Fabrication and Characterization of MnBi/Co and MnBi/FeCo Nanocomposite Bulk Magnets

We report the fabrication of MnBi/Co and MnBi/FeCo\textbf{ }nanocomposite bulk magnets by consolidating the hard and the soft phase powder particles under a magnetic field followed by subsequent sintering process. The anisotropic micro and submicron hard magnetic MnBi particles were first prepared by low energy cryo ball milling at liquid nitrogen temperature. MnBi/Co and MnBi/FeCo nanocomposite powders were then prepared by using different fraction of chemically synthesized Co nanowires and FeCo nanoparticles as the soft magnetic phase. The saturation magnetization ($M_{s})$ of the composite magnets increases with addition of the soft phase while the coercivity first increases and then decreases. The MnBi/Co and MnBi/FeCo nanocomposite bulk magnets have reached an enhanced magnetization value ($M_{s} \quad =$ 78 and 80.6 emu/g) with 30 wt. {\%} of Co nanowires and FeCo nanoparticles, respectively compared to the single phase MnBi bulk magnet ($M_{s} \quad =$ 52 emu/g).