Effects of milling conditions on the magnetic properties of MnBi alloys

MnBi has recently attracted large attention due to its potential for permanent magnetic applications. Although it does not present high saturation magnetization, it has large coercivity, above 1 T, which results in a theoretical BH_max value above 17 MGOe. The MnBi single phase is difficult to prepare by using techniques as arc-melting, rapid solidification and sintering because the melting temperature of Bi (544 K) is much lower than that of Mn (1519 K). Furthermore, the magnetic properties are strongly dependent on processing; the heat treatment after casting, ball milling conditions, and bulk magnet fabrication processes were found to have large effects on the energy product of MnBi magnets. In this work we report the effects of low-energy ball milling (LEBM) conditions on the magnetic properties of MnBi alloys.