Microstructural defects associated with enhanced magnetic flux pinning in YBCO/DyBCO/YBCO multilayered thin films

We investigated the nature of microstructural defects existing in YBCO/DyBCO/YBCO multilayers deposited by pulsed laser deposition on CeO2-buffered sapphire substrates to clarify the origin of magnetic flux pinning enhancement observed in these films. A relatively thin YBCO film contains high concentrations of antiphase boundaries (APBs) and short-range stacking faults (SFs) oriented along the ab plane. Multilayering thin layers of YBCO with DyBCO results in a similar highly faulted microstructure, with APBs and SFs homogeneously distributed throughout the thickness. In addition, multilayers have incorporated elongated defects, parallel to the c-axis direction, emanating from the DyBCO intermediate layer and extending towards the top YBCO layer. Multilayers have also developed long-range SFs which intersect the c-axis-oriented elongated defects and are mostly concentrated in the region of the DyBCO and the upper YBCO layer, indicating a correlation between the formation of the two types of defects. The microstructural features of the YBCO/DyBCO/YBCO multilayers correlate well with the evaluation of the magnetic field angular dependence of J(c), which revealed a significant enhancement when the field is aligned along the ab plane (H parallel to ab).