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Title: Artificial Pinning Centers in (Y,RE)-Ba-Cu-O Superconductors: Recent Progress and Future Perspective
A microscopic understanding of vortex pinning in type II superconductors began with the theoretical discovery of magnetic vortices by Abrikosov, which received the 2003 Nobel Prize in Physics [1, 2]. When type II superconductors are exposed to magnetic fields (H), the magnetic field enters as quantized vortices, each with a fundamental flux j0 = 2.07 × 10−11 T cm−2 , or 2.07 × 10−15 Wb. The vortex core size on the order of the superconducting coherence length can be very small, e.g. ∼1–2 nm for the cuprate family of high-temperature superconductors (HTSs). The vortices electrically interact with each other by repelling, and act collectively together as a flux lattice that is affected by the intrinsic crystal lattice properties and microstructure defects. For superconducting power applications where applied magnetic fields are in the range of 0.1 T to >30 T, the areal number density of the vortices can reach incredibly high values. For example, for an applied magnetic field of 5 T, the vortex areal density is around 2.5 × 1011 cm−2 , which translates to inter-vortex spacing of about 20 nm (assuming a square lattice for vortices). Somewhat surprisingly, if the crystal lattice for type II superconductors, such as HTS cuprates [3] is nearly perfect without any defects to pin vortices, the vortices can move collectively and almost freely in an applied magnetic field due to Lorentz forces, which results in electrical resistance at a fairly low critical current density Jc(H, T) at an applied magnetic field (H) and temperature (T). In order to realize useful critical current densities in type II superconductors, imperfections and defects must be added to the crystal lattice to effectively pin vortices. The simplest example of this was achieved in the (Y, RE)Ba2Cu3O7 (where RE is rare earth elements) family by depositing thin films, in which high densities of dislocations and other growth defects are added into the film microstructure and dramatically increase the critical current density Jc(77 K, H//c-axis) > 106 A cm−2 compared to Jc (77 K) < 103 A cm−2 for single crystals [4–6]  more » « less
Award ID(s):
1508494
PAR ID:
10149355
Author(s) / Creator(s):
Date Published:
Journal Name:
Superconductor science technology
Volume:
33
ISSN:
1361-6668
Page Range / eLocation ID:
040301
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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