• Journal of the Korean Magnetics Society
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• v.10 no.3
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• pp.112-117
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• 2000

We inserted CoO layer in NiO spin-valves to improve on magnetoresistance and exchange coupling field. The magnetoresistance ratio was increased from 4.5 % to 5.5 % with the increase of CoO thickness. We can not find the dependence between (111) texture and exchange coupling by the measurement of XRD of CoO/NiO spin-valves. The surface roughness of CoO layer, 6.1 $\AA$ is twice more than that of NiO layer, 3.1 $\AA$. The increase of exchange coupling field and coercive field in the CoO/NiO spin-valves will be due to increasing roughness. We prepared the NiO/CoO/NiO/CoO/NiO spin-valves to reduce coercive field and the coercive field decreased from 110 Oe to 50 Oe, and the coupling field is not changed from 70 Oe.

• Korean Journal of Materials Research
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• v.13 no.6
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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.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.135-135
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.15.1-15.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 1995.10a
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• pp.86-87
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• 1995

• Proceedings of the Korean Magnestics Society Conference
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• 2001.10a
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• pp.52-53
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• 2001

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.111-111
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• 2017

• Proceedings of the Korean Magnestics Society Conference
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• 1999.10a
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• pp.100-101
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• 1999

• Journal of the Korean Magnetics Society
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• v.24 no.3
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• pp.81-85
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• 2014

Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ nanocomposite ferrite were prepared by sol-gel combustion method. Nanocomposite was calcined at temperature range of $600{\sim}900^{\circ}C$ for 1 h. According to the diffraction patterns, hard/soft nanocomposite was indicated to the coexistence of the magnetoplumbite structural $BaFe_{12}O_{19}$ and spinel $Ni_{0.5}Zn_{0.5}Fe_2O_4$ and agree with the standard data (JCPDS 10-0325). The particle size of nanocomposite turn out to be less than 90 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite ($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that for the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite. $(BH)_{max}$ is increased, generally.

• 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.