• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.788-789
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• 2006

Microstructure and soft magnetic properties of bulk amorphous and/or nanocrystalline $Fe_{73.5}Cu_1Nb_3Si_{13.5}B_9$ alloys prepared by consolidation at 5.5GPa were investigated. The relative density of the bulk sample 1 (from amorphous powders) was 98.5% and the grain sizes were about 10.6nm. While the relative density and grain sizes of bulk sample 2 (from nanocrystalline powders) are 98% and 20.1nm, respectively. Particularly, the bulk samples exhibited a good combined magnetic property: for Sample1, $M_s=125emu/g$ and $H_c=1.5Oe;$ for Sample2, $M_s=129emu/g$ and $H_c=3.3Oe$. The success of synthesizing the nanocrystalline Fe-based bulk alloys will be encouraging for the future development of bulk nanocrystalline soft magnetic alloys.

• Journal of Magnetics
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• 제5권3호
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• pp.102-105
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• 2000

The extremely soft magnetic behaviors in the nanocrystalline $Fe_81B_11Nb_7Cu_1$ alloy annealed at 450 $\circ C$ and 550 $\circ C$ for 1 hour in a vacuum were investigated by means of the magnetoimpedance (MI) effect and the incremental permeability. Because the MI effect can be obtained only in ultra-soft magnetic materials, the improvement of magnetic softness by proper thermal treatment was carefully monitored by the MI effect for all annealed samples. The changes of the incremental permeability as a function of an external field were also measured to verify the magnetic softness along with the MI measurement.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.466-472
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• 2000

The extremely soft magnetic behaviors in the nanocrystalline Fe$_{81}$B$_{11}$Nb$_{7}$Cu$_{1}$ alloy annealed at 450 $^{\circ}C$ and 550 $^{\circ}C$ for 1 hour respectively in a vacuum were obtained, and examined by means of the magnetoimpedance(MI) effect and the incremental permeability. Because the MI effect can be obtained only in ultra-soft magnetic materials, the improvement of magnetic softness by proper thermal treatment was carefully monitored by the MI effect for all annealed samples. The changes of the incremental permeability as a function of an external field were also measured to verify the magnetic softness along with the MI measurement.ent.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.786-787
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• 2006

The magnetic inductance of nanocrystalline $Fe_{73}Si_{16}B_7Nb_3Cu_1$ and an amorphous FeSiB powder sheet has been investigated to identify RFID performance. The powder was mixed with binder and solvent and tape-casted to form films. Results show annealing significantly influenced on the inductance of the material. The surface oxidation of the particles was the main reason for the reduced inductance. The maximum inductance of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ alloy was about $88{\mu}H$ at 17.4 MHz, about 65% greater compared to the FeSiB alloy. The higher inductance in the nanocrystalline alloy indicates it may be used as a potential replacement of current RFID materials.

• 한국자기학회지
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• 제14권2호
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• pp.59-64
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• 2004

나노 결정립 구조를 갖는 Fe-Al-O 연자성 산화막을 이온빔 에칭법으로 에칭하면서 연자기적 특성의 변화를 조사하였다. 두께가 감소할수록 보자력과 각형비가 증가하고 AFM 으로 조사한 표면굴곡도 증가하는 것으로 보아 결정립의 크기가 증가하는 것으로 판단된다. 이러한 현상은 비정질을 열처리한 나노결정립 연자성 재료와 다르게 성막하는 과정의 온도 상승에 의한 결정성장이 원인으로 판단된다. 따라서 우수한 연자성 박막을 제조하기 위해서는 두께 및 성막시간 등 최적 제조조건을 찾아야 한다. 마그네트론 스퍼터링법으로 제조된 Fe-Al-O 산화막의 경우 900 nm 이상에서 보자력이 1 Oe 이하인 연자성 박막을 얻을 수 있었다.

• Journal of Magnetics
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• 제7권1호
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• pp.21-23
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• 2002

The magnetoimpedance of $Fe_{91.5-x}Zr_7B_xCu_1Al_{0.5}$alloys has been measured to investigate the influence of structural changes in the nanocrystallization process after thermal treatment. Annealing was performed at temperatures of $350^\circ{C}$, $450^\circ{C}$, and $550^\circ{C}$ for 1 hour in a vacuum. Ultra soft magnetic behavior was observed in the samples annealed at $550^\circ{C}$. The magnetoimpedance ratio and the longitudinal permeability ratio coincided with the softness of the magnetic properties of the thermally treated samples.

