The effect of APC/YBCO interface on the angular range of effective pinning by one-dimensional artificial pinning centers in YBa₂Cu₃O_7-xnanocomposite 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.

Enhancing magnetic pinning by BaZrO3nanorods forming coherent interface by strain-directed Ca-doping in YBa2Cu3O7−xnanocomposite films

“…The significant enhancement in the ML film along all B orientations at 65 K corresponds well with similar enhancement in J c (5 T) shown in figure 6(b). This angular enhancement in J c for the 2% BZO-YBCO ML (relative to the 2% BZO-YBCO SL case) is consistent with what has been reported on the BHO/YBCO nanocomposite films in which the BHO 1D-APC/YBCO interface is coherent [37,58]. At 77 K (red curves of figure 6(b)), the angular range of higher J c (θ) in the ML sample becomes slightly reduced, most probably due to the T c effect.…”

“…As expected, the data shows a monotonic decrease in the normalized F pmax with θ and the highest enhancement factor of 1.7 is at θ = 0 • as expected. At 65 K when the T c effect is negligible, larger enhancement factors can be observed in the entire angular range despite a similar trend of monotonic decreasing enhancement factors with increasing θ angles, which is similar to the case of BHO 1D-APCs that also form a coherent interface with YBCO matrix [37,58]. The highest enhancement factor of 1.7 is at θ = 0 • and it is ∼1.0 at θ = 67 • .…”

Interface Engineering for Enhanced Magnetic Vortex Pinning by 1D-BZO APCs in a Wide Angular Range

“…The dramatic enhancement Fp,max and Bmax along B//c in the 6% ML sample is not surprising considering the expected benefits of improved BZO/YBCO interface and reduced strain field overlap at high concentration of the BZO 1D APCs. This angular enhancement in ML films is comparable to what has been reported on the BHO/YBCO nanocomposite films in which the 1D-APC/YBCO interface is coherent [20,21].…”

“…Specifically, this is illustrated in a peak of Jc(T) centered at T=0, or B//c-axis (T represents the tilt angle of the B field away from the c-axis in the plane perpendicular to Jc) in the 1D-APCs/REBCO nanocomposites. A more recent study in probing the effect of the enhanced pinning efficiency of 1D-APCs on the angular range of the enhanced pinning with the pinning efficiency, through a comparison of the angular dependence of the peak pinning force density (Fpmax) and its location (Bmax) on the BZO 1D APC/YBCO and BHO 1D-APC/YBCO nanocomposite films [20,21], has revealed a broader angular range of enhanced pinning of T >67q in the latter, suggesting the further benefit of a coherent 1D-APC/YBCO interface in reducing the Jc anisotropy with respect the B field orientations.…”

Controlled BZO Nanorod Growth and Improved Flux Pinning in YBCO Films Grown on Vicinal STO Substrates

“…Step-Edge Strain-Induced BZO Nanorod Growth. In the STO film, the predominantly semicoherent interface strain 10,45,46 caused by YBCO/BZO leads to a decrease in the overall quality of the YBCO matrix between the BZO nanorods. This is due to the formation of a high density of misfit dislocations.…”