Thermally activated flux dissipation in c-axis-oriented YBa2Cu3O7−δ ultrathin films |
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Authors: | J J Sun L Z Zheng B R Zhao B Xu J W Li B Yin F Wu S L Jia L Li and Z X Zhao |
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Institution: | National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China |
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Abstract: | The resistive transitions of ultrathin YBa2Cu3O7?δ (YBCO) films with thicknesses 75 and 200 Å were studied under magnetic fields. For the 75 Å film under a 5 T parallel magnetic field (Hbab-plane), no broadening of the resistive transition occurred. In the perpendicular magnetic field (H ab-plane), the broadening of the resistive transition of the 75 Å film is larger than that of the 200 Å thick film. The flux activation energy U was found to be linearly dependent on the temperature and logarithmically dependent on the magnetic field for both 75 and 200 Å films, which means the two samples have a two-dimensional vortex lattice. Furthermore, the activation energy U also increased with the film thickness, indicating that the magnetic correlation length in the c-axis direction lc is larger than the 200 Å for bulk YBCO. |
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Keywords: | Resistive transition Flux lattice Ultrathin film YBa2Cu3O7?δ |
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