It was noted that Fe was a possible matrix metal for use in MgB2 conductors. Its ferromagnetic nature produced several new problems in the computation of critical currents. It was shown, by means of finite-element method computations, that the measurement situation for the short-sample critical currents in the case of an MgB2/Fe wire differed considerably from that for a conventional superconductor. The critical current of a MgB2/Fe coil was calculated, based upon the engineering permeability. The computational model presented was applied to a small solenoidal MgB2/Fe coil. On the basis of the results, a non-linear conductor geometry-dependent shift was proposed for the measured short-sample critical current curve to give values for the critical current of the coil.

Critical Current of an MgB2 Coil with a Ferromagnetic Matrix. A.Stenvall, A.Korpela, R.Mikkonen, P.Kovác: Superconductor Science and Technology, 2006, 19, 32-8