• 대한기계학회논문집A
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• 제28권3호
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• pp.245-250
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• 2004

This paper proposes a new method of measuring an air interface distance between a solid immersion lens(SIL) applied magneto-optic technology and the disk surface. For applying near-field recording (NFR) technology to the magneto-optic storage devices for the next generation, it is positively necessary to maintain the small air gap under about 100㎚. We design an apparatus that consists of some optical components such as a prism, a polarizer and an analyzer. By using the Fresnel reflection coefficient equation, Jones matrices calculation and Malus's law, we establish a mathematical model for understanding the characteristics of the system. The simulations are based on the mathematical model and through the simulation results which is made with various cases we can estimate the performance of the new optical gap sensor system. Experimental results, which are also based on the mathematical model for specific cases, are in good agreement with simulated ones and demonstrate the possibility as the new optical gap sensor.

• The Korean Journal of Ceramics
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• 제1권2호
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• pp.91-95
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• 1995

Polycrystalline bismuth- and aluminum- substituted dysporsium and yttrium iron garnet (Bi2R3-xAlyFe5-yO12, R=Dy or Y, $0\leqx\leq3, \; 0\leqy\leq3$) films have been prepared by pyrolysis. The crystallization temperatures, the solubility limit of bismuth ions into the garnet phase, and magnetic and magneto-optic properties of the films have been investigated as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures as a function of bismuth and aluminum concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration. It was found that the crystallization temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained temperatures of these films rapidly decreased as bismuth concentration (x) increased up to x=1.5 and then remained unchanged at x>1.5, whereas, showed no changes as aluminum concentration (y) increased up to y=1.0 and then gradually increased at y>1.0. The solubility limit of bismuth ions was x=1.8 when y=0 but increased to x=2.3 when y=1.0. It was demonstrated that the magnetic and magneto-optic properties of the dysprosium iron garnet films could be tailored by bismuth and aluminum substitution suitable for magneto-optic recording as follows. The saturation magnetization and coercivity data obtained for the films indicated that the film composition at which the magnetic compensation temperature became room temperature was y=1.2 when x=1.0. Near this composition the coercivity and the squareness of the magnetic hysteresis loop of the films were several kOe and unit, respectively. The Curie temperatures of the films increased with the increase of x but decreaed with the increase of y, and was 150-$250^{\circ}C$ when x=1.0 and y=0.6-1.4. The Faraday rotation at 633 nm of the films increased as x increased but decreased as y increased, and was 1 deg/$\mu\textrm{m}$ when x=1.0 and y=1.0. Based on the data obtained, the appropriate film composition for magneto-optic recording was estimated as near x=1.0 and y=1.0 or $BiDy_2AlFe_4O_{12}$.

• Journal of Magnetics
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• 제3권2호
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• pp.49-54
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• 1998

Dependence of magnetic and magneto-optic properties on composition of amorphous NdFe alloys has been studied to identify a promising magneto-optic recording material in the wavelength of a blue laser beam. From the view point of crystallographic state, perpendicular magnetic anisotropy energy and polar Kerr rotation angle, the Nd-rich region was found to be suitable for the research purpose.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1994년도 추계연구발표회 논문개요집
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• pp.90-91
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• 1994

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1994년도 추계연구발표회 논문개요집
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• pp.96-97
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• 1994

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 추계연구발표회 논문개요집
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• pp.24-25
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• 1998

• 한국자기학회지
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• 제14권2호
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• pp.65-70
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• 2004

도메인 확장형 광자기 디스크 시스템(magnetic amplifing magnetooptical system; MAMMOS)의 기록마크 시뮬레이션을 위한 온도분포와 재생신호를 연구하였다. 정지된 디스크에서 레이저 빔에 의한 기록층과 이웃하는 층들의 온도 분포를 계산하였으며, 마크 크기와 길이 및 위치를 계산하였다. 또한 마크 모양에 따른 재생신호의 크기, 기록층에 기록되는 마크의 재생신호 및 판독층에서 확대된 재생신호를 시뮬레이션 하였다. 간소화된 열전달 특성 모델을 계산함으로써, 기록층과 인접한 층에서의 온도분포를 시간의 함수로 계산하였다. 마크 크기는 디스크가 회전할 때 기록 빔 펄스 파형에 의한 온도분포로부터 계산하였으며, 기록빔 펄스 파형으로부터 디스크의 온도분포를 이용하여 마크의 길이와 위치를 계산하였다. 재생신호는 디스크의 반사도 패턴과 가우시안 빔의 컨볼루션 연산을 이용하여 계산하였다. 판독층에서 빔 크기만큼 확대된 도메인의 재생신호가 기록층에서의 초승달 모양 마크에 기한 재생신호보다 2배 이상 증가되는 것을 알 수 있었다.

• Journal of Magnetics
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• 제3권1호
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• pp.21-30
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• 1998

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media, due to large Kerr rotation angle in the wavelength of a blue laser beam. however, since multilayer structure, as well as amorphous structure, is a non-equilibrium state in terms of free energy and MO recording is a kind of thermal recording which is conducted aound Curie temperature (Tc) of the recording media, when the multilayer is used for the MO recording media, changes in the multilayer structure are occurred as the amorphous structure do. Therefore, the assessment of the structural stability in the Co/Pd multilayer is crucially important both for basic research and applications. As the parameter of the structural stability in this research, modulation amplitude and particle size of the Co/Pd multilayer are measured in terms of Ar sputtering pressure and heat treatment temperature. From the results of the research, we find out that the magnetic exchange energy in the structural changes of a magnetic multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Journal of Magnetics
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• 제8권1호
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• pp.50-59
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• 2003

Spatial light modulators (SLMs) are centrally important devices in volumetric recording, data Processing, Pattern recognition and other optical systems. Various types of reusable SLMs with two-dimensional pixel arrays have been intensively developed. Of these, magneto-optic spatial light modulators (MOSLMs) have advantages of high switching speed, robustness, nonvolatility, and radioactive resistance. In this article, we review recent development work on MOSLMs, mainly in relation to our own studies.

• Journal of Magnetics
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• 제2권2호
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• pp.58-66
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• 1997

Recently, artificially modulated magnetic multilayer materials, for examples giant magnetoresistant magnetic head materials and magneto-optic recording materials in the wavelength of a blue laser beam, attract great attention in the electronics industry due to their unique properties derived from the modulated multilayer structure. Since the multilayer structure as well as amorphous structure, is non-equilibrium state in terms of free energy, an assessment of the thermal staibility in the multilayer structure is crucially importnat both for basic research and applications. In this review paper, effective microscopic interdiffusion process in the two dimensional multilayer structure will be described in terms of steep concentration gradient effect, strain effect and magnetic transition effect.