• Applied Science and Convergence Technology
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• 제23권5호
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• pp.273-278
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• 2014

Using ab initio calculations, the effects of uniaxial, biaxial, and hydrostatic strains on the magnetocrystalline anisotropy of $L1_0$-orderd FePt and CoPt alloys were systematically investigated. Interestingly, the rates and the signs of magnetocrystalline anisotropy changes of FePt and CoPt were determined by the directions and dimensions of strains. The calculation results are consistent with the previous experimental observations and are expected to provide directions to tailor magnetic properties of various types of $L1_0$-ordered FePt and CoPt systems.

• 한국광학회지
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• 제23권6호
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• pp.274-280
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• 2012

기존의 반사형 타원계에 광분할기와 프리즘 등의 광학소자를 추가하여 $8.0{\mu}m$ 보다 작은 면적에서 시료의 광학이방성을 측정할 수 있는 수직반사형 타원계를 제작하였다. 수직반사 구조를 구현하기 위해 사용된 광학소자들의 편광작용을 보정하여 광학이방성 측정의 정확도를 향상시켰다. 비편광 광분할기를 사용하고 사분파장 위상지연자를 장착하며 광섬유를 제거하고 파장영역을 최적화하여 광학이방성인자 측정값의 표준편차를 0.00083 으로 줄이고 방위각 변화에 따른 rutile 시료의 광학이방성인자의 변동폭을 0.015 이하로 줄일 수 있었다.

• 한국자기학회지
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• 제6권3호
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• pp.158-164
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• 1996

동시진공증착으로 제조한 Tb/Co 조성변조 다층박막의 자기적 성질 및 광자기적 성질을 Tb의 두께 및 Tb/Co 각 층의 두께 비에 대하여 연구하였으며 열처리시 자기적 거동의 변화를 분석하였다. Tb의 두께가 $12{\AA}$일 때가 가장 큰 범위에서 수직자기이방성을 보였고, 최고 $6.52{\times}10^{6}erg/cc$의 수직자기이방성 에너지 값을 얻었다. Tb의 두께가 $12{\AA}$에서 최대 수직자기이방성을 보이는 것은 Tb/Co 계면에서의 Tb-Co이종 원자쌍뿐만 아니라 Tb-Tb, Co-Co 동종 원자쌍도 수직자기이방성에 기여하기 때문으로 사려된다. Kerr 회전각$({\theta}_k)$은 수직자기이방성 에너지$(K_{u})$와 비례, 평균 스핀분산각$(\alpha)$과는 반비례하는 거동을 보였으며 Tb두께 $12{\AA}$, 두께비 1.55에서 최대 Kerr 회전각 $0.28^{\circ}$를 얻었다. 열처리시 나타나는 비정상적인 이력곡선은 Tb층의 우선적인 산화로 Tb의 유효조성이 감소하여 조성이 보상점 근처로 이동하게 되어 Co층과의 보자력 차이가 커져서 나타난다.

• 한국자기학회지
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• 제4권2호
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• pp.179-183
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• 1994

자왜 또는 자기이방성의 측정에 사용되는 전자석의 여자전류를 측정에 필요한 수초간만 흘려서 에너지 소모 및 측정시의 최대난점인 시료의 온도변화의 문제를 극소화하였다. 따라서 전자석의 냉각장치는 생략되고 크기와 전원의 용량도 극소화되었다. 공기간격 22 mm, 자극의 단면적 $40{\times}25mm^{2}$에서 0.5 T의 자장발생에는 180 W의 전원으로 족하였다. 시료의 자왜와, 자기이방성에 의한 토크를 전기용량센서에 의하여 측정하여 $10^{-8}$의 자왜분해능과 1 nJ의 토크 분해능을 얻었다. $0.02{\times}0.8{\times}10mm^{2}$의 연자성 리본의 형상이방성을 이용하여 이방성 측정시의 토크값을 교정하였다.