• 한국자기학회지
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• 제5권5호
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• pp.601-605
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• 1995

Magnetic properties of FeTaN and FeTaC films deposited by DC magnetron reactive sputter were investigated, and correlated with their microstructures. The optimum magnetic properties of Hc : 0.25 Oe, Bs : 14.5 kG, and ${\mu}'$ : 4000 (5MHz) are observed in the $Fe_{78.8}Ta_{8.5}N_{12.7}$ film, and Hc : 0.25 Oe, Bs : 14.5 kG, and ${\mu}'$ : 2700 (5MHz) in the $Fe_{75.6}Ta_{8.1}C_{16.3}$ film. In both FeTaN and FeTaC films with minimum grain size show the best soft magnetic properties. Thermal stability of the soft magnetic properties of FeTaN is found to be higher than FeTaC for similar compositons. TaN and TaC particles form to retard the growth of $\alpha$-Fe grains. TaN particles in FeTaN show higher efficiency in retarding the grain growth during heat treatments resulting the higher thermal stability, compared to TaC particles in FeTaC films.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.473-479
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• 2000

The nanocrystalline Fe$_{84}$Zr$_{7}$B$_{6}$Cu$_{1}$ $Al_{2}$ alloy was annealed at 450 $^{\circ}C$ and 550 $^{\circ}C$ for l hour to achieve the ultra-soft magnetic properties such as large magnetoimpedence ratio(MIR), the incremental permeability ratio(PR), nearly zero coercivity, zero magnetostriction, etc. The PR and MIR of the sample were measured from 100 kHz to 10 MHz at a cryogenic chamber where the temperature can be varie from 10 K to 300 K. The increment of MIR value is proportional to increasing temperature. The maximum PR values measured at high frequency above 1 MHz remain almost same despite of the temperature variation from 10 K to 300 K except the sharpness in PR curves. However, the maximum PR values measured below 1 MHz show drastic increment at above 150K due to thermal activation of magnetic domains.s.s.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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• pp.3-6
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• 2002

Effect of Ag additive element on microstructure of $Fe_{87-x}Zr_7B_6Ag_x$, magnetic thin films on Si(001) substrates has been investigated using Transmission Electron Microscopy(TEM) and X-ray Diffraction(XRD). All samples with additive Ag element were made by DC-sputtering and subjected to annealing treatments of $300^{\circ}C{\siim}600^{\circ}C$ for 1 hr. TEM and XRD showed that perfectly amorphous state in Ag-free Fe-based films was observed in as-deposited condition. The as-deposited Fe-based films with the presence of Ag constituent have a mixture of Fe-based amorphous and nano-sized Ag crystalline phases. In this case, additive element, Ag was soluted into Fe-based matrix. With the increase in additive element, Ag, insoluble nano-crystalline Ag particles were dispersed in the Fe-based amorphous matrix. Crystallization of Fe-based amorphous phase in the matrix of $Fe_{82}Zr_7B_6Ag_5$ thin films occurred at an annealing temperature of $400^{\circ}C$. Upon annealing, the amorphous-Ag crystalline state of Fe-Zr-B-Ag films was transformed into the mixture of Ag crystalline phase + Fe-based amorphous phase + ${\alpha}$-Fe cluster followed by the crystallization process of ${\alpha}$-Fe nanocrystalline + Ag crystalline phases.

• 한국분말재료학회지
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• 제16권1호
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• pp.33-36
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• 2009

In order to increase the magnetic loss for electromagnetic(EM) wave absorption, the soft magnetic $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was used as the basic material in this study. The melt-spun strip was pulverized using an attrition mill, and the pulverized flake-shaped powder was crystallized at $540^{\circ}C$ for 1h to obtain the optimum grain size. The Fe-based powder was mixed with 2 wt% $BaTiO_3$, $0.3{\sim}0.6$ wt% carbon black, and polymer-based binders for the improvement of electromagnetic wave absorption properties. The mixture powders were tape-cast and dried to form the absorption sheets. After drying at $100^{\circ}C$ for 1h, the sheets of 0.5 mm in thickness were made by rolling at $60^{\circ}C$, and cut into toroidal shape to measure the absorption properties of samples. The characteristics including permittivity, permeability and power loss were measured using a Network Analyzer(N5230A). Consequently, the properties of electromagnetic wave absorber were improved with the addition of both $BaTiO_3$ and carbon black powder, which was caused by the increased dielectric loss of the additive powders.