• Title/Summary/Keyword: Superconductivity and magnetism

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Phenomenological Theory of Superconductivity and Magnetism in Ho$_{1-x}Dy_xNi_2B_2C$

  • Doh, Hyeon-Jin;Sigrist, Manfred;Cho, B.K.;Lee, Sung-Ik
    • 한국초전도학회:학술대회논문집
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    • v.9
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    • pp.196-199
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    • 1999
  • The coexistence of the superconductivity and magnetism in the Ho1-xDyxNi2B2C is studied by using Ginzburg-Landau theory. This material violates the standard do Gennes scaling showing the coexistence and complex interplay of superconducting and magnetic order yielding an anomalous phase diagram. We propose a phenomenological model which includes two magnetic and two superconducting order parameters accounting for the multi-band structure of this material. We describe the magnetic fluctuations and order and demonstrate that they lead to anomalous behavior of the upper critical field. The doping dependence of Tc in Ho1-xDyxNi2B2C showing a reentrance behavior are analyzed yielding a very good agreement with experimental data.

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Phase Diagram of Spin Density Wave and $\pi$ Phase Shifted Superconductivity in the Fe Pnictide Superconductors (철 초전도체에서 스핀 밀도 파와 $\pi$ 위상 차 초전도성의 상전이 그림)

  • Lee, Na-Young;Choi, Han-Yong
    • Progress in Superconductivity
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    • v.11 no.2
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    • pp.112-117
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    • 2010
  • We examine phase transition of the spin density wave and $\pi$ phase shifted superconductivity in the Fe pnictide superconductors. The phase diagram is described in the plane of the temperature T and the doping x with the combination of Ginzburg-Landau expansion of the free energy near the multi-critical temperature $T_c$ and the self-consistent numerical iterations of the gap equations. The phase separation or coexistence is determined by computing the 4-th order terms of the free energy which is confirmed by the numerical calculations. We can show the phase coexistence when the spin density wave is incommensurate. And the first order phase transition is observed near the boundary between commensurate and incommensurate spin density wave.

Observation of bubble dynamics under water in high-magnetic fields using a high-speed video camera

  • Lee, Seung-Hwan;Minoru Takeda
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.04a
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    • pp.291-298
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    • 2004
  • The observations of rapid motion of bubbles under water for approximately 50 ms or less in high-magnetic fields of 10 T have been carried out successfully for the first time. The observation system constructed is composed of a high-speed video camera, a telescope, a cryostat with a split-type superconducting magnet, a light source, a mirror and a transparent sample cell. Using this system, the influence of magnetic field on the path and shape of single bubbles of O$_2$ (paramagnetism) and N$_2$ (diamagnetism) has been examined carefully. Experimental values describing the path are in good agreement with theoretical values calculated on the basis of the magneto-Archimedes effect, despite the effect of magnetism on the bubble. However, no effect of magnetism on the shape of the bubble is observed. In addition, the influence of magnetic field on drag coefficient of the bubble is discussed.

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Observation of bubble dynamics under water in high-magnetic fields using a high-speed video camera

  • Lee, Seung-Hwan;Takeda, Minoru
    • Journal of Navigation and Port Research
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    • v.28 no.2
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    • pp.141-148
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    • 2004
  • The observations of rapid motion of bubbles under water for approximately 50ms or less in high . magnetic fields of 10 T have been carried out successfully for the first time. The observation system constructed is composed of a high-speed video camera, a telescope, a cryostat with a split-type superconducting magnet, a light source, a mirror and a transparent sample cell. Using this system, the influence of magnetic field on the path and shape of single bubbles of $O_2$(paramagnetism) and $N_2$ (diamagnetism) has been examined carefully. Experimental values describing the path are in good agreement with theoretical values calculated on the basis of the magneto-Archimedes effect, despite the effect of magnetism on the bubble. However, no effect of magnetism on the shape of the bubble is observed In addition, the influence of magnetic field on drag coefficient of the bubble is discussed.

f-electron Dualism as a Reason of Superconductivity in Ferromagnetic UGe2

  • Troc, Robert
    • Journal of Magnetics
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    • v.9 no.3
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    • pp.89-95
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    • 2004
  • Magnetization and electrical resistivity measurements in the wide temperature and field ranges were performed on single crystals of $UGe_2$. The presence of extremely large anisotropy in the temperature dependence of the susceptibility and magnetization has confirmed the previously published results. The dependence of spontaneous magnetization, ${\sigma}_s$, on temperature has been inferred from the Arrot plot and compared to that determined from neutron diffraction data. The earlier transversal and present longitudinal results on the magnetoresistivity are discussed in the terms of possible f-electron dualism in $UGe_2$ and its connection with the occurrence of superconductivity under pressure in this compound.