Spin Diffusion Processes in Solid ^3He-^4He Mixtures Near the BCC-HCP Phase Transition at the Melting Curve

The spin diffusion coefficient of 1% ^3He in solid of ^ 4He has been measured in the vicinity of the BCC-HCP phase transition at the melting curve by pulsed NMR. The applied spin echo technique does allow to distinguish the contributions from all of coexisting phases. In addition to well-known diffusion in BCC, HCP, and bulk liquid phases the new fast diffusion process is observed and the diffusion coefficient of this process is shown to be close to that in liquid mixture being dependent on the time between the NMR pulses (bounded diffusion). The possible reason for the effect may be connected with formation of liquid droplets during the BCC-HCP transition.