The Effect of Hydrogen Adsorption on the Magnetic Properties of a Surface Nanocluster of Iron

TL;DR

This study investigates how hydrogen adsorption affects the magnetic properties of an iron nanocluster on a copper surface, revealing a monotonic decrease in magnetic moment with hydrogen coverage and elucidating the underlying electronic interactions.

Contribution

It combines density functional theory calculations with an Alexander-Anderson model to analyze hydrogen's impact on magnetic moments and electronic structure of iron nanoclusters.

Findings

Hydrogen adsorption reduces the magnetic moment of the Fe cluster.

Charge transfer of 0.4 electrons occurs to each H atom from Fe and Cu.

Magnetic moment reduction is mainly due to increased minority spin d-states.

Abstract

The effect of hydrogen adsorption on the magnetic properties of an Fe$_3$ cluster immersed in a Cu(111) surface has been calculated using densifty functional theory and the results used to parametrize an Alexander-Anderson model which takes into account the interaction of d-electrons with itinerant electrons. A number of adatom configurations containing one to seven H-atoms were analyzed. The sequential addition of hydrogen atoms is found to monotonically reduce the total magnetic moment of the cluster with the effect being strongest when the H-atoms sit at low coordinated sites. Decomposition of the charge density indicates a transfer of 0.4 electrons to each of the H-atoms from both the Fe-atoms and from the copper substrate, irrespective of adsorption site and coverage. The magnetic moment of only the nearest neighbor Fe-atoms is reduced and mainly due to increased population of minority spin d-states. This can be modeled by increased indirect coupling of d-states via the conduction s-band in the Alexander-Anderson model.