Enhanced Critical Current Density in Heterostructural YBCO/Ca-Doped YBCO Multilayers

Abstract

We conducted experiments involving BZO-added YBCO/Ca-doped YBCO heterostructures with varying layer numbers to investigate the role of Ca doping and the mechanism behind the enhanced J c . Our findings reveal that the inclusion of Ca-doped layers enhances the quality of the YBCO matrix within the BZO-added layer by reducing microstrain and the formation of other crystalline defects, while also optimizing the oxygen content of YBCO with the increasing layer number. These structural improvements lead to a significant increase in self-field J c (0), which is also observed to correspond to an increase in in-field J c (B) without directly impacting flux pinning. The remarkable enhancement in J c at 65 K can be explained by a theoretical model, where the improvement in J c at high temperatures is attributed to the more coherent interface between the BZO nanorods and the YBCO matrix. Therefore, we conclude that the overall enhancement of J c in the Ca-doped heterostructures is attributed to the improved crystalline structure rather than enhanced flux pinning.