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Title: New anisotropic MnBi permanent magnets by field-annealing of compacted melt-spun alloys modified with Mg and Sb

Abstract

A technique has been designed for manufacturing rare-earth-free MnBi-based magnets capable of filling the existing "gap" between the ferrite and rare-earth permanent magnets. Whereas the earlier approaches relied on sintering of fine and easily degrading single-crystal MnBi particles, the new method achieves refinement of the key α-MnBi phase through melt-spinning combined with appropriate alloying. Modification of the MnBi alloys with Mg and Sb generates a high-coercivity nanostructure of the metastable β' phase. A subsequent compaction at 150 °C produces fully dense materials while converting the β' phase into the stable α phase. Lastly, a short annealing at 265–300 °C in a magnetic field of 3 T increases the fraction of the α phase to 97–98% and aligns the c axes of the α crystallites. A maximum energy product (BH) max of 11.5 MGOe and an intrinsic coercivity Hc of 5.6 kOe have been obtained in a magnet with the nominal composition Mn 50Bi 46.5Mg 3Sb 0.5. Because the coercivity increases with temperature, the maximum energy product of this magnet is still as high as 8.9 MGOe at 175 °C. Increasing the Sb content to 1.5 at.% increases the H c to 9.3 kOe, but at the same time inhibits themore » development of the texture thus decreasing the (BH) max. The addition of Mg was found to increase the c lattice parameter of the α phase resulting in an unusually large ratio c/a ≈1.432.« less

Authors:
 [1];  [1];  [2]
  1. Univ. of Delaware, Newark, DE (United States)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Univ. of Delaware, Newark, DE (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1561557
Alternate Identifier(s):
OSTI ID: 1562554
Grant/Contract Number:  
FG02-90ER45413; EE0007794
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Magnetism and Magnetic Materials
Additional Journal Information:
Journal Volume: 495; Journal Issue: C; Journal ID: ISSN 0304-8853
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; metals and alloys; permanent magnets; rapid-solidification; high magnetic fields; magnetic measurements; X-ray diffraction

Citation Formats

Gabay, Alexander M., Hadjipanayis, George C., and Cui, Jun. New anisotropic MnBi permanent magnets by field-annealing of compacted melt-spun alloys modified with Mg and Sb. United States: N. p., 2019. Web. doi:10.1016/j.jmmm.2019.165860.
Gabay, Alexander M., Hadjipanayis, George C., & Cui, Jun. New anisotropic MnBi permanent magnets by field-annealing of compacted melt-spun alloys modified with Mg and Sb. United States. doi:10.1016/j.jmmm.2019.165860.
Gabay, Alexander M., Hadjipanayis, George C., and Cui, Jun. Fri . "New anisotropic MnBi permanent magnets by field-annealing of compacted melt-spun alloys modified with Mg and Sb". United States. doi:10.1016/j.jmmm.2019.165860.
@article{osti_1561557,
title = {New anisotropic MnBi permanent magnets by field-annealing of compacted melt-spun alloys modified with Mg and Sb},
author = {Gabay, Alexander M. and Hadjipanayis, George C. and Cui, Jun},
abstractNote = {A technique has been designed for manufacturing rare-earth-free MnBi-based magnets capable of filling the existing "gap" between the ferrite and rare-earth permanent magnets. Whereas the earlier approaches relied on sintering of fine and easily degrading single-crystal MnBi particles, the new method achieves refinement of the key α-MnBi phase through melt-spinning combined with appropriate alloying. Modification of the MnBi alloys with Mg and Sb generates a high-coercivity nanostructure of the metastable β' phase. A subsequent compaction at 150 °C produces fully dense materials while converting the β' phase into the stable α phase. Lastly, a short annealing at 265–300 °C in a magnetic field of 3 T increases the fraction of the α phase to 97–98% and aligns the c axes of the α crystallites. A maximum energy product (BH)max of 11.5 MGOe and an intrinsic coercivity Hc of 5.6 kOe have been obtained in a magnet with the nominal composition Mn50Bi46.5Mg3Sb0.5. Because the coercivity increases with temperature, the maximum energy product of this magnet is still as high as 8.9 MGOe at 175 °C. Increasing the Sb content to 1.5 at.% increases the Hc to 9.3 kOe, but at the same time inhibits the development of the texture thus decreasing the (BH)max. The addition of Mg was found to increase the c lattice parameter of the α phase resulting in an unusually large ratio c/a ≈1.432.},
doi = {10.1016/j.jmmm.2019.165860},
journal = {Journal of Magnetism and Magnetic Materials},
number = C,
volume = 495,
place = {United States},
year = {2019},
month = {9}
}

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