Abstract
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.
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