Influence of Grain Boundary on Coercivity in Rare-earth Permanent Magnet with Grain Surface Defects
POSTER
Abstract
Coercivity (Hcj) microstructure-sensitive characteristic of Nd-Fe-B or Sm-Co magnet results in their complex and rigorous fabrication process. To improve Hcj by optimizing microstructure in magnets has been researched as a hot topic. Micromagnetic simulations (MS) have successfully clarified the factors affecting Hcj, such as grain size, grain defect, grain boundary (BG) and disorientation. But few studies have focused on a collective effect of above factors while the real magnets involve many unfavorable factors to Hcj.
We investigate the effect of BG between two different non-ideal Nd2Fe14B grains on Hcj by finite element MS. One grain contains surface defects with a reverse magnetization field (Hdefect) and connects with another non-defect grain through BG (thickness-T). Variation of Hcj with T can be divided into three parts: (1) When T is very thin, the magnet belongs to the rigid model and Hcj = Hdefect; (2) When T becomes thicker, the magnet transforms into the exchange-spring model. BG acts as pinning points and Hcj increases with T; (3) When T is large, the magnet is the decoupled model. BG is as a new nucleation site with a reverse magnetization field (HBG) and Hcj = min (Hdefect, HBG).
We investigate the effect of BG between two different non-ideal Nd2Fe14B grains on Hcj by finite element MS. One grain contains surface defects with a reverse magnetization field (Hdefect) and connects with another non-defect grain through BG (thickness-T). Variation of Hcj with T can be divided into three parts: (1) When T is very thin, the magnet belongs to the rigid model and Hcj = Hdefect; (2) When T becomes thicker, the magnet transforms into the exchange-spring model. BG acts as pinning points and Hcj increases with T; (3) When T is large, the magnet is the decoupled model. BG is as a new nucleation site with a reverse magnetization field (HBG) and Hcj = min (Hdefect, HBG).
*Grant No. 2014CB643702, 51590880, KJZD-EW-M05, 2016YFB0700903
Presenters
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Rui Li
- State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences
- the institute of physics