Magnetic properties of Mn–Al system alloys produced by mechanical alloying

Mechanical alloying of Mn-Al and Mn-Al-C powder mixtures resulted in the formation of α-Mn solid solution. Heat treatment of these mechanically alloyed powders resulted in the formation of the metastable τ phase. The mechanically alloyed powders annealed at relatively low temperatures (500–700 °C) showed small saturation magnetization of less than 1 emu/g in both Mn–Al and Mn–Al–C powders. On the other hand, the Mn–Al powders showed saturation magnetization of 8 emu/g and their Mn–Al–C counterparts exhibited large saturation magnetization of more than 20 emu/g when annealed at relatively high temperature (800–1100 °C). Although the annealed Mn–Al powders showed small coercivity, the Mn–Al–C powders exhibited large coercivity, up to 3.3 kOe, after selected heat treatment.