Variation of c-axis correlation on vortex pinning by ab-plane non-superconducting layers in YBa₂Cu₃O₇ films

In YBa₂Cu₃O₇ (YBCO) + BaSnO₃ (BSO)/PrBa₂Cu₃O₇ (PrBCO) multilayer films, behavior of vortices pinned by BSO nanorods was evaluated to discuss influence of ab-plane non-superconducting layers on c-axis correlated vortex pinning. Critical current density (J_c) and activation energy for thermally activated flux flow in magnetic field parallel to the c-axis were reduced by the PrBCO layers and a c-axis peak in an angular dependence of J_c became small, as YBCO + BSO layer thickness decreased or PrBCO layer thickness increased. Irreversibility temperature and trapping angle were not changed by the PrBCO layers for thick YBCO + BSO layers and thin PrBCO layers. This indicates that the ab-plane non-superconducting layers accelerated the vortex motion along the ab-plane without changing the vortex structure. Thin YBCO + BSO layers or thick PrBCO layers resulted in much more drastic degradation of the c-axis correlated vortex pinning due to two dimensional vortex nature or partially prevailed vortex structure, which decreased not only J_c and activation energy, but also irreversibility temperature and trapping angle. Thus, the c-axis correlation of vortex pinning is varied by addition of the ab-plane non-superconducting layers.