• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.145-150
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• 1996

The magnetic thin films can be prepared without vacuum process and under the low temperature ( < $100^{\circ}C$) by ferrite plating. We have performed ferrite plating of $Fe_{3-x}Mn_{x}O_4(x=0.0~0.023)$ films on glass plate at $80^{\circ}C$. We got the film $9000\AA$ in thickness, having a mirror-like luster. The composition parameter, x, in the $Fe_{3-x}Mn_{x}O_4$ films is much smaller then the corresponding on, x', in the reaction solution(x/x'=O.04). The saturation magnetization($M_{s}$) of $Fe_{3}O_{4}$ ferrite film as measured by a VSM was $M_{s}$=480 emu/cc which agrees with $Fe_{3}O_{4}$ bulk samples.

• Journal of the Korean Magnetics Society
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• v.12 no.5
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• pp.163-167
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• 2002

In order to study the temperature dependence of the magnetostatic wave modes for an YIG thin film, grown by a liquid phase epitaxy method, The ferromagnetic resonance was performed by an FMR spectrometer in the temperature range -140$\^{C}$∼200$\^{C}$. The magnetostatic surface wave and backward volume wave modes show periodic excitations in parallel configuration. The resonance fields of all modes and intensities decreased with decreasing the temperature. All magnetostatic modes can be well explained by the Walker and Damon-Eshbach theory. The calculated saturation magnetization Ms of the YIG thin film was increased with decreasing the temperature. The line widths of magnetostatic modes changed in various trends with decreasing the temperature.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.710-715
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• 2001

반응소결공정(RSP : Reaction Sintering Process)을 이용하여 YF댸₃와 Fe₂O₃의 성분에 소결첨가재 Bi₂O₃를 첨가하여 YIG를 합성하였다. Bi₂O₃첨가량과 소결온도에 따른 YIG 소결체의 미세구조 및 자기적 특성변화에 대해 주사전자현미경, X-선 회절분석기 및 시료 진동형 자력계를 이용하여 조사하였다. 소량의 소결첨가재 Bi₂O₃첨가시 YIG 소결체의 격자상수는 12.387에서 12.420 Å으로 증가하였다. 이는 상대적으로 이온반경이 큰 Bi 이온이 12면체 Y 이온 자리로 치환되었기 때문인 것으로 여겨진다. Bi₂O₃를 1.0 wt% 첨가하였을 때 비교적 균질한 미세구조를 보였으며, 1350℃에서 소결한 YIG의 밀도가 이론밀도의 98% 이상의 치밀화를 보였다. Bi₂O₃가 0.0 wt%에서 1.5 wt%로 첨가량이 증가함에 따라 상온에서의 포화자화값(M/sub s/)은 조금씩 증가하는 경향을 보였으나 큰 변화는 없었다. 반응소결공정을 이용 YIG 소결시 소결첨가제 Bi₂O₃가 1.0 wt%이고, 소결온도 1350℃에서 비교적 우수한 소결특성과 자기특성을 가지는 YIG 소결체를 얻을 수 있었다.

• Journal of the Korean Magnetics Society
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• v.3 no.3
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• pp.221-228
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• 1993

The general requirements of recording media include recording performance, environmental stability, runnability on the drive or deck, and manufacturability. CoCrMo thin films were prepared using RF sputtering system for a study on chemical stability. Surface degradation of the CoCrMo thin film was studied by SEM, XPS and AES. Surface degradation was found to be dependent of sputtering condition and Mo content. Addition of Mo to CoCr thin film improved dramatically its surface degradation resistance in dilute sulfuric acid, as indicated by active-passive transition appeared in electrochemical polarization curve. Futhermore, the passive current density was decreased with increasing Mo content. The reduction in a number density of corrosion sites by Mo addition vms observed, after accelerated corrosion test. AES survey indicated that corrosion occured on the site with Cr depletion and highly concentrated chloride ions.

• Journal of the Korean Magnetics Society
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• v.19 no.4
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• pp.147-151
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• 2009

The saturation magnetization and uniaxial anisotropy constant were obtained from magnetization and torque curves measurement in high resistive CoFeHfO thin film. The measured results were used for the analysis of the microwave complex permeability based on Landau-Lifshitz-Gilbert (LLG) theory. The high resistive CoFeHfO thin films showed very low damping constants of ${\alpha}$ = 0.014. The results are interpreted in terms of various magnetic phase with very low damping constant, which were existing inside the CoFeHfO thin film, through the linewidth analysis of the ferromagnetic resonance signal with magnetic field.

