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

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
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• pp.147-149
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• 2011

• 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.

• 한국전기전자재료학회논문지
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• 제27권7호
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• pp.462-467
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• 2014

In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about $1{\mu}m$ and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6~4 while those values at above 500 MHz were decreased 0.4~2.5 according to the change of contents of FeSiCr and Fe50Ni powders. As a result, the reflection loss can be moved to the lower frequency from 2~3 GHz to 1~1.5 GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.

• 한국표면공학회지
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• 제51권6호
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• pp.354-359
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• 2018

NaCl-induced hot corrosion behavior of ASTM T22 (Fe-2.25Cr-1Mo), T91 (Fe-9Cr-1Mo), T92 (Fe-9Cr-1.8W-0.5Mo), 347HFG (Fe-18-Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels was studied after spraying NaCl on the surface. During corrosion at $600-800^{\circ}C$ for 50-100 h, thick, non-adherent, fragile, somewhat porous oxide scales formed. All the alloys corroded fast with large weight gains owing to fast scaling and destruction of protective oxide scales. Corrosion rates increased progressively as the corrosion temperature and time increased. Corrosion resistance increased in the order of T22, T91, T92, 347HFG, and 310H, suggesting that the alloying elements of Cr, Ni, and W beneficially improved the corrosion resistance of steels. Basically, Fe oxidized to $Fe_2O_3$, and Cr oxidized to $Cr_2O_3$, some of which further reacted with FeO to form $FeCr_2O_4$ or with NiO to form $NiCr_2O_4$.

• 한국자기학회지
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• 제23권5호
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• pp.149-153
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• 2013

이 연구에서는 방사광 연 X선 광흡수 분광법(soft x-ray absorption spectroscopy: XAS)을 이용하여 $TCr_2O_4$(T = Fe, Co, Ni) 스피넬 산화물들의 전자 구조를 연구하였다. 전이금속 이온들의 2p 준위의 흡수에 의한 XAS 측정으로부터 T(T = Fe, Co, Ni) 이온들의 원자가는 공통적으로 2가($T^{2+}$)이며, Cr 이온의 원자가는 3가 ($Cr^{3+}$) 임을 발견하였다. 그리고 T 이온들은 정사면체 대칭성을 가진 A 사이트에 주로 위치하고, Cr 이온은 정팔면체 대칭성을 가진 B 사이트에 주로 위치함을 알 수 있었는데, 이러한 발견을 통하여 $TCr_2O_4$는 정상 스피넬에 가까운 구조를 가지고 있다고 결론지을 수 있다. 또한 $FeCr_2O_4$와 $NiCr_2O_4$에서는 얀-텔러 변형이 중요한 역할을 하지만, $CoCr_2O_4$는 얀-텔러 변형이 없는 입방체 구조를 유지하는 원인을 알 수 있었다. 그러므로 $TCr_2O_4$에서 $Cr^{3+}$ 상태의 이온들과 $T^{2+}$ 상태의 이온들 간의 반강자성 결합이 이 산화물들의 자성 특성을 결정하는데 중요한 역할을 한다고 생각된다.

• 한국자기학회지
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• 제17권4호
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• pp.156-161
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• 2007

어레이(away) 자성센서 개발을 위해 고진공 스퍼터링 증착장비를 이용하여 스펙큘러형(specular type) Glass/Ta(5)/NiFe(7)/IrMn(10)/NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) 거대자기저항-스핀밸브(giant magnetoresistive-spin valves; CMR-SV)박막을 제작하였다. 다층박막 시료를 $20{\times}80{\mu}m^2$의 미세 활성영역을 가진 15개 어레이를 $8{\times}8mm^2$ 영역 내에 최적화한 제작 조건으로 광 리소그래피 패터닝 하였다. Cu를 증착하여 만든 2단자 전극법으로 측정한 자성특성은 15개 모든 소자들이 균일한 자기저항특성을 나타내었고, 5 Oe 근방에서 가장 민감한 자기저항비 자장민감도와 출력전압들은 각각 0.5%/Oe, ${\triangle}$V: 3.9 mV이었다. 형상자기이방성이 적용된 상부 자유층 $CoFe/O_2/NiFe$층은 하부 고정 자성층 $IrMn/NiFe/O_2/CoFe$층 자화 용이축과 직교하였다. 측정시 인가전류 값을 각각 1 mA에서 10 mA까지 인가하였을 때 출력 작동 전압 값은 균일하게 증가하였으며, 자장감응도도 거의 일정하여 미세 외부자장에 민감한 나노자성소자로서 좋은 특성을 띠었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.250-250
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• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.

• Journal of Magnetics
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• 제17권4호
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• pp.245-250
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• 2012

Ferromagnetic resonance and X-ray specular reflectivity measurements were performed on $Ni_{81}Fe_{19}/Ir_{20}Mn_{80}/Co_{90}Fe_{10}$ exchange bias trilayers, which were grown using the pulsed-DC magnetron sputtering technique on Si(100)/$SiO_2$(1000 nm) substrates, to investigate the evolution of the interface roughness and exchange bias and their dependence on the NiFe layer thickness. The interface roughness values of the samples decrease with increasing NiFe thickness. The in-plane ferromagnetic resonance measurements indicate that the exchange bias field and the peak-to-peak line widths of the resonance curves are inversely proportional to the NiFe thickness. Furthermore, both the exchange bias field and the interface roughness show almost the same dependence on the NiFe layer thickness. The out-of plane angular dependent measurements indicate that the exchange bias arises predominantly from a variation of exchange anisotropy due to changes in interfacial structure. The correlation between the exchange bias and the interface roughness is discussed.

• 마이크로전자및패키징학회지
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• 제14권3호
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• pp.51-55
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• 2007

Ni-Fe 전해도금 시 전류밀도, 펄스주기와 전류인가 방식, 도금욕의 Fe 이온의 농도, 첨가제 등의 인자들이 도금 층의 조성, 표면형상, 표면 경도에 미치는 영향에 관하여 연구하였다. 시편에 가해지는 전류밀도, 전류인가방식과 Fe이온의 농도를 변화시킴으로써 Ni-Fe의 도금 층 내에 Ni-Fe의 조성을 조절하는 것이 가능하였고 또한 첨가제의 양을 변화시킴으로써 표면형상이 변화됨을 확인하였다. PC를 사용한 경우 직류를 사용한 경우보다 높은 $550{\sim}600Hv$의 경도값을 얻을 수 있었다. 사카린을 첨가한 경우 도금층의 잔류응력을 낮추어 균열이 없는 도금층을 얻었다. Ni-Fe의 단면의 조성을 분석함으로써 도금 층의 두께에 따른 조성의 변화를 확인하였다.