Muon spin relaxation in these C15 Laves phase compounds was measured by using the zero magnetic field technique. It was found that, at temperatures below 100K, where the H atoms were essentially static, they diffused via a tunnelling process. It was also observed that, in this temperature range, the muons diffused much more quickly when H was not present in the sample. As the temperature was increased, a motional narrowing occurred, and the muons were then believed to undergo over-barrier hopping.

M.Kemali, P.R.Stonadge, D.K.Ross, S.M.Bennington: Journal of Alloys and Compounds, 1995, 231, 259-61