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A method has been proposed to create disorder in helium crystals by their deformation immediately during the experiment. Precise measurements of the pressure have been performed at a constant volume in samples of various qualities. It has been revealed that excess pressure, which is characterized by the quadratic temperature dependence typical of the disordered glassy phase and of the dislocation contribution to the pressure, is observed in the deformed crystals along with the phonon contribution to the pressure. The effect is observed in the supersolid-state region and disappears after the careful annealing of the crystals. The ultraslow relaxation of the pressure also characteristic of the glassy phase has been observed in the process of annealing of the crystals. The obtained experimental results have been analyzed in the framework of the dislocation model and the model of two-level tunneling states.

The pulsed NMR technique was used to investigate diffusion on the BCC-HCP phase-equilibrium and melting curves of a dilute solution of 3He in 4He. The contributions from all coexisting phases were identified using the spin-echo method. It is established that, along with the contributions from the equilibrium BCC and HCP phases or from bulk liquid (in the melting curve measurements), there is an additional diffusional process that is characterized by an anomalously high diffusion coefficient. It is found that the latter is close to the diffusion coefficient in liquid helium, while the diffusion itself is spatially restricted. The observed effect may be caused by the formation of liquid droplets in the course of the BCC-HCP transition.

New features are observed for the pressure in a phase-separated dilute solid solution of 4He in 3He subjected to multiple temperature cycling within the phase-separation region. The results are explained within the framework of the hypothesis of A.F. Andreev and D.I. Pushkarov that the vacancies in a crystal without ideal periodicity are surrounded by clusters with a periodic structure. The equation for determining the radius of a cluster of pure 4He in a solution of 4He in 3He is refined. This hypothesis is shown to provide quantitative agreement between the calculated and experimental data under the assumption that the homogenization of the phase-separated solution is accompanied by the formation of metastable vacancies with a concentration of ∼(4–5)×10−5.