• Applied Microscopy
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• 제45권1호
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• pp.9-15
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• 2015

In the present study, microstructural evolution in CuCrFeNi, CuCrFeNiMn, and CuCrFeNiMnAl alloys has been investigated. The as-cast CuCrFeNi alloy consists of a single fcc phase with the lattice parameter of 0.358 nm, while the as-cast CuCrFeNiMn alloy consists of (bcc+fcc1+fcc2) phases with lattice parameters of 0.287 nm, 0.366 nm, and 0.361 nm. The heat treatment of the cast CuCrFeNiMn alloy results in the different type of microstructure depending on the heat treatment temperature. At $900^{\circ}C$ a new thermodynamically stable phase appears instead of the bcc solid solution phase, while at $1,000^{\circ}C$, the heat treated microstructure is almost same as that in the as-cast state. The addition of Al in CuCrFeNiMn alloy changes the constituent phases from (fcc1+fcc2+bcc) to (bcc1+bcc2).

• 한국자기학회지
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• 제19권5호
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• pp.165-170
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• 2009

준안정 상태인 덩치 fcc Fe는 반강자성 상태가 기저 상태인 것으로 알려져 있고 적절한 fcc 금속 표면 위에 fcc Fe를 성장시킬 수 있음이 보고된 바 있다. 본 연구에서는 fcc 금속 (001) 표면 위의 Fe 원자층의 자성을 연구하기 위해 Cu(001), Rh(001), Pd(001), Ag(001) 표면 위의 Fe 단층의 자성을 제일원리계산 방법 중 자성 연구에 가장 적합한 총퍼텐셜선형보강평면파(fullpotential linearized augmented plane wave; FLAPW) 방법을 사용하여 연구하였다. 고려한 계 중에서 2차원 격자상수가 가장 작은 Cu(001) 표면과 가장 큰 Ag(001) 표면 위의 Fe 단층은 강자성이 비교적 큰 에너지 차이로 Fe-fcc 금속 층간 거리에 관계없이 안정적이었고, 중간 크기의 2차원 격자상수를 가진 Rh(001)과 Pd(001) 표면 위의 Fe 단층은 반강자성 상태가 안정적이었으나, 층간 거리가 커짐에 따라 강자성 상태가 안정적일 수도 있는 것으로 계산되었다. 계산된 자기모멘트는 1Fe/Cu(001), 1Fe/Rh(001), 1Fe/Pd(001), 1Fe/Ag(001)의 강자성 상태에서 2.811, 2.945, 2.987, 2.990 $_{{\mu}B}$이었고, 반강자성 상태에서는 2.624, 2.879, 2.922, 3.001 $_{{\mu}B}$이었다.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.308-311
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• 2015

https://nano.edison.re.kr/에서 제공하는 Linear Combination of Atomic Orbitals 기반 Density Functional Theory 전자구조계산 SW을 이용하여 정렬된 FCC 결정구조의 PtFe와 원자의 배열이 무질서한 PtFe의 산소 발생 반응의 과전압을 알아보았다. 화학 반응에 참여하는 정렬된 FCC PtFe의 표면 방위는 표면 에너지 계산을 통해 (111) 면으로 설정하였다. 과전압 값은 산소 발생 반응의 각 단계의 자유 에너지 변화를 계산하여 양의 반응 에너지이다. 과전압 측정 결과 정렬된 FCC 결정구조의 PtFe와 원자의 배열이 무질서한 PtFe의 과전압은 각 각 0.623875eV, 0.603118eV 이다.

• 한국자기학회지
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• 제26권4호
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• pp.129-132
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• 2016

열분해법으로 합성한 FePt 나노입자를 $NH_3+H_2$ 혼합가스 질화법으로 상변태와 동시에 질화시킨 FePtN 나노입자의 특성을 분석하였다. 초기 합성된 FePt 나노입자는 fcc 구조를 가졌으며, 보자력과 포화자화는 각각 247.34 Oe와 27.308 emu/g를 나타내었다. 혼합가스 질화법으로 열처리한 입자는 XRD 분석 결과 fcc 구조에서 fct 구조로 상변태가 진행되었으며, 열처리 온도의 증가에 따라 (111) 피크의 $2{\theta}$가 shift되는 특성을 나타내었다. fct 구조의 FePtN의 보자력과 포화자화는 각각 1058.2 Oe and 32.718 emu/g를 나타내었으며, 합성된 FePtN 나노자성입자는 고밀도 자기기록매체와 생체의료 분야에서의 응용이 기대 된다.

