MUON-HYDROGEN CORRELATION IN AMORPHOUS-ALLOYS

Muon spin relaxation has been measured in the amorphous transition-met al alloy Zr2Pd containing a high concentration of interstitial hydroge n. The nuclear spin dipole moments of the metal atoms in this alloy ar e relatively small with the result that the local magnetic field at th e muon arises almost entirely from the nuclear moments of the hydrogen atoms. Even at the lowest temperature of measurement, similar to 10 K , the relaxation profiles are consistent with fluctuating local fields . The correlation time is typically a few microseconds and varies only slowly with temperature up to about 100 K. On the other hand, above 2 50 K, where the diffusion hopping rate of the hydrogen atoms is about 10(7)-10(8) s(-1) as measured by nuclear relaxation methods, the corre lation times vary more rapidly with temperature and may be described i n terms of activation energies which are similar to the activation ene rgies of the hydrogen diffusion. In addition the correlation time of t he local field at the muon was found to be greater than the average in terval between hops of the hydrogen atoms, a puzzling result which has been found in earlier experiments on similar alloys. The present data confirm the generality of this feature. However, it has not been poss ible to offer a fully convincing explanation of the mechanism which ma y lead to it.