Magnetization measurements for grain boundary phases in Ga-doped Nd-Fe-B sintered magnet

JOURNAL OF ALLOYS AND COMPOUNDS

卷:752

Article

Niitsu, K.¹  Sato, A.²  Sasaki, T. T.³  Sawada, R.²  Cho, Y.²  Takada, Y.⁴  Sato, T.⁴  Kaneko, Y.⁴  Kato, A.⁵  Ohkubo, T.³  Shindo, D.^1,6  Hono, K.³  Murakami, Y.^1,2,7 

[1] RIKEN, Ctr Emergent Matter Sci CEMS, Wako, Saitama 3510198, Japan

[2] Kyushu Univ, Dept Appl Quantum Phys & Nucl Engn, Fukuoka 8190395, Japan

[3] Natl Inst Mat Sci, Elements Strategy Initiat Ctr Magnet Mat ESICMM, Tsukuba, Ibaraki 3050047, Japan

[4] Toyota Cent Res & Dev Labs Inc, Nagakute, Aichi 4801192, Japan

[5] Toyota Motor Co Ltd, Adv Mat Engn Div, Susono 4101193, Japan

[6] Tohoku Univ, Inst Multidisciplinary Res Adv Mat IMRAM, Sendai, Miyagi 9808577, Japan

[7] Kyushu Univ, Ultramicroscopy Res Ctr, Fukuoka 8190395, Japan

关键词: Permanent magnets;    Nd-Fe-B;    Coercivity;    Grain boundary;    Transmission electron microscopy;   

DOI  :  10.1016/j.jallcom.2018.04.055

来源: Elsevier

【 摘 要 】

The magnetism of grain boundary (GB) phases in the Nd-rich Ga-doped Nd-Fe-B sintered magnet that shows unusually high improvement in coercivity by post-sinter optimal heat treatment was studied using electron holography. Transmission electron microscopy observations identified three types of GB phases with distinct structures, i.e., Ia(3)over-bar-type, amorphous-type, and Nd-6 (Fe,Ga)(14)-type. The magnetic flux densities of these three GB phases were systematically analyzed by measuring the phase shifts of incident electrons, and all of these GB phases are concluded to be nonferromagnetic. Unlike the standard commercial sintered magnets, this study has shown that the Nd2Fe14B grains in the optimally heat treated Nd-rich Ga-doped sintered magnet are exchange decoupled by the formation of the three types of nonferromagnetic GB phases. The observations provide useful information for GB engineering of Nd-Fe-B sintered magnets, which is key for further improvements of their coercivities without relying on grain size refinement. (C) 2018 Elsevier B.V. All rights reserved.

【 授权许可】

Free