Positive muons in nanocrystalline transition metals diffusion and magneticnanostructure

Systematic studies with Muon Spin Rotation (mu SR) on nano-Cu and nano-Ni s amples produced by pulsed electrodeposition, demonstrates that the diffusio n of mu+ in nanocrystalline metals is influenced by the nanostructure. In n ano-Cu the mobility of muons is reduced at higher temperatures, where they can reach the grain boundaries. In nano-Ni the appeareance of a longitudina l relaxation is interpreted to be due to muon diffusion to magnetically dis ordered regions. In the framework of this model, we are able to estimate ho w the thickness of these magnetically disordered region increases with temp erature. (C) 1999 Acta Metallurgica Inc.