Synthesis and characterization of rare-earth-free magnetic manganese bismuth nanocrystals

Earth abundant manganese bismuth (MnBi) has long been of interest due to its large magnetocrystalline anisotropy and high energy density for advanced permanent magnet applications. However, solution synthesis of MnBi phase is challenging due to the reduction potential mismatch between Mn and Bi elements. In this study, we show a versatile MnBi synthesis method involving the metal co-reduction followed by thermal annealing. The magnetically hard MnBi crystalline phase is then exchange coupled with magnetically soft cobalt coating. Our processing approach offers a promising strategy for manufacturing rare-earth-free magnetic nanocrystals.