Magnetic nanodoping: Atomic control of spin states in cobalt doped silver clusters

Abstract

The interaction of magnetic dopants with delocalized electron states can result in interesting many-body physics. Here, the magnetic properties of neutral and charged finite silver metal host clusters with a magnetic cobalt atom impurity were investigated experimentally by exploiting the complementary methods of Stern-Gerlach molecular beam deflection and x-ray magnetic circular dichroism spectroscopy and are accompanied by density functional theory calculations and charge transfer multiplet simulations. The influence of the number of valence electrons and the consequences of impurity encapsulation were addressed in free size-selected, singly cobalt-doped silver clusters CoAg_{n}^{0,+} (n=2–15). Encapsulation of the dopant facilitates the formation of delocalized electronic shells with complete hybridization of the impurity 3d- and the host 5s-derived orbitals, which results in impurity valence electron delocalization, effective spin relaxation, and a low-spin ground state. In the exohedral size regime, spin pairing in the free electron gas formed by the silver 5s electrons is the dominating driving force determining the local 3d occupation of the impurity and therefore, adjusting the spin magnetic moment accordingly.