Thermal stability of MnBi magnetic materials

Journal Article · Mon Jan 27 00:00:00 EST 2014 · Journal of Physics. Condensed Matter

DOI:https://doi.org/10.1088/0953-8984/26/6/064212· OSTI ID:1134714

Cui, Jinfang ^[1]; Choi, J. P. ^[1]; Li, G. ^[1]; Polikarpov, E. ^[1]; Darsell, J. ^[1]; Overman, N. ^[1]; Olszta, M. ^[1]; Schreiber, D. ^[1]; Bowden, M. ^[2]; Droubay, T. ^[1]; Kramer, Matthew J. ^[3]; Zarkevich, Nikolay A. ^[3]; Wang, L L. ^[3]; Johnson, Duane D. ^[3]; Marinescu, M. ^[4]; Takeuchi, I. ^[5]; Huang, Q. Z. ^[6]; Wu, H. ^[5]; Reeve, H. ^[7]; Vuong, N. V. ^[8] ; Liu, J P. ^[8]

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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

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.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• DOE Contract Number: DE-AC02-07CH11358
• OSTI ID: 1134714
• Report Number(s): IS-J 8245
• Journal Information: Journal of Physics. Condensed Matter, Vol. 26, Issue 6; ISSN 0953-8984
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
non rare earth permanent magnet
MnBi
thermal decomposition
positive temperature coefficient