Abstract

The ball-milling and incorporating of cobalt (Co) are demonstrated as viable routes to produce exchange coupled hard/soft magnets from arc-melted manganese bismuth (MnBi) ingots. Properties of MnBi/Co magnets aligned by magnetic field parallel and perpendicular to the sample’s plane are comparable but strongly influenced by the Mn:Bi ratio and heat treatments on the ball-milled MnBi powders. By annealing 290 ºC for 40 h, the powder with Mn:Bi ratio of 2:1 leads to the highest coercivity and magnetization. In the case of MnBi sintered at 1,000 ºC for 20 min, the formation of Bi<inf>2</inf>O<inf>3</inf> nanowires enhances the coercivity but the magnetization is reduced with the decrease in the MnBi phase.