| Project/Area Number |
60460065
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | Kyushu University |
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Principal Investigator |
AOMINE Takafumi Research Institute of Fundamental Information Science, Kyushu University, 理学部, 教授 (50037206)
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| Co-Investigator(Kenkyū-buntansha) |
MIZUNO Kazuo Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 大学院総合理工学研究科, 助手 (00200006)
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| Project Period (FY) |
1985 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥7,400,000 (Direct Cost: ¥7,400,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1985: ¥3,400,000 (Direct Cost: ¥3,400,000)
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| Keywords | Superconductivity / Thin film / Hysteresis / Memory / Critical current / ブリッジ / マイクロブリッジ |
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| Research Abstract |
Critical currents of constricted superconducting films which are called bridges show hysteresis in low perpendicular magnetic fields. A purpose of this work was to make a fundamental study of a memory using the hysteresis.
It was observed that the hysteresis occurred in not only bridges made of Nb and NbN but also oxilde superconductors with a high critical temperature. In order to enlarge the magnetic field range with the hysteresis, it is necessary that the length of the constricted part is short, its width is narrow, the width of the bank is wide, and the thickness of the bank is thicker than that of the constricted part. Furthermore, it was found that the lower temperature made the field range with the hysteresis large. In the fields below a value as well as above a value, the hysteresis does not occur.
If we try to apply the above hysteresis to a new memory, it is interesting to know how a bridge voltage under a constant current responds to a magnetic field with a short pulse 1-50 n
… More
s. The measurement showed that the bridge voltage decreased when the above short pulse was applied. However, this decrease was independent of the polarity of a magnetic field. Then we considered that the response occurred for the hysteresis due to a current which was induced under the magnetic-field pulse.
The qualitative explanation for the origin of the hysteresis was given. The current which flows at the constricted part is an algebraical sum of an external current and the current generating in the bank due to a magnetic field. When the sum reaches the pair-breaking current, the external current is considered to be a measured critical current. The current coming from the bank and going out has a hysteresis in a magnetic field owing to the flux distribution having the hysteresis under an edge pinning. This explanation is supported by the experimental results about the influence of a magnetic field applied above a critical temperature and argon ion bombardment on the hysteresis of the critical current. Less
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