Muon diffusion and relaxation in YCo2

Muons were expected to gain additional information about the spin fluctuati ons proposed for this enhanced paramagnetic system. At the lowest temperatu res the mu(+)SR signal can be explained by a static Kubo-Toyabe relaxation function. On raising the temperature an interplay is suggested to occur bet ween muon diffusion and electronic relaxation of "Co-clusters" surrounding a Co vacancy yielding a maximum in the fluctuation rate versus temperature curve. This behaviour is similar to that found in the case of paramagnetic impurities in nonmagnetic metals, the "Co-cluster" moment being the analogu e to the impurity spin. (C) 2000 Elsevier Science B.V. All rights reserved.