Magnetic Shells of Co Clusters

Abstract

Magnetic properties of Co_N clusters for N=13-147 are discussed bycalculating the electronic states of the clusters with the localspin-density functional method. Two kinds of oscillatory behavior are observed in the magnetism of the Co clusters. First, the magnetic moment per atom oscillates with increasing the clustersize. This oscillatory size dependence is simulated by an electronic shellmodel, where the discreteness of the energy levels derived from4s/4p-electrons originates the oscillation. Second, the localmagnetic moment oscillates from the surface to the center of the clusters, that is, a large magnetic moment at the surface atomic shell decreases at the second shell, increases at the thirdshell and again decreases at the fourth shell from the surface. The local density of states of 3d electrons changes shell by shell, parallel to the oscillation of the local magnetic moment.