• Journal of Magnetics
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• 제9권2호
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• pp.60-64
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• 2004

In this paper calculations of magnetisation and magnetoresistance characteristics of the Spin Valve (SV) and Pseudo Spin Valve (PSV) spintronics structures are reported and compared with the experimental data. The magnetisation reversal process was analysed with respect to the Stoner- Wohlfahrt model of total surface energy in terms of uniaxial anisotropy, exchange coupling between ferromagnetic layers, unidirectional exchange anisotropy of pinned layer (modelled by exchange coupling between magnetisation of pinned layer and net magnetisation of antiferromagnetic layer with high anisotropy). The numerical simulation of the model to the experimental magnetisation data yielded the above parameters for SV and PSV structures. These parameters were used to more sophistically micromagnetic modelling tool originating from the project called Object Oriented Micromagnetic Framework. Influence of the shape anisotropy of the Magnetic Tunnelling Junction cell used in MRAM was simulated by means of micromagnetic simulations. Results were compared to those obtained from the spot Kerr measurements.

• 대한기계학회논문집B
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• 제22권3호
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• pp.280-293
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• 1998

Numerical study on turbulent and mean structures of a turbulent boundary layer with longitudinal and spanwise pressure gradient is carried out by using Reynolds-stress-model (RSM). The existence of pressure gradient in a turbulent boundary layer causes the skewing or divergence of rates of strain, which contributes to production of turbulent kinetic energy. Also, this augmentation of production due to extra rates of strain can increase the turbulent mixing and cause the anisotropy of turbulent intensities in the outer layer. This paper uses the Reynolds Stress Model to capture anisotropy of turbulent structures effectively and is devoted to compare the results computed by using RSM and the standard k-.epsilon. model with experimental data. It is concluded that the RSM can produce the more accurate predictions for capturing the anisotropy of turbulent structure than the standard k-.epsilon. model.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2014년도 임시총회 및 하계학술연구발표회
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• pp.120-121
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• 2014

We investigate the field-dependence of energy barrier for various cell diameters and two type of geometry through the NEB method. We find that the energy barrier can depend strongly on the cell size when the switching is governed by the domain wall motion. Moreover we also examine the cell size dependence of energy barrier for two type of cell geometry. In the presentation, we will discuss the effect of domain wall formation and more various cell size on the energy barrier in detail.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 임시총회 및 하계학술연구발표회
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• pp.81-81
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• 2012

• 한국전기전자재료학회논문지
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• 제14권2호
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• pp.139-144
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• 2001

In this study, we have investigated the photoinduced birefringence of Ag plarized-photodoping in double-layer of Ag doped chalcognide thin films and dependence of polarization states in chalcogenide thin films. Also, we have investigated the polarization dependence of photoinduced birefringence and the anisotropy of absorption in an amorphous As$\sub$40/Ge$\sub$10/Se$\sub$15/S$\sub$35/ chalcogenide thin films using two 632.8nm He-Ne lasers, which have a smaller energy than the optical energy gap (E$\sub$OP/) of the film, i.e., an exposure of sub-bandgap light (hν$\sub$op/). The photoinduced phenomena of Ag polarized-photodooping increasing the linear dichroism(d), about 84% and birefringence(Δn), about 23%. It will offer lots of information for the photodoping mechanism and analysis of chalcogenide thin films.

• Journal of Magnetics
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• 제3권3호
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• pp.78-81
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• 1998

Large magneto crystalline anisotropy energy and demagnetization energy of rare earth-transition metal (RF-TM) alloys play roles of bottlenecks towards their commercial applications for giant magnetostrictive and blue wavelength magneto optical recording materials, respectively. To solve the above problems, boron is added into amorphous RE-TM alloys to produce its electron transferring. The boron added amorphous RE-TM alloys show novel magnetic and magneto-optical properties as follows; 1) an amorphous $(Sm_{33}Fe_{76})$97B3 alloy obtains the magnetostriction of$ -550{times}10^{-6}$ at 400 Oe compared with saturation magnetostriction of$ -60{\times}10^{-6}$ in conventional Ni based alloys, 2) an amorphous$ (Nd_{33}Fe_{67})_{95}B_5$ alloy increases effective magnetic anisotropy to$ -0.5{\times}10^{-6} ergs/cm^3 from -3.5{\times}10^6 ergs/cm^3$ without boron, which correspond to the polar Kerr rotation angles of 0.52$^{\circ}$and 0.33$^{\circ}$, respectively. These results attribute to selective 2p-3d electron orbits exchange coupling (SEC).