Influence of ferromagnetic layer on critical current of a superconducting wire

We investigated how a 10-50 mu m layer from soft ferromagnetic material, incorporated in the architecture of a composite superconducting tape, could influence the capability of the tape to transport electrical current. Numerical procedure was developed to calculate the local distribution of magnetic field and current in the condition when all the superconductor is carrying its critical current density. It was found that the concentration of magnetic flux in ferromagnetic layers allows to reduce the local value of magnetic flux density felt by the superconductor. In this way, the critical current of the tape in low applied magnetic fields can be improved. This theoretical prediction is confirmed by experimental observation.