• 열처리공학회지
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• 제14권2호
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• pp.81-88
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• 2001

The effects of post-oxidation and sulfnitriding treatments on the phase transformation in the nitrided case of tool steels have been studied. Dense and compact $Fe_3O_4$ layer was formed at the outer surface of nitride compound layer by post-oxidation treatment and multi layer of iron sulfide(FeS) was formed in the compound layer by sulfnitriding treatment. The surface hardness decreased because of formation of the soft oxide or sulfide at the nitride surface. Diffusion layer of nitride case was not affected by post-oxidation treatment or sulfnitriding treatment of nitrided alloy tool steels.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.81-81
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• 2003

• 한국자기학회지
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• 제17권3호
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• pp.124-127
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• 2007

비정질 $Co_{70.5}Fe_{4.5}Si_{15}B_{10}$층을 갖는 자기터널접합(magnetic tunneling junctions; MTJ)를 연구하였다. 비정질 자유층이 MTJ의 스위칭 특성에 미치는 영향을 중점적으로 이해하기 위하여 기존의 사용된 CoFe 그리고 NiFe층들을 대신하여 비정질 강자성체 CoFeSiB을 사용하였다. CoFeSiB은 CoFe과 NiFe보다 각각 낮은 포화자기장($M_s:\;560\;emu/cm^3$)과 높은 자기이방성 상수($K_u:\;0.2800\;erg/cm^3$)를 갖는다. CoFeSiB층들의 사이에 1.0 nm Ru층 삽입시 $-0.003\;erg/cm^3$ 교환결합에너지($J_{ex}$)를 나타내었다. $Si-SiO_2-Ta$ 45/Ru 9.5/IrMn 10/CoFe 7/$AlO_x$/CoFeSiB 7 또는 CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60(in nm) MTJ 구조의 터널접합에 대하여 실험 및 시뮬레이션 결과를 통하여 낮은 $J_{ex}$에 기인하는 스위칭 자기장(switching field; $H_{sw}$)의 시료 크기 의존성이 나타나는 것을 알 수 있었다. CoFeSiB 합성형 반강자성 구조는 micrometer뿐만 아니라 submicrometer 시료 크기영역에서도 보자력($H_c$)의 감소와 민감도를 증가 시킴으로써 자기 스위칭 특성에 유리한 것으로 확인 되었다.

• Journal of Magnetics
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• 제2권1호
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• pp.7-11
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• 1997

The dependence of magnetoresistance (MR) ratio on various variables like the thickness of the second Co layer, on the presence of cap layer, on deposition field (Hdep) and on annealing in Co/Cu/Co sandwiches was investigated. Spin-valve sandwiches were deposited on the corning glass by means of the 3-gun dcmagnetron sputtering at a 5 mTorr partial Ar pressure and room temperature. The deposition field was varied from 70 Oe to 720 Oe. The MR curve was measured by the four-terminal method with applied magnetic field up to 1000 Oe perpendicular to the direction of a current in the film plne. The MR ratio of glass/Fe(50${\AA}$)/Co(17${\AA}$)/Cu(24${\AA}$)/Cot(${\AA}$) fabricated by making 50 ${\AA}$ of Fe buffer layer has the maximum value of 8.2% when the thickness of the second Co layer was 17${\AA}$and the deposition field was 350 Oe. In the case of glass/Fe(50${\AA}$)/Co(17${\AA}$)/Cu(24${\AA}$)/Cot(${\AA}$) with Cu cap layer on top, the decrease in the MR ratio seemed to relate with the oxidation of the second Co layer. Samples prepared with deposition field showed greater MR ratios through the formation of more complete spin valve films. After annealing for 2 hours at 300$^{\circ}C$, the MR ratio of the samples prepared with deposition field decreased rapidly while the MR raito of the sample prepared without the field remained.

• 한국초전도ㆍ저온공학회논문지
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• 제23권2호
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• pp.14-18
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• 2021

We investigated the structural suitability of GdFeO₃ (GdFO) as a buffer layer for the GdBa₂xCu₃O_7-x (GdBCO) superconducting films. GdFO films with different thicknesses and GdBCO thin films were all prepared by using a pulsed laser deposition technique. The analyses of X-ray diffraction and EXAFS data indicates that the c-axis parameter increases and the Fe-O bond length decreases with the GdFO thickness due to the compressive stain induced by the lattice mismatch between GdFO and STO substrate and as a result, the Debye-Waller factor, an index of disorder in the local structure near the Fe-O bond, increases with the GdFO thickness. However, for the GdBCO/GdFO bilayer structure, the Debye-Waller factor decreases as the GdFO thickness increases indicating a diminished disorder by the structural coupling between GdFO and GdBCO. These results indicate that an appropriate thickness of GdFO is required to be utilized as a magnetic buffer layer for the GdBCO superconducting films.

