• Title/Summary/Keyword: NiFe

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A Study on the Magnetic Properties and Microstructures of Ni-Fe/NiO Bilayers with Various Ar Presure in NiO Deposition (NiO 증착시의 Ar 압력 변화에 따른 Ni-Fe/NiO 이층막의 자기적특성과 미세구조에 대한 연구)

  • 노재철;이두현;김용성;서수정;박경수
    • Journal of the Korean Magnetics Society
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    • v.8 no.6
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    • pp.369-373
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    • 1998
  • The exchange anisotropy between NiO antiferromagnetic layer and NiFe ferromagnetic layer has been investigated in NiFe(10 nm)/NiO(60 nm) formed by magnetron sputtering. The NiO films were sputtered from nickel oxide using R. F. poser and NiFe, Ta were deposited using D. C. power under Ar atmosphere. Above all. we studied the exchange anisotropy of Ni-Fe/NiO bilayer, and focused especially on the effect of NiO depostion condition. Our experimental data showed that the dominant factor for determining the exchange anisotropy properties was the Ar pressure during NiO deposition. The better exchange anisotropy properties were found when the NiO film was deposited at low Ar pressure probably due to the flatten interface and the epitaxial tendency of NiO grains and NiFe grains. However, as Ar pressure increased, interfacial diffusion at NiFe/NiO interface and oxygen content of NiO film increase, and consequently reduced the exchange anisotropy. We concluded that the flatten interface and relatively low oxygen content of NiO layer are dominant factors for the enhancement of the exchange anisotropy in NiFe/NiO bilayer.

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Effects of Ultrathin Co Insertion Layer on Magnetic Anisotropy and GMR Properties of NiFe/Cu/Co Spin Valve Thin Films (NiFe/Cu 계면에 삽입된 Co 층이 NiFe/Cu/Co 스핀밸브 박막의 거대자기저항 특성과 자기이방성에 미치는 영향)

  • 김형준;조권구;주승기
    • Journal of the Korean Magnetics Society
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    • v.9 no.5
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    • pp.251-255
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    • 1999
  • NiFe(60 $\AA$)/Co(0$\AA$$\leq$x$\AA$$\leq$15$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were prepared on 4$^{\circ}$ tilt-cut Si(111) substrates with a 50 $\AA$ thick Cu underlayer without applying any external magnetic field during the deposition, and the effects of inserted ultrathin Co layer on magnetic anisotropy and GMR properties of the NiFe(60 $\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valves were investigated. As the ultrathin Co layer was inserted into the NiFe/Cu interface of the spin valves, GMR ratio was increased from about 1.5% to 3.5%, and the easy axis of NiFe(60 $\AA$) layer was rotated by 90$^{\circ}$. Accordingly, it was aligned along the same direction with the easy axis of Co(30 $\AA$)layer. Therefore, squared R-H curves was obtained in the spin valves, which is favorable properties for the digital GMR devices such as MRAM. In order to investigate the change of magnetic anisotropy of NiFe layer of the spin valves in more details,XRD measurement was performed using NiFe(500 $\AA$) and NiFe(500 $\AA$)/Co(10 $\AA$) thin films on the same templates. Strong (220) NiFe peak was observed in both films regardless of the inserted Co layer, so it was thought that the variation of magnetic anisotropy of NiFe layer is from the interface effect, the change of interface from NiFe/Cu to NiFe/Co, rather than the volume effect such as the change of magnetocrystalline effect.

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Effects of Atomic Intermixing of Ta/NiFe Interface on Magnetoresistance and Magnetic Properties in a Ta/NiFe/Cu/NiFe/FeMn/Ta Spin Valve Structure (Ta/NiFe/Cu/NiFe/FeMn/Ta계 스핀밸브 제조시 Ta/NiFe 계면원자섞임이 스핀밸브의 자기저항과 자기적 특성에 미치는 영향)

  • 오세층;이택동
    • Journal of the Korean Magnetics Society
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    • v.8 no.5
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    • pp.288-294
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    • 1998
  • Effect of degree of intermixing at the Ta/NiFe interface induced by varying applied substrate bias voltage during NiFe free layer deposition on change of magnetoresistance in Substrate/Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve multilayers was investigated. It was found that the optimum NiFe free layer thickness showing a maximum MR increase with increasing the bias voltage. The increase of the optimum thickness was due to the increase of the intermixed layer thickness with a bias voltage. The weak ferromagnetic or non ferromagnetic intermixed layer plays as a spin-independent scattering region and does not contribute on spin-dependent scattering. The existence of the intermixed layer was proved by the means of electrical resistivity and magnetization changes. In the present study, the optimum "effective" free layer thickness which gives the highest MR ratio was a constant independent of the magnitude of the bias voltage we have used.have used.

