• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.253-254
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• 2006

초미세립 복합상 영구자석은 연 경자성상의 크기와 분포에 큰 영향을 받는 자성재료이다. 또한, 결정립간 교환상호작용력은 초미세립 복합상 영구자석의 잔류자속밀도에 큰 영향을 미친다. 이에 $Nd_8Fe_{86-x}Nb_xB_6$(x=0, 1, 2, 3) 조성으로 급냉자성 분말을 제조하고, 열처리 후 자기특성을 평가하였다. Nb 첨가에 따른 $Nd_2Fe_{14}B$ 상과 $\alpha$-Fe 상과의 교환상호작용력을 Henkel(${\delta}M$) plot을 통해 평가하고, 각 상의 크기와 분포를 조사하여 자기특성 변화를 합리화하였다. 본 연구에서 얻은 최대 자기특성은 $B_r$ = 9.791 kG, $_iH_c$ = 5.565 kOe, 그리고 $(BH)_{max}$ = 14.61 MGOe였고, Nb를 첨가함으로서 보자력이 증가하였다.

• Journal of Magnetics
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• v.9 no.2
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• pp.27-33
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• 2004

Magnetic properties of $Nd_4Fe_{77.5}B_{18.5}$ compound in term of exchange coupling between $Nd_2Fe_{14}B$ and $Fe_3B$ magnetic nano crystals in melt spun powders were characterized by varying the quenching speed in mass production line. The exchange coupled phenomenon was characterized as functions of nano crystal size and volume fraction of each magnetic phase which was possible by employing Henkel plot (${\delta}M$) and refined Mossbauer spectroscopy. The optimized magnetic properties obtained from the present volume production line were: $B_r= 11.73 kG,{_i}H_c/ = 3.082 kOe$, and $(BH)_{max} = 12.28 MGOe.$ The volume fraction of each magnetic phase for those conditions giving the grain size of 10 nm were ${\alpha}-Fe; 4.2%, Fe_3B; 60.1 %$, and $Nd_2Fe_{14}B; 35.7%$. The superior magnetic properties in the $Nd_2Fe_{14}Fe_3B$ based nanocomposites were confirmed to be dependant on the volume fraction of $Fe_3B$.

• Journal of Magnetics
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• v.10 no.1
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• pp.14-22
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• 2005

Precisely refined Mossbauer study and nano structure observation revealed that intergranular phase formed between a-Fe and Nd₂Fe₁₄B phase in NdFeNbB alloys plays a significant role on the magnetic properties. The intergranular interaction was characterized in term of Henkel Plot (δM plot), and hyperfine field, quardrupole splitting and isomer shift were refined to predict the presence and role of the intergranular phase. By the addition of Nb into Nd₈Fe₈₆B₆ composition, coercivity was found to increase by 25% due to the refinement of average grain size of both the soft and hard magnetic phases which was decreased from 50 nm of virgin Nd/sub 8/Fe/sub 86/B/sub 6/ to 25 nm in Nd₈Fe ₈₅Nb₁B₆ alloys. The role of Nb addition was confirmed to stabilize the Nd₂Fe₁₄B lattice preventing from thermal vibration of the corresponding sites substituted Fe by Nb atoms in all sites in the Nd₂Fe₁₄B lattice. The enhanced coercivity was originated from the exchange hardening of soft and amorphous phases surrounding the hard magnetic Nd₂Fe₁₄B crystal.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.23-29
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• 2017

In this study, the influences of magnetization reversal and magnetic interaction on the coercivity of Sr-ferrite particles with different sizes were investigated through various magnetic measurements. The shape of the initial magnetization curve and the magnetic field dependence of the coercive force indicate that the magnetization reversal changes from domain nucleation to wall pinning as the particle size decreases. On the other hand, the Henkel plot, interaction field factor and ${\Delta}M(H)$ obtained from the DCD and IRM curves show that the strength of the dipolar interaction is increased with increasing the particle size. Therefore, it can be concluded that coercivity is closely related to magnetic interaction as well as magnetization reversal mechanism.