The Evolution of Magnetism in Iron from the Atom to the Bulk

TL;DR

This paper investigates how the magnetic moment in iron clusters evolves from small to bulk sizes using first-principles calculations, revealing size-dependent and surface effects on magnetism.

Contribution

It provides a detailed first-principles analysis of magnetic moments in various iron cluster geometries, highlighting non-monotonic size dependence and surface influence.

Findings

Magnetic moment decreases with increasing cluster size.

Faceted surface clusters have lower magnetic moments.

Magnetic moment varies non-monotonically with size.

Abstract

The evolution of the magnetic moment in iron clusters containing 20 to 400 atoms is investigated using first-principles numerical calculations based on density-functional theory and real-space pseudopotentials. Three families of clusters are studied, characterized by the arrangement of atoms: icosahedral, body-centered cubic centered on an atom site, and body-centered cubic centered on the bridge between two neighboring atoms. We find an overall decrease of magnetic moment as the clusters grow in size towards the bulk limit. Clusters with faceted surfaces are predicted to have magnetic moment lower than other clusters with similar size. As a result, the magnetic moment is observed to decrease as function of size in a non-monotonic manner, which explains measurements performed at low temperatures.