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Temperature-dependent first-order reversal curve measurements on unusually hard magnetic low-temperature phase of MnBi

Muralidhar, Shreyas and Gräfe, Joachim and Chen, Yu-Chun and Etter, Martin and Gregori, Giuliano and Ener, Semih and Sawatzki, Simon and Hono, Kazuhiro and Gutfleisch, Oliver and Kronmüller, Helmut and Schütz, Gisela and Goering, Eberhard J. (2017):
Temperature-dependent first-order reversal curve measurements on unusually hard magnetic low-temperature phase of MnBi.
In: Physical Review B, American Physical Society, pp. 024413, 95, (2), ISSN 2469-9950, [Online-Edition: http://dx.doi.org/10.1103/PhysRevB.95.024413],
[Article]

Abstract

We have performed first-order reversal curve (FORC) measurements to investigate the irreversible magnetization processes in the low-temperature phase of MnBi. Using temperature-dependent FORC analysis, we are able to provide a clear insight into the effects of microstructural parameters such as grain diameter, shape, and surface composition on the coercivity of nucleation hardened permanent magnet MnBi. FORC diagrams of MnBi show a unique broadening and narrowing of the coercive field distribution with increasing temperature. We were able to microscopically identify the reason for this behavior, based on the shift in the single domain critical diameter from nearly 1 to 2 μm, thereby changing the dependence of coercivity with particle size. This is based on a strong increase in the uniaxial anisotropy constant with increasing temperature. Furthermore, the results also give an additional confirmation that the magnetic hardening in low-temperature phase MnBi occurs due to nucleation mechanisms. In our case, we show that temperature-dependent FORC measurements provide a powerful tool for the microscopic understanding of high-performance permanent magnet systems.

Item Type: Article
Erschienen: 2017
Creators: Muralidhar, Shreyas and Gräfe, Joachim and Chen, Yu-Chun and Etter, Martin and Gregori, Giuliano and Ener, Semih and Sawatzki, Simon and Hono, Kazuhiro and Gutfleisch, Oliver and Kronmüller, Helmut and Schütz, Gisela and Goering, Eberhard J.
Title: Temperature-dependent first-order reversal curve measurements on unusually hard magnetic low-temperature phase of MnBi
Language: English
Abstract:

We have performed first-order reversal curve (FORC) measurements to investigate the irreversible magnetization processes in the low-temperature phase of MnBi. Using temperature-dependent FORC analysis, we are able to provide a clear insight into the effects of microstructural parameters such as grain diameter, shape, and surface composition on the coercivity of nucleation hardened permanent magnet MnBi. FORC diagrams of MnBi show a unique broadening and narrowing of the coercive field distribution with increasing temperature. We were able to microscopically identify the reason for this behavior, based on the shift in the single domain critical diameter from nearly 1 to 2 μm, thereby changing the dependence of coercivity with particle size. This is based on a strong increase in the uniaxial anisotropy constant with increasing temperature. Furthermore, the results also give an additional confirmation that the magnetic hardening in low-temperature phase MnBi occurs due to nucleation mechanisms. In our case, we show that temperature-dependent FORC measurements provide a powerful tool for the microscopic understanding of high-performance permanent magnet systems.

Journal or Publication Title: Physical Review B
Volume: 95
Number: 2
Publisher: American Physical Society
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 17 Jan 2017 12:44
Official URL: http://dx.doi.org/10.1103/PhysRevB.95.024413
Identification Number: doi:10.1103/PhysRevB.95.024413
Funders: We would like to acknowledge the financial support from the Deutsche Forschungsgemeinschaft for the G8 project High Performance Permanent Magnets Sustainable for Next Generation (HPPMSNG).
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