• Progress in Superconductivity
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• 제11권2호
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• pp.135-140
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• 2010

We propose a variational wave function for the ground state of the magnetic heavy fermion (HF) systems, in which both the Kondo and the RKKY interactions are variationally incorporated and the local f-orbital state exists as a linear combination of a full local moment state and a fully compensated state (mixed wave state). We describe the mechanism for the mixed wave ground state based on the large-N treatment of the Kondo lattice Hamiltonian added with RKKY interaction. With the mixed wave ground state we can explain several puzzling experiments in magnetic HF compounds such as a small value of local moment, coexistence of the antiferromagnetic (AFM) and the paramagnetic (PM) phases, local quantum criticality, etc.

• Journal of Magnetics
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• 제15권1호
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• pp.1-6
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• 2010

The magnetic properties of amorphous Fe were investigated by examining the electronic structures of structurally disordered Fe systems generated from crystalline bcc and fcc Fe using a Monte-Carlo simulation. As a rst principles band method, the real space spin-polarized tight-binding linearized-mun-tin-orbital recursion method was used in the local spin density approximation. Compared to the crystalline system, the electronic structures of the disordered systems were characterized by a broadened band width, smoothened local density of states, and reduced local magnetic moment. The magnetic structures depend on the short range configurations. The antiferromagnetic structure is the most stable for a bcc-based disordered system, whereas the noncollinear spin spiral structure is more stable for a fcc-based system.

• 한국재료학회지
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• 제4권6호
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• pp.704-709
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• 1994

Crystal Structure and Magnetic Properties of $(LaS)_xCrS_2(x \approx 1.20$)가 1273K에서 $La_S_3$ , Cr, S의 혼합물의 반응으로부터 합성되었다. $(LaS)_xCrS_2( x\approx 1.20$)의 XRD회절 pattern은 monoclinic의 LaS-부격자, triclinic의 $CrS_{2}$-부격자와 그들의 초격자로서 해석되었다. 부격자의 온도의존성을 저온에서 X-선 회절분석으로 조사하였다. 77K~실온의 온도역에서 $(LaS)_xCrS_2(x \approx 1.20$)의 자기자화율을 Faraday balance법으로 측정하였다. $(LaS)_xCrS_2(x \approx 1.20$)은 실온 $\sigma$ -H plot에서 paramagnetic한 거동을 나타내었다. 관측된 유효자기 moment($\mu_{eff}$)는 $Cr^{3+}$을 spin-only에 의한 것과 $La^{3+}$을 spin-only와 orbital에 의한 것으로 계산할 경우 잘 일치되었다.

• Investigative Magnetic Resonance Imaging
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• 제18권1호
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• pp.70-74
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• 2014

방선균증은 그람 양성 혐기성 균인 악티노미세스과 (Actinomycetaceae)로 인하여 발생하며, 안구 감염의 원인으로서의 방선균증은 드물다고 알려져 있다. 저자들은 60세 남자에게서 발견된 안구 봉와직염을 포함한 경부안면형과 중추신경계형 방선균증의 자기공명영상 소견을 보고하고자 한다. T1 강조 안구 자기공명영상에서 안구를 비롯한 두경부에 다수의 비정상적 조영증강 병변이 보였으며, 일부에서는 농양들으로 생각되는 저 신호강도들을 포함하고 있었다. 병변은 절개 생검을 통하여 방선균증으로 진단되었고, 이후 페니실린계 항생제를 사용하여 완치되었다.

• Bulletin of the Korean Chemical Society
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• 제26권12호
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• pp.1965-1968
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• 2005

Extended H$\ddot{u}$ckel molecular calculations have been used to analyze how the magnitude of exchange coupling is influenced by the structural distortions in a series of dinuclear six-coordinate copper(II) complexes bridged by the planar bis-bidentate oxalate anion. Copper(II) ions have distorted octahedral surroundings, one being axially elongated and the other compressed. The magnetic interaction is strong in the former complexes and very weak in the latter. This is interpreted as resulting from a switching of magnetic spin orbitals due to the structural distortions (bond elongation or compression) of the copper sites.

