Exchange coupling in transition-metal nano-clusters on Cu(001) and Cu(111) surfaces

TL;DR

This study uses density-functional calculations to explore how exchange interactions in small transition-metal clusters on copper surfaces depend on factors like hybridization, shape, and atomic orbitals, revealing complex magnetic behaviors.

Contribution

It provides detailed insights into the mechanisms influencing exchange coupling in transition-metal nano-clusters on Cu surfaces, highlighting the roles of hybridization and cluster shape.

Findings

Exchange coupling depends on ferromagnetic and antiferromagnetic mechanisms.

Hybridization broadening affects coupling strength.

Cluster shape influences magnetic interactions.

Abstract

We present results of density-functional calculations on the magnetic properties of Cr, Mn, Fe and Co nano-clusters (1 to 9 atoms large) supported on Cu(001) and Cu(111). The inter-atomic exchange coupling is found to depend on competing mechanisms, namely ferromagnetic double exchange and antiferromagnetic kinetic exchange. Hybridization-induced broadening of the resonances is shown to be important for the coupling strength. The cluster shape is found to weaken the coupling via a mechanism that comprises the different orientation of the atomic d-orbitals and the strength of nearest-neighbour hopping. Especially in Fe clusters, a correlation of binding energy and exchange coupling is also revealed.