• Title/Summary/Keyword: NiFe

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Exchange Bias Study by FMR Measurment (강자성 공명에 의한 Exchange Bias 연구)

  • Yoo, Yong-Goo;Park, Nam-Seok;Min, Seong-Gi;Yu, Seong-Cho
    • Journal of the Korean Magnetics Society
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    • v.15 no.5
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    • pp.265-269
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    • 2005
  • Exchange bias effect of a various layered thin films were studied by FMR measurment. In plane angular dependence of a resonance field distribution which measured by FMR was analysed as a combined effect of an unidirectional anisotropy and an uniaxial anisotropy. Exchange biased NiFe/IrMn, IrMn/NiFe/IrMn, and NiFe/IrMn/CoFe thin films showed larger unidirectional anisotropy field and uniaxial anisotropy field with compared to that of an unbiased NiFe single thin film. In case of NiFe/Cu/IrMn, the film with thick Cu layer exhibited a similar trend to the unbiased NiFe thin film. NiFe/IrMn/CoFe thin film showed two resonance field distribution due to different ferromagnetic layers. In additon to the resonance field, the line width was also analysed with related to exchange bias effect.

A First-principles Study on Magnetic and Electronic Properties of Ni Impurity in bcc Fe

  • Rahman, Gul;Kim, In-Gee
    • Journal of Magnetics
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    • v.13 no.4
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    • pp.124-127
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    • 2008
  • The magnetic and electronic properties of Ni impurity in bcc Fe ($Ni_1Fe_{26}$) are investigated using the full potential linearized augmented plane wave (FLAPW) method based the generalized gradient approximation (GGA). We found that the Ni impurity in bcc Fe increases both the lattice constant and the magnetic moment of bcc Fe. The calculated equilibrium lattice constant of $Ni_1Fe_{26}$ in the ferromagnetic state was 2.84 A, which is slightly larger than that of bcc Fe (2.83 ${\AA}$). The averaged magnetic moment per atom of $Ni_1Fe_{26}$ unit cell was calculated to be $2.24{\mu}_B$, which is greater than that of bcc Fe (2.17 ${\mu}_B$). The enhancement of magnetic moment of $Ni_1Fe_{26}$ is mainly contributed by the nearest neighbor Fe atom of Ni, i.e., Fe1, and this can be explained by the spin flip of Fe1 d states. The density of states shows that Ni impurity forms a virtual bound state (VBS), which is contributed by Ni $e_{g{\downarrow}}$ states. We suggest that the VBS caused by the Ni impurity is responsible for the spin flip of Fe1 d states.

A Study on Diffusion Behavior in NiFe/Ag Bilayer Films deposited by ion Beam Sputtering Methods (이온빔 스퍼터링 방법으로 증착한 NiFe/Ag 박막의 확산 거동)

  • 지재범;이성래;문대원
    • Journal of the Korean institute of surface engineering
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    • v.35 no.2
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    • pp.107-112
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    • 2002
  • We have studied diffusion behavior of NiFe/Ag bilayer deposited by on silicon Ion Beam Sputtering methods. The diffusion behavior of NiFe and Ag in NiFe/Ag thin film is analyzed by Medium Energy Ion Scattering Spectroscopy. For samples without Ta underlayer, silicides such as Ni-Si or Fe-Si were formed at Si substrate and NiFe interface. In contrast, Ag predominantly diffused into the NiFe layer probably through their grain boundaries for Ta underlayered samples.

MAGNETORESISTANCE OF NiFeCo/Cu/NiFeCo/FeMn MULTILAYERED THIN FILMS WITH LOW SATURATION FIELD

  • Bae, S.T.;Min, K.I.;Shin, K.H.;Kim, J.Y.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.570-574
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    • 1995
  • Magnetoresistance of NiFeCo/Cu/NiFeCo/FeMn uncoupled exchange biased sandwiches has been studied. The magnetoresistance change ratio, ${\Delta}R/R_{s}$ showed 4.1 % at a saturation field as low as 11 Oe in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(23\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. In this system, the magnetoresistance was affected by interlayer material and thickness. When Ti and Cu were used as the interlayer material in this structure, maximum magnetoresistance change ratio were 0.32 % and 4.1 %, respectively. 6.1 % MR ratio was obtained in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(15\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. The magnetoresistance change ratio decreased monotonically as the interlayer thickness increased. It was found that the exchange bias field exerted by FeMn layer to the adjacent NiFeCo layer was ~25 Oe, far smaller than that reported in NiFe/Cu/NiFe/FeMn spin valve structure(Dieny et. al., ~400 Oe). The relationship between the film texture and exchange anisotropy ha been examined for spin valve structures with Ti, Cu, or non-buffer layer.