• Journal of Magnetics
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• 제15권2호
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• pp.51-55
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• 2010

The electronic and magnetic properties of Cu-doped GaN with a Cu concentration of 6.25% and 12.5% are examined theoretically using the full-potential linear muffin-tin orbital method. The magnetic moment of Cu atoms decreases with increasing Cu concentration. The spin-polarization of Cu atoms is reduced due to the Cu d-d interaction depending on the distance between the nearest neighbouring Cu atoms. Cu atoms exhibits a clustering tendency in GaN. For Cu-adsorbed GaN thin films with a surface coverage of 0.25, the ferromagnetic state is found to be the energetically favourable state with an induced magnetic moment of $0.54\;{\mu}_B$ per supercell.

• Journal of Magnetics
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• 제5권3호
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• pp.76-80
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• 2000

Soft x-ray standing waves produced by a multilayer interference substrate add depth-sensitivity to magnetic circular dichroism to resolve changes in Co magnetism across a 10${\AA}$ distance from the Co center to the Co-Pd interface of a Pd/Co/Pd trilayer having in-plane magnetization. Large enhancements of in-plane orbital and spin magnetic moments, as well as the number of d holes, are strongly localized in a thin interface layer. These results provide new insight into the phenomenon of magnetic anisotropy at buried interfaces, and suggest a broad applicability of such standing wave measurements to interface magnetism studies.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.207-216
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• 2000

Soft x-ray standing waves produced by a multilayer interference substrate add depth-sensitivity to magnetic circular dichroism to resolve changes in Co magnetism across a 10 ${\AA}$ distance from the Co center to the Co-Pd interface of a Pd/Co/Pd trilayer having in-plane magnetization. Large enhancements of in-plane orbital and spin magnetic moments, as well as the number of d holes, are strongly localized in thin interface layer. These results provide new insight into the phenomenon of magnetic anisotropy at buried interfaces, and suggest a broad applicability of such standing wave measurements to interface magnetism studies.

• Journal of Astronomy and Space Sciences
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• 제36권2호
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• pp.75-86
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• 2019

UV Psc is a typical RS CVn type system undergoing dynamic chromosphere activity. We performed photometric observations of the system in 2015 and secured new BVR light curves showing well-defined photometric waves. In this paper, we analyzed the light curves using Wilson-Devinney binary code and investigated the orbital period of the system. The combination of our light curve synthesis with the spectroscopic solution developed by previous investigators yielded the absolute parameters as: $M_1=1.104{\pm}0.042M_{\odot}$, $R_1=1.165{\pm}0.025R_{\odot}$, and $L_1=1.361{\pm} 0.041L_{\odot}$ for the primary star, and $M_2=0.809{\pm}0.082M_{\odot}$, $R_2=0.858{\pm}0.018R_{\odot}$, and $L_2=0.339 {\pm}0.010L_{\odot}$ for the secondary star. The eclipse timing diagram for accurate CCD and photoelectric timings showed that the orbital period may vary either in a downward parabolic manner or a quasi-sinusoidal pattern. If the latter is adopted as a probable pattern for the period change, a more plausible account for the cyclic variation may be the light time effect caused by a circumbinary object rather than an Applegate-mechanism occurring via variable surface magnetic field strengths.

• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.17-27
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• 2007

Minimum-time attitude maneuvers of three-axis stabilized spacecraft are presented to study the feasibility of using three magnetic torquers perform large angle maneuvers. Previous applications of magnetic torquers have been limited to spin-stabilized satellites or supplemental actuators of three axis stabilized satellites because of the capability of magnetic torquers to produce torques about a specific axes. The minimum-time attitude maneuver problem is solved by applying a parameter optimization method for orbital cases to verify that the magnetic torque system can perform as required. Direct collocation and a nonlinear programming method with a constraining method by Simpson's rule are used to convert the minimum-time maneuver problems into parameter optimization problems. An appropriate number of nodes is presented to find a bang-bang type solution to the minimum-time problem. Some modifications in the boundary conditions of final attitude are made to solve the problem more robustly and efficiently. The numerical studies illustrate that the presented method can provide a capable and robust attitude reorientation by using only magnetic torquers. However, the required maneuver times are relatively longer than when thrusters or wheels are used. Performance of the system in the presence of errors in the magnetometer as well as the geomagnetic field model still good.