• 한국자기학회지
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• 제6권2호
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• pp.80-85
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• 1996

$Nd_{2}Fe_{14}B/Fe_{3}B$ 복합자성상을 근간으로 한 급냉제조된 합금을 외부 자장중에서 열처리를 함으로써 자기특성이 월등하게 좋아짐을 확인하였다. $Nd_{4}Fe_{73.5}Co_{3}(Hf_{1-x}-Ga_{x})B_{18.5}$ 조성 합금을 1~5 kOe 자장중에서 열처리함으로써 연자성의 기지상$(Fe_{3}B)$ 및 강자성상$(Nd_{2}Fe_{14}B)$의 결정입도가 20% 감소하였고, 그 결과 잔류자속밀도 $(B_{r})$ 및 최대자기에너지적, ${(B.H)}_{max}$가 30% 이상 증가하였다. 이러한 증가는 입도의 감소 뿐만 아니라 미세입도의 고른 분포에도 기인한 것으로 판단되었다. 보자력의 극대점은 잔류자속밀도와는 달리 특정결정입도에서 발생하며, 이러한 기구를 교환상호작용변수 와 연관하여 설명한다. $Nd_{4}Fe_{73.5}Co_{3}Hf_{0.5}Ga_{0.5}B_{18.5}$ 합금을 자장중 열처리한 결과 ${(B.H)}_{max}=15.8$ MGOe의 고에너지적을 얻을 수 있음을 확인하였다.

• 한국자기학회지
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• 제19권2호
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• pp.52-56
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• 2009

[CoFe/Cu/CoFe]/IrMn 다층박막에 대하여 자유층 CoFe 두께에 따른 상호교환결합력, 교환결합세기, 보자력, 자기저항비, 자장감 응도 등의 자기저항 특성을 관찰하였다. IrMn 층을 통해 유도된 강자성체/비자성체/강자성체 구조인 CoFe(t)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)/IrMn($80\;{\AA}$) 다층박막은 자유층 CoFe 두께 $30\;{\AA}$일 때 작은 보자력과 높은 자장감응도를 유지하는 연자성 특성을 보였다. 반면에 자유층 CoFe 두께 $90\;{\AA}$일 때 큰 보자력과 낮은 자장감응도를 보였다. 양호한 연자성 특성을 갖은 $2{\times}8{\mu}m^2$ 크기의 CoFe($30\;{\AA}$)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)]/IrMn($80\;{\AA}$) 스핀밸브 소자를 제작하였다. 길이방향의 센싱전류와 폭방향의 고정층의 용이축 방향을 택하여 2 단자법으로 측정한 소자의 연자성 자기저항 특성인 자기저항비와 자장감응도는 각각 3.0%와 0.3%/Oe 이었다.

• Journal of Magnetics
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• 제10권1호
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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.

• 한국자기학회지
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• 제4권2호
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• pp.179-183
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• 1994

자왜 또는 자기이방성의 측정에 사용되는 전자석의 여자전류를 측정에 필요한 수초간만 흘려서 에너지 소모 및 측정시의 최대난점인 시료의 온도변화의 문제를 극소화하였다. 따라서 전자석의 냉각장치는 생략되고 크기와 전원의 용량도 극소화되었다. 공기간격 22 mm, 자극의 단면적 $40{\times}25mm^{2}$에서 0.5 T의 자장발생에는 180 W의 전원으로 족하였다. 시료의 자왜와, 자기이방성에 의한 토크를 전기용량센서에 의하여 측정하여 $10^{-8}$의 자왜분해능과 1 nJ의 토크 분해능을 얻었다. $0.02{\times}0.8{\times}10mm^{2}$의 연자성 리본의 형상이방성을 이용하여 이방성 측정시의 토크값을 교정하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 전문대학교육위원
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• pp.150-154
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• 2005

This paper is presented for the development of the brushless DC(BLDC) spindle motors for hard disk drives. A new BLDC Motor has the use of insulated, compacted, iron powder for the armature core material of BLDC motors. Insulated iron powder in this paper is generally called soft magnet composite(SMC). The SMC is used for the stator of the motor instead of the laminated steel core. The motor used by SMC can have the good advantages in condition of the high frequency input power and small sized motor. It gets much more high efficiency than laminated steel core at same input power. The proposed motor has a technique of speed sensorless control. Experimental results show the performance of the proposed BLDC spindle motors for an HDD.

