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

• Published in: IEEE transactions on magnetics Vol. 50; no. 11; pp. 1 - 4
• Main Authors: Moon, Ki Woong, Jeon, Kwang-Won, Kang, Min, Kang, Min-Kyu, Byun, Yangwoo, Kim, Jin Bae, Kim, Hwijun, Kim, Jongryoul
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Magnetic hysteresis; Magnetic resonance imaging; Magnetism; Perpendicular magnetic anisotropy; Powders; Saturation magnetization; Temperature measurement; LTP; (BH) \(_{\max }\); MnBi; melt spinning; permanent magnets
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2014.2329555

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/cm 3 , 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.