Hybrid artificial pinning centers of elongated-nanorods and segmented-nanorods in YBa₂Cu₃O₇films

Abstract

To control the anisotropy of critical current density (Jc), hybrid artificial pinning centers (APCs) of elongated-nanorods and segmented-nanorods were incorporated into YBa2Cu3O7 films. The elongated-nanorods and segmented-nanorods were formed by fabricating multilayer films using YBa2Cu3O7+BaSnO3 targets with a different BaSnO3 content. According to the elastic calculation, the BaSnO3-free YBa2Cu3O7 regions between BaSnO3 segmented-nanorods were highly strained, resulting in their alignment along the c-axis. Pinning of the vortex kinks and straight vortices by the nanorod ends improved Jc in a wide range around B//ab. The angular dependence of Jc systematically varied with the multilayer structure of layer thickness and BSO content. Jc depended on the layer thickness even with keeping the constant average BSO content, showing that the BaSnO3 distribution, as well as the average BaSnO3 content, affected the Jc. The hybrid pinning effect of elongated-nanorods and nanorod ends improved the Jc anisotropy although the effect was not so large in the present films. The control of strain and interface is expected to lead to further improvement of Jc.

Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods

“…This is in contrast to the BZO doped sample which provides only straight and continuous nanorods 2 . Additionally, the BCO particles between the rod layers can provide some extra pinning 9 as compared to works with multilayer architecture having undoped YBCO between the nanorod layers, although the different alignment of the nanorods in these cases may also affect the strength of the pinning 16,17 .…”

“…Thus, for the best result, application-related design is needed. In addition to mixing different types of dopants, multilayer structures containing layers of BZO doped YBCO 14,15 or BSO doped YBCO 16,17 along with layers of undoped YBCO have also been studied. The segmented nanorods that are formed by depositing undoped YBCO between the layers of doped YBCO provide larger pinning force especially in the direction of B|| ab plane of YBCO, as compared to the continuous nanorods.…”

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

“…In the high-temperature superconductor (HTS) films, the insertion of artificial pinning centers (APCs) within the YBa 2 Cu 3 O 7– x (YBCO) matrix has been shown to have huge potential for a great variety of future power applications. − Notably, the controllable microstructures that form secondary phase nonsuperconducting flux traps play a crucial role in addressing the issue of excellent flux pinning performance of HTS thin films and coated conductors. For instance, the epitaxially c -axis-oriented YBCO films with strongly correlated columnar defects such as BaZrO 3 (BZO), BaSnO 3 (BSO), or BaHfO 3 (BHO) nanorods have been proved to attain the remarkably improved in-field critical current density J c ( B ) when the direction of the magnetic field is parallel to the column. − Moreover, tilted nanocolumns or otherwise mixed APC morphology within the YBCO lattice can reduce the vortex hopping between the defects, increasing J c in a broad angular range that can lead to improved overall vortex pinning and general angular isotropy, regardless of the direction of the magnetic field. − …”

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

“…This is consistent with the expectation that Ca/Cu replacement takes place after the APCs are formed and hence would not interrupt the epitaxial growth of the APCs. Nevertheless, Figure 1a indicates that the APCs in the ML are segmented by the CaY123 spacers but the relative thinness (~ 10 nm) of the spacers may ameliorate some of the pinning detriments associated with truncated APC growth in multilayer YBCO structures with much thicker YBCO spacers [29][30][31]. Furthermore, significant YBCO lattice distortions are largely absent in the ML.…”