Grain size dependence of coercivity of hot-deformed Nd–Fe–B anisotropic magnets

Liu, Jiangwei; Sepehri-Amin, H.; Ohkubo, T.; Hioki, K.; Hattori, Atsushi; Schrefl, T.; Hono, K.

doi:10.1016/j.actamat.2014.09.021

Cited by 186 publications

(57 citation statements)

References 25 publications

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“…The absolute value of β increases from 0.312%/ C for a grain size of 30 nm to 0.337%/ C for a grain size of 130 nm. This result suggests that the temperature coef cient of coercivity deteriorates with increase of the grain size, which is in agreement with experimental observations 13,23) . Based on the nucleation model, the coercivity of Nd-Fe-B permanent magnets is expressed as:…”

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of supporting

confidence: 81%

“…The coercivity as a function of grain size is shown in Fig. 3 (b) and is compared with that of the experimental results of sintered magnets and hot-deformed Nd-Fe-B magnets 1,13,23) . The grain size dependence of the coercivity in the simulation follows a similar trend as the experimental observations.…”

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

“…Une and Sagawa demonstrated a high coercivity of 2 T using ultra ne-grained Nd-Fe-B sintered magnet (D ~ 1 µm) that was processed by controlling the oxygen atmosphere rigorously using the press-less sintering route 12) . In addition, Liu et al has shown experimentally that the thermal stability of coercivity can be improved when the grain size of Nd-Fe-B magnet decreases 13) . Then a question arises: what is the underlying physics on the coercivity enhancement mechanism and improvement of thermal stability of coercivity by the grain size reduction?…”

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

“…To enable the magnet to be used at elevated temperature, a low absolute value of β is desirable. Liu et al reported that β value improves to the range of ~−0.4-0.5% C −1 by the reduction of grain size to ~250-500 nm in hot-deformed NdFe-B magnets 13) . Sepehri-Amin et al employed micromagnetic simulations to understand the underlying physics of the grain size dependence of β.…”

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

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Micromagnetic Simulations of Magnetization Reversals in Nd-Fe-B Based Permanent Magnets

2016

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Finite element micromagnetic simulation was employed to explain how the microstructure of Nd-Fe-B permanent magnets such as grain size, grain shape, and grain boundary composition in uence the magnetization reversals and coercivity. Micromagnetic simulations showed that local demagnetization factor decreases as grain size decreases, which is attributed to a higher coercivity in ne-grained anisotropic permanent magnets. Lower demagnetization factor is also responsible for a lower temperature dependence of coercivity in the magnets with a smaller grain size. It was also found that the reduction of the magnetization of the grain boundary phase in hot-deformed Nd-Fe-B magnets leads to the coercivity enhancement due to a stronger pinning force against magnetic domain wall motion. The coercivity of Nd-Fe-B magnets cannot be enhanced by the reduction of the grain size alone unless the grain boundary phase become non-ferromagnetic, indicating that the role of the grain boundary phase is more pronounced in the Nd-Fe-B magnets with a smaller grain size.

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Section: Effect Of Grain Size On Coercivity and Thermal Stability Of supporting

confidence: 81%

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

Section: Effect Of Grain Size On Coercivity and Thermal Stability Of mentioning

confidence: 99%

See 2 more Smart Citations

Micromagnetic Simulations of Magnetization Reversals in Nd-Fe-B Based Permanent Magnets

2016

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“…1 One can notice a trend towards searching new hard magnetic materials with a reduced content of rare earth elements or some other systems free of these ingredients with |BH| max parameter in order of 100-200 kJ/m 3 , which should be sufficient for many applications. [2][3][4][5][6][7][8][9][10][11][12][13] It seems that the best solution of this challenge may be the composites of soft and hard magnetic phases. In this case, strong exchange interactions between magnetic moments associated with the different phases can leads to the so-called spring-magnetism, and in a consequence, combination of high magnetic remanence as well as maximum energy product.…”

Section: Introductionmentioning

confidence: 99%

Influence of cooling rate on structural and magnetic properties of (Fe78Nb8B14)1-xTbx alloys

et al. 2017

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Graphene Nanoplatelets as Novel Additive to Enhance Coercivity of Hot‐Deformed Magnets by Tuning Microstructures

Wang

Liu

et al. 2018

Adv Materials Inter

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In this work an effective approach of tuning the microstructures and enhancing the coercivity of hot‐deformed Nd‐Fe‐B magnets without obvious remanence loss by adding graphene nanoplatelets (GNPs) is proposed. Based on the microstructure characterization, the adjacent Nd2Fe14B grains on the interfaces are in polygonal shape with the small grain size less than 100 nm, and the GNPs are mainly around the interfaces of the melt‐spun ribbons. Due to the outstanding mechanical, electrical, and thermal properties, the GNPs can act as the steric hindrance additives and thermal conducting medium, which is helpful to restrain the growth of Nd2Fe14B grains effectively and decrease or even eliminate the coarse grains region. As a result, the coercivity of hot‐deformed Nd‐Fe‐B magnets is enhanced remarkably with their refined microstructure; the coercivity is substantially improved by 33.2% from 785 to 1046 kA m−1 with the GNPs additive amount from 0 to 0.2 wt%, while the remanence loss is also as low as 1.56% from 1.28 to 1.26 T. This work reported here suggests that the GNPs have great potentials in fabricating materials with controlled grain growth properties.

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Grain size dependence of coercivity of hot-deformed Nd–Fe–B anisotropic magnets

Cited by 186 publications

References 25 publications

Micromagnetic Simulations of Magnetization Reversals in Nd-Fe-B Based Permanent Magnets

Micromagnetic Simulations of Magnetization Reversals in Nd-Fe-B Based Permanent Magnets

Influence of cooling rate on structural and magnetic properties of (Fe78Nb8B14)1-xTbx alloys

Graphene Nanoplatelets as Novel Additive to Enhance Coercivity of Hot‐Deformed Magnets by Tuning Microstructures

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