Magnetic moments of small cobalt clusters revisited: The contribution of 3d and 4s electrons

Abstract

The magnetic moment of small cobalt clusters shows large variations with the cluster size, both theoretically and experimentally. In this work we present results from density functional calculations using both the hybrid B3-LYP as well as the pure PBE functional for the geometrical structure and spin magnetic moments of neutral Con and cationic Con+ cluster with n ranging from 3 to 10. While the 3d electrons give a spin magnetic moment of 2μB per cobalt atom with few exceptions, most of the variation in the spin magnetic moments can be traced back to varying number of unpaired electrons in the manifold of 4s dominated orbitals. In particular, small highly symmetric clusters with more than one unpaired electron in spatially degenerate orbitals from the 4s manifold show substantially increased magnetic moments.