• Journal of Magnetics
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• v.7 no.3
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• pp.94-97
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• 2002

The dependence on nickel oxide thickness and a ferromagnetic layer thickness in unidirectional and isotropic exchange-coupled NiO/NiFe(Fe) bilayer films was investigated by magnetic force microscopy to better understand the relation between magnetic domain structure and exchange biasing at microscopic length scales. As the NiO thickness increased, the domain structure of unidirectional biased films formed smaller and more complex in-plane domains. By contrast, for the isotropically coupled films, large domains generally formed with increasing NiO thickness including a cross type domain with out-of plane magnetization orientation. The density of the cross domain is proportional to exchange biasing field, and the fact that the domain mainly originated from the strongest exchange coupled region was confirmed by imaging in an applied external field during a magnetization cycle.

• Journal of Magnetics
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• v.7 no.1
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• pp.9-13
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• 2002

The dependences of microscopic magnetic domain on film thickness in unidirectional and isotropic exchange-coupled NiO/NiFe bilayers were investigated by magnetic force microscopy to better understand for exchange biasing. As NiO thickness increases, microscopic domain structure of unidirectional biased film changed to smaller and more complicated domains. However, for isotropic-coupled film a new cross type domain appeared with out-of plane magnetization orientation. The density of the cross domain is proportional to exchange biasing fields and the fact that the domain was originated by the strongest exchange coupling region was confirmed from the dynamic domain configuration during a magnetization cycle.

• Proceedings of the Korean Magnestics Society Conference
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• 1995.10a
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• pp.54-55
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• 1995

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.221-225
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• 2005

Formation of a narrow magnetic domain wall is demonstrated by micromagnetics simulations. It is found that the domain wall width can be shrunk in a local exchange coupled system. The local exchange coupled system means that only a part of a ferromagnetic layer has an exchange coupling with another ferromagnetic layer. The system can be considered as two parts in the lateral dimensions: one is an exchange coupled region and another is a free region. Since the two regions have quite different local switching fields, the domain wall will be formed at the interface between the two regions at moderate field ranges.

• Journal of Magnetics
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• v.1 no.2
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• pp.69-74
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• 1996

Justeresos loops of melt-spun Nd13Fe77B10 cooled down at remanent state were measured at 4.2 K and 250 K. The hysteresis loops were analysed on the basis of the Stoner-Wohlfarth (S-W) model, the inter-grain exchange coupled single domain (SD) model and micromagnetism. The coercivity higher than that predicted from the S-W model and the striking shift of the thin minor loop along the H-axix observed at the fields of Hmax=4MA/m at 4.2 K indicated new evidences for the inter-grain exchange interaction . The S-W model failed in explaining the high iHc and the shift of the thin minor loop. The exchange coupled SD model was found to explain the experimental results qualitatively without difficulties associated with the S-W model. The micromagnetic calculations using a finite element technique simulated the experimental results fairly well quntitatively.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.75-82
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• 2010

A recent progress on the prediction of the thermal stability of a nanostructured exchange-coupled trilayer is reviewed. An analytical/numerical combined method is used to calculate its magnetic energy barrier and hence the thermal stability parameter. An important feature of the method is the use of an analytical equation for the total energy that contains the magnetostatic fields. Under an assumption of the single domain state, the effective values of all the magnetostatic fields can be obtained by averaging their nonuniform values over the entire magnetic volume. In an equilibrium state, however, it is not easy to calculate the magnetostatic fields at the saddle point due to the absence of suitable methods of the accessing its magnetic configuration. This difficulty is overcome with the use of equations that link the magnetostatic fields at the saddle point and critical fields. Since the critical fields can readily be obtained by micromagnetic simulation, the present method should provide accurate results for the thermal stability of a nanostructured exchange-coupled trilayer.

• Journal of the Korean Magnetics Society
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• v.26 no.2
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• pp.50-54
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• 2016

We analyzed the angular dependence of ferromagnetic resonance linewidth in exchange coupled CoFe/MnIr bilayers. The maximum and minimum linewidth was observed in the easy and hard direction of unidirectional anisotropy by exchange coupling, respectively, and it was well agreed with the angular dependence of exchange bias field. The maximum linewidth was due to the twist of CoFe magnetization near CoFe/MnIr interface from direction of pinned MnIr spin to direction of applied magnetic field. While, minimum linewidth more higher than that of CoFe was related to rotatable anisotropy field, and explained by easy axis distribution of MnIr grains.

• Journal of Magnetics
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• v.13 no.2
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• pp.43-52
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• 2008

The objective of this paper is to review the magnetic and magneto-transport properties of Co/$Co_2TiSn$ consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/$Co_2TiSn$ system, which has a $Co_2$TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/$Co_2TiSn$ thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/$Co_2TiSn$ films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.1-5
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• 2000

A waveguide of coupled optical modulator was fabricated on LiNbO$_3$ based on proton exchange with self-aligned thin film electrode method. The electrode pattern was designed using a self-aligned method. After proton exchange process, the waveguide was prepared by annealing process. The initial crossover state of the fabricated 2$\times$2 coupled optical modulator was observed with controlling the annealing process variables and the structure of self-aligned thin film electrodes. It was shown form the present work that the measured crosstalk is -29.5[dB] and 8.0[V] of detected modulating voltage.

• Journal of the Korean Magnetics Society
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• v.27 no.3
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• pp.77-81
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• 2017

The rotatable anisotropy effect was observed in the ferromagnetic resonance measurement in exchange coupled ferromagnetic/antiferromagnetic thin films and it was due to rotation of antiferromagnetic layer by the exchange coupling energy. We analyzed the CoFe thickness dependence of rotatable anisotropy field and ferromagnetic resonance linewidth in exchange coupled $CoFe(t_F)/MnIr(2.5nm)$ thin films. The rotatable anisotropy field was inversely propositional to the CoFe thickness and it was well fitted by the rotatable anisotropy energy of $0.96erg/cm^2$. The ferromagnetic resonance linewidth were linearly propositional to the rotatable anisotropy field in $t_F$ < 50 nm, while it was more dominated by the eddy current effect in $t_F$ > 50 nm.