1994 Fiscal Year Final Research Report Summary
Characterization of oxide superconductors by means of fluctuation-conductivity analysis
| Project/Area Number |
05650319
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Oyama National College of Technology |
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Principal Investigator |
MORI Natsuki Dept.of Electrical Engineering, Prof., 電気工学科, 教授 (60149911)
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| Co-Investigator(Kenkyū-buntansha) |
OZAKI Hajime Waseda Univ. Faculty of science, Prof., 理工学部, 教授 (10063679)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Oxide superconductors / Superconducting fluctuation / Impurity-effect / Transport properties / Films of oxide superconductors |
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| Research Abstract |
In this study, we have investigated physical properties of cuprate superconductors by means of analyzing fluctuation conductivity sigma' above Tc. First, we have analyzed sigma' (T) characteristics in YBa_2Cu_3O_7 (YBCO) containing impurities. From the analysis, we have obtained that the fluctuation amplitude in both YBCO systems with zinc and nickel decreases with increasing impurity concentration, and that the result is more pronounced for the YBCO systems having less oxygen contents. This indicates that non-magnetic impurity (zinc) as well as magnetic impurity (nickle) decrease Tc and suppress the superconducting fluctuation. The observed impurity-effect is different from what we expect in the BCS theory, supporting the validity of negative-U model as a mechanism of high-Tc superconductivity.
Next we have adopted the above-metioned method to MOCVD-deposited YBCO thin films in order to characterize the film quality. The Tc of the films decreases with increasing the number of thermal cycling, and consequently the fluctuation amplitude tends to be lower. This indicates that the film quality is reflected on the behavior of the fluctuation conductivity.
Finally, we have carried out x-ray diffraction and ac susceptibility chi measurements to characterize the films. As a result, we have found that both the FWHM of the diffraction patters and the imaginary part of the chi increases by repeating the thermal cycling, thus indicating the correlation between these parameters. We suggest that the measurement of chi also gives a useful way of characterizing the film quality. In line with the suggestion, we will continue to study the ac susceptibility characterization as well as the fluctuation conductivity analysis.
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Research Products
(8 results)