• 한국분말재료학회지
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• 제11권3호
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• pp.242-246
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• 2004

FePt nanoparticles for high-density magnetic recording media were synthesized by the simultaneous chemical reduction of Fe(acac) $_2$ and Pt(acac) $_2$ with 1,2-hexadecanediol as the reducing reagent. TEM images showed that the shape of as-synthesized FePt nanoparticle was spherical and average particle size was 3 nm. Also, SAD pattern showed that crystal structure was disordered FCC (face centered cubic). These FCC structured nanoparticles were transformed FCT (face centered tetragonal) structure by annealing at 55$0^{\circ}C$ for 30 min in Ar atmosphere. XRD analysis revealed that as-synthesized FePt nanoparticles were transformed from disordered FCC to ordered FCT. Finally, the coercivity of 2 kOe for FePt nanoparticles with FCT structure was obtained by VSM measurement.

• 한국표면공학회지
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• 제29권3호
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• pp.195-202
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• 1996

The composition, the microstructure and the magnetic properties(HC and Hk) of Fe-Co-Ni alloy electrodeposits were investigated according to the electrolysis conditions using sulfate bath paddle agitated. The current efficiency of the alloys electrodeposition was considerably low in the range of 16∼50%. The Fe content(wt.%) of the alloy increased from 20% to 57% with current density, while Ni content of them decreased in the range of 70∼24% respectively, and Co content was nearly constant. As a result, Fe/Ni ratio of the alloy increased from 0.3 to 2.0 showing the anomalous codeposition. The structure of the alloy changed from fcc to the mixed one of fcc+bcc with the increase of Fe/Ni ratio. The preferred orientation of the alloy with fcc and bcc structure were (220) and (110) respectively. The alloy with Fe/Ni ratio(0.3∼l.2) had the lowest coercivity of 0.4∼0.8 Oe.

• Journal of Korean Vacuum Science & Technology
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• 제5권2호
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• pp.43-46
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• 2001

Fe-Au alloys are characterized by the complete solubility, and exhibit an fcc-bcc structural transformation at the Fe-rich side. The magneto-optical(equatorial Ken effect : EKE) and optical properties of Fe$\_$1-x/Aux (0 < x < 1) were investigated in the 0.5 - 5.0 eV energy range. The x-ray diffraction study shows the structural fcc-bcc transformation about 80 at. % of Fe. Noticeable changes in the optical properties caused by the fcc-bcc structural transformation was observed. The shape and intensity of the EKE spectra as well as the field dependence of the magneto-optical response were also significantly changed. It is thought that these changes are mainly comes from the induced magnetic moment in Au(and/or the emhanced magnetic moment of Fe). The nature of the prominent structure observed in the UV range of the magneto-optical Ken effect of Au/Fe multilayered films are disscussed in connection with the above results.

• 한국재료학회지
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• 제16권2호
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• pp.137-143
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• 2006

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

• Journal of Magnetics
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• 제13권4호
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• pp.144-148
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• 2008

The size and surface effects on the magnetism of a fcc Fe (001) surface was investigated by performing firstprinciples calculations on 3, 5, 7, and 9 monolayers fcc Fe (001) single slabs with two different two-dimensional lattice constants, ${\alpha}=3.44{\AA}$ (System I) and 3.65 ${\AA}$ (System II), using the all-electron full-potential linearized augmented plane wave method within a generalized gradient approximation. The surface layers were coupled ferromagnetically to the subsurface layer in both systems. However, the magnetism of the inner layers was quite different from each other. While all the inner layers of System II were ferromagnetically coupled in the same way as the surface layer, the inner layers of System I showed a peculiar magnetism, bilayer antiferromagnetism. The calculated spin magnetic moments per Fe atom were approximately 2.7 and 2.9 ${\mu}_B$ at the surface for Systems I and II, respectively, due to the almost occupied Fe d-state being in the majority spin state and band narrowing. The spin orientations of System I were out-of-plane regardless of its thickness, whereas the orientation of System II changed from out-of-plane to in-plane with increasing thickness.

• 한국자기학회지
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• 제12권4호
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• pp.132-136
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• 2002

유리기관 위에 이온 빔 증착(ion beam deposition ; IBD)법으로 제작한 버퍼층(buffer layer) Si의 두께에 따른 ［NiFe/FeMn/NiFe］3층박막의 결정성과 교환결합세기(exchange bias field ; H$_{ex}$)를 조사하였다. 버퍼층 Si는 NiFe층을 fcc(111)로 매우 우세하게 초기에 결정성장 시켰다. Si/NiFe 위의 증착된 FeMn층은 ${\gamma}$-fcc(111)구조로 성장함에 따라 안정되고 큰 H$_{ex}$를 가졌고, 버퍼 110 Oe로 거의 일정하였으며, 상부 FeMn/NiFe 이중구조의 H$_{ex}$는 300 Oe까지 증가하였다. 버퍼층이 Ta일 경우와 비교해서 Si일 때 H$_{ex}$와 결정성이 향상되었다.이 향상되었다.