• Journal of Magnetics
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• 제16권1호
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• pp.23-26
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• 2011

The effects of titanium ions on the crystallographic and spin-rotation transitions in iron sulfide have been examined by M$\"{o}$ssbauer spectroscopy in the temperature range of 78 to 600 K. It is noted that the titanium impurity of $Ti_{0.02}Fe_{0.98}S$ affects both the crystallographic and spin-rotation transitions of the iron sulfide. 2% impurity of $Ti^{2+}$ in FeS causes the increase in the difference between the spin rotation and ${\alpha}$ transition temperature by as much as 10 K compared with that for FeS. Both 1c and 2c structures coexist in the range between the ${\alpha}$ transition temperature and approximately 26 K, with a smaller hyperfine field corresponding to the 1c structure. The spin-rotation temperature for $Ti_{0.02}Fe_{0.98}S$ was measured to be 365 K, which is 10 K lower than the ${\alpha}$ transition temperature. By the 2% impurity of $Ti^{2+}$ in FeS the N$\'{e}$el temperature appreciably is not affected.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.611-615
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• 1999

Piezoelectric properties of PMN-PZT ceramics with $CeO_2$ impurity were investigated. Mechanical quality factor, $Q_m$ of 1792, 1285 and the electromechanical coupling coefficient, $k_p$ of 0.52, 0.54 were obtained from the specimen with 0.25 and 0.5 mole % $CeO_2$ respectively. Curie temperature was decreased with the addition of $CeO_2$ while the electric coercive field was proportional to the amount of impurity. Based on the system ceramics with 0.5 mole % cerium oxide, a Rosen type piezoelectric transformer was fabricated and tested. Voltage step-up ratios of 230 and 13 were obtained from the transformer at no load and $100 k\Omega$ resistance, respectively. Experimental results showed a potential of the transformer for the practical use coupled with the expected strength increase by the grain size refinement.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.5-8
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• 1989

Conventional ceramic method has been used to prepare the green phase, $Y_2BaCuO_5$, commonly observed in 90-K superconductor $YBa_2Cu_3O_P{7-{\delta}}$as an impurity phase. The powder X-ray diffraction analysis indicates that $Y_2BaCuO_5$ has an orthorhombic symmetry with lattice parameter of a = 12.2 $\AA$, b = 5.61 $\AA$, and c = 7.14 $\AA.$ The average g-value 2.13 observed in ESR spectrum is attributable to Cu2+ stabilized in $C_{4v}$ field. From the magnetic susceptibility ($\mu$eff = 2.29 BM) and the ESR measurements, it is confirmed that Cu(II) $3d^9$ electrons in $Y_2BaCuO_5$ are localized and can be characterized by Curie-Weiss behavior. Optical reflectance spectrum shows a broad absorption peak around 680 nm due to dxy ${\rightarrow}$ $dx^2-y^2$ eletronic transition.

• Journal of Magnetics
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• 제6권3호
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• pp.77-79
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• 2001

The semi-empirical superposition model has been applied to calculate the zero field splitting parameters of $Mn^{2+}$ion in $LiTaO_3$ single crystal, assuming that $Mn^{2+}$ion occupies one of two possible sites: $Li^{l+} \;or\; Ta^{5+}$ site, respectively. The 2nd-order axial zero field splitting parameters are $958\times10^{-4}cm^{-1}\; at\; Li^{1+}$ site and $193\times 10^{-4}cm^{-1} \;at\; Ta^{5+}$ site for $Mn^{2+}$ions. The 4th-order zero field splitting parameters at $Li^{l+} \;and\; Ta^{5+}$ sites are also determined. These calculated zero field splitting parameters are very important to determine the substitutional sites of doped impurity ions in $LiTaO_3$ crystal.

• 한국진공학회지
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• 제12권S1호
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• pp.36-39
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• 2003

Field-domain dynamics and current self-oscillations are theoretically studied in quantum-well (QW) negative-effective-mass (NEM) $p^{+}pp^{+}$ diodes when the electric field is applied along the direction of the well. The origin of current self-oscillations is the formation and traveling of electric-field domains in the p-base. We have accurately considered the scattering contributions from carrier-impurity, carrier-acoustic phonon, and carrier-optic phonon. It's indicated that, both the applied bias and the doping concentration largely influence the current patterns and self-oscillating frequencies, which lie in the THz range for the NEM $p^{+}pp^{+}$ diode with a submicrometer p-base. The complicated field-domain dynamics is presented with the applied bias as the controlling parameter.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권12호
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• pp.587-591
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• 2001

This paper describes the general and efficient design method of an axial and a radial shim coils to correct field impurities of various harmonic orders in the imaging volume of Magnetic Resonance Imaging magnet. Shim coils are optimized by BCLSF subroutine of IMSL, which is the well-known commercial package for optimization, aiming at maximizing the magnitude of the desired field component as well as minimizing other field components. In order to evaluate their effect, the developed method was applied to the MRI magnet constructed in KERI.