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Magnetism and Magnetocrystalline Anisotropy of Ni/Fe(001) Surface: A First Principles Study (Ni/Fe(001)의 자성과 자기이방성에 대한 제일원리계산)

  • Kwon, Oryong;Hong, Soon Cheol
    • Journal of the Korean Magnetics Society
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    • v.25 no.4
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    • pp.101-105
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    • 2015
  • Recent theoretical calculations predicted that a system composed exclusively of 3d transition metals without 4d/5d transition metals or rare earth metals can have strong perpendicular magnetocrystalline anisotropy (MCA) if Fe and Ni layers are arranged appropriately. They considered only Fe-terminated surfaces, noting that Fe/MgO(001) and CoFeB/MgO(001) show strong perpendicular MCA. In this paper, we investigate magnetism and MCA of Ni/Fe(001) surface where Ni layer is positioned at the surface, by using complementarily the first principles calculational methods of Vienna Ab-initio Simulation Package (VASP) and Full-potential Linearized Augmented Plane Wave (FLAPW) method. Comparing results of magnetism and MCA obtained by VASP with the results by FLAPW method, we find the VASP results do not show big difference from results by FLAPW method. Magnetic moments of Fe and Ni are enhanced due to strong hybridization between Fe and Ni bands. MCA of Ni/Fe(001) is parallel to the surface, which implies the surface termination plays a crucial role in determining MCA of a system.

CoFe Layer Thickness and Plasma Oxidation Condition Dependence on Tunnel Magnetoresistance (CoFe의 삽입과 산화조건에 따른 자기 터널 접합의 자기저항특성에 관한 연구)

  • 이성래;박병준
    • Journal of the Korean Magnetics Society
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    • v.11 no.5
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    • pp.196-201
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    • 2001
  • The dependence of CoFe interfacial layer thickness and plasma oxidation condition on tunneling magnetoresistance (TMR) in Ta/NiFe/FeMn/NiFe/Al$_2$O$_3$/NiFe/Ta tunnel junctions was investigated. As the CoFe layer thickness increases, TMR ratio rapidly increases to 13.7 % and decreases with further increase of the CoFe layer thickness. The increase of TMR with the CoFe thickness up to 25 was thought to be due mails to the high spin-polarization of CoFe. The maximum MR of 15.3% was obtained in the Si(100)/Ta(50 )/NiFe(60 )/FeMn(250 )/NiFe(70 )/Al$_2$O$_3$/NiFe(150 )/Ta(50 ) magnetic tunnel junction with a 16 Al oxidized for 40 sec using a Ar/O$_2$ (1:4) mixture gas.

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Exchange bias in NiFe/FeMn/NiFe multilayers

  • Sankaranarayanan, V.K.;Lee, Y.W.;Shalyguina, E.E.;Kim, C.G.;kim, C.O.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05a
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    • pp.55-58
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    • 2003
  • FeMn based spin valves often consist of a NiFe/FeMn/NiFe trilayer structure. We have investigated the evolution of exchange bias at the bottom and top interfaces in the NiFe(5nm)/FeMn(x)/NiFe(5nm) trilayer structure as a function of FeMn thickness in the range 3 nm to 30 nm. The XRD results indicate (111) textured growth for NiFe and FeMn layers. The magnetization studies using VSM show two hysteresis loops corresponding to the bottom NiFe seed layer and top NiFe layers with greater bias for the bottom NiFe layer, for FeMn thickness equal to and above 5 nm. The larger exchange bias for the bottom seed layer is confirmed by the surface sensitive MOKE hysteresis loop measurements which show gradual weakening of the MOKE hysteresis loop for the bottom NiFe layer with increasing FeMn thickness. The observed large exchange bias in a spin valve structure is usually attributed to the pinning NiFe layer on top of the FeMn layer, even when a NiFe seed layer of a few nm thickness is present, whereas, in reality it may be arising from the bottom seed layer, as shown by the present study.

