Co nanoprecipitates formed in Ag upon ion implantation: their lattice dynamical properties

We have investigated the lattice dynamics of nanoparticles of Co embedded i n Ag, created by ion implantation and subsequent annealing. Around 600 degr ees C ferromagnetic particles are strongly populated. A careful comparison of the Mossbauer component intensities at two measuring temperatures shows that the particles' size distribution is bimodal, with a Debye temperature close to bulk Co for the taller part and decreasing with size towards the v alue for substitutional Co in Ag for the smallest part. theta(D) of the sma llest particles compares well with the value that we obtain from MD calcula tions on a tiny (405 atoms) embedded fcc Co cluster.