Phase separation and diffusion processes in concentrated He3–He4 solid mixtures

• Published in: Low temperature physics (Woodbury, N.Y.) N.Y.), 2009-11, Vol.35 (11), p.829-836
• Main Authors: Grigor’ev, V. N., Degtyarev, I. A., Lisunov, A. A., Maidanov, V. A., Rubanskii, V. Yu, Rubets, S. P., Rudavskii, E. Ya, Rybalko, A. S., Tikhii, V. A.
• Format: Article
• Language: English
• ISSN: 1063-777X; 1090-6517
• DOI: 10.1063/1.3266908

The kinetics of phase separation in quantum crystals of concentrated He3–He4 mixtures containing 34.0, 61.3, and 89.9% He3 are investigated experimentally by the method of precision barometry. The variation of the pressure P(T) of the system upon stepwise cooling and heating is registered. The P(T) curves observed in the experiment are compared with a theory based on a diffusion description of the kinetics of isotropic phase separation. This yields the first information about the mass diffusion coefficient in the whole concentration range. It is shown that in concentrated mixtures the mass diffusion coefficient is several orders of magnitude lower than in dilute mixtures, owing to the interaction of impurities and the presence of elastic strains in the crystal. At the same time, because of the high concentration of new-phase nuclei and the small diffusion length, the phase transition process takes place over a comparatively short time.