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Magnetic Properties of Three-layered Ferromagnetic Films with a NiFeCuMo Intermediately Super-soft Magnetic Layer (강자성층 사이에 초연자성 NiFeCuMo 중간층을 삽입한 3층 박막구조의 자기적 특성)

  • Choi, Jong-Gu;Lee, Sang-Suk
    • Journal of the Korean Magnetics Society
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    • v.20 no.4
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    • pp.129-133
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    • 2010
  • Two-layered ferromagnetic alloy films (NiFe, CoFe) with a Conetic (NiFeCuMo) intermediately soft magnetic layer of different thickness were investigated to correlate the coercivity values and magnetization process with the strength of saturation field of hard axis. Thickness dependence of the $H_{EC}$ (coercivity of easy axis), $H_{HS}$ (saturation field of hard axis.), and X (susceptibility) of NiFe and NiFeCuMo thin films for the glass/Ta(5 nm)/[CoFe or NiFe(5 nm-t/2)]/NiFeCuMo(t = 0, 4, 6, 8, 10 nm)/[CoFe or NiFe(5 nm-t/2)]/Ta(5 nm) films prepared by the ion beam deposition method was measured. The magnetic properties $H_{EC}$, $H_{HS}$, and X of two-layered ferromagnetic CoFe, NiFe films with a NiFeCuMo intermediately super-soft magnetic layer were strongly depended on the thickness of NiFeCuMo layer. The value of the coercivity and magnetic susceptibility of the NiFeCuMo film decreased by 25% and doubled relative to that of the NiFe film.

Effects of Permalloy Multilayered Schemes and CoZrNb Intermediate Layer on Recording Characteristics of CoCr/NiFe Media (Permalloy 다층화와 CoZrNb 중간층이 CoCr/NiFe 매체의 기록특성에 미치는 영향)

  • 장평우;이택동;박관수
    • Journal of the Korean Magnetics Society
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    • v.4 no.1
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    • pp.20-24
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    • 1994
  • The read/write characteristics of CoCr/NiFe double layered media are strongly affected by the magnetic properties of NiFe magnetic soft layer as well as those of CoCr recording layer. Modification of the permalloy layer by NiFe/Ge multilayer scheme resulted in the higher recording sensitivity and the higher reproduced voltage of CoCr/NiFe medium and this is attributed to the higher permeability of the back layer and high perpendicular anisotropy of the CoCr recording layer. Although higher permeability of back layer results in higher recording sensitivity, the increment of the reproduced voltage was not remarkable, which can be confirmed in the FEM numerical analysis. On the contrary, peak shift characteristics of the CoCr/NiFe medium with the NiFe multi back layer was deteriorated compared to that of the CoCr/NiFe medium with NiFe single back layer. Insertion of ferromagnetic thin CoZrNb intermediate layer between CoCr and NiFe layer was effective to ensure large reproduced voltage and low peak shift. These recoridng characteristics were also discussed in connection with microstructural characteristics.

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Analysis of Giant Magnetoresistance Behavior of NiFeCo/Cu/NiFeCo/FeMn Valves (NiFeCo/Cu/NiFeCo/FeMn 스핀밸브 구조의 자기저항 거동 해석)

  • 배성태;김진영;민경익;신경호
    • Journal of the Korean Magnetics Society
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    • v.6 no.2
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    • pp.112-116
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    • 1996
  • 스퍼터링법으로 제조한 NiFeCo/Cu/NiFeCo/FeMn 스핀밸브 자성 다층막의 자기적 성질과 자기저항에 대해 연구하였다. Cu 사잇층 두께가 15 .angs. 인 경우 약 6%의 자기저항을 얻을 수 있었다. NiFeCo/FeMn에서 교환이방성 자계는 약 20 Oe 정도였는데, 이는 NiFe/FeMn 계 스핀밸브 구조에서 보고된 값(100 Oe 이상) 보다 현저히 작은 것이다. 3 mTorr에서 제조한 NiFeCo 박막은 약 10 Oe 정도의 큰 보자력을 보임으로써 비슷한 조건에서 제조한 NiFe 박막의 경우(약 2 Oe)보다 상당히 큰 값을 갖는 것으로 관찰되었다. 작은 교환이방성 자계와 큰 보자력으로 인해 음 .rarw. 양 방향과 양 .rarw. 음 방향의 자화거동에 있어서 비대칭적인 자기저항 이력곡선 거동을 보이는 것으로 나타났다.

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Exchange and Interlayer Coupling in NiO Spin Valve Films (NiO 스핀밸브 박막에서 교환결합과 사잇층 결합에 관한 연구)

  • 박창만;고성호;황도근;이상석;이기암
    • Journal of the Korean Magnetics Society
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    • v.7 no.5
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    • pp.258-264
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    • 1997
  • Exchange and interlayer couplings between a NiFe ferromagnetic layer and an antiferromagnetic NiO layer in NiO/NiFe/Cu/NiFe spin-valve films prepared by rf/dc magnetron sputtering were investigated. The interlayer coupling field ($H_{int}$ decreased with the Cu layer thickness, and the exchange coupling field $(H_{ex}$ saturated to 90 Oe. the magnetitudes of $H_{ex}$ and $H_{int}$ decreased with increasing thickness of the pinned NiFe layer. The increase of $H_{int}$ with the free NiFe layer may be due to the increased magnetization.

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Magnetic Behaviors of Isolated Fe-Co-Ni Nanoparticles in a Random Arrangement

  • Yang, Choong Jin;Kim, Kyung Soo;Wu, Jianmin
    • Journal of Magnetics
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    • v.6 no.3
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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.

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Exchange Bias Modifications in NiFe/FeMn/NiFe Trilayer by a Nonmagnetic Interlayer

  • Yoon, S.M.;Sankaranarayanan V.K.;Kim, C.O.;Kim, C.G.
    • Journal of Magnetics
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    • v.10 no.3
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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.