The quantum states in metal clusters bunch into supershells with associated orbitals having shapes resembling those in atoms, giving rise to the concept that selected clusters could mimic the characteristics of atoms and be classified as superatoms. Unlike atoms, the superatom orbitals span over multiple atoms and the filling of orbitals does not usually exhibit Hund’s rule seen in atoms. Here, we demonstrate the possibility of enhancing exchange splitting in superatom shells via a composite cluster of a central transition metal and surrounding nearly free electron metal atoms. The transition metal d states hybridize with superatom D states and result in enhanced splitting between the majority and minority sets where the moment and the splitting can be controlled by the nature of the central atom. We demonstrate these findings through studies on TMMg _n clusters where TM is a 3d atom. The clusters exhibit Hund’s filling, opening the pathway to superatoms with magnetic shells.

Using the self-consistent-field molecular-orbital theory and the density-functional approximation, we show that vanadium could become magnetic if its size and dimension were constrained. This is illustrated for vanadium forming clusters with body-centered-cubic (bcc) geometry as well as for linear chains. The magnetic moment of the bcc clusters is found to vanish abruptly as the size increases, while the clusters always retain their moment in the linear-chain configurations. The moments are also found to be finite for large interatomic spacings irrespective of the cluster topology, and tend to vanish when the interatomic distances are reduced. The results are explained by using a simple Stoner criterion.