Flux pinning properties in YBCO films with growth-controlled nano-dots and heavy-ion irradiation defects

In order to clarify the influence of size and spatial distribution of three-dimensional pinning centres (3D-PCs) on hybrid flux pinning, columnar defects (CDs) were installed by using 200 MeV Xe ions along the c-axis direction into quasi-multilayered films consisting of YBa2Cu3Oy layers and pseudo layers of BaSnO3. The positive effect of the BaSnO3 doping on the hybrid flux pinning stands out for the critical current density Jc around B || c in high magnetic field and/or inclined magnetic field off the c-axis, which is more remarkable for the multilayered film grown at higher temperature, possibly due to larger BaSnO3 nano-dots. In the case of the in-plane distributed BaSnO3 nano-dots, the Jc around B || ab is remarkably enhanced, whereas there is a detrimental effect on the Jc around B || c. These imply that the tuning of 3D-PCs is one of the keys to improve the Jc at all magnetic field orientations for the hybrid flux pinning.