• Journal of Magnetics
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• 제14권1호
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• pp.42-46
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• 2009

The measurement of external magnetic field orientation using Giant Magneto Impedance (GMI) sensors has been performed. A soft magnetic alloy of $Co_{30}Fe_{34}Ni_{36}$ was electroplated on a Si wafer with a CoFeNi seed layer. V-shaped microwire patterns were formed using a conventional photolithography process. An external magnetic field was generated by a rectangular AlNiCo permanent magnet. The reference direction was defined as the external magnetic field direction oriented in the middle of 2 GMI devices. As the orientation of the magnetic field deviated from the reference direction, variation in the field component along each device introduced voltage changes. It was found that, by taking the voltage difference between the left and right arms of the Vshaped device, the nonlinearity of each device could be significantly reduced. The fabricated angle sensor had a linear range of approximately $70^{\circ}$ and an overall sensitivity of approximately 10 mV.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1029-1030
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• 2007

This paper describes the dynamic analysis method and the characteristics of rotating type transverse flux motors excited by permanent magnets; the machine is called TFRM in here. A prototype of TFRM, made by combing soft magnetic composite (SMC) core, is introduced first, then the magneto static and dynamic analysis methods are explained. Analysis results are compared with measured results, and finally the effects of the proposed dynamic analysis method and the characteristics of TFRM are discussed.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.267-268
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• 2002

Microbeam is a new avenue of radiation research especially in radiation biology and radiation protection. Selective irradiation of an ionizing particle to a targeted cell organelle may disclose such mechanisms as signal transaction among cell organelles and cell-to-cell communication in the processes toward an endpoint observed. Bystander effect, existence of which is clearly evidenced by application of the particle microbeam to biological experiments, suggests potential underestimation in the conventional risk estimation at low particle fluence rates, such as environment of space radiations in ISS (International Space Station). To promote these studies we started the construction of our microbeam facility (named as SPICE) to our HVEE Tandem accelerator (3.4 MeV proton and 5.1 MeV $^4$He$\^$2+/). For our primary goal, "irradiation of single particle to cell organelle within a position resolution of 2 micrometer in a reasonable irradiation time", special features are considered. Usage of a triplet Q magnet for focussing the beam to submicron of size is an outstanding feature compared to facilities of other institutes. Followings are other features: precise position control of cell dish holder, design of the cell dish, data acquisition of microscopic image of a cell organelle (cell nucleus) and data processing, a reliable particle detection, soft and hard wares to integrate all these related data, to control and irradiate exactly determined number of particles to a targeted spot.

• 한국자기학회지
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• 제21권6호
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• pp.225-230
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• 2011

자성 재료는 전기적 에너지와 기계적 에너지간 상호 전환 가능한 특성을 가지고 있기 때문에 발전 및 모터 분야 등에 널리 적용되고 있다. 그 중에서도 모터 분야의 효율성 향상을 위해서 외부의 자장 없이도 지속적으로 자성 특성을 나타내는 영구 자석은 그 활용도가 매우 높다. 특히, 영구 자석은 최대 자기적이 높은 희토류 자석이 개발된 후 이를 중심으로 개발 및 응용분야가 지속적으로 확대되었다. 그러나, 최근 모터의 용도가 확대되는 추이에 따라서 회토류 자석의 사용이 증대됨에 따라서 희토류 원자재 수급 문제에 봉착하여 이를 해결하기 위해 희토류 저감 및 대체 자석에 대한 연구 분야가 중요한 이슈가 되고 있다. 본 보고서에서는 현재 사용 되고 있는 영구 자석에 대해 설명하고 이를 대체할 수 있는 기술 중 가능성이 높은 방법으로써 exchange-coupling 현상을 이용한 영구 자석 개발 기술에 대해 기술하고자 한다.

• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1703-1707
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• 2018

Ferromagnetic ${\tau}-phase$ $Mn_{54}Al_{46}C_{2.44}$ particles were synthesized, and its composites with commercial $Sm_2Fe_{17}N_3$ and synthesized $Fe_{65}Co_{35}$ powders were fabricated. Smaller grain size than the single domain size of the $Mn_{54}Al_{46}C_{2.44}$ without obvious grain boundaries and secondary phases is the origin for the low intrinsic coercivity. It was confirmed that the magnetic properties of the $Mn_{54}Al_{46}C_{2.44}$ can be enhanced by magnetic exchange coupling with the hard magnetic $Sm_2Fe_{17}N_3$ and soft magnetic $Fe_{65}Co_{35}$. The high degrees of the exchange coupling were verified by calculating first derivative curves. Thermo-magnetic stabilities of the composites from 100 to 400 K were measured and compared. It was demonstrated that the $Mn_{54}Al_{46}C_{2.44}$ based composites containing $Sm_2Fe_{17}N_3$ and $Fe_{65}Co_{35}$ could be promising candidates for future permanent magnetic materials with the proper control of purity, magnetic properties, etc.