The sphericity, , is introduced to describe the morphology of the magnetic grains. The effect of on the magnetic properties of rare earth-transition metal (RE-TM) permanent magnets was investigated using the micromagnetic simulation, where randomly aligned, irregular-shaped grains with ferromagnetic/non-ferromagnetic grain boundary (GB) phases were considered. For the simulated RE-TM systems, the coercivity increases significantly with the increase in . In particular, with 10 nm thick non-ferromagnetic GB phase, the coercivity, 1.74 MA/m, for к = 0.9 increases by 22% compared to 1.43 MA/m for к = 0.6 in the Nd2Fe14B system. Among the simulated materials, the SmCo5 system displays the largest increment in coercivity, increasing by 0.82 MA/m from 7.61 MA/m for к = 0.6 to 8.43 MA/m for к = 0.9. Magnetization reversal patterns under different external fields indicate that the dependence of coercivity on is attributed to the formation of local reversals at different regions and mechanisms of reversal propagation. Meanwhile the effect of cannot be neglected even at elevated temperatures. The simulated results of (Dy0.47Nd0.53)2Fe14B systems with the non-ferromagnetic GB layer of 4 nm at a temperature of 450 K show that the coercivity for к = 0.9 (1.88 MA/m) increased by 23% compared with that of к = 0.6 (1.52 MA/m). Our study demonstrates that the sphericity can be used as a key parameter to design high-coercivity RE-TM magnets.
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7 March 2021
Research Article|
March 02 2021
Micromagnetic study of sphericity effect in bulk permanent magnets Available to Purchase
C. S. Kim
;
C. S. Kim
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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S. L. Ding
;
S. L. Ding
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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J. H. Kim;
J. H. Kim
3
School of Water Resources and Environment, China University of Geosciences
, Beijing 100871, People’s Republic of China
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C. Yun;
C. Yun
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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W. Y. Yang
;
W. Y. Yang
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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J. Z. Han;
J. Z. Han
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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S. Q. Liu;
S. Q. Liu
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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H. L. Du;
H. L. Du
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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C. S. Wang;
C. S. Wang
a)
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
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J. B. Yang
J. B. Yang
a)
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
4
Beijing Key Laboratory for Magnetoelectric Materials and Devices
, Beijing 100871, People’s Republic of China
5
Collaborative Innovation Center of Quantum Matter
, Beijing 100871, People’s Republic of China
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C. S. Kim
1,2
S. L. Ding
1,2
J. H. Kim
3
C. Yun
1,2
W. Y. Yang
1,2
J. Z. Han
1,2
S. Q. Liu
1,2
H. L. Du
1,2
C. S. Wang
1,2,a)
J. B. Yang
1,2,4,5,a)
1
Institute of Condensed Matter and Materials Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
2
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University
, Beijing 100871, People’s Republic of China
3
School of Water Resources and Environment, China University of Geosciences
, Beijing 100871, People’s Republic of China
4
Beijing Key Laboratory for Magnetoelectric Materials and Devices
, Beijing 100871, People’s Republic of China
5
Collaborative Innovation Center of Quantum Matter
, Beijing 100871, People’s Republic of China
J. Appl. Phys. 129, 093901 (2021)
Article history
Received:
December 13 2020
Accepted:
February 09 2021
Citation
C. S. Kim, S. L. Ding, J. H. Kim, C. Yun, W. Y. Yang, J. Z. Han, S. Q. Liu, H. L. Du, C. S. Wang, J. B. Yang; Micromagnetic study of sphericity effect in bulk permanent magnets. J. Appl. Phys. 7 March 2021; 129 (9): 093901. https://doi.org/10.1063/5.0040434
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