Enhanced Flux Pinning Properties of YBCO Thin Films With Various Pinning Landscapes

Abstract

Pinning enhancement for YBa ₂ Cu ₃ O _7-δ (YBCO) thin films is critical for their future applications such as superconducting cables, generators, and motors. In this study, several pinning landscapes are introduced and compared for improving the superconducting properties of YBCO thin films. First, BaZrO ₃ (BZO) nanoparticles have been doped into YBCO matrix providing uniform defect pinning centers and resulting in the superconducting property enhancement. Second, a magnetic nanocomposite of (La _0.7 Sr _0.3 MnO ₃ (LSMO)) _x (CeO ₂ ) _1-x (with compositions of LSMO and CeO ₂ varied from 50:50 to 70:30) has been incorporated into YBCO as either a cap layer or a buffer layer. Using this approach, both magnetic pinning and defects pinning are introduced in the systems. Third, multilayers of (LSMO) _0.5 (CeO ₂ ) _0.5 /YBCO have been deposited to achieve uniform defect and magnetic pinning effects through the film thickness. The superconducting properties (critical temperature T _c , and especially the critical current density J _c ) are compared for all the YBCO films with different pinning landscapes, and the corresponding pinning mechanisms are also discussed for each case. It is found that the pinning effect of YBCO film with magnetic nanocomposite layer is more significant under lower applied field, compared to the BZO-YBCO film. Through this comparison study, optimum pinning landscapes with combined defects and magnetic pinning approaches are proposed.