• Journal of the Korean Magnetics Society
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• v.19 no.4
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• pp.126-132
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• 2009

We have studied physical properties of MnAs thin films grown by Molecular-Beam Epitaxy as well as their post-growth annealing effects. The samples grown at $600^{\circ}C$ show the preferred crystal orientation of type-B independent of substrate whereas type-A is observed for the samples grown at below $200^{\circ}C$. The sample grown at $600^{\circ}C$ on GaAs(001) substrate is magnetized to only one direction even on the easy axis of magnetization. The magnetic properties are vastly enhanced after post-growth annealing for both MnAs/Si(001) sample with no ferromagnetism and ferromagnetic MnAs/GaAs(001) grown at $200^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.6 no.2
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• pp.93-97
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• 1996

The effects of annealing after deposition on the magnetic and magneto-optical properties of MnSbPt thin films prepared by rf sputtering were investigated. The MnSbPt alloy thin films were annealed in a vacuum with $10^{-5}$ Torr and the air, respectively, as a function of temperature and time. The films annealed at $300^{\circ}C$ for 4 hours was found to have the highest value of the saturation magnetization. The films annealed in the air did not show any thermal degradations, which indicates their chemical stability for the magneto-optical recording process. It was revealed that the $Mn_{43}Sb_{46}Pt_{11}$ films annealed at $300^{\circ}C$ for 4hours in a vacuum with $10^{-5}$ Torr exhibit high Kerr rotation angle of $0.8^{\circ}$ for the incident wavelength of 550nm, which is ascribed to the increase of the volume ratio of Clb phase. However, similar to the PtMnSb alloy thin films, these films are still horizontally magnetized and have the coercive field less than 400 Oe.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.118.1-118.1
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• 2012

In situ observations from the Wind spacecraft that statistically analyzed the solar wind proton at 1 AU has indicated that the measured proton temperature anisotropies seems to be regulated by the oblique instabilities (the mirror and oblique firehose). This result is in contradiction with the prediction of linear kinetic theory that the ion-cyclotron (for ${\beta}_{\parallel}$ < 2) and parallel firehose (for ${\beta}_{\parallel}$ <10) would dominate over the oblique instabilities. Various kinds of physical mechanisms have been suggested to explain this disagreement between the observations and linear theory. All of the suggestions consider the solar wind as a unoform magnetized plasma. However the real space environment is replete with the intermediate spatio-temporal scale variations associated with various physical quantities, such as the magnetic field intensity and the solar wind density. In this paper we present that the pervasive intermediate-scale temporal variation of the local magnetic field intensity can lead to the modification of the proton temperature anisotropy versus beta inverse correlation for temperature-anisotropy-driven instabilities. By means of quasilinear kinetic theory involving such temporal variation, we construct the simulated solar wind proton data distribution associated the magnetic fluctuations in (${\beta}_{\parallel}$, $T_{\perp}/T_{\parallel}$) space. It is shown that the theoretically simulated proton distribution and a general trend of the enhanced fluctuations bounded by the oblique instabilities are consistent with in situ observations. Furthermore, the measure magnetic compressibility can be accounted for by the magnetic spectral signatures of the unstable modes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1377-1383
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• 2014

This paper deals with eddy current loss of magnetic coupling with radial permanent magnet (PM) using analytical method such as a space harmonic method. Superposition of two kinds analysis model is used to analyze eddy current loss induced in inner PM and outer PM of magnetic coupling. When the eddy current is induced, the environmental temperature increases, and the permanent magnet(PM) characteristics are degraded because the performance of PM is greatly influenced by temperature rise. Hence, the calculation of eddy current loss becomes an important factor in the magnetic coupling. In order to analyze eddy current loss, first, on the basis of the magnetic vector potential and two-dimensional(2-D) polar-coordinate system, the magnetic field solutions of the radial magnetized PM are obtained. And we obtain the analytical solutions for the eddy current density produced by permanent magnet. Lastly, analytical solutions for eddy current loss are derived by using equivalent, electrical resistance calculated from magnet volume and analytical solution for eddy current density. This analytical results are validated by comparing with the 2-D finite element analysis (FEA).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.25-31
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• 2008

