Synthesis and Magnetic Properties of MnBi(LTP) Magnets With High-Energy Product

MnBi magnets were prepared by melt-spinning, annealing, ball-milling, magnetic alignment, and subsequent hot compaction process. Mn-Bi melt-spun ribbons contained mainly unreacted Mn and Bi phases, including the low-temperature phase of MnBi. To increase the amount of this MnBi phase, these melt-spun ribbons were annealed under an oxygen-controlled atmosphere. As a result, a maximum saturation magnetization value of 57.90 emu/g was obtained when the melt-spun ribbons were annealed at 300 °C for 12 h. Bulk magnets fabricated by magnetic alignment and hot compaction processes showed a density of 8.71 g/cm³, a M_r/M_s ratio of 0.79, and a (BH)_max value of 6.7 MGOe at room temperature. With the temperature increasing, the coercivity changed from 6387 Oe at room temperature to 18540 Oe at 150 °C and a (BH)_max measured 5.5 MGOe at 150 °C.