高温超伝導体の臨界電流特性 Critical Current Properties in High Tc Superconductors

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Based on a statistic study in a random pin medium, we have proposed a new method to describe current transport properties in high <i>T</i><sub>c</sub> superconductors (HTS). The theoretical results are compared with measured electric field (<i>E</i>) vs. current density (<i>J</i>) curves in a YBCO film with magnetic fields up to 12T. The nonlinear <i>E-J</i> curves can be characterized by a power function [(<i>J-J</i><sub>cm</sub>)/<i>J</i><sub>0</sub>]<sup>m</sup> with three parameters: the minimum value of critical current density (<i>J</i><sub>c</sub>) denoted by <i>J</i><sub>cm</sub>, the variance of the distribution, <i>J</i><sub>0</sub>, and exponent, <i>m</i>, which determines the shape of <i>J</i><sub>c</sub> distribution. Magnetic field (<i>B</i>) and temperature (<i>T</i>) dependencies of the <i>E-J</i> curves can be attributed to the thermodynamic properties of <i>J</i><sub>cm</sub> and typical value of <i>J</i><sub>c</sub>, denoted by <i>J</i><sub>k</sub>(≡<i>J</i><sub>cm</sub>+<i>J</i><sub>0</sub>) through the corresponding macroscopic pinning force densities <i>J</i><sub>cm</sub><i>B</i> and <i>J</i><sub>k</sub><i>B</i>, respectively, as in the similar form in low <i>T</i><sub>c</sub> superconductors. The present method allows us to estimate the statistic <i>J</i><sub>c</sub> distribution from <i>E-J</i> curves. Moreover, <i>B</i>- and <i>T</i>-dependencies of the <i>E-J</i> curves can be predicted in a (<i>B, T</i>)-plane based on the scaling properties of the pinning force densities. The present method has also been compared with the so called <i>n</i>-value model: <i>E(J)</i>=<i>E</i><sub>c</sub>(<i>J/J</i><sub>c</sub>)<sup>n</sup>. It has been shown that the value of exponent <i>n</i> and <i>J</i><sub>c</sub> determined by an electric-field criterion, <i>E</i><sub>c</sub>, can be plotted as a function of <i>B</i> and <i>T</i>. Additionally, the relationship between these parameters, <i>n</i> and <i>J</i><sub>c</sub>, and material properties such as pin distribution and its thermodynamic properties can be clarified by this analysis. These results are useful not only to estimate critical current properties in HTS materials but also to design HTS-based devices by taking into account operation conditions such as <i>B, T</i> and power dissipation.

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  • 低温工学  

    低温工学 34(7), 322-331, 1999-07 

    CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

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各種コード

  • NII論文ID(NAID)
    10002194611
  • NII書誌ID(NCID)
    AN00333419
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    03892441
  • NDL 記事登録ID
    4810495
  • NDL 雑誌分類
    ZM35(科学技術--物理学)
  • NDL 請求記号
    Z15-388
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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