Enhanced Flux Pinning Properties in $\hbox{YBa}_{2}\hbox{Cu}_{3}\hbox{O}_{7-\delta}$/ $(\hbox{CoFe}_{2}\hbox{O}_{4})_{0.3}(\hbox{CeO}_{2})_{0.7} $ Multilayer Thin Films

Abstract

A combined defect and magnetic pinning effect has been demonstrated in this work for improving critical current density $(J_{c})$ of $\hbox{YBa}_{2}\hbox{Cu}_{3}\hbox{O}_{7-\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 $\hbox{CoFe}_{2}\hbox{O}_{4}$ and non-magnetic $\hbox{CeO}_{2}$ . As a demonstration, the composition of $(\hbox{CoFe}_{2}\hbox{O}_{4})_{0.3}(\hbox{CeO}_{2})_{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 $\sim$ 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 $\hbox{MA/cm}^{2}$ at 77 K. The enhanced $J_{c}$ properties are attributed to both magnetic pinning from $\hbox{CoFe}_{2}\hbox{O}_{4}$ and defect pinning from $\hbox{CeO}_{2}$ , as well as the well-designed pinning landscapes.