• Journal of Magnetics
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• 제17권4호
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• pp.265-270
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• 2012

We report improved low-field magnetoresistance (LFMR) effects of the $La_{0.7}Sr_{0.3}Mn_{1+d}O_3-Mn_3O_4$ composite films with the nominal composition of $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-50 mol% $Mn_3O_4$. The composite films were fabricated by ex-situ solid phase crystallization (SPC) of amorphous films at the annealing temperature region of $900-1100^{\circ}C$ for 2 h in a pure oxygen atmosphere. The amorphous films were deposited on polycrystalline $BaZrO_3$ (poly-BZO) substrates by dc-magnetron sputtering at room temperature. The Curie temperatures ($T_C$) of all composite films were insignificantly altered in the range of 368-372 K. The highest LFMR value of 1.29 % in 0.5 kOe with the maximum dMR/dH value of $37.4%kOe^{-1}$ at 300 K was obtained from 900 nm-thick composite film annealed at $1100^{\circ}C$. The improved LFMR properties of the composite films are attributed to effective spin-dependent scattering at the $La_{0.7}Sr_{0.3}Mn_{1+d}O_3$ grain boundaries sharpened by adjacent chemically compatible $Mn_3O_4$ grains.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.13-13
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• 2010

Switching an elementary excitation by injecting a single carrier would offer the exciting opportunity for the ultra-high data storage technologies. However, there has been no methodology available to investigate the interaction of low energy discrete carriers with nano-structures. In order to map out the spatial dependency of such single carrier level interactions, we developed a pulse-and-probe algorithm, combining with low temperature scanning tunneling microscopy. The new tool, which we call single carrier spectroscopy, allows us to track the interaction with the target macrostructure with tunneling carriers on a single carrier basis. Using this tool, we demonstrate that it is possible not only to locally write and erase individual bi-solitons, reliably and reversibly, but also to track of creation yields of single and multiple bi-solitons. Bi-solitons are pairs of solitons that are elementary out-of-phase excitations on anti-ferromagnetically ordered pseudo-spin system of Si dimers on Si(001)-c(42) surfaces. We found that at low energy tunneling the single bisoliton creation mechanism is not correlated with the number of carriers tunneling, but with the production of a potential hole under the tip. An electric field at the surface determines the density of the local charge density under the tip, and band-bending. However a rapid, dynamic change of a field produces a potential hole that can be filled by energetic carriers, and the amount of energy released during filling process is responsible for the creation of bi-solitons. Our model based on the field-induced local hole gives excellent explanation for bi-soliton yield behaviors. Scanning tunneling spectroscopy data supports the existence of such a potential hole. The mechanism also explains the site-dependency of bi-soliton yields, which is highest at the trough, not on the dimer rows. Our study demonstrates that we can manipulate not just single atoms and molecules, but also single pseudo-spin excitations as well.

• 한국자기학회지
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• 제3권4호
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• pp.284-288
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• 1993

급속냉각기술로 제조된 $Sm_{2}Co_{3}B_{7}$ 화합물의 저온자기특성(77~450 K 범위)과 결정구조를 연구하여 경자성 재료로서의 응용가능성을 조사하였다. P6/mmm 공간격자의 $Sm_{2}Co_{3}B_{7}$은 150~160 K에서 spin-reorientation 현상을 보였으며, 결정자기이방성 자계(Ha)는 300 k 에서 135 kOe, 77 K 에서 725 kOe의 거대 이방화 에너지를 보였다. 그러나 자기능률(magnetic moment)은 25 emu/g에 그쳤다. Rietveld 분석에 의하여 $Sm_{2}Co_{3}B_{7}$의 결정구조를 밝혔으며 B(4h) 원자는 지금까지 보고된 바와는 달리 Sm(2e) 면에 위치한 것이 아니고 Sm(2e) 면에서 $0.792\;{\AA}$ 떨어져 Sm(2e)면과 Co($6i_{1}$) 면 사이에 위치함을 알았다.

• 대한화학회지
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• 제39권5호
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• pp.421-426
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• 1995

2-Hydroxyethyl methacrylate(HEMA)와 ethylene glycol dimethacrylate(EDGMA)로부터 수용액중에서 친수성 3차원 메타아크릴레이트 고분자 망상의 수화겔을 제조하여 NMR 분석법에 의해 그 친수성 메타아크릴레이트와 물 사이의 상호작용에 대하여 연구하였다. 적은 양의 물을 함유하고 있는 수화겔의 스핀-격자 이완시간$(T_1)$을 측정한 결과 물 양성자 주위의 다른 두 환경에 따른 $T_{1a}$와 $T_{2b}$가 나타났다. Poly(2-hydrocyethyl methacrylate)[p(HEMA)]-$(10{\%}\; H_2O)$ 수화겔에 대한 $T_{1a}$와 $T_{1b}$가 각각 $16.4{\times}10^{-3}\; sec$와 $58.2{\times}10^{-3}\;sec$이고, 가교된 EGDMA-p(HEMA)- $(10{\%}\; H_2O)$ 수화겔에 대한 $T_{1a}$와 $T_{2b}$가 각각 $13.2{\times}10^{-3}\; sec$와 $23.1{\times}10^{-3}\; sec$이었다. 또한 수화겔들에 대해 스핀-스핀 이완시간$(T_2)$를 측정한 결과 $p(HEMA)-(H_2O)_n$ 및 가교된 $EDGMA-p(HEMA)-(H_2O)_n$의 계에 $(T_2)$값은 물 함량이 증가함에 따라 증가하였다. $(T_2)$값들은 $(T_1)$의 값들보다 약 10배 작게 나타나고 스핀이완원리와 일치하였다.

