Synthesis of Rare Earth Free Permanent Magnets

Rare earth magnet studies have paved the way to produce permanent magnets that significantly impact green energy applications. However, rare earth alloys are also increasingly expensive and strategically undesirable that opens up a great opportunity for the study of low‐cost and environmentally sustainable magnetic metal alloys such as MnBi and nonequilibrium tetragonal FeCo. These compounds are characterized by uniaxial hexagonal or tetragonal crystal structures that are the basis for large magnetocrystalline anisotropies. One promising approach to fabricate the tetragonally distorted FeCo alloys is to epitaxially grow with the adjacent another material in the superlattice layer‐bylayer form. MnBi binary alloy is a magnetic material with many favorable properties: large magnetic anisotropy and high‐spin polarization in its low‐temperature phase (LTP) and the high magneto‐optical Kerr effect in the quenched high‐temperature phase (HTP). The structural and magnetic properties of the MnBi have been investigated using XRD, neutron diffraction, and magnetic measurements.