The angular range of effective pinning by one-dimensional artificial pinning centers in BaZrO3/YBa2Cu3O7-x nanocomposite films

Abstract

Nanoscale c-axis-aligned one dimensional artificial pinning centers (1D-APC) in superconducting YBa2Cu3O7-x (YBCO) films have been shown to provide strong correlated pining to magnetic vortices at magnetic field H//c-axis. A question arises on how the pinning effectiveness is sustained as the H-orientation (θ) deviates from the c-axis and how such an angular range is correlated to the pinning efficiency of an individual 1D-APC. To shed lights on this question, this work investigates the angular range of pinning effectiveness of the BaZrO3 (BZO) 1D-APCs in BZO/YBa2Cu3O7-x nanocomposites as the strain field overlap is systematically varied by increasing the BZO doping level in the range of 2-6 vol.% and by the introduction of the secondary Y2O3 nanoparticles (3D APCs). By evaluating the maximum pinning force density (Fp, max), its location Hmax, and the α values of the nanocomposites normalized to that of the reference YBa2Cu3O7-x film as functions of θ 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. In most samples, the 1D-APCs can provide enhanced Hmax in the range of θ ∼0°-60°. However, the Fp, max values only in nanocomposites with high pinning efficiency 1D-APCs exceed that of the YBa2Cu3O7-x over a smaller range up to θ ∼ 37°. Finally, the introduction of 3D APCs results in reduction of the α values over nearly the entire angular range. This study reveals the importance in improving individual 1D-APC’s pinning efficiency and hence extending its angular range of effective pinning.

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

“…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 • .…”

“…The J c (B) values were determined using the 1 µV cm −1 criterion on the I-V characteristic. The selection of the θ angles is based on a preliminary test of the F p (B) and J c (B) curves to ensure the difference between the curves at these angles is not negligible [37]. The pinning force density (F p ) was calculated from the equation F p = J c × B.…”

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.…”

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

“…Various APCs of different morphologies, including c-axis aligned one-dimensional nanorods (1D-APCs), ab-plane aligned twodimensional planar defects (2D-APCs), and three-dimensional nanoparticles (3D-APCs) have been reported through the addition of secondary dopants like BaZrO 3 (BZO), BaHfO 3 (BHO), BaSnO3 (BSO), YBa2(Nb/Ta)O6, Y2O3, etc. in YBCO (or other rare-earth variation of YBCO) to form APC/YBCO nanocomposites films [7][8][9][10][11][12][13][14][15].…”