Permanent magnet with MgB2 bulk superconductor

TL;DR

This paper demonstrates that MgB2, a high-temperature superconductor, can serve as a stable, high-field permanent magnet at 20 K, offering a cost-effective and practical alternative for advanced magnetic applications.

Contribution

The study shows MgB2's potential as a high-temperature, stable, and industrially fabricable permanent magnet without rare-earth metals, suitable for cryocooler-based systems.

Findings

Maintains 3 T magnetic field at 20 K for a week with high stability

Exhibits uniform magnetic field distribution similar to single-crystalline magnets

Can be fabricated at low cost using polycrystalline bulk material

Abstract

Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging (MRI). The recent global helium shortage has quickened research into high-temperature superconductors (HTSs) materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB2 permanent bulk magnet was detrmined. Because MgB2 is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB2 bulks promising for the next generation of Tesla-class permanent-magnet applications.