The effect of APC/YBCO interface on the angular range of effective pinning by one-dimensional artificial pinning centers in YBa2Cu3O7-x nanocomposite films

Abstract

The APC/YBCO interface has been reported to directly affect the pinning efficiency of 1D APCs at B//c-axis. This raises a question on how the APC/YBCO interface affects angular range of the pinning effectiveness for a given 1D APC. In this work, two types of 1D APCs of different APC/YBCO interfaces and hence pinning efficiencies were selected to understand the correlation of the pinning efficiency at B//c-axis and the angular range of the effectiveness. Specifically, BaZrO3 (BZO) and BaHfO3 (BHO) 1D APCs were selected for a comparative study in the APC/YBCO nanocomposite films. The BZO and BHO 1D APCs have comparable diameters in the range of 5-6 nm. In the doping range of 2-6 vol.%, both BZO and BHO form c-axis aligned 1D APCs in YBCO films. However, differences are present at their interfaces with YBCO. While the BZO/YBCO interface is semi-coherent, a coherent BHO/YBCO interface has been found to be critical to the higher pinning efficiency of the BHO 1D APCs. Therefore, they provide ideal systems for investigation of the angular range of pinning effectiveness by 1D APCs. By evaluating the nanocomposites’ maximum pinning force density (Fp, max ) and its location Bmax , normalized to that of the reference YBCO film as functions of magnetic field (B) orientation at temperatures of 65–77 K, a quantitative correlation between the pinning efficiency of the BZO 1D-APCs and their effective angular range was obtained. Our results indicate that all 1D APCs can provide enhanced Bmax over certain angular ranges away from the c-axis. However, 1D APCs with higher pinning efficiency, such as BHO 1D APCs can have enhanced Fp, max over the entire angular range of B-orientations at temperatures of 65-77 K with respect to that for the reference YBCO sample.