• 한국진공학회지
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• 제8권4A호
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• pp.461-464
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• 1999

Planar type thin film inductors have a potential for the application of miniaturized DC-DC converters. For those high current applications, the magnetic film with high current capability is required. The current capability of magnetic films is mainly determined from high saturation magnetization (4$\piM_s$) as well as large anisotropy field $(H_k)$. We fabricated a double rectangular spiral thin film inductor which consist of magnetic layer, coil and insulator. Highest inductance values as well as best frequency characteristics can be obtained from 5 MHz and quality factor exhibit about 7.

• Journal of Magnetics
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• 제20권1호
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• pp.11-20
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• 2015

In this work, Monte Carlo simulation was employed to model the stretchable Ising monolayer film to investigate the effect of the spatial distance variation among magnetic atoms on magnetic behavior of the film. The exchange interaction was considered as functions of initial interatomic distance and the stretched distance (or the strain). Following Bethe-Slater picture, the magnetic exchange interaction took the Lennard-Jones potential-like function. Monte Carlo simulations via the Wolff and Metropolis algorithms were used to update the spin systems, where equilibrium and dynamic magnetic profiles were collected. From the results, the strain was found to have strong influences on magnetic behavior, especially the critical behavior. Specifically, the phase transition point was found to either increase or decrease depending on how the exchange interaction shifts (i.e. towards or away from the maximum value). In addition, empirical functions which predict how the critical temperatures scale with initial interatomic distance and the strain were proposed, which provides qualitatively view how to fine tune the magnetic critical point in monolayer film using the substrate modification induced strain.

• 한국표면공학회지
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• 제31권5호
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• pp.261-265
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• 1998

We investigated compositional separation of Co-23%Cr magnetic alloy thin films with varying film thicknesses. Saturation magnetization and magnetic microstructures were investigated using vibrating sample magnetometer (VSM) and scanning probe microscope (SPM), respectively. Saturation magnetization was as 700 emu/cc for films below 50 nm-thick, and changed to 430 emu/cc for the ones above 2000 nm-thick. This may be due to increment of molar volume of Cr-enriched phase as film thickness increases. The surface grain size in AFM (atomic force microscope) measurement becomes larger as film thickness increases. The MFM (magnetic force microscope) reveals that magnetic microstructure is changed from the fine spherical domains to the maze type domains as film thickness increases. We conclude that employing thickness of Co-22%Cr films below 50 nm is favorable for high density recording in order to enhance perpendicular saturation magnetization and SNR (signal to noise ratio).

• 센서학회지
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• 제26권3호
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• pp.186-191
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• 2017

In this study, we investigated the simultaneous detection properties of organic vapor, pressure difference, and magnetic field using a single rugate-structured free-standing porous silicon (RFPS) thin film. Both the wavelength and the intensity of the rugate peaks were changed in the reflectivity spectrum measured at the thin film surface while the organic vapor was exposed to the RFPS thin film. However, when the pressure difference and the magnetic field were exposed to the film, only the rugate peak intensity was changed. Therefore, it is possible to distinguish whether or not the organic vapor is detected by simultaneously changing the rugate peak wavelength and intensity. In addition, a method of distinguishing between the pressure difference and the magnetic field detection signal has been derived by rapidly modulating the direction of the magnetic field. This study shows that it is possible to simultaneously detect and distinguish various objects using a single RFPS thin film, and it is found that porous silicon can be utilized as a sensor sufficiently.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.294-294
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• 2014

Developing magnetic thin films with desirable physical properties is a key step to promote research in spintronics. Organic-based magnetic material is a relatively new kind of materials which has magnetic properties in a molecular and microscopic level. These materials have been constructed by the coordination between 3d transition metal and organic materials producing long-range magnetic orders with a relatively high transition temperature. However, these materials were mostly synthesized as a form of powder, which is difficult to study for their physical properties as well as apply for electronic/spintronic devices. In this study, we have employed physical vapor deposition (PVD) to develop a new organic-based hybrid magnetic film that is achieved by the coordination of Fe and tetracyanoquinodimethane (TCNQ). The IR spectra of the grown film show modified CN vibration modes in TCNQ, which suggest a strong bonding between Fe and TCNQ. The thin film has both ferromagnetic and semiconducting behaviors, which is suitable for molecular spintronic applications. The high resolution photoemission (HRPES) spectra also show shift of 1s peak point of nitrogen and the carbon 1s peaks display traces of charge transfer from Fe to TCNQ as well as shake-up features, which suggest strong bonding and anti-bonding nature of coordination between Fe and TCNQ.

