Magnetism of Co nanocluster films

A cluster-beam technique is used to produce nearly monodispersed nanoclusters of Co while independently varying their size and concentration. The Co clusters are embedded in Cu and ${\mathrm{SiO}}_2$ to form films with cluster size varying from 300 to 9000 atoms and Co concentration varying from 10 to 50 vol %. The Co magnetization ${(M}_s)$ increases with increasing cluster size and decreases with increasing Co concentration for a given cluster size but is always less than the bulk value. First-principles calculations are used to analyze the experimental data in terms of the local environment effects at the cluster-matrix interface and spin-glass-like behavior due to the strong ferro- and antiferromagnetic intercluster exchange interactions for small separations.