Muon trapping and diffusion in Al and In after electron irradiation at 9 K

Abstract

The transverse spin relaxation of positive muons has been measured on an Al single crystal and on polycrystalline In after irradiation with 2 MeV electrons at 9 K or 11 K, sample transfer at 4.2 K, and various subsequent annealing treatments. The Al data are analysed in terms of diffusion-limited trapping by vacancies. This yields a muon diffusivityDμ which within experimental accuracy is proportional toT between 4 K and 50 K, indicating that in this temperature intervalDμ is dominated by one-phonon-assisted incoherent tunnelling. In In only very small effects due to the irradiation could be observed. The muons appear to be localized in octahedral interstices. From the motional averaging taking place above about 20 K the diffusivity ofDμ in In is deduced.