Influence of disorder on Hc2-anisotropy and flux pinning in MgB2

Michael Eisterer 

Atomic Institute of the Austrian Universities, Stadionallee, Wien 1020, Austria

Abstract

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 Hc2 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).

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Presentation: invited oral at E-MRS Fall Meeting 2004, Symposium E, by Michael Eisterer
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-29 15:15
Revised:   2009-06-08 12:55
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