• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.778-781
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• 2002

MI(Magneto-Impedance) sensor which is made by thin films has significantly high detecting sensitivity in weak magnetic field. It also has a merit to be able to build in the low power system. Its structure is simple, which makes it easier to prepare a miniature. In this study, its magnetic permeability and anisotropy field$(H_k)$ as a function of a thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and excellent soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and $320^{\circ}C}$ respectively for 2 hours. Anisotropy field$(H_k)$ of film is measured by using a MH loop tracer. Its magnetic permeability of a film is measured over the frequency range from 1 MHz to 750MHz. It has shown that the magnetic permeability of amorphous CoZrNb film is decreased due to the skin effect with increasing a thickness of the CoZrNb film, and hence its driving frequency is lowered. And, it was examined on the permeability and impedance to fabricate the MI sensor which acts at a low frequency by thickening a CoZrNb film relatively.

• 전자공학회논문지A
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• 제32A권1호
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• pp.97-102
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• 1995

The ferromagnetic resonance properties of Mg ferrites which have various porosity grain size, and saturation magnetization are measured at one frequency. This allows a determination of the anisotropy field(Ha). The saturation magnetization multiplied by porosity is the resonance magnetic field. As the saturation magnetization increases, the linewidth decerases due to decrement of magnetic inhomogenity in sample. the porosity is a major factor broadening the linewidth for Mg ferrite when porosity is more thatn 6%, and the anisotropy field is dominant when porosity is less than 6%.

• 한국자기학회지
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• 제23권2호
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• pp.37-42
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• 2013

본 연구에서는 NiFe 박막 시편을 마그네트론 스퍼터링 방법으로 제조하여 박막면 기준으로 수직면(out-of-plane) 자기장 방향과 수평면(in-plane) 자기장 방향에 따른 강자성 공명 자기장을 측정하였다. 수직면 자기장 방향에 따른 강자성 공명 자기장으로부터 유효자화량($M_{eff}$)을 도출하였으며, NiFe 두께에 따른 $M_{eff}$의 감소는 $K_s=-0.23\;erg/cm^2$의 값을 갖는 표면 이방성 상수에 기인하였다. 또한 수평면 자기장 방향에 따른 강자성 공명 자기장으로부터 수평면에서의 일축 이방성 자기장을 도출하였다. 한편, 일축 이방성 에너지의 자화 용이축이 두께가 감소함에 따라 시편 제조 시 인가한 자기장의 반대 방향으로 회전하고 있었으며, 이러한 현상은 시편 표면에 형성된 NiFeO의 반강자성 특성에 의한 현상으로 설명하였다.

• Journal of Magnetics
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• 제4권1호
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• pp.33-37
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• 1999

Unidirectional magnetic anisotropy field ($H_an$) was investigated for thin films of $CdCr{2-2x}In_{2X}Se_4 (0$\leq$x$\leq$0.2). This anisotropy originates from the microscopic anisotropic Dzyaloshinskii-Moriya (DM) interaction which arise from the spin-orbit scattering of the conduction electrons by the nonmagnetic impurities. This interaction maintains the remanent magnetization in the direction of the initial applied field. Then the single easy direction of the magnetization is parallel to the direction of the magnetic field. The anisotropy produced by field cooling is unidirectional I.e. the spins system deeps some memory of the cooling field direction. The chalcogenide spinel of$ CdCr_{2-2x}In){2X}Se_4$belongs to the class of the magnetic semiconductors. The magnetic disordered state is obtained when ferromagnetic structure is diluted by In. Then we have the mixed phase characterised by coexistence the magnetic long range ordering (IFN-infinite ferromagnetic network) and the spin glass order (Fc-finite clusters). The total magnetic anisotropy energy depends on the state of magnetic ordering. In our study we concentrated on the magnetic state with reentrant transition and spin glass state. The polycrystalline $ CdCr_{2-2x}In){2X}Se_4$ thin films were obtained by rf sputtering technique. We applied the ferromagnetic resonance (FMR) and M-H loop techniques for determining the temperature composition dependencies of Han. From the experimental data, we have found that Han decreases almost linearly when temperature is increased and in the low temperature is about three times bigger at SG state with comparison to the state with REE.

• Journal of Magnetics
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• 제18권4호
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• pp.380-385
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• 2013

We find a metastable vortex state of the perpendicular magnetic anisotropy free layer in spin transfer torque magnetic tunneling junctions by using micromagnetic simulations. The metastable vortex state does not exist in a single layer, and it is only found in the trilayer structure with the perpendicular magnetic anisotropy polarizer layer. It is revealed that the physical origin is the non-uniform stray field from the polarizer layer.