The field of induction motor is magnetized and demagnetized for each reversal of the current. This field component of the motor accounts for most of the reactive component of inductive load. Reactive power needs to sustain the electromagnetic field required for the induction motor to operate. Power factor of induction motor is usually low and power factor correction needs. Power factor becomes low by the effect of the reduction operation of load capacity. In most cases, Capacitor capacity for the power factor correction should be complied with the recommendation by the motor capacity. But Capacitor value for power factor correction can't change during the normal operation. In this paper, we analyzed characteristics of power and power factor changing by load fluctuation of low-voltage small size induction motor and show that lower power factor correction's parameter of existing recommendation should be revised by new value.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.474-474
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• 2010

현재 반도체시장의 확장으로 인해서 기존의 300mm 웨이퍼에서 450mm의 웨이퍼를 사용하는 공정으로 변화하는 추세이다. 450mm 웨이퍼로 대면적 화되면서 기존 300mm 공정 때보다 훨씬 효율적인 플라즈마 소스 즉, 고밀도이고, 고균등화(high uniformity) 플라즈마 소스를 필요로 한다. 본 논문에서는 고밀도 플라즈마 소스인 유도 결합형 플라즈마(Inductively Coupled Plasma ; ICP)에 축 방향의 약한 자기장을 인가시킨 자화된 유도결합형 플라즈마(Magnetized Inductively Coupled Plasma : MICP)[1]를 제안하여 기존 ICP와의 차이점을 살펴보았다. 실험 방법으로 레이저 유기 형광법(Laser Induced Fluorescence : LIF)[2]을 이용하여 플라즈마 쉬스(Sheath) 내의 전기장을 외부 자기장의 변화에 따라 높이별로 측정하고 그 결과로부터 쉬스의 전기적 특성을 살펴보았다. 플라즈마의 특성상 탐침이나 전극에 전압을 인가하면 그 주위로 디바이 차폐(Debye Shielding)현상이 일어나서 플라즈마 왜곡이 일어난다. 그렇기에 플라즈마, 특히 플라즈마 쉬스의 특성을 파악하기 위해서 레이저라는 기술을 사용하였다. 레이저는 고가의 장비이고 그 사용에 많은 경험지식(know-how)를 필요로 하지만 플라즈마를 왜곡시키지 않고, 플라즈마의 밀도, 온도, 전기장 등 많은 상수(parameter)들을 얻어 낼 수 있다. 또한 3차원적으로 높은 분해능을 가지고 있는 장점이 있다. 강한 전기장이 있는 곳에서 입자들의 고에너지 준위가 전기장의 세기에 비례하여 분리되는 Stark effect[3] 이론을 이용하여 플라즈마 쉬스내의 전기장을 측정하였다. 실험은 헬륨가스 700mTorr 압력에서 이루어졌다. 기판의 파워를 50W에서 300W까지 변화시키면서 기판에 생기는 쉬스의 전기장의 변화를 살펴보았고, 자기장을 인가한 후 동일한 실험을 하여 자기장의 유무에 따른 플라즈마 쉬스의 전기장 변화를 살펴보았다. 실험결과 플라즈마 쉬스의 전기장의 변화는 기판의 파워와 플라즈마 밀도에 크게 의존함을 알았다. 기판의 파워가 커질수록 쉬스의 전기장은 커지고, 기판에 생기는 Self Bias Voltage역시 음의 방향으로 커짐을 확인 하였다. 또한 자기장을 걸어주었을 경우 쉬스의 두께가 얇아짐으로써 플라즈마의 밀도가 증가했음을 확인 할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.792-800
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• 2021

This paper presents a new structure for a linear active magnetic bearing using a Halbach magnet array. The proposed magnetic bearing consisted of a Halbach magnet array, center magnet, and single coil. The proposed linear active magnetic bearing has a high dynamic force compared to the previous study. The high dynamic force could be obtained by varying the thickness of a horizontally magnetized magnet. The new structure of Halbach linear active magnetic bearing has a high dynamic force. Therefore, the proposed linear active magnetic bearing increased the bandwidth of the system. Magnetic modeling and optimal design of the new structure of the Halbach linear active magnetic bearing were performed. The optimal design was executed on the geometric parameters of the proposed linear active magnetic bearing using Sequential Quadratic Programming. The proposed linear active magnetic bearing had a static force of 45.06 N and a Lorentz force constant of 19.54 N/A, which is higher than previous research.

