Systematic variation of hybrid APCs into YBCO thin films for improving the vortex pinning properties

The effect of hybrid (columnar and spherical) artificial pinning centers (APCs) on the vortex pinning properties of YBCO thin films is studied in this paper on the basis of variation of critical current density J_C with applied magnetic field and also with the orientation of the applied magnetic field. YBCO+BSO3% composite target is used for preparing film with 1-D (columnar) APCs, whereas the same composite target is modified by putting two differently sized (2.2 area% and 3 area%) Y₂O₃ sectored pieces for preparing films having different concentrations of 3-D (spherical) APCs along with 1-D APCs. Film consisting of only 1-D APCs exhibits enhanced in-fieldJ_C values as compared to the one without any APC, and the ones consisting of hybrid APCs exhibit even betterJ_C-B characteristics with increase in the fraction of 3-D APCs. F_pmax. values increase systematically with incorporation of 1-D and 1-D + 3-D APCs, and it also shifts toward higher applied magnetic fields. Film with 1-D APCs exhibits strongJ_C peak at Θ = 0° (H//c-axis), whereas films consisting of hybrid APCs exhibit enhancedJ_C at all the investigated angular regime. A possible mechanism of vortex pinning in samples with hybrid APCs is also discussed, suggesting the role of 1-D and 3-D APCs.