| Project/Area Number |
09650019
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | KYUSHU INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
MATSUSHITA Teruo Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Professor, 情報工学部, 教授 (90038084)
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| Co-Investigator(Kenkyū-buntansha) |
OTABE Edmund Soji Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Research Associate, 情報工学部, 助手 (30231236)
FURUKAWA Shoji Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Associate Professor, 情報工学部, 助教授 (30199426)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | high-temperature superconductor / flux line / correlation length / flux bundle size / dimensionality / pinning potential |
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| Research Abstract |
From measurements of the peak effect for the critical current density (Jc) in a two-dimensional Bi-2212 single crystal using the Campbell method, it was found that there exist two stable states with different values of Jc in the vicinity of the peak field and that the peak effect itself was a transition of a first order accompanied by a discontinuous change in Jc. It was concluded that this was the transition for the flux pinning induced by the crossover of flux lines from the three-dimesional state to the two-dimensional one. However, the magnetic correlation length along the flux line directed to the c-axis was of the order of 10 micrometers even in the two-dimensional state at high fields. This is completely different from the prediction of the pancake vortex model that flux lines are disconnected in each region between two CuO2 planes. It is speculated that there remains a strong magnetic coupling along the length of each flux line around the normal core due to the quantization of
… More
magnetic flux, whereas the correlation of the phase of the superconductivity along the length is weakened.
The relaxation rate of magnetization and the irreversibility field were measured for a Bi-2212 single crystal, a Bi-2223 tape wire and a melt-processed Sm-123 bulk specimen with different dimensionalities of superconductivity, and good agreements were obtained with the prediction or the flux creep-flow model. This shows that the two-dimensional superconductor is significantly influenced by the flux creep because of the small volume of the flux bundle. This small volume does not originate from the short length as predicted by the pancake vortex model, as mentioned above, but from the small transverse size. The backing layer is almost insulating and is relatively thick in two-dimensional superconductors. Hence, the mean condensation energy density along the flux line is small, resulting in the small elastic modulus for the shearing deformation of the flux line lattice. As a result, the shearing deformation of the flux line lattice occurs easily under the thermally activated flux motion and the flux bundle composed of small numbers of flux lines is formed. Typical number of flux lines is one in the most two-dimensional Bi-2212, about 4 in the most three-dimensional Sm-123 and about 2 in medium Bi-2223. Less
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