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Upper Critical Field and Irreversibility Line Determined by
Transport Measurement of the New Superconductor MgB2 |
JIN Hao;WEN Hai-Hu;LI Shi-Liang;ZHAO Zhi-Wen;NI Yong-Ming;REN Zhi-An;CHE Guang-Can;YANG Hai-Peng;LIU Zhi-Yong;ZHENG Dong-Ning;ZHAO Zhong-Xian |
National Laboratory for Superconductivity, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080
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Cite this article: |
JIN Hao, WEN Hai-Hu, LI Shi-Liang et al 2001 Chin. Phys. Lett. 18 823-825 |
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Abstract Resistive transitions of the new superconductor MgB2 are carried out under magnetic fields from 0 to 8 T. It is found that the irreversibility field Hirr(T) and the upper critical field Hc2(T) obtained are very close to those determined in the magnetic measurement. By using the Arrhenius activation law ρ = ρ0exp(-U/kBT), the activation barrier U has been determined by the low dissipation part of R(T) curves. It is found that U kBT manifests a very weak thermal activation and thermal fluctuation effect. This may further indicate that the flux dynamics near Hirr(T) is induced by strong quantum fluctuation and tunneling of vortices.
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Keywords:
74.25.Fy
74.60.Ge
74.70.Ad
74.25.Dw
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Published: 01 June 2001
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