Large variations in the magnetization of Co clusters induced by noble-metal coating

We report calculations of the electronic and magnetic properties of small Co clusters, coated with Ag or Cu, performed with a parametrized tight-binding method. For a given number of Co atoms in a cluster, we obtain a large range of magnetization values, depending on the size and shape of the coating. The noble metal develops a net polarization that changes appreciably the total magnetic moment of the cluster. This result is reinforced by ab initio calculations for mixed slabs, where the corrugation of a nonmagnetic covering also produces important variations in the total magnetic moment.