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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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