Robust Magnetic Moments on Impurities in Metallic Clusters: Localized Magnetic States in Superatoms

Abstract

Introducing magnetic impurities into clusters of simple metals can create localized states for higher angular momentum quantum numbers (l = 2 or 3) that can breed magnetism analogous to that in virtual bound states in metallic hosts, offering a new recipe for magnetic superatoms. In this work, we demonstrate that MnCa(n) clusters containing 6-15 Ca atoms show a spin magnetic moment of 5.0 μB irrespective of the cluster size. Theoretical analysis reveals that the Mn d states hybridize only partially with superatomic states and introduce extra majority and minority d states, largely localized at the Mn site, with a large gap. Successive addition of Ca atoms introduces superatomic states of varying angular momentum that are embedded in this gap, allowing control over the stability of the motifs without altering the moment. Assemblies of such clusters can offer novel electronic features due to the formation of localized magnetic "quasibound states" in a confined nearly free electron gas.