QFS2016 Book of Abstracts

Abstracts

P2.25 Plastic Flow of Solid 3 He at Low Temperatures. Rubets Serhii(1), Lisunov Oleksandr(1), Maidanov Volodymir(1), Rubanskyi Valentin(1,2), Rudavskii Eduard(1), Smirnov Serhii(1) 1) ILTPE - B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Department of Physics of Quantum Fluids and Crystals, Prospekt Nauky 47, Kharkiv 61103 , UKRAINE 2) University of Massachusetts Amherst, Department of Physics, MA 01003-9337 USA Plastic flow of solid 3 He through a porous membrane frozen in the crystal is observed in the temperature range 0.1 - 1.0 K. It was found that the temperature dependence of the flow velocity has two characteristic regions - at temperatures above ≈ 0.2 K, the velocity decreases exponentially with lowering temperature, which corresponds to the thermally activated process, and at low temperatures the velocity is independent on T, which indicates the quantum mechanism of mass transfer. The experimental results can be explained within the vacancy model under special conditions or within the model of the motion of dislocations in the Peierls potential relief. P2.26 PRESSURE GRADIENTS AND MAGNETIC RELAXATION IN QUENCHED HCP 3 He- 4 He CRYSTALS Birchenko Oleksandr, Mikhin Nikolay, Fysun Yana, Rudavskii Eduard B.Verkin Institute for Low Temperature Physics and Engineering, DEPARTMENT FOR QUANTUM LIQUIDS AND CRYSTALS The samples of hcp solid mixture (1.0% 3 He in 4 He) are studied by pulse NMR technique. Samples are grown by blocked capillary method under different growth rates (about 8, 2, and 0.08 mK/s). NMR technique is used for phase identification by measurements of diffusion coefficient D, spin-lattice and spin-spin relaxation times ( T 1 and T 2 ) at temperatures of 1.3 – 2.0 K and pressures of 34 – 36 bar. Along with D and T 1 , T 2 for the hcp phase, we simultaneously observed the D and T 1 , T 2 typical for liquid for growth rates 8 and 2 mK/s. That means liquid-like inclusions are formed in solid hcp matrix during fast crystallization. It has been established, that in the quenched samples there is continuous pressure relaxation due to local pressure gradients in the samples. It is also shown that the slower growth rate corresponds to smaller size of liquid droplets. Finally, the transition of the liquid droplets to some new state is observed.

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