Spin–lattice relaxation in the bcc phase of phase-separated [sup 3]He–[sup 4]He solid mixtures

Mikhin, N. P.; Maidanov, V. A.; Polev, A. V.
April 2002
Low Temperature Physics;Apr2002, Vol. 28 Issue 4, p239
Academic Journal
The spin-lattice relaxation time in two samples of ³He-[sup 4]He solid mixtures with initial concentrations of 0.5% ³He in [sup 4]He and 0.5% [sup 4]He in ³He is measured by the pulsed NMR method. As a result of phase separation, in both cases two-phase crystals form, having the same helium concentration in the concentrated bcc phase. However, in the first sample the bcc phase forms as small inclusions in an hcp matrix, while in the second sample the bcc phase is the matrix. It is established that in the second case the spin-lattice relaxation occurs in the same way as in pure bulk ³He, while in the first case one observes anomalous behavior of the spin-lattice relaxation time at low temperatures. Experiments have shown that this anomaly is due not to the possible influence of the small [sup 4]He impurity but to the small dimensions of the inclusions of the of the bcc phase. In this case the main contribution to the relaxation is apparently due to defects formed at the boundaries of the bcc inclusions and the hcp matrix.


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