Structure Dependent Magnetic Coupling in Cobalt-Doped Silicon Clusters

The structure of cobalt-doped silicon clusters, Si_nCo⁺ (n = 5-8) and Si_nCo₂⁺ (n = 8-12), is investigated in a combined infrared multiple photon dissociation spectroscopy and density functional theory study. The singly doped clusters have exohedral structures in which the Co atom substitutes an atom of bare Si_n+1⁺ clusters. In the doubly doped Si_nCo₂⁺ clusters, the second Co atom is adsorbed to the singly doped counterparts and, for n ≥ 9, one of the Co atoms is encapsulated by a silicon cage. Computational analysis of the electronic and magnetic properties of the identified isomers indicates a distance dependent magnetic coupling between the Co atoms in the Si_nCo₂⁺ clusters.