Temperature dependent pinning efficiency in multilayer and single layer BZO/YBCO nanocomposite films

Abstract

The BaZrO3/YBa2Cu3O7 (BZO/YBCO) interface has been found to affect the vortex pinning efficiency of one-dimensional artificial pinning centers (1D-APC) of BZO. A defective BZO/YBCO interface due to a lattice mismatch of ∼7.7% has been blamed for the reduced pinning efficiency. Recently, we have shown incorporating Ca0.3Y0.7Ba2Cu3O7-x spacer layers in BZO/YBCO nanocomposite film in multilayer (ML) format can lead to a reduced lattice mismatch ∼1.4% through the enlargement of lattice constant of YBCO via Ca diffusion and partial Ca/Cu replacement on Cu-O planes. In this work, the effect of this interface engineering on the BZO 1D-APC pinning efficiency is investigated at temperatures of 65-81 K through a comparison between 2 and 6 vol.% BZO/YBCO ML samples with their single-layer (SL) counterparts. An overall higher pinning force (Fp ) density has been observed on the ML samples as compared to their SL counterparts. Specifically, the peak value of Fp (Fp,max ) for the 6% BZO/YBCO ML film is about ∼ 4 times of that of its SL counterpart at 65 K. In addition, the location of the Fp,max (B max) in the ML samples shifts to higher values as a consequence of enhanced pinning. For the 6% BZO/YBCO ML sample, a much smaller “plateau-like” decrease of the Bmax with increasing temperature was observed, which is in contrast to approximately linear decrease of Bmax with increasing temperature in the 6% SL film. This result indicates the importance of restoring the BZO/YBCO interface quality for better pinning efficiency of BZO 1D-APCs especially at higher BZO doping concentration.