中国物理B ›› 1994, Vol. 3 ›› Issue (12): 917-924.doi: 10.1088/1004-423X/3/12/006

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IRREVERSIBILITY LINE AND THERMAL DEPINNING IN YBa2Cu3O7-δ

闻海虎, 赵忠贤   

  1. State Key Laboratory for Superconductivity, Institute of Physics, Academia Sinica, Beijing 100080, China
  • 收稿日期:1994-05-14 出版日期:1994-12-20 发布日期:1994-12-20

IRREVERSIBILITY LINE AND THERMAL DEPINNING IN YBa2Cu3O7-$\delta$

WEN HAI-HU (闻海虎), ZHAO ZHONG-XIAN (赵忠贤)   

  1. State Key Laboratory for Superconductivity, Institute of Physics, Academia Sinica, Beijing 100080, China
  • Received:1994-05-14 Online:1994-12-20 Published:1994-12-20

摘要: By measuring magnetic torque moment in a field-sweeping process, the temperature and field dependence of the critical current density j (with a criterion of electric field) and the normalized relaxation rate Q = d lnj/d ln E of a YBa2Cu3O7-δ thin film were obtained. With a minimum current density (jmin = 10A·cm-2) the irreversibility lines at different sweeping rates were determined. It was found that these irreversibility lines cannot be fitted to either the melting line or the vortex-glass transition. All the data can be interpreted by the thermally-assisted-flux-flow model. Further investigation shows that, at irreversible tem-perature and field, Uc is much smaller than kBT, which indicates that the thermal depinning is the real origin of the irreversibility line.

Abstract: By measuring magnetic torque moment in a field-sweeping process, the temperature and field dependence of the critical current density j (with a criterion of electric field) and the normalized relaxation rate Q = d lnj/d ln E of a YBa2Cu3O7-$\delta$ thin film were obtained. With a minimum current density (jmin = 10A·cm-2) the irreversibility lines at different sweeping rates were determined. It was found that these irreversibility lines cannot be fitted to either the melting line or the vortex-glass transition. All the data can be interpreted by the thermally-assisted-flux-flow model. Further investigation shows that, at irreversible tem-perature and field, Uc is much smaller than kBT, which indicates that the thermal depinning is the real origin of the irreversibility line.

中图分类号:  (Critical currents)

  • 74.25.Sv
74.25.Op (Mixed states, critical fields, and surface sheaths) 74.25.Ha (Magnetic properties including vortex structures and related phenomena)