We report the results of an NMR imaging study of 3He-4He mixture crystals in coexistence with the liquid. Data were obtained for 7 different 3He concentrations between 0.7% and 12.12%, in the temperature range between 0.45 K and 1.3 K, along the melting curve. We imaged the spatial distribution of the density 3He, and that of T1 and T2 relaxation times in the solid and in the liquid along the vertical direction of the experimental cell, perpendicular to the solid-liquid interface. We find significant differences between the dynamics of 3He atoms in hcp and bcc solid phases. These can be attributed to the different properties of thermally activated vacancies in the two phases. Specifically, in the bcc phase above 1 K, vacancy induced motion of 3He atoms in the solid is faster than the motion in the liquid. We interpret this finding in terms of a 3He-vacancy bound state. Finally, we examine our results within the broader context of finding a consistent description of the properties of vacancies in solid He.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Materials Science(all)
- Condensed Matter Physics