• Journal of Magnetics
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• 제14권4호
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• pp.168-171
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• 2009

We propose a new type of spin torque nano-oscillator structure with an exchange- biased free rotating layer. The proposed spin torque nano-oscillator consists of a fixed layer and a free rotating layer with an additional anti-ferromagnetic layer, which leads to an exchange bias in the free rotating layer. The spin dynamics of the exchange-biased free rotating layer can be described as an additional exchange field because the exchange bias manifests itself by the existance of a finite exchange bias field. The exchange bias field plays a similar role to that of a finite external field. Hence, microwave generation can be achieved without an external field in the proposed structure.

• E2M - 전기 전자와 첨단 소재
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• 제8권3호
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• pp.332-339
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• 1995

In this paper, it was investigated the guided field intensity distribution of the channel in the silver & potassium ion-exchange glass-waveguide. The guided field intensity distribution analysis of ion-exchange glass-waveguide was based on the combination of the WKB dispersion relationship method with a Gaussian distribution function of refractive index profile and the Field Shadow method to the modeling of the channel waveguide. As the results of the channel waveguide modeling, it was represented 2-dimensional and 3-dimensional field distribution of ion-exchange glass waveguide.

• Journal of Magnetics
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• 제9권4호
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• pp.97-100
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• 2004

In the present work exchange coupling between ultrathin Fe ($8{\AA}$) and Tb ($12{\AA}$) layers separated by Au spacer of varied thickness ($3-20{\AA}$) was studied. Anomalous Hall effect measurements showed weakly damped oscillating dependence of the Hall conductivity as a function of Au spacer thickness. Disagreement of the observed damping with the RKKY model of interlayer exchange coupling was explained by the influence of external magnetic field on the behaviour of exchange coupling oscillations. It was confirmed by Hall-like effect measurements at zero applied magnetic field and also illustrated by corresponding estimations.

• 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.

• 한국재료학회지
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• 제13권7호
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• pp.447-452
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• 2003

Effects of annealing and thickness of Co layer in Co/IrMn bilayers on the magnetic properties have been investigated. The highest interfacial exchange coupling energy($J_{K}$ = 0.12 erg/$\textrm{cm}^2$) was obtained for 10 nm Co layer thickness. Exchange bias field is inversely proportional to the magnetization, the thickness of the pinned layer, and the grain size of antiferromagnetic layer. Also it is related to the interfacial exchange energy difference, which is expected to depend on the surface roughness. These results almost agree with the random-field model of exchange anisotropy proposed by Malozemoff. Exchange bias field decreased slowly with increasing annealing temperature up to X$300^{\circ}C$. However, exchange bias field increased above $300^{\circ}C$.

• 한국자기학회지
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• 제12권4호
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• pp.143-148
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• 2002

일축이방성을 부여한 NiO/NiFe 박막을 제작하고 이들의 강한 교환결합력과 약한 교환결합력의 분포에 대하여 조사하였다. 제작된 시편들의 교환결합력의 크기는 VSM 측정과 이방성자기저항측정을 통하여 확인하였으며, 회귀분석법을 통하여 두 교환결합력의 상호관계를 조사하였다. NiO(60nm)/NiFe(10nm)시편의 경우 전체 교환결합력 중에서 차지하는 약한 교환결합력의 크기는 외부인가자장의 크기에 관계없이 일정한 비율($\alpha$=0.2~0.4)을 나타내었고 이는 약한 교환결합을 하는 영역이 일정하게 존재함을 보여준다. 교환결합력의 크기가 서로 다른 시편의 경우는 교환결합력의 크기가 작을수록 전체 교환결합력 중에서 차지하는 약한 교환결합력의 크기가 컸으며, 교환결합력의 크기가 증가할수록 그 비율이 감소하였다. 이는 약한 교환결합을 하는 영역이 일정하게 존재한다고 가정할 경우 전체의 평균 교환결합력의 크기가 감소함에 따라 그 비율이 증가한 것으로 해석할 수 있다. 따라서 NiO/NiFe 박막에서 강한 교환결합을 하는 영역과 약한 교환결합을 하는 영역이 일정하게 존재함을 알 수 있다.

