ホーム > 研究活動 > 口頭発表(2016) > Micromagnetic simulation on the grain alignment dependence of coercivity in Nd-Fe-B sintered magnets

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Micromagnetic simulation on the grain alignment dependence of coercivity in Nd-Fe-B sintered magnets

REPM2016

2016年8月28日(日)

Tadakatsu Ohkubo(NIMS), Hirotaka Yokota(TDK Corporation ,NIMS), Tohru Oikawa(TDK Corporation ,NIMS), Tohmas Schrefl(Danube University Krems) and Kazuhiro Hono(NIMS)

概要

One enigma about the coercivity of Nd-Fe-B magnets is its crystal orientation dependence. Experimentally, it is well known that the coercivity of the isotropic magnet is larger than that of anisotropic magnet [1]. This simple experimental behavior cannot be reproduced using finite element micromagnetic simulations as long as the magnetization reversal is governed by the nucleation [2].
In this study, we employed finite element micromagnetic simulation to realize the grain alignment dependence of coercivity. In the case of real magnets, many reversed magnetic domains are observed at remanent state, because of the damaged surface grains by on the surface of bulk magnets. To consider this, we made an initial model in which the magnetic domains of surface grains were reversed from the beginning. Then, maicromagnetic simulations of the demagnetization process were done with different grain alignment. The obtained coercivity decreased with increasing the grain alignment as observed experimentally. Furthermore, it was confirmed that the demagnetization field near the reversed grains increased with increasing the alignment, which explain the reduction of coercivity for the perfectly aligned polycrystalline microstructure.
[1] Y. Matsuura et al., J. Magn. Magn. Mat., 336, 88 (2013).
[2] J. Fujisaki et al., IEEE Trans. Magn., 50, 7100704 (2014).


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