• 한국자기학회지
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• 제9권6호
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• pp.296-300
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• 1999

DC 마그네트론 스퍼터링 방법으로 금속 마스크를 사용하여 십자형태로 substrate/Ta/NiFe/FeMn/NiFe/CoFe/Al2O3/CoFe/NiFe와 substrate/Ta/NiFe/CoFe/Al2O3/CoFe/NiFe/FeMn/NiFe 스핀 터널링 접합 구조를 제조하였다. 이러한 구조에서 절연층(Al2O3)의 형성조건과 각 층의 두께와 파워에 대한 증착율에 변화를 주어 24.3%의 자기 저항비를 얻었다. 두 종류의 구조에 대한 자기적 특성 비교와 Corning glass 7059와 Si(111) 기판의 종류에 따른 결과를 비교하였으며 소자 제조때 수반되는 온도변화에 대한 특성변화를 알아보고자 열처리를 하였다. 열처리 결과 자기 저항비는 15$0^{\circ}C$까지는 어느 정도 일정한 값을 유지하다가 18$0^{\circ}C$ 열처리 후 갑자기 감소하는 결과를 얻었다.

• 한국자기학회지
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• 제13권2호
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• pp.53-58
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• 2003

Mn층 삽입에 의한 NiFe/[FeMn/Mn]$_{80}$/NiFe 다층박막에서 열처리에 따른 교환결합세기의 변화를 조사하였다. Ta(50$\AA$)/NiFe(150 $\AA$)/[F $e_{53}$M $n_{47}$(1.25 $\AA$)/Mn(0 $\AA$, 0.11 $\AA$, 0.3 $\AA$)]$_{80}$/NiFe(90 $\AA$)/Ta(50 $\AA$) 다층박막을 이온빔 증착 스퍼터링법으로 제작하였다. 삽입한 Mn 총 두께가 0 $\AA$, 9 $\AA$, 그리고 24 $\AA$인 다층박막에 대해 조사된 fcc 결정조직의 x-선 회절세기의 비인 NiFe(111)/FeMn(111)값은 각각 0.65, 0.90, 그리고 1.5이었다. Mn이 삽입되지 않은 시료인 경우, 열처리 온도 30$0^{\circ}C$에서 상부 NiFe층의 교환결합세기는 260 Oe로 유지한 후 35$0^{\circ}C$에서 사라졌다. Mn 삽입층의 두께가 0.11 $\AA$, 0.3 $\AA$인 두개의 시료에 대해, 300 $^{\circ}C$에서 상부 NiFe층의 교환결합세기는 각각 310 Oe와 180 Oe로 유지한 후 40$0^{\circ}C$에서 모두 사라졌다. 한편 하부 NiFe층의 교환결합세기는 250 $^{\circ}C$까지 100 Oe에서 70 Oe로 감소하는 동일한 경향을 보여 주었고, 300 $^{\circ}C$ 이상부터는 증가하는 경향이 관찰되었다. 다층박막 내에 뿔뿔이 산란하여 이동하는 Mn 원자의 확산은 주로 결정 조직의 결함이 생성되고 치밀도가 약한 상부 NiFe 층에 영향을 주고 있음을 알 수 있었다. 극 초박막 형태로 Mn 원자층의 삽입에 의한 NiFe/[FeMn/Mn]80/NiFe 다층박막에서 교환결합세기와 열적 안정성 향상을 보여 주었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.212-212
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• 2003

Many of the spin valve multilayer structures with FeMn as antiferromagnetic layer consist of a NiFe/FeMn/NiFe trilayer where the bottom NiFe layer is the seed layer to facilitate the growth of (111) gama-FeMn antiferromagnetic phase and the top NiFe layer forms the pinned layer[1], In this study, exchange bias of bottom NiFe layer has been investigated as functions of thicknesses of top and bottom NiFe in NiFe/FeMn/NiFe, prepared by rf magnetron sputtering, MH-loop was measured by vibration sample magnetometer (VSM). Two hysteresis loops are corresponded to bottom and top layers, similar to reported loops in spin valve structure. Exchange bias of bottom NiFe could be induced by the interfacial coupling between bottom NiFe and FeMn. But those coupling are strongly dependent on the top and bottom NiFe thicknesses, revealing anomalous character ul exchange bias of bottom NiFe layer.

• Journal of Magnetics
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• 제16권2호
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• pp.97-100
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• 2011

Bilayers of soft NiFe (150 nm-420 nm) on hard Ni (150 nm) were prepared by electrodeposition. The process of magnetization reversal in the NiFe/Ni bilayers was then investigated. The hysteresis loop generated by a magnetization reversal of soft NiFe under a positive saturation state of a hard Ni layer shows a shift along the negative field axis, which is clear evidence for the exchange spring effect in the NiFe/Ni bilayers. The dependence of the coercive field $H_c$ and exchange bias field Hex on the thickness of the NiFe layer was also investigated. As the NiFe thickness increases from 150 nm to 420 nm, both $H_c$ and $H_{ex}$ decrease rapidly from $H_c$= 51.7 Oe and $H_{ex}$ = 12.2 Oe, and saturate to $H_c$ = 5.8 Oe and $H_{ex}$ = 3.5 Oe.

