Muon spin depolarization rates and hyperfine decoupling curves impliedthe existence of a neutral muonium center to high temperatures in AlN, providing an experimental model for interstitial atomic hydrogen. This center has a hyperfine interaction close to that of the free atom, but with a small temperature-dependent dipolar contribution indicating weak anisotropy. The site assignment was considered, and results were presented on the diffusion of these centres in AlN and associated conversion rates obtained from the depolarization data. Low-temperature motion was due to tunnelling while thermally activated processes dominate at high temperatures. Diffusion-limited conversion out of the mobile atomic state was observed in both regimes.

Diffusion and Conversion Dynamics for Neutral Muonium in Aluminum Nitride. H.N.Bani-Salameh, R.L.Lichti, Y.G.Celebi, S.F.J.Cox: Physical Review B, 2006, 74[24], 245203 (8pp)