• Journal of Magnetics
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• 제11권2호
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• pp.77-82
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• 2006

The structure and magnetic properties of Fe-Ni films, deposited by DC magnetron sputtering on Si(111) wafer, have been studied. The spin wave stiffness constant is determined by Brillouin light scattering (BLS) and compared with the value obtained from magnetization measurements. The range of exchange interaction was determined as 0.4 atomic distances in the film deposited in a bias magnetic field, which is 1/2 that in the film grown in no bias magnetic field. The results show that the dimensions of exchange coupling increased by the sputtering in the magnetic field.

• Journal of Magnetics
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• 제10권4호
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• pp.133-136
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• 2005

The NiMn/NiFe bilayer structure which was short time annealed in order to induce unidirectional anisotropy were studied as a function of annealing temperature. The maximum exchange bias field of NiMn/NiFe bilayer was presented at $250^{\circ}C$ after short time annealing process with no external field. The appearance of exchange bias was due to phase transformation of NiMn layer. In plane angular dependence of a resonance field distribution which measured by FMR was analysed as a combined effect of unidirectional anisotropy and uniaxial anisotropy. The resonance field and the line width from FMR measurement were also analysed with annealing temperature.

• 한국자기학회지
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• 제15권5호
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• pp.265-269
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• 2005

강자성 공명 측정을 통하여 다양한 층 구성을 갖는 교환 바이어스 박막들의 교환 결합 특성에 대해 연구하였다. 공명자기장의 각도의존 실험을 통하여 일축방향이방성 자기장과 일축이방성 자기장을 구하여 분석하였다. NiFe 단일 박막과 비교하여 교환 바이어스된 NiFe/IrMn, IrMn/NiFe/IrMn, NiFe/IrMn/CoFe 박막들은 큰 일축방향이방성 자기장을 나타내었으며, 일축이방성 자기장 또한 큰 값을 나타내었다. 그러나 NiFe/Cu/IrMn의 경우, Cu의 두께가 두꺼울 때는 매우 작은 일축방향이방성 자기장을 나타내었으며, NiFe 단일 박막과 비슷한 크기의 일축이방성 자기장을 나타내었다. NiFe/IrMn/CoFe 박막의 경우 NiFe와 CoFe 강자성층들에 의해 두 개의 공명 자기장이 나타났다. 그 외에 공명 자기장의 선폭에 관한 분석이 교환 바이어스 특성과 연관하여 논의되어졌다.

• Journal of Magnetics
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• 제16권2호
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• pp.83-87
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• 2011

The vortex-driven magnetization process of micron-sized, exchange-coupled square elements with composition of $Ni_{80}Fe_{20}$ (12 nm)/$Ir_{20}Mn_{80}$ (5 nm) is investigated. The exchange-bias is introduced by field-cooling through the blocking temperature (TB) of the system, whereby Landau-shaped vortex states of the $Ni_{80}Fe_{20}$ layer are imprinted into the $Ir_{20}Mn_{80}$. In the case of zero-field cooling, the exchange-coupling at the ferromagnetic/antiferromagnetic interface significantly enhances the vortex stability by increasing the nucleation and annihilation fields, while reducing coercivity and remanence. For the field-cooled elements, the hysteresis loops are shifted along the cooling field axis. The loop shift is attributed to the imprinting of displaced vortex state of $Ni_{80}Fe_{20}$ into $Ir_{20}Mn_{80}$, which leads to asymmetric effective local pinning fields at the interface. The asymmetry of the hysteresis loop and the strength of the exchange-bias field can be tuned by varying the strength of cooling field. Micromagnetic modeling reproduces the experimentally observed vortex-driven magnetization process if the local pinning fields induced by exchange-coupling of the ferromagnetic and antiferromagnetic layers are taken into account.