• 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.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.126-127
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• 1998

• Journal of the Korean Magnetics Society
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• v.14 no.4
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• pp.115-119
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• 2004

We measured in-plane 2 dimensional magnetization vector using two pick-up coil sets and investigate the relationship between magnetization vector and anisotropic magnetoresistance. We can determine magnetization vector by measuring magnetic moment in x and y direction simultaneously. As the uniaxial magnetic anisotropy of permalloy film increases, magnetoresistance approaches the expectation which is calculated from the angle between current vector and magnetization vector. Magnetoresistance ratio is linearly proportional to the y moment magnitude which is parallel to the current direction.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.46-50
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• 2002

Soft magnetic Mumetal thin film was fabricated under magnetic field at various substrate temperatures. High vacuum annealing was carried out at 200$\^{C}$ during 1 hr. The in-plane anisotropy of Mumetal thin film was determined from hysteresis loops measured by VSM when the sample axis varied from the field direction from 0°to 180°. As the substrate temperature increases, the coercivity in easy direction decreases, but uniaxial anisotropy deviates from the field direction. After vacuum annealing at 200$\^{C}$ for 1 hr, the uniaxial anisotropy is improved irrespective of substrate temperature. When the substrate temperature was 50$\^{C}$, the anisotropy field is 4.3 Oe. As the substrate temperature increases anisotropy field decreases. Uniaxial anisotropy of Mumetal thin film was formed best at 50$\^{C}$ before and after annealing.

• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.10-14
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• 2011

We have measured the ferromagnetic resonance (FMR) signal in as deposited and $400^{\circ}C$ annealed CoFeB/MgO thin film to investigate the annealing effect on magnetic anisotropies and FMR linewidth (${\Delta}H_{PP}$). The uniaxial anisotropy field ($H_{K1}$) was only observed in the as deposited sample. Whereas, in the $400^{\circ}C$ annealed sample, the biaxial anisotropy field ($H_{K2}$) was additionally observed in accompany with uniaxial anisotropy field ($H_{K1}$). The appearance of biaxial anisotropy fields was originated from the crystalline growth of bcc CoFeB(001) from the MgO(001) interface and by the B diffusion during thermal annealing. Also, the ${\Delta}H_{PP}$ of $400^{\circ}C$ annealed sample was increased compared with that of as deposited sample, which was due to the broad distribution of the magnetization axis by the biaxial anisotropy.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.70-79
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• 2000

We carried out NPT-ensemble (constant-number of particles, pressure, and temperature) Molecular Dynamics (MD) simulations for measuring strength anisotropy under uniaxial compressive stress rotated to the crystallographic axes in $\alpha$-quartz. Uniaxial compressive strengths of a single quartz crystal were measured in directions of the a- and c-axis. Measured uniaxial strength of a single quartz crystal was higher in the direction parallel to the c-axis than that measured in the direction normal to the c-axis. However the reverse was found in calculated uniaxial strengths by MD simulation. The contradictive result of strengths was observed in both cases but was found to be different in origin. Strength anisotropy of defectless $\alpha$-quartz crystal in MD simulation is basically caused by structural difference of quartz. By contrast, anisotropy of measured strength in the uniaxial compression test is related to oriented micro-defects developed during crystal growth.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.111-120
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• 2008

The characteristic of induced anisotropy is investigated in this study for the Pohang mudstone involving the cut plane discontinuity. The uniaxial and triaxial compression tests are performed for anisotropic rocks with artificial joint to look into anisotropic strength characteristics. Both the uniaxial compressive strength and triaxial compressive strength show the lowest value at the angle of cut plane, ${\beta}=30^{\circ}$ and the shoulder type of anisotropy is obtained. Anisotropy ratio (Rc) in uniaxial compression measures 9.0, whereas Rc=1.29-1.98 in triaxial compression is appeared. A series of analyses are made with the test results to derive the suitable parameter values when it is applied to the Ramamurthy (1985) failure criterion. The result of uniaxial compression test is analyzed by introducing the n-index into Ramamurthy failure criterion. The result shows that, n=l is suitable for ${\beta}=0^{\circ}{\sim}30^{\circ}$ and n=3 is suitable for ${\beta}=30^{\circ}{\sim}90^{\circ}$. To analyze the result of triaxial compression test by Ramamurthy failure criterion, anisotropy ratio in uniaxial compression test is added to Ramamurthy's equation and material constants are estimated by modified Ramamurthy's equation. When these values are applied back to Ramamurthy failure criterion, the predicted values are well fitted to the test results. And strength anisotropy for failure criteria of Jaeger (1960), McLamore & Gray (1967) and Hoek & Brown (1980) are also investigated.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.11a
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• pp.32-35
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• 1991

• Proceedings of the Korean Magnestics Society Conference
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• 1997.11a
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• pp.110-111
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• 1997

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.329-333
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• 1996

We have studied the magnetoresistance and the magnetic anisotropy of Cu/(NiFe/Ni/NiFe) metallic multi layers grown on Si(100), Si(111), $4^{\circ}\;tilt-cut\;Si(111)$ or glass substrate. When the multilayer was grown on $4^{\circ}\;tilt-cut\;Si(111)$ with $50\;{\AA}$ of Cu underlayer, an in-plane uniaxial anisotropy was observed. On the other substrates such as Si(100), Si(111) or glass with Cu underlayer, however, no appreciable anisotropy was shown. The multilayer grown with NiFe or Ni underlayer or without underlayer did not show any arnsotropy even on $4^{\circ}\;tilt-cut\;Si(111)$. When $10\;{\AA}$ of NiFe was deposited prior to the Cu underlayer, the anisotropy in Cu/(NiFe/Ni/NiFe) multilayer disappeared.