• 한국자기학회지
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• 제26권6호
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• pp.179-184
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• 2016

스핀전달토크(Spin-Transfer Torque: STT) MRAM의 상용화를 위해서는 낮은 반전전류와 높은 열적 안정성을 동시에 만족해야 하고, 이를 위해서는 큰 스핀 분극, 강한 수직자기이방성 에너지을 가지는 물질이 요구된다. 본 연구에서는 STT-MRAM에 적합한 물질로 알려진 B2 CoFe 면심에 X(O, F, S, Cl) 원자가 위치한 $CoFeX_3$ 합금의 전자구조와 자기결정이방성(Magnetocrystalline anisotropy: MCA) 에너지를 계산하였다. X 원자가 F나 Cl일 때는 페르미 준위에서의 스핀 분극율이 각각 97 %, 96 %로, 반쪽 금속에 근접한 전자구조를 가짐을 확인할 수 있었다. 뿐만 아니라 표면이 Co 원자로 끝나는 5층 박막은 모든 X에 대해 수직 자기이방성를 가졌으며, 특히 $CoFeCl_3$의 자기이방성 에너지는 약 1.0 meV/cell로 상당히 컸다. 따라서 6, 7 족 원소를 잘 활용하면 높은 스핀 분극율과 강한 수직 자기이방성를 동시에 가지는 물질을 제조할 수 있게 되어 STT-MRAM의 상용화에 기여를 할 수 있을 것으로 기대한다.

• 분석과학
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• 제11권1호
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• pp.73-78
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• 1998

미오글로빈 시안착물(MbCN) 단백질에 대한 NMR의 HMQC 연구는 수소와 결합된 상자기성 heme 탄소 시그날의 완전한 지정을 가능토록 해준다. 이러한 상자기성 MbCN에 대한 HMQC 실험의 적용은 heme시그날뿐만 아니라 상자기성 아미노산에 대해 결합된 수소와 탄소간의 coherence를 지정하여주며 자연존재량 $^{13}C$시그날의 지정이 모든 low-spin 상자기성 heme단백질에서도 가능하다. 이러한 시그날 지정 전략은 정자기성 영역에서 공명하는 수소 시그날의 지정을 위해 사용되는 NOE에만 의존하는것 보다 훨씬 명확한 시그날지정이 가능하다. 2,4-비닐기의 ${\alpha}$-탄소들과 7-프로피온기의 ${\beta}$-탄소에서 특이한 anti-Curie형태를 보이는 것은 그들이 heme평면에 존재하고 있지 않다는 증거가 된다. Proximal His에 의해 유도된 heme의 전자 및 자성의 비대칭은 heme탄소 시그날공명이 $25^{\circ}C$에서 250 ppm의 범위에 이르도록 한다. 이러한 heme 탄소 시그날 공명은 미오그로빈 heme의 전자구조를 분석하는데 있어서 수소 시그날의 공명보다 더욱 민감한 증거로 작용할수 있다.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.12-19
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• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.235-235
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• 2006

Triphenylamine derivatives play important roles as hole transporting materials in organic light emitting devices. However, low molecular weight triphenylamine derivatives show low glass transition temperature and aggregation behavior, and the vapor deposition step of low molecular weight materials is incompatible with large area display fabrication. Conventional polymer PEDOT-PSS HTL has serious drawbacks such as the ITO anode corrosion, poor surface energy match with aromatic EMLs. To solve these problems, we introduced crosslinkable units to triphenylamine-based polymers to make insoluble HTL by thermal curing following spin-coating. Electrochemical and optical properties of the new hole transporting materials were investigated. In addition, the device characteristics obtained with new hole transporting polymers were investigated in details.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.431-432
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• 2008

We have investigated low temperature sintering characteristics of organic Ag complex. Organic Ag complex was coated on the glass substrate by spin coating method. The coated Ag complex was sintered in an air atmosphere. The sintering temperature was varied from 100 to $300^{\circ}C$ and sintering time was varied from 1 to 4 min. The thickness of the coated film was significantly decreased as the film was sintered at the temperature between 110 and $120^{\circ}C$. The sintered Ag film at temperature higher than $115^{\circ}C$ shows very low sheet resistance less than 1 ${\Omega}{/\square}$.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1277-1282
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• 2014

Concentrated flux interior permanent magnet (CFIPM) motors have the advantage that their utilization of flux linkage is more efficient than that of general IPM motors and CFIPM motors are suitable for washing machine motors, which demand low-speed, high-torque specifications. However, low efficiency occurs in the low-speed high-torque mode considering the high-speed operation for spin mode. This paper proposes a magnet overhang structure between the rotor core that reduces leakage flux and improves efficiency for a CFIPM in wash mode. Optimization of the 3D design of magnet overhang structures is performed to improve the efficiency with the same quantity of permanent magnets. The validity of the optimal design is experimentally verified through the fabrication of prototypes.