Journal of Magnetics

The Korean Magnetics Society (한국자기학회)
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The Origin of Coercivity Enhancement of Sintered NdFeB Magnets Prepared by Dy Addition

  • Yu, N.J. (Magnetism key laboratory of Zhejiang Province, China Jiliang University) ;
  • Pan, M.X. (Magnetism key laboratory of Zhejiang Province, China Jiliang University) ;
  • Zhang, P.Y. (Magnetism key laboratory of Zhejiang Province, China Jiliang University) ;
  • Ge, H.L. (Magnetism key laboratory of Zhejiang Province, China Jiliang University)
  • Received : 2012.12.17
  • Accepted : 2013.07.01
  • Published : 2013.09.30
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Abstract

The effect of Dy addition on the microstructure and magnetic properties of the sintered NdFeB magnets was investigated. The results of the microstructure analysis showed that Dy-free and Dy-doped samples are composed of $Nd_2Fe_{14}B$ (P42/mnm) and a trace of Nd-rich phase. Dy addition reduces significantly the pole density factor of (004), (006) and (008) crystal faces as estimated by the Horta formula. Accordingly, the coercivity of the Dy-doped sample increases from 2038 $kA{\cdot}m^{-1}$ up to 2288 $kA{\cdot}m^{-1}$. The $H_{cj}(T)/M_s(T)$ versus $H^{min}_N/M_s(T)$ (Kronm$\ddot{u}$ller-plot) behavior shows that the nucleation is the dominating mechanism for the magnetization reversal in these two kinds of magnets, and two microstructural parameters of ${\alpha}_k$ and $N_{eff}$ are obtained. The Kronm$\ddot{u}$ller-Plot gives evidence for an increase of the ${\alpha}_k$ responsible for an increase of the coercivity as the result of the increase of the magnetic field as the magnetic domain reversed.

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References

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