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A study on the magnetoresistive characteristics of ${[Ni/Fe/Cu]}_{20}$ multilayers (${[Ni/Fe/Cu]}_{20}$ 다층 박막의 자기저항 특성에 관한 연구)

  • 이후산;민경익;주승기
    • Journal of the Korean Magnetics Society
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    • v.3 no.4
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    • pp.289-292
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    • 1993
  • [Ni/Fe/Cu] and [Fe/Ni/Fe/Cu] multilayers were prepared with three gun rf-magnetron sputtering, and dependence of magnetoresistance on the Ni IFe thickness ratio was investigated. Vaccum annealing was tried to invetigated the effect of annealing. Oscillation of magnetoresistance on the Cu spacer thickness was dbserved in these two kinds of multilayers. When the thickness of Fe inserted into the Ni/Cu interface was about $3\;\AA$. the maximum value of magnetoresistance(13 %) could be observed. In a sample of $1~2\;\AA$ Fe thickness, saturation field decreased significantly, while magnetoresistace decreased slightly in comparison with the sample of $3\;\AA$ Fe. In ${[Cu(23\;\AA)/Fe(1\;\AA)/Ni(18\;\AA)/Fe(1\;\AA)]}_{20}/Fe(80\;\AA)/Si$, 6 % magnetoresistance with 100 Oe saturation field could be obtained. No appreciable change in magnetoresistance and saturation field could be observed by low temperature annealing. Formation of Ni-Fe alloy was not confinred.

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Enhancement of Exchange Coupling Field and Thermal Stability by an Ultra-thin Mn Inserted layer on NiFe/[FeMn/Mn]80/NiFe Multilayers (NiFe/[FeMn/Mn]80/NiFe 다층박막에서 극-초박막 Mn 삽입에 의한 교환결합세기와 열적 안정성 향상)

  • Kim, Bo-Kyung;Lee, Jin-Yong;Ham, Sang-Hee;Lee, Sang-Suk;Hwang, Do-Guwn
    • Journal of the Korean Magnetics Society
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    • v.13 no.2
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    • pp.53-58
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    • 2003
  • Annealing effects of exchange bias fields ($H_{2ex}$(top), $H_{lex}$ (bottom)) on composite type NiFe/[FeMn/Mn]$_{80}$/NiFe multilayers have been studied. Three samples with ultra-thin Mn inserted layers on glass/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 $\AA$) were prepared by ion beam sputtering. The average x-ray diffraction peak ratios NiFe(111) of FeMn (111) fcc textures for the Mn inserted total thicknesses of 0 $\AA$, 9 $\AA$, and 24 $\AA$ were about 0.65, 0.90, and 1.5, respectively. For the sample without Mn inserted layer, the $H_{2ex}$ of 260 Oe up to 300 $^{\circ}C$ disappeared at 350 $^{\circ}C$. For two multilayer samples with ultra-thin Mn layers of 0.11 $\AA$ and 0.3 $\AA$, the $H_{2exs}$ of 310 Oe and 180 Oe up to 300 $^{\circ}C$ endured of 215 Oe and 180 Oe at 350 $^{\circ}C$, respectively. The $H_{ex}$ (bottom)s of three samples decreased from 100 Oe to 70 Oe up to 250 $^{\circ}C$, while these values increased beyond 300 $^{\circ}C$. This observation can be attributed to less diffusive path of Mn atoms in bottom NiFe than top NiFe layer. The top and bottom coercive fields slightly varied about 5 Oe∼10 Oe. From these results, we could obtain the enhancement of exchange coupling intensity and thermal stability by an ultra-thin Mn inserted layer on NiFe/[FeMn/Mn]$_{80}$/NiFe Multilayers.