Muon spin relaxation was measured in amorphous alloys which contained a high concentration of interstitial H. The nuclear spin dipole moments of the metal atoms in the alloy were relatively small, with the result that the local magnetic field at the muon arose almost entirely from the nuclear moments of the H atoms. Even at about 10K, the relaxation profiles were consistent with fluctuating local fields. The correlation time was typically equal to a few microseconds, and varied only slowly with temperatures of up to about 100K. At temperatures above 250K, where the diffusion hopping rate of the H atoms was between 107 and 108/s, as measured by using nuclear relaxation methods, the correlation times varied more rapidly with temperature and could be described in terms of activation energies which were similar to the activation energy for H diffusion. The correlation time of the local field at the muon was found to be greater than the average interval between hops of the H atoms. The present data confirmed the generality of this phenomenon, but it was not possible to offer an entirely convincing explanation for it.

M.Kemali, R.L.Havill, J.M.Titman: Philosophical Magazine B, 1995, 72[2], 275-84