Critical Fields and Critical Currents in MgB2

Abstract

We review recent measurements of upper (Hc2) and lower (Hc1) critical fields in clean single crystals of MgB2, and their anisotropies between the two principal crystallographic directions. Such crystals are far into the "clean limit" of Type II superconductivity, and indeed for fields applied in the c-direction, the Ginzburg-Landau parameter k is only about 3, just large enough for Type II behaviour. Because m0Hc2 is so low, about 3 T for fields in the c-direction, MgB2 has to be modified for it to become useful for high-current applications. It should be possible to increase Hc2 by the introduction of strong electron scattering (but because of the electronic structure and the double gap that results, the scatterers will have to be chosen carefully). In addition, pinning defects on a scale of a few nm will have to be engineered in order to enhance the critical current density at high fields.

BOROMAG Conference Invited paper. To appear in Supercond. Sci. Tech

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Cited by in corpus (8)

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• BCS-like critical fluctuations with limited overlap of Cooper pairs in FeSe
• Penetration depth anisotropy in two-band superconductors
• Reversible magnetization measurement of the anisotropy of the London penetration depth in MgB2 single crystals
• Raman Scattering Investigation of Electron Phonon Coupling in Carbon substituted MgB2
• Quantitative imaging of flux vortices in type-II superconductor MgB${}_2$ using Cryo-Lorentz Transmission Electron Microscopy
• Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field