• Journal of Magnetics
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• 제6권3호
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• Journal of Magnetics
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• 제10권3호
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• pp.99-102
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• 2005

Modification in exchange bias of a NiFe/FeMn/NiFe trilayer, on introduction of a nonmagnetic Al layer at the top FeMn/NiFe interface, is investigated in multilayers prepared by rf magnetron sputtering. The introduction of Al layer leads to vanishing of bias of the top NiFe layer. But the bias for the bottom NiFe layer increases steadily with increasing Al layer thickness and attains bias (230 Oe) which is greater than that of the trilayer without the Al layer (150 Oe). When the top NiFe layer thickness is varied, exchange bias has highest value at 12 nm thickness for 1 nm thicknes of Al layer. Ion beam etching of the top NiFe layer also leads to an enhancement in bias for the bottom NiFe layer.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.190-191
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• 2002

Granular feromagnets는 non-magnetic maxtrix 안에 nanometer-sized의 ferromagnetic grain들 구성된다. Co-Cu,Co-Ag, Fe-Ag, NiFe-Ag $^1$을 포함하는 이미 알려진 다른 Granular 금속 합금들의 giant magnetoresistance 에 관계하여 Granular feromagnets 에 대해 조사하였다. Bulk상태의 NiFe와 Mn 혼화되기 쉽다.$^2$ 그리고 Mn은 열처리된 다층박막의 NiFe의 lattice에 쉽게 수용되어진다.$^3$ 이번 실험에서는 metastable한 fcc solid solution NiFe-Mn 박막이 열처리 하에서 NiFe과 Mn으로 분리되었다. (중략)

• Journal of Magnetics
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• 제17권2호
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• pp.86-95
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• 2012

This study investigated the effects of adding a third alloying element, Ni, to create $Fe_{70-x}Pd_{30}Ni_x$ (x = 2, 4, 6, 8 at.% Ni) ferromagnetic shape memory alloys (FSMAs). The Ni replaced a portion of the Fe. The $Fe_{70-x}Pd_{30}Ni_x$ alloys were homogenized through hot and cold forging to gain a ~38% reduction in thickness, next they were solution-treated (ST) with annealing recrystallization at $1100^{\circ}C$ for 8 h and quenched in ice brine, and then aged at $500^{\circ}C$ for 100 h. Investigation of the microstructures and magnetostriction indicated that the greater Ni amount in the $Fe_{70-x}Pd_{30}Ni_x$ alloys reduced saturation magnetostriction at room temperature (RT). It was also observed that it was more difficult to generate annealed recrystallization. However, with greater Ni addition into the $Fe_{70-x}Pd_{30}Ni_x$ (x = 6, 8 at.% Ni) alloys, the $L1_0+L1_m$ twin phase decomposition into stoichiometric $L1_0+L1_m+{\alpha}_{bct}$ structures was suppressed after the $500^{\circ}C$/100 h aging treatment. The result was that the $Fe_{70-x}Pd_{30}Ni_x$ (x = 6, 8 at.% Ni) alloys maintained a high magnetostriction and magnetostrictive susceptibility (${\Delta}{\lambda}{_\parallel}{^s}/{\Delta}H$) after the alloys were aged at $500^{\circ}C$ for 100 h. This magnetic property of the $Fe_{70-x}Pd_{30}Ni_x$ (x = 6, 8 at.% Ni) alloys make it suitable for application in a high temperature (T > $500^{\circ}C$) and high frequency environments.

• 한국자기학회지
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• 제11권4호
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• pp.163-167
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• 2001

DC 마그네트론 스퍼터링법으로 증착된 700 $\AA$의 NiFe 박막을 박막 증착시 형성시킨 자화용이축에 수직한 자기장을 인가하여 열처리한 후 일축 이방성 자기장의 회전을 조사하였다. NiFe 박막은 열처리온도 160 $^{\circ}C$에서 자화용이축과 자화곤란축을 구분할 수 없는 등방적인 상태가 되었고, 열처리온도가 증가함에 따라 다시 일축 이방성을 갖는 상태가 되었다. 열처리 온도가 400 $^{\circ}C$ 이상인 경우에 급격한 보자력의 증가를 보였다. 열처리 온도가 400 $^{\circ}C$인 경우에 XRD 분석과 AES depth profile은 NiFe 박막 내에서 (111) 방향으로 결정성장이 활발히 일어나며 인접한 전극 Au와 상호화산 현상도 광범위하게 일어남을 보여주었다.

• 한국표면공학회지
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• 제36권6호
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• pp.455-460
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• 2003

Microstructural and magnetic properties of nanocrystalline Fe-46 wt%Ni and Fe-36 wt%Ni alloys were investigated. Alloys were prepared by the electrodeposition process. The electrolytes were iron sulfate/nickel chloride-based and iron chloride/nickel sulfamate-based solutions. Fe-46 wt%Ni alloy was FCC structure with grain size of 10 nm, but FCC and BCC phases were found in Fe-36 wt%Ni alloy and its grain size was smaller. Effective permeability of Fe-36 wt%Ni alloy was higher than that of Fe-46 wt%Ni alloy in the high frequency range because of large electrical resistivity and small eddy current loss resulted from grain size decrease. Up to $300^{\circ}C$ of annealing temperature, grain growth of Fe-Ni alloys slowly occured. Conversely, annealing above $450^{\circ}C$ led to a drastic grain growth. In that case, effective permeability was decreased at the temperature lower than $300^{\circ}C$ but at $300^{\circ}C$ or higher effective permeability was increased. At the high frequency of 1 MHz, electrodeposited Fe-Ni alloys had higher effective permeability with an decrease in the grain size.