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Enhancement of the high-magnetic-field critical current density of superconducting MgB2 by proton irradiation


Magnesium diboride, MgB2, has a relatively high superconducting transition temperature1, placing it between the families of low- and high-temperature (copper oxide based) superconductors. Supercurrent flow in MgB2 is unhindered by grain boundaries2,3, making it potentially attractive for technological applications in the temperature range 20–30 K. But in the bulk material, the critical current density (Jc) drops rapidly with increasing magnetic field strength4. The magnitude and field dependence of the critical current are related to the presence of structural defects that can ‘pin’ the quantized magnetic vortices that permeate the material, and a lack of natural defects in MgB2 may be responsible for the rapid decline of Jc with increasing field strength3. Here we show that modest levels of atomic disorder induced by proton irradiation enhance the pinning of vortices, thereby significantly increasing Jc at high field strengths. We anticipate that either chemical doping or mechanical processing should generate similar levels of disorder, and so achieve performance that is technologically attractive in an economically viable way.

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Figure 1: Simulated6 damage profiles produced in MgB2 by proton irradiation.
Figure 2: Effect of irradiation on the superconducting transition.
Figure 3: Effect of irradiation on the field-dependence of Jc at 20 K; the behaviour at other temperatures is similar.
Figure 4: Temperature dependence of the irreversibility field H * for different damage levels.


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We are grateful to M. Stoneham and J. Matthews for advice on radiation damage. This work was supported by the UK Engineering and Physical Sciences Research Council.

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Correspondence to Y. Bugoslavsky.

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Bugoslavsky, Y., Cohen, L., Perkins, G. et al. Enhancement of the high-magnetic-field critical current density of superconducting MgB2 by proton irradiation. Nature 411, 561–563 (2001).

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