Muon spin relaxation was measured, using the zero magnetic field technique, in a Laves compound that contained interstitial H. At low temperatures, the relaxation profiles had the characteristic form which was associated with fluctuating local fields. The correlation time was almost independent of the temperature. As the temperature was increased above about 100K, a motional narrowing took place in which the correlation time of the local field decreased rapidly. A comparison with the hopping rate of the H atoms, as measured by means of nuclear magnetic relaxation, showed that the change in the correlation time was consistent with an increasingly rapid motion of the H atoms. When the sample was cooled, an hysteresis occurred in which the motional narrowing was retained to lower temperatures. The hysteresis of the muon relaxation rate, together with parallel changes in the nuclear magnetic relaxation, were explained in terms of phase changes which were known to occur in this alloy.

M.Kemali, R.L.Havill, J.M.Titman, D.K.Ross: Journal of Alloys and Compounds, 1995, 231, 255-8