• Title/Summary/Keyword: uniaxial anisotropy

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A Semi-graphical Analysis on the Sublattice Anisotropy of a Two Sublattice System with Uniaxial Anisotropy: Application to Pr2Fe14B

  • Kim, Y.B.;Jin-Han-Min
    • Journal of Magnetics
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    • v.3 no.3
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    • pp.74-77
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    • 1998
  • A method to analyze the anisotropy constants of a two sublattice system with uniaxial anisotropy has been investigated by extending the Sucksmith and Thompson's method to higher order anisotropy terms. Using the method, a set of anisotropy constants for Pr-sublattice of $Pr_2Fe_{14}B at 4.2K has been obtained as K_{1Pr}=5210 J/kg, K_{2Pr}=-7200 J/kg, K_{3Pr}=-770 J/kg, K_{4Pr}=4940 J/kg and K_{SPr}=700 J/kg for N_{PrFe}=2.2 T/Am^2kg^{-1}.$ The magnetization calculated by an energy minimum method by using the sublattice anisotropy constants well reproduced the experimental results and satisfied the simulation assumptions.

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Prediction of Sheet Metal Necking with Anisotropic Hardening (이방성 가공경화를 고려한 냉간 압연강판의 넥킹 예측)

  • 인정제;김권희;함주희
    • Transactions of Materials Processing
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    • v.10 no.2
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    • pp.160-166
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    • 2001
  • Uniaxial necking is studied for steel sheets with initial anisotropy. The state of anisotropy is continuously altered by subsequent tensile deformation at angles to the rolling direction. The orientations of orthotropy axes are changed before the onset of necking. A simple hardening rule which incorporates the rotations of orthtropy axes is proposed and the necking strains are predicted at angles to the rolling direction. Predicted results show good agreement with the experiments.

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A study on anisotropic characteristics of axial strengths in $\alpha$-quartz by using molecular dynamics simulation and uniaxial compression test (분자동력 학 시뮬레이션과 일축압축강도시험을 이용한 $\alpha$-quartz의 결정축에 따른 강도이방성 검토)

  • ;;市川康明;河村雄行
    • 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.

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Ellipsometric Expressions for Two Uniaxially Anisotropic Layers Coated on a Multilayered Substrate (두개의 단축이방성 박막이 있는 다층박막 시료의 타원식)

  • Kim, Sang Youl
    • Korean Journal of Optics and Photonics
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    • v.26 no.2
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    • pp.115-120
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    • 2015
  • Explicit expressions are derived for the effective reflection coefficients of obliquely incident light on a multilayered substrate coated with two uniaxially anisotropic films. Based on these reflection coefficients, ellipsometric constants are obtained as function of the tilt and azimuthal angles of the optical axes of the uniaxial films. Explicit expressions are provided, which can be used to separate the effects of surface anisotropy for anisotropic film from that of its bulk anisotropy, so that these expressions may be utilized in characterizing the surface anisotropy of alignment layers.

Magnetic and Microwave Absorbing Properties of Ti-and Co-Substituted Barium Ferrite (BaFe12-2X TiXCoXO19)

  • Han-Shin Cho;Yong-Jin Kim;Sung-Soo Kim
    • Journal of Magnetics
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    • v.4 no.2
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    • pp.65-68
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    • 1999
  • The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).

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Annealing Temperature Dependence of Exchange Bias Effect in Short Time Annealed NiFe/NiMn Bilayer Thin Film by FMR Measurement

  • Yoo, Yong-Goo;Park, Nam-Seok;Min, Seong-Gi;Yu, Seong-Cho
    • Journal of Magnetics
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    • v.10 no.4
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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.

Effect of Annealing on the Magnetic Anisotropy of Amorphous $Co_{89}Nb{8.5}Zr{2.5}$Thin Films ($Co_{89}Nb{8.5}Zr{2.5}$ 비정질 박막의 이방성에 미치는 열처리 효과)

  • 김현식;민복기;송재성;오영우
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.6
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    • pp.486-492
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    • 1998
  • The amorphous Co-based magnetic films have a large saturation flux density, a low coercive force, and a zero magnetostriction constant. Therefore, they have been studied for application to magnetic recoding heads and micro magnetic devices. However, it was found that the magnetic anisotropy was changed for each film fabrication processes. In this study, we investigated how to control the anisotropy of sputtered amorphous $Co_{89}Nb{8.5}Zr{2.5}$ films. After deposition, the rotational field annealing ant the uniaxial field annealing were performed under the magnetic field of 1.5 kOe. the annealing was done at the temperature range from 400 to $600^{\circ}C$ for one hour. As-deposited amorphous $Co_{89}Nb{8.5}Zr{2.5}$ thin film had saturation magnetization ($4\piM_5$) of 0.8 T, coercive force($_IH_C$) of 1.5 Oe, and anisotropy field($H_k$) of 11 Oe. The amorphous $Co_{89}Nb{8.5}Zr{2.5}$ thin films annealed by rotational field annealing at $500^{\circ}C$ for one hour was found to be isotropy, and $4\piM_5$ of 0.9 T was obtained from these films, Also, the magnetic anisotropy of as-deposited films could be controlled by uniaxial field annealing at $400^{\circ}C$ for one hour. Anisotropy field($H_k$) of 17 Oe and $4\piM_5$ of 1.0 T were obtained by this method.

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Effect of the Growing Temperature on the Induced Anisotropy of Mumetal Thin Film (Mumetal 박막의 성장온도가 유도자기이방성에 미치는 영향)

  • Lee, Young-Woo;Kim, Cheol-Gi;Kim, Chong-Oh
    • 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.

Thermal Annealing Effect on Ferromagnetic Resonance Properties in CoFeB/MgO Thin Film (CoFeB/MgO 박막 재료의 열처리에 따른 강자성공명 특성)

  • Yoon, Seok-Soo;Kim, Dong-Young
    • 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.

Strength Anisotropy through Artificial Weak Plane of Mudstone (인공연약면을 따른 이암의 강도이방성에 관한 연구)

  • Lee, Young-Huy;Jeong, Ghang-Bok
    • 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.