• Ceramist
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• v.8 no.1
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• pp.50-56
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• 2005

압전재료의 다양한 에너지 변환특성 중 기계-전기 에너지간 변환 특성만을 이용하고자 하는 경우로 한정하고, 압전재료의 물성 및 진동모드, 재료물성 평가 사례들을 요약하여 소개하였다. 그러나 이상에서 설명한 압전특성은 매우 개략적인 개념으로서 우수한 압전 응용부품을 개발하기 위해서는 몇 가지 유의할 사항들이 있다. 압전재료는 보다 기본적으로 열에너지, 기계에너지, 전기에너지, 나아가서 Maxwell 방정식에 의해서 전기장과 연결되는 자기에너지까지도 연결시켜서 상호간에 에너지 변환작용을 일으킬 수 있는 특성을 가진다. 기계적 변형(S) = 탄성변형효과 + 역압전효과 + 열팽창효과 전기적 변위(D) = 압전효과 + 유전효과 + 초전효과 즉, 압전 응용부품이 온도변화 및 자기장이 인가되는 환경에서 순수하게 압전현상만을 이용하고자 한다면, 응용분야 및 주위환경에 따라 압전세라믹 소자가 외부 환경변화에 반응을 하지 않도록 적절한 차단 대책을 수립하여야만 한다. 그러나 압전재료의 외부 자기장의 변화에 대한 반응도는 전기장에 대한 반응도에 비해서 매우 작으므로 통상 무시해도 무방하다고 본다. 그리고 압전재료에서 전기장-기계장의 선형성이 보장되는 크기에는 뚜렷한 한계가 있고, 선형성 영역을 벗어나면 이력특성에 의해 비선형 특성 및 포화상태를 보이게 된다는 점 또한 주의하여야 할 점이다. 또한 압전특성은 Curie 온도이하에서만 존재하고, 그 이상의 온도에서는 쌍극자들의 지나친 운동성에 의해 결정 대칭성이 변하여 압전특성이 소멸되므로 사용 온도 구간에 엄격한 제한을 두어야 함도 응용에 유의하여야 한다.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.42-44
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• 2012

We have studied a means to control the composition of nickel-iron thin films. By changing current and voltage applied to a electroplating electrolyte we could manipulate the relative concentration of nickel and iron in the thin films, which caused variations of coercivity, squareness, and saturation magnetic field. As we increase the content of iron in the thin films by using potentiostatic and galvanostatic plating, the grain size was increased and the coercivity was reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.899-903
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• 2013

A self-bearing is an electric machine that achieves both rotational actuation and magnetic levitation using a single magnetic structure. To be able to stably levitate the rotor in a self-bearing, one needs to have an inverse of the force-current model. However, the force-current model in a self-bearing motor is typically not square. Furthermore, the elements of the matrix vary with respect to the rotational angle, resulting in singularities of the pseudo-inverse at various angles. In this paper, we propose a new force-current model that eliminates the singularities by adding a constraint in coil currents. This constraint eliminates the flux density in the stator core so that the saturation problem in the previous study is avoided. By implementing this force-current model, we are able to implement a levitation controller for a toroidally-wound self-bearing BLDC motor. The model inversion and levitation are validated experimentally.

• Journal of the Korean Magnetics Society
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• v.12 no.4
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• pp.154-159
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• 2002

Amorphous FeBSiNb alloy ribbons having bulk glass forming ability and high saturation magnetic flux density were produced by single-roller melt spinning apparatus in the thickness range of 22∼102㎛. With the increase of thickness, the coercive force and squareness ratio decreased, while maximum permeability and AC permeability increased. However electrical resistivity was almost constant. Furthermore refined and complex magnetic domain structure was observed in thicker ribbons owing to the change in internal magnetic anisotropy. For the alloy with the thickness of 81㎛, small coercive force of 24 mOe and high effective permeability of 12,000 at 1㎑ were obtained, those are considered to be better comparing to the conventional soft magnetic amorphous alloys (∼20 ㎛). The good soft magnetic properties of the thick FeBSiNb amorphous alloys were attributed to the decrease in surface pinning effect during wall motion, appearance of perpendicular anisotropy and resulted domain refinement.

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.97-103
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• 2001

Polycrystalline thin films of La$_{2}$3/Sr$_{1}$3/MnO$_3$(LSMO) were prepared by water-based sol-gel processing on thermally oxidized Si(100) substrate. The thickness dependence of the low-field tunnel-type magnetoresistance properties at room temperature was studied. Tunnel-type magnetoresistance at low-field is found to be strongly dependent on film thickness. Maximum value of tunnel-type magnetoresistance of LSMO thin films was appeared at the film thickness of ~1500 $\AA$. This behavior can be explained in terms of dead layer between LSMO thin film and Si(100) substrate and thermal lattice strain effect in the LSMO thin films.