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

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.