To control the anisotropy of critical current density (Jc), hybrid artificial pinning centers (APCs) of elongated-nanorods and segmented-nanorods were incorporated into YBa2Cu3O7 films. The elongated-nanorods and segmented-nanorods were formed by fabricating multilayer films using YBa2Cu3O7+BaSnO3 targets with a different BaSnO3 content. According to the elastic calculation, the BaSnO3-free YBa2Cu3O7 regions between BaSnO3 segmented-nanorods were highly strained, resulting in their alignment along the c-axis. Pinning of the vortex kinks and straight vortices by the nanorod ends improved Jc in a wide range around B//ab. The angular dependence of Jc systematically varied with the multilayer structure of layer thickness and BSO content. Jc depended on the layer thickness even with keeping the constant average BSO content, showing that the BaSnO3 distribution, as well as the average BaSnO3 content, affected the Jc. The hybrid pinning effect of elongated-nanorods and nanorod ends improved the Jc anisotropy although the effect was not so large in the present films. The control of strain and interface is expected to lead to further improvement of Jc.

Multilayers (MLs) comprising of YBa2Cu3O7(YBCO)+BaSnO3(BSO) layers with different BSO content were fabricated, and their critical current density (Jc) was measured to understand influence of ML structure on vortex pinning. Elongated and segmented nanorods were observed in the MLs, and ab-plane aligned nanoparticles appeared depending on BSO content. When BSO formed only elongated and segmented nanorods in MLs, Jc exhibited a linear relationship between Jc in the single layer films. On the other hand, when MLs contained ab-plane aligned nanoparticles in addition to nanorods, Jc decreased with lower-Jc-layer fraction more rapidly. These results suggest that Jc was degraded due to easy vortex flow along the lower-Jc-layers, and that the acceleration of vortex motion depended on the type of lower-Jc-layers. Vortex behavior which is not observed in conventional systems such as single layer films and bulk samples is strongly expected in MLs, since fine tuning of pinning center structure is possible.