Magnetic Moments of Chromium-Doped Gold Clusters: The Anderson Impurity Model in Finite Systems

TL;DR

This study investigates how the magnetic moment of chromium impurities in gold clusters depends on size and electronic structure, using spectroscopy and density functional theory, and interprets results through the Anderson impurity model.

Contribution

It demonstrates the size-dependent magnetic behavior of chromium-doped gold clusters and links electronic shell effects to magnetic moment preservation using the Anderson impurity model.

Findings

Full magnetic moments preserved in closed-shell clusters.

Large local moments observed in open-shell clusters.

Energy gap stabilizes impurity magnetic moments.

Abstract

The magnetic moment of a single impurity atom in a finite free electron gas is studied in a combined x-ray magnetic circular dichroism spectroscopy and density functional theory study of size-selected free chromium-doped gold clusters. The observed size-dependence of the local magnetic moment can essentially be understood in terms of the Anderson impurity model. Electronic shell closure in the host metal minimizes the interaction of localized impurity states with the confined free electron gas and preserves the full magnetic moment of $\unit[5]{\mu_B}$ in $\mathrm{CrAu}_{2}^{+}$ and $\mathrm{CrAu}_{6}^{+}$ clusters. Even for open-shell species, large local moments are observed that scale with the energy gap of the gold cluster. This indicates that an energy gap in the free electron gas generally stabilizes the local magnetic moment of the impurity.