Correlation Between Flux Pinning Properties and Interfacial Defects in ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}/{\rm CeO}_{2}$ Multilayer Thin Films

Abstract

YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (YBCO) thin films doped with either secondary nanoparticles or nanolayers have demonstrated enhanced flux pinning properties in applied magnetic field. One possible reason for the enhanced flux pinning properties is the interfacial defects generated at the heterogeneous interfaces between YBCO and nanoparticles/nanolayers. In this work, we conducted a systematic study to correlate the pinning properties of YBCO thin films with interfacial defect density by introducing CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> multilayered structures. Multilayered YBCO thin films with 1-, 2-, and 4- CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interlayers and a pure YBCO reference thin film were prepared by pulsed laser deposition through alternating YBCO and CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> targets. A detailed microstructure and superconducting property analysis was conducted by X-ray diffraction (XRD), high resolution cross-sectional transmission electron microscopy (TEM), and physical properties measurement system (PPMS) with vibrating sample magnetometer (VSM). The result showed that introducing CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanolayers can effectively increase the interfacial defects without degrading the epitaxy quality of YBCO films. We found that an optimum density of interfacial defects in YBCO matrix is needed for the enhanced self-field and in-field performance.