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Title: Thermal stability of MnBi magnetic materials

MnBi has attracted much attention in recent years due to its potential as a rare-earth-free permanent magnet material. It is unique because its coercivity increases with increasing temperature, which makes it a good hard phase material for exchange coupling nanocomposite magnets. MnBi phase is difficult to obtain, partly because the reaction between Mn and Bi is peritectic, and partly because Mn reacts readily with oxygen. MnO formation is irreversible and harmful to magnet performance. In this paper, we report our efforts toward developing MnBi permanent magnets. To date, high purity MnBi (>90%) can be routinely produced in large quantities. The produced powder exhibits 74:6 emu g1 saturation magnetization at room temperature with 9 T applied field. After proper alignment, the maximum energy product (BH) max of the powder reached 11.9 MGOe, and that of the sintered bulk magnet reached 7.8 MGOe at room temperature. A comprehensive study of thermal stability shows that MnBi powder is stable up to 473 K in air.
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  1. Pacific Northwest National Laboratory
  2. Environmental Molecular Sciences Laboratory
  3. Ames Laboratory
  4. Electron Energy Corporation
  5. University of Maryland
  6. National Institute of Standards and Technology
  7. United Technologies Research Center
  8. University of Texas
Publication Date:
OSTI Identifier:
Report Number(s):
IS-J 8245
Journal ID: ISSN 0953-8984
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics. Condensed Matter; Journal Volume: 26; Journal Issue: 6
IOP Publishing
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
36 MATERIALS SCIENCE non rare earth permanent magnet, MnBi, thermal decomposition, positive temperature coefficient