One step pressing-annealing to produce LTP MnBi magnets
Keywords:Rare-earth free magnets, Manganese bismuth, Pressing, Annealing
AbstractThe production process for the high-purity low-temperature-phase (LTP) manganese bismuth (MnBi) magnets requires arc-melting, grinding and annealing materials under inert atmosphere. However, the formation of MnO is practically unavoidable during these steps since both Mn and MnBi are easily oxidized even by trace amounts of oxygen. In this work, an oxygen-free pressing-annealing system is developed to facilitate the synthesis of LTP MnBi with minimal oxidization. The semi-automatic pressing is carried out by using the compression piston and the load cell is used to measure the pressing force. The copper plate and cylindrical container are heated by nichrome filament heating. Mn and Bi precursors in powder form are simultaneously pressed and annealed allowing one step formation of LTP MnBi in argon atmosphere chamber. The vibrating sample magnetometry reveals the hysteresis loop of MnBi samples with ferromagnetic characteristics.
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