• 한국재료학회지
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• 제4권5호
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• pp.535-540
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• 1994

Thin film magnet was fabricated by radio frequency magnetron sputtering using $Nd_13/(Fe.Co)_{70}B_{17}$ alloy target and magnetic properties were investigated according to sputtering conditions from the metallurgical point of view. we could obtain the best preferred orientation of $Nd_2Fe_{14}B$ phase at substrate temperatures between $450^{\circ}C$ and $460^{\circ}C$ with the input power 150W, and thin films had the anisotropic magnetic properties. But, as the thickness of thin film increased, the c-axis orientation gradually tended to be disordered and magnetic properties also become isotropic. Just like Nd-Fe-B meltspun ribbon, the microstructure of thin film magnet was consisted of very find cell shaped $Nd_2Fe_{14}B$ phase and the second phase along grain boundary. While, domain structure showed maze patterns whose magnetic easy axis was was perpendicular to film plane of thin film. It was concluded from these results that the perpendicualr anisotropy in magnetization was attributed to the perpendicular alignment of very find $Nd_2Fe_{14}B$ grains in thin film.

• Applied Microscopy
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• 제48권4호
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• pp.128-129
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• 2018

Soft ferromagnetic materials are utilized for various electromagnetic devices such as magnetic recording heads and magnetic shielding. In situ observation of magnetic microstructures and domain wall motions are prerequisite for understanding and improving their magnetic properties. In this work, by the Fresnel (out-of-focus) method of Lorentz microscopy, we observe the domain wall motions of polycrystalline Ni/Ti thin film layers triggered by single-shot laser pulse. Random motions of domain walls were visualized at every single pulse.

• Journal of Magnetics
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• 제16권4호
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• pp.403-407
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• 2011

Metal-insulator type, nano-granular soft magnetic films have been reviewed from the viewpoint of high frequency magnetic materials. The formation of nano-granular structure is related to the magnitude of heat of formation of intergranule materials. Variation of the ratio of granule phase to intergranule phase in the film is found to produce various characteristics in the magnetic properties of the film. The HRTEM observation reveals that neighboring granules in the film with above 60 at.% Co, contact at considerable points and the films show soft magnetic properties which are explainable in terms of the random anisotropy model for nano-crystalline materials. Addition of Ni group elements in Co-O based films enhances their anisotropy field up to 400 Oe and they exhibit excellent frequency response of permeability. Also, large electromagnetic noise suppression effect is demonstrated as one of their potential applications.

• 한국자기학회지
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• 제3권3호
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• pp.208-214
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• 1993

Ta을 미량 첨가한 Co-Cr-Ta 박막의 높은 수직보자력의 원인을 알아보기위하여 회전우력자력계 (torque magnetometer)와 진동시료형 자력계(VSM)를 이용하여 Co-Cr 박막과 Co-Cr-Ta 박막의 수직자기이방 성에너지를 조사하였다. Co/sub 81.7/Cr/sub 16.7/Ta/sub 1.6/ 박막의 수직이방성에너지는 동일 기판온도에 서 성막한, 비슷한 용질원자량의 Co/sub 81/Cr/sub 19/ 박막보다 높았다. 그 원인을 분석하기 위하여 as- sputtered 상태의 박막들을 annealing 처리한 후 수직자기이방성에너지의 변화를 조사하였다. annealing 처 리에 의해 수직자기이방성에너지는 감소하였다. 이러한 annealing 처리에 의한 수직자기이방성에너지의 감 소량은 CoCrTa 박막의 경우 더 켰으며, annealing 처리후의 수직자기이방성에너지는 이원계 및 삼원계 박막 에서 비슷한 값을 보였다. 이는 Ta 첨가에 의해 as-sputtered 박막내 용질원자의 편석(segregation) 정도가 증가하며, 이러한 편석 의 증가로 박막내에 형태자기이방성의 기여가 증가하여 수직자기이방성에너지의 증가가 있었던 것으로 해석 된다. 또한 이 러한 용질원자의 편석의 증가에 의한 수직자기이방성에너지의 증가로 박막의 보자력도 증가 한 것으로 생각된다.

• 한국표면공학회지
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• 제44권4호
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• pp.137-143
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• 2011

The internal stress and magnetic properties (coercivity and squareness) of Ni-Fe nano thin film synthesized by electrodeposition method were studied as a function of acidic chloride bath conditions (composition and temperature) and current density. Fe deposition patterns were different depending on the temperature of the solution, the stress of film decreased with increasing the solution temperature, and the depending on the amount of Fe deposition showed a parabolic shape. The grain size of film was inversely proportional to stress of thin film. The internal stress of thin film and magnetic properties were deeply relevant, and the stress of thin film had a relationship with bath conditions and grain size of the thin film surface.