• 열처리공학회지
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• 제14권2호
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• pp.103-109
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• 2001

Plasma nitrocarburising and post oxidation were performed on SM45C steel using a plasma nitriding unit. Nitrocarburising was carried out with various methane gas compositions with 4 torr gas pressure at $570^{\circ}C$ for 3 hours and post oxidation was carried out with 100% oxygen gas atmosphere with 4 torr at different temperatures for various times. It was found that the compound layer produced by plasma nitrocarburising consisted of predominantly ${\varepsilon}-Fe_{2-3}(N,C)$ and a small proportion of ${\gamma}-Fe_4(N,C)$. With increasing methane content in the gas mixture, ${\varepsilon}$ phase compound layer was favoured. In addition, when the methane content was further increased, cementite was observed in the compound layer. The very thin oxide layer on top of the compound layer was obtained by post oxidation. The formation of Oxide phase was initially started from the magnetite($Fe_3O_4$) and with increasing oxidation time, the oxide phase was increased. With increasing oxidation temperature, oxide phase was increased. However the oxide layer was split from the compound layer at high temperature. Corrosion resistance was slightly influenced by oxidation times and temperatures.

• Journal of Magnetics
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• 제5권2호
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• pp.50-54
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• 2000

NiMn-pinned spin valve films consisting of a layered glass/NiFe/Co/Cu/Co/NiFe/NiMn/Ta stack were made by do magnetron sputtering. After deposition, the structure was annealed in a series of cycles each including three hours at $220^\circ C, 2\times10^{-6}$ Torr, in a field of 350 Oe, to create an ordered antiferromagnetic structure in the NiMn layer and produce a strong unidirectional pinning field in the pinned magnetic layer, Optimum spin valve properties were obtained after seven annealing cycles, or 21 hours at $220^\circ C$, and were : MR ratio 1%, exchange coupling field 620 Oe, and coercivity of pinned layer 250 Oe. The exchange coupling field remained constant up to an operating temperature of $175^\circ C$, and the blocking temperature was about $380^\circ C$.

• 열처리공학회지
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• 제1권1호
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• pp.8-12
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• 1988

This study has been carried out to evaluate gaseous nitrocarburizing treatment undertaken for pure iron at $570^{\circ}C$ in an atmosphere containing 50% endothermic gas, generated from natural gas, and 50% ammonia. The results obtained from the experiment are as follows ; 1) The microstructure of gaseous nitrocarburized pure iron consists of the compound layer on the surface and the diffusion zone beneath it. The compound layer progresses uniformly into ferrite with a thickness of $20{\mu}$ obtained after treating for 3 hours. 2) Chemical analysis has shown that the compound layer has a C/N ratio of 0.19 and that the average combined interstitial content of the compound layer is about 30 atomic percent, which is close to the lower limit of the ${\varepsilon}$-carbonitride phase field in Fe-C-N phase diagram. 3) X-ray diffraction analysis has revealed that the compound layer consists mainly of the c.p.h. phase, ${\varepsilon}-Fe_3$(C.N) and a small amount of $Fe_4N$ and traces of ferrite are also present in the compound layer. 4) The microhardness of the compound layer is about 600 V.H.N and shows a relatively sharp fall-off at the compound layer/diffusion zome interface. 5) The average actual degree of ammonia dissociation is calculated to be 27% for a gaseous nitrocarburizing treatment carried out at $570^{\circ}C$.

• 열처리공학회지
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• 제13권4호
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• pp.217-223
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• 2000

The boronizing effects of STD 61 steel have been studied on the micro structure and hardness. The STD 61 Steel was soaked in molten salt, consisted of KCl, $BaCl_2$, NaF, $B_2O_3$, FeB, and Ce, at various temperatures and times. The boronizing conditions for the peak hardness were the temperature range of $900^{\circ}C$ to $950^{\circ}C$ for 5 hr and that of $1000^{\circ}C$ for 3 hr, respectively. Four boride layers such as FeB, $Fe_2B$, ${\alpha}$ and matrix layer surface were observed from the microscopic surface examination. The thickness of boride layer was increased by increasing the boronizing time and the temperature. The structure of boride layer was tooth shape.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권3호
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• pp.141-157
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• 2001

Highly reliable packaged 64kbit ferroelectric memories with $0.8{\;}\mu\textrm{m}$ CMOS ensuring ten-year retention and imprint at 125^{\circ}C$ have been successfully developed. These superior reliabilities have resulted from steady integration schemes free from the degradation, due to layer stress and attacks of process impurities. The resent results of research and development for ferroelectric memories at Hynix Semiconductor Inc. are summarized in this invited paper.