2Cu 3O 7−x + BaZrO 3 + Y 2O 3 (YBCO + BaZrO 3 + Y 2O 3) mixed films were prepared on SrTiO 3/MgO substrates by pulsed-laser deposition from an YBCO + BaZrO 3 target with a thin Y 2O 3 sector stuck on the top. The pinning properties for the double-doped YBCO + BaZrO 3 + Y 2O 3 thin film were enhanced in comparison with a pure YBCO sample prepared in the same experimental conditions. The maximum global pinning forces F P for the double-doped sample are 12.8 GN/m 3 at 77K, 46.3 GN/m 3 at 65K, and 122 GN/m 3 at 40K. In the double-doped sample, the angular dependence of J c showed a broad peak at B//c due to the flux pinning by c-axis correlated defects, combined with a plateau, due to the flux pinning by isotropic pinning centres. Consistently, both BaZrO 3 nanorods parallel to the c-axis and Y 2O 3 nanoparticles randomly dispersed inside the YBCO matrix were observed in TEM images.