Magnetic shielding in MgB2/Fe superconducting wires

TL;DR

This study investigates how an iron sheath enhances the critical current in MgB2 superconducting wires, revealing magnetic interactions beyond simple shielding and demonstrating improved performance at various temperatures and magnetic fields.

Contribution

It provides new insights into magnetic interactions between iron sheaths and MgB2 superconductors, showing enhanced vortex pinning and critical current behavior.

Findings

Iron sheath improves critical current beyond magnetic shielding effects.

Peak effect in critical current observed at lower temperatures and higher fields.

Doping MgB2 with nano-SiC enhances vortex pinning without affecting the magnetic interaction.

Abstract

Transport critical current (Ic) was measured for MgB2/Fe round wires, with magnetic field oriented perpendicular to the wire and parallel to it. Measurements were made on a wire with pure MgB2 core and another wire where MgB2 core was doped with nano-size SiC. This doping strongly improved the vortex pinning in MgB2. The field dependence of Ic was strongly improved due to the presence of the iron sheath. At 30K, Ic did not depend on the field for fields between 0.09 and 0.7T. At lower temperatures, Ic increased with the field, after initial decrease, resembling a "peak effect". This effect was extended to higher fields as the temperature went down: at 10K the peak appeared at 3.5T. This improvement was not due to mere magnetic shielding by iron, but more likely to an interaction between the iron sheath and superconductor. Improvement of vortex pinning did not affect the range of fields within which this effect was observed.