Enhanced Flux Pinning Properties in YBa2Cu3O7-δ/(CoFe2O4)0.3(CeO2)0.7 Multilayer Thin Films

A combined defect and magnetic pinning effect has been demonstrated in this work for improving critical current density (J(c)) of YBa2Cu3O7-delta (YBCO) thin films. Most of the previous work has focused on either defect pinning or magnetic pinning. In this work, we introduced a unique nanocomposite with two phases, e.g., ferrimagnetic CoFe2O4 and non-magnetic CeO2. As a demonstration, the composition of (CoFe2O4)(0.3)(CeO2)(0.7) was chosen for this study. The nanocomposite was incorporated into YBCO films as multilayers, i.e., 1-, 2-, and 4-interlayers. A detailed study on the microstructural and superconducting properties was conducted. The results show that the critical temperature remains at similar to 90 K even after introducing interlayers. More importantly, the films with interlayers show enhanced self-field and in-field J(c), especially the 2-interlayer sample with J(c)(sf) of 6.36 MA/cm(2) at 77 K. The enhanced J(c) properties are attributed to both magnetic pinning from CoFe2O4 and defect pinning from CeO2, as well as the well-designed pinning landscapes.