The upper critical field and flux pinning in MgB₂ single crystals were investigated. The implications of these properties for technical applications are discussed and compared with transport properties of polycrystalline bulk samples and iron sheathed wires. In these untextured materials current percolation is important, especially at high magnetic fields. It is shown that the anisotropy of the upper critical field influences the "irreversibility line" and that the application range MgB₂ is limited by the smallest upper critical field (i.e., for the field direction perpendicular to the boron planes).
Disorder, introduced by neutron irradiation with neutrons, enhances the upper critical field, reduces the anisotropy and drastically changes flux pinning. While the enhanced H_c2 and the reduced anisotropy generally improve the transport properties of the polycrystalline samples, the contribution of the radiation-induced defects to flux pinning is small compared to the as-grown defect structure (grain boundary pinning).

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/1867 must be provided.

1. Local assessment of the current flow in large bulk superconductors and in coated conductors by the newly established magnetoscan technique - theory and experiment