• Journal of Magnetics
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• 제4권3호
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• pp.88-91
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• 1999

A series of NiO/NiFe bilayer films are deposited with the variation of Ar sputtering pressure for the NiO layers only. As the pressure for the NiO layers increases, the exchange anisotropy field (HEX) decreases gradually and becomes extinct at 2.5 mTorr, at which the maximum coercive force (HC) in the NiO/NiFe films is obtained. Randomly oriented columnar structures with HEX a few tens of Oe and oriented columnar structures with zero HEX are observed in the NiP layers by highvoltage hihg-resolution transmission electron microscopy. The vanishing of the HEX in the oriented structures is attributed to the lack of exchange anisotropy energy (EEX) between NiO and NiFe layers, which results in little contribution of interfacial unidirectional pinning anisotropy to the interface of NiO/NiFe bilayer.

• Macromolecular Research
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• 제15권5호
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• pp.396-402
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• 2007

The dielectric properties and various pattern-forming states of dual-frequency material in a nematic phase, as well as its mixture containing low concentrations of reactive monomers, are reported. The dielectric relaxation behaviors of nematic MLC 2048 are presented and compared to its mixture containing both mesogenic and nonmesogenic reactive monomers. The sign-inversion frequency of the dielectric anisotropy was significantly shifted on the addition of small amounts of the reactive monomers. However, all three mixtures used in this study essentially exhibited the same field-induced instabilities at different frequencies and voltage domains of the applied electric field. A broad band of modulated states were found to exist above a critical voltage and within a voltage dependent frequency band in the vicinity of the sign-inversion frequency, $f_I$, of the dielectric anisotropy. As the $f_I$ of the mixtures shifted, so did the bands of the modulated state of the different mixtures and the temperatures, which were well matched with the measured $f_I$ value.

• Geomechanics and Engineering
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• 제11권4호
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• pp.515-530
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• 2016

In this paper, five different quantitative parameters were proposed for the characterization of the primary roughness which is the component of surface morphology that prevails during large strike-slip faults of more than 50 m. These parameters are mostly the anisotropic properties of rock surface morphology at various scales: (i) coefficient ($k_a$) and degree (${\delta}_a$) of apparent structural anisotropy of surface; (ii) coefficient ($k_r$) and degree (${\delta}_r$) of real structural anisotropy of surface; (iii) surface anisotropy function P(${\varphi}$); and (iv) degree of surface waviness ($W_s$). The coefficient and degree of apparent structural anisotropy allow qualifying the anisotropy/isotropy of a discontinuity according to a classification into four classes: anisotropic, moderately anisotropic/isotropic and isotropic. The coefficient and degree of real structural anisotropy of surface captures directly the actual surface anisotropy using geostatistical method. The anisotropy function predicts directional geometric properties of a surface of discontinuity from measurements in two orthogonal directions. These predicted data may subsequently be used to highlight the anisotropy/isotropy of the surface (radar plot). The degree of surface waviness allows qualifying the undulation of anisotropic surfaces. The proposed quantitative parameters allows their application at both lab and field scales.

• 비파괴검사학회지
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• 제23권6호
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• pp.635-644
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• 2003

To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.

• 한국자기학회지
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• 제15권1호
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• pp.25-29
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• 2005

고상에피택시방법으로 성장한 YIG 박막의 온도에 따른 자기특성의 변화를 결정이방성과 수직이방성을 중심으로 측정하였다. 고상에피택시법의 열처리 온도가 낮을 경우 전위가 발생하여 응력을 해소함으로써 수직이방성이 유도되지 않았으나 높은 온도에서 열처리된 박막에는 우수한 에피택시성장으로 잔류응력이 축적되어 수직이방성이 유도되었다. 수직이방성자장은 기판과 박막의 열팽창계수의 차이로 결정자기이방성이 없어지는 온도까지 선형으로 감소하였고, 보자력도 온도가 증가하면 감소하였다. YIG(111) 에피택시박막에 수직이방성이 유도되었을 경우 결정이방성상수 $K_1$을 $H_k=4K_1/3M_s$로부터 결정할 수 있었다. 온도에 따른 초자화율의 거동은 Hopkinson 효과로 잘 설명되어졌으며 측정결과를 이용하명 상자성 자화율이 큰 기판위에 성장한 박막의 큐리온도를 쉽게 측정할 수 있었다.