Muon location and muon dynamics inDyNi5

In DyNi5, the muon localizes at the 6 i ~1/2,0,0.1! interstitial site and below ;80 K a second muon site becomes populated, the metastable 6 ring site. We determine the mean residence time of the muon in this ring site and analyze its temperature dependence with a multiphonon quantum diffusion process. The coincidence energy is measured to be Ea /k B5400 ~20! K and the tunneling matrix element J50.21 ~7! meV. A comparison with GdNi5 gives insight in the muon potential well scheme in these compounds. We attribute the large diversity of muon sites in RNi5 series, where R is a rare earth element, to the relatively low density of states at the Fermi level.