Restricted Diffusion in Nonequilibrium Superfluid Inclusions in Solid Helium

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• 作者：N. P. Mikhin ; A. P. Birchenko ; Ya. Yu. Fysun…
• 关键词：NMR ; Two ; phase mixture ; Restricted diffusion ; \(^{3}\) ; He–\(^{4}\) ; He mixture
• 刊名：Journal of Low Temperature Physics
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：185
• 期：3-4
• 页码：305-312
• 全文大小：585 KB
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics
  Condensed Matter
  Characterization and Evaluation Materials
  Magnetism and Magnetic Materials
  
• 出版者：Springer Netherlands
• ISSN：1573-7357
• 卷排序：185

文摘

Diffusion processes are investigated with NMR technique in the two-phase system of solid helium matrix with superfluid inclusions. The system is formed by rapid cooling, and liquid inclusions are nonequilibrium. The diffusion coefficients of \(^{3}\)He are measured in each of the coexisting phases in a sample of a solid \(^{3}\)He–\(^{4}\)He mixture with 1.0 % \(^{3}\)He using the spin-echo technique in the presence of a magnetic field gradient. It was found that the diffusion coefficient in superfluid inclusions decreases with the increasing diffusion length, which is a feature of restricted diffusion. The data obtained allowed us to estimate the typical size of the inclusions. It is shown that inclusion size decreases with time. A similar study on the equilibrium in liquid–crystal two-phase system, formed by rapid cooling of the sample near the melting curve, is performed for comparison. In this case, the restricted diffusion in the liquid phase also was observed; however, the system was stable, and the diffusion coefficient is sensitive to changes in temperature only.