• 한국자기학회지
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• 제24권3호
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• pp.71-75
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• 2014

정비조성으로 성장시킨 $LiTaO_3$ 단결정 및 비정비조성으로 성장시킨 $LiTaO_3$ 단결정 내에 불순물로 도핑된 $Fe^{3+}$ 상자성 불순물 이온의 바닥 상태에서의 에너지 준위를 계산하였다. $LiTaO_3$ 단결정 내에서 육방정계 대칭성을 갖는 $Fe^{3+}$ 이온의 전자 상자성 공명 상수인 분광학적 분리인자 g 및 영자기장 갈라지기 D 값을 이용하여 6개의 에너지 준위 사이의 에너지 준위를 계산하였다. 자기장을 결정학적 주축 ([100], [001], [111])과 나란하게 가하여 자기장을 증가시켜 감에 따라 얻은 에너지 준위 갈라지기는 자기장을 가한 방향에 따라서 서로 다른 값을 나타내었다. ${\mid}{\pm}5/2$ > ${\leftrightarrow}{\mid}{\pm}3/2$ >및 ${\mid}{\pm}3/2$ > ${\leftrightarrow}{\mid}{\pm}1/2$ > 사이의 전이에서 계산한 영자기장 갈라지기 값은 정비조성으로 성장시킨 $LiTaO_3$ 단결정과 비정비조성으로 성장시킨 단결정의 경우에 각각 12.300 GHz, 6.150 GHz와 59.358 GHz, 29.679 GHz이다. 결정성장 조건에 따라 에너지 준위가 상당히 다른 것으로 나타났다.

• Transactions on Electrical and Electronic Materials
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• 제2권1호
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• pp.27-31
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• 2001

$\beta$-$In_2S_3$ and $\beta$-$In_2S_3$:$Co^{2+}$ thin films were grown using the spray pyrolysis method. The thin films crystallized into tetragonal structures. The indirect energy band gap of the thin films was found to be 2.32 eV for $\beta$-$In_2S_3$ and 1.81 eV for $\beta$-$In_2S_3$:$Co^{2+}$(Co:1.0 mol%) at 198K. The direct energy band gap was found to be 2.67 eV for $\beta$-$In_2S_3$ and 2.17 eV for $\beta$-$In_2S_3$:$Co^{2+}$(Co:1.0 mol%). Impurity optical absorption peaks were observed for the ${\beta}$-$In_2S_3$:$Co^{2+}$ thin films. These impurity absorption peaks are assigned, based on the crystal field theory, to the electron transitions between the energy levels of the $Co^{2+}$ ion sited in $T_{d}$ symmetry.

• 한국진공학회지
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• 제8권2호
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• pp.121-126
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• 1999

Cu thin film was deposited by a self-ion assisted beam source (SIAB) and the assessment of the Cu films was given. Some characteristics of the source and the experimental procedure are described at various conditions such as total power, ionization efficiency, and ion current vs. deposition rate. The dependence of crystalline structure, impurity concentration, and resistivity of the Cu films deposited by SIAB on acceleration voltage are discussed.

• 전기의세계
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• 제16권4호
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• pp.11-16
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• 1967

A physical analysis is applied to the measured phenomena of aromatic organic compounds under the uniform electric field of 0.1MV/cm through 1.5MV/cm, when they are irradiated or non-irradiated respectively. Upon the observations about irradiation effects, space charge effects and their temperature dependance, the conditions of lattice defects act conspicuously on electric conductrivity, photo conductivity and dielectric breakdown. Although the qualitative agreement with Frohlich's high energy criterion theory for the above mechanisms is poor, it is concluded that the phenomena of aromatic compounds may possibly be due to the effect of lattice defects or impurity centers generated by .gamma.-ray irradiations.