| Project/Area Number |
07454080
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
MIZUSAKI Takao Kyoto University, Graduate School of Science, Prof., 大学院・理学研究科, 教授 (20025448)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Yutaka Kyoto University, Graduate School of Science, Research Assistant, 大学院・理学研究科, 助手 (60205870)
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| Project Period (FY) |
1995 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥7,800,000 (Direct Cost: ¥7,800,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1995: ¥4,700,000 (Direct Cost: ¥4,700,000)
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| Keywords | helium / crystal growth / NMR-imaging / nucleation of crystal / nuclear-ordered solid / Suhl instability / frost heave / nuclear magnetic resonance / 超低温 / 超流動 / 結晶化波 / 固体ヘリウム / 個体ヘリウム / 核整列個体 / 磁気共鳴 |
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| Research Abstract |
Studies of crystal growth (and melt) of nuclear-ordered solid ^3He in superfluid ^3He at ultra-low temperatures will explore detailed and microscopic mechanisms of crystal growth since latent heat of solidification of nuclear-ordered solid becomes very small and superfluity guarantee good heat and mass transport during crystal growth and melt as well as the ^4He case which has been studied thoroughly. Unique feature of the ^3He case is the dominant contribution of spin supercurrent to the crystal growth since there exists a large magntization difference between solid and liquid.
(1)We studied crystal growth and melt of nuclear-ordered ^3He in 1 mmphi cylindrical sample cell and found a large difference of the rates of growth and melt. The growth mechanism should be the screw-dislocation assisted one and the step velocity is limited by the pair-breaking velocity of superfluid B phase. On the other hand, the melt is rather very fast and we could not measure any quantitative data yet but t
… More
he surface of the solid on the melting process seems to be a rough surface. Further research is on progress by using the NMR-imaging technique (MRI) described below.
(2)The nucleation problem of solid in a supercooled liquid ^4He has been investigated. as a function of temperature. We found that the nucleation rate becomes temperature-independent and concluded that nucleation occured by quantum tunneling mechanism. We will extend this studies to the ^3He case at ultra-low temperatures.
(3)We studied frost heave of ^4He from porous media when ^4He is in the superfuild state. We proposed the dissipation mechanism of the growth of frost and compared it with our data.
(4)We developed the MRI technique applicable at ultra-low temperatures. We applied the MRI to visualize ^3He-^4He phase separation boundary. We achieved 2-dimensional space resolution of about 10 mum by this technique.
(5)With connection of the above MRI,spin dynamics of nuclear-ordered solid ^3He has been stueied and the Suhl instability of the uniform mode of NMR was observed under certain conditions. Less
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