Observation of Andreev-Pushkarov vacancy clusters in phase-separated solidsolutions of He-4 in He-3

New features are observed for the pressure in a phase-separated dilute soli d solution of He-4 in He-3 subjected to multiple temperature cycling within the phase-separation region. The results are explained within the framewor k of the hypothesis of A.F. Andreev and D.I. Pushkarov that the vacancies i n a crystal without ideal periodicity are surrounded by clusters with a per iodic structure. The equation for determining the radius of a cluster of pu re He-4 in a solution of He-4 in He-3 is refined. This hypothesis is shown to provide quantitative agreement between the calculated and experimental d ata under the assumption that the homogenization of the phase-separated sol ution is accompanied by the formation of metastable vacancies with a concen tration of similar to (4-5) x 10(-5). (C) 2001 MAIK "Nauka/ Interperiodica" .