Controlling the Critical Current Anisotropy of YBCO Superconducting Films by Incorporating Hybrid Artificial Pinning Centers

摘要

BaSnO 3 (BSO) nanocolumns and Y 2BaCuO5 (Y211) nanoparticles have been successfully incorporated into YBCO thin films by premixed and surface-modified target approach. The effect of these artificially incorporated nanostructures on the vortex pinning properties of YBCO films is investigated based on the variation of critical current density (JC) with applied magnetic field and its variation with respect to the orientation of the applied magnetic field at two different temperatures: 77 and 65 K. The incorporation of Y211 nanoparticles into both YBCO and YBCO + BSO2% films results in improved JC-H characteristics, which is reflected in the enhanced pinning force density (Fp) values. The angular dependent JC measurement reveals that the YBCO film containing BSO nanocolumns exhibits JC peak along the c-axis, whereas the film containing Y211 nanoparticles exhibits isotropic enhancement in the JC values along the entire investigated angular regime. The YBCO film consisting of both kinds of nanostructures (BSO nanocolumns together with Y211 nanoparticles), on the other hand, exhibits mixed characteristics of different kinds of pinning: strong c-axis JC peak together with isotropically enhanced JC in the intermediate angular regime. A possible vortex pinning mechanism due to different kinds of artificially incorporated nanostructures is also discussed.