• Journal of Magnetics
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• 제5권4호
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• pp.139-142
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• 2000

The interlayer coupling between adjacent ferromagnetic layers was examined for CoFe/Cu/NiFe trilayer systems. A series of films of CoFe (20 nm)/Cu($t_{cu}$)/NiFe (20 nm) trilayers with Cu spacer thickness, $t_{cu}$, in the range of 1~10 m was deposited on Si(100) wafers at room temperature by DC magnetron sputtering. In order to understand the dependence of the magnetic interaction between ferromagnetic $Co_{90}Fe_{10}$ (wt.%) and $Ni_{81}Fe_{19}$ (wt.%) layers separated by a nonmagnetic Cu spacer on the Cu layer thickness, we investigated the derivative ferromagnetic resonance (FMR) spectra. The FMR results were analyzed using the model of Layadi and Art-man for interlayer interaction. The interlayer coupling constant decreases in an oscillatory manner as the Cu spacer thickness increases up to 10 nm and approaches zero above 10 nm. The interlayer coupling constant is positive for all samples. Hence, it seems that the exchange coupling between adjacent CoFe and NiFe layers separated by a Cu layer is ferromagnetic.

• 한국자기학회지
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• 제18권6호
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• pp.232-236
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• 2008

[CoFe/Pt/CoFe]/IrMn 다층박막에 대하여 반강자성체 IrMn층 두께 의존성 및 열적안정성, 수평으로 전환하는 각도에 의존하는 수직자기 이방성 특성을 관찰하였다. IrMn층을 통해 유도된 강자성체/비자성체/강자성체 구조인 [CoFe($10{\AA}$)/Pt($8{\AA}$)/CoFe($10{\AA}$)]/IrMn 다층박막은 IrMn 두께 $7{\AA}$부터 상호교환결합력이 형성되었고, 열처리 온도 $250^{\circ}C$까지 열적안정성을 유지하였다. 수직자기 이방성 [CoFe/Pt/CoFe]/IrMn 다층박막에서 바닥 CoFe층과 Pt층을 사이에 두고 반강자성체인 IrMn층에 의해 고정되어 있는 상부 CoFe층간의 상호교환결합력은 이방성 측정 각도가 $0^{\circ}$, $60^{\circ}$일 때 각각 1,000 Oe, 1,500 Oe로, $90^{\circ}$일 때 $\infty$ Oe로 나타났다.

• Journal of Magnetics
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• 제14권3호
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.229-229
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• 2003

Enhancement of the exchange bias and optimization of the structure have been the focus that many researchers studied, recently [1]. In this report, magnetic properties of MTJs with structure of Si/Ta (5)/Cu (10)/ Ta (5)/ Ni$\sub$80/Fe$\sub$20/ Cu (5)/ Mn$\sub$75Ir$\sub$25/ (10)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Al-O (1.5)/ Co$\sub$70/Fe$\sub$30/ (2.5)/ Ni$\sub$80/Fe$\sub$20/ (t)/ Ta (5) (t=0,10, 30, 60 and 100 nm, respectively) were investigated. The relationship between the structure and magnetic parameters of interfacial exchange coupling and interlayer coupling in as-deposited and annealed junctions was studied. The temperature dependence of exchange coupling was considered.

• 한국자기학회지
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• 제16권2호
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• pp.130-135
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• 2006

강자성체/비자성 금속/강자성체/반도체 구조에서 층간교환강호작용(interlayer exchange coupling) 에너지가 외부 인가전압으로 제어 가능함을 이론적으로 보였다. 비자성 금속층으로 격리된 두 강자성층 사이의 층간교환상호작용 에너지는 강자성체/비자성 금속 계면에서 전자의 스핀에 의존하는 반사율의 차이에 의해 결정된다는 것은 잘 알려진 사실인데, 이를 각자성체/비자성 금속/강자성체/반도체 구조에 적용하여 층간교환상호작용 에너지가 강자성체/비자성 금속/강자성체 계면에서 전자의 반사율뿐 아니라 강자성체/반도체 계면에서의 반사율에도 의존한다는 것을 보였다 강자성체/반도체 계면에 생기는 Schottky 장벽의 높이와 두께는 인가전압으로 바꿀 수 있고, 그에 따른 전자의 반사율이 인가전압에 의해 바뀔 수 있음을 알 수 있었다. 결과적으로 일차원 자유전자 모델을 사용하여 외부 인가 전압으로써 두 강자성체 사이의 층간 교환 상호작용 에너지를 제어할 수 있다는 것을 확인하였다.

• 한국재료학회지
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• 제13권6호
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• pp.369-373
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• 2003

Magneto-optic Kerr Effect(MOKE), AFM and magnetoresistance measurements have been carried out on as-deposited and annealed Magnetic Tunnel Junctions(MTJs) with junction sizes 180, 250, 320 and 380 $\mu\textrm{m}$ in order to investigate the correlation among interlayer exchange coupling, surface roughness and junction size. Relatively irregular variations of coercivity $H_{c}$ (∼17.5 Oe) and interlayer exchange coupling $H_{E}$ (∼17.5 Oe) are observed over the junction in as-deposited sample prepared by DC magnetron sputtering. After annealing at $200^{\circ}C$, $H_{c}$ decreases to 15 Oe, while $H_{ E}$ increases to 20 Oe with smooth local variation. $H_{E}$ shows very good correlation with surface roughness across the junction in agreement with Neel's orange peel coupling. The increasing slope per $\mu\textrm{m}$ of normalized $H_{c}$ and $H_{E}$ are same near junction edge along free-layer direction irrespective of junction size, giving relatively uniform $H_{c}$ and $H_{ E}$ for wider junction size. Thickness profiles of the junctions measured with $\alpha$-step show increasingly flat top surface for larger junctions, indicating better uniformity for large. junctions in agreement with the normalized$ H_{c}$ and H$/_{E}$ curves. TMR ratios also increase with increasing junction size, indicating improvement for larger uniform junctions.

• Journal of Magnetics
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• 제8권1호
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• pp.13-17
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• 2003

The longitudinal magnetooptical Kerr effect was used to analyse magnetic domains in soft magnetic ${(Fe_{97}A1_3)}_{85}N_{15}$/$Al_{2}O_{3}$ multilayers in order to get microscopic understanding of interlayer exchange coupling. The measuring system consists of a Kerr microscope, a CCIR camera (with an 8-bit framegrabber), 16 bit digital camera and computer system for real-time image processing and to control external magnetic field and cameras. The strength of ferromagnetic (EM) coupling as a function of the spacer thickness of $Al_2O_3$ was investigated. It was found that strong FM-coupling, strong uniaxial anisotropy and coherent rotation of the magnetization have been observed for the spacer thickness in the range of 0.2 nm $\leq$ t $\leq$ 1 m, however, weak FM-coupling, patch domains and $360^{\circ}$-walls occur for the spacer thickness of t = 2.5 nm. At a spacer thickness of t $\geq$ 5 nm transition takes place from weak FM-coupling to the decoupled state where complex interlayer interactions and different types of the domain walls were observed.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.177-177
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• 2003

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.219-219
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• 2003

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.202-203
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• 2004