• Journal of Astronomy and Space Sciences
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• v.39 no.2
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• pp.67-77
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• 2022

The elements that impact the dynamics and collaborations of waves and particles in the magnetosphere of planets have been considered here. Saturn's internal magnetosphere is determined by substantiated instabilities and discovered to be an exceptional zone of wave activity. Interchanged instability is found to be one of the responsible events in view of temperature anisotropy and energization processes of magnetospheric species. The generated active ions alongside electrons that constitute the populations of highly magnetized planets like Saturn's ring electron current are taken into consideration in the current framework. The previous and similar method of characteristics and the perturbed distribution function have been used to derive dispersion relation. In incorporating this investigation, the characteristics of electromagnetic ion cyclotron wave (EMIC) waves are determined by the composition of ions in plasmas through which the waves propagate. The effect of ring distribution illustrates non-monotonous description on growth rate (GR) depending upon plasma parameters picked out. Observations made by Cassini found appropriate for modern study, have been applied to the Kronian magnetosphere. Using Maxwellian ring distribution function of ions and detailed mathematical formulation, an expression for dispersion relation as well as GR and real frequency (RF) are evaluated. Analysis of plasma parameters shows that, proliferating EMIC waves are not developed much when propagation is parallelly aligned with magnetosphere as compared to waves propagating in oblique direction. GR for the oblique case, is influenced by temperature anisotropy as well as by alternating current (AC) frequency, whereas it is much affected only by AC frequency for parallel propagating waves.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.375-382
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• 2007

Nondestructive testing (NDT) by using the electromagnetic methods are useful for detecting cracks on the surface and subsurface of the metal. However, when the material contains both ferromagnetic and paramagnetic materials, it is difficult for NDT to detect and analyze cracks using this method. In addition the existence of a partial ferromagnetic material can be incorrectly characterized as a crack in the several cases. On the other hand a large crack has sometimes been misunderstood as a partially magnetized region. Inconel 600 is an important material in atomic energy plant. A nickel film is coated when a crack a appears on an Inconel substrate. Cracks are difficult to detect on the combined material of an Inconel substrate with a nickel film, which are paramagnetic and ferromagnetic material respectively. In this paper, a scan type magnetic camera, which uses a complex induced current-magnetic flux leakage (CIC-MFL) method as a magnetic source and a linearly integrated Hall sensor array (LIHaS) on a wafer as the magnetic sensors, was examined for its ability to detect cracks on the combined material. The evaluation probability of a crack is discussed. In addition the detection probability of the minimum depth was reported.

• Journal of the Korean Magnetics Society
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• v.23 no.6
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• pp.193-199
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• 2013

The regional distribution of magnetic isotropy depending on the post annealing condition for the dual-type structure GMR-SV (giant magnetoresistance-spin valve) of NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe multilayer was investigated. The rotation of in-plane ferromagnetic layer induced by controlment of the post annealing temperature inside of the vacuum chamber. The magnetoresistive curves of a dual-type IrMn based GMR-SV depending on the direction of the magnetization easy axis of the free layer and the pinned layer are measured by between $0^{\circ}$ and $360^{\circ}$ angles for the applied fields. The optimum annealing temperature having a steady and isotropy magnetic sensitivity of 1.52 %/Oe was $107^{\circ}C$ in the rotational section of $0{\sim}90^{\circ}$. By investigating the switching process of magnetization for an arbitrary measuring direction, the in-plane orthogonal magnetization for the dual-type GMR-SV multilayer can be used by a high sensitive biosensor for detection of magnetized micro-beads.