Tuning magnetism in graphene nanoribbons via strain and adatoms

TL;DR

This study explores how strain and hydrogen adatoms influence the magnetic properties of zigzag graphene nanoribbons, revealing tunable magnetic moments and potential for magnetic applications in carbon nanostructures.

Contribution

It demonstrates the effects of strain and adatoms on magnetism in ZGNRs using combined tight-binding and DFT methods, introducing a suitable impurity model for H adsorption.

Findings

Strain enhances edge magnetic moments via band structure modifications.

H adatoms exhibit edge-dependent magnetic coupling, especially AFM.

Magnetic moments form discrete plateaus related to band structure changes.

Abstract

We investigate the impact of strain and adsorbed H adatoms on the magnetic properties of zigzag graphene nanoribbons (ZGNRs) using a combination of tight-binding and density functional theory methods for both, ferromagnetic (FM) and antiferromagnetic edge configurations (AFM). Our study reveals that longitudinal strain induces a significant enhancement in the edge magnetic moment, that we attribute to strain-driven modifications in the band structure. In addition, we describe H~adatoms within the tight-binding approach by employing both an unrelaxed vacancy model and the Anderson impurity model. By comparing to density functional theory results, we corroborate that the Anderson impurity model is best suited to describe H adsorption. We then focus on the metallic FM edge configuration of the ZGNRs to better exploit the tuning of its properties. We find that the magnetic configuration of H~adatoms is strongly influenced by the edges, with an AFM coupling between edges and the H~adatom. In fact, the magnetic spatial pattern of the H adatom differs to that found in graphene due to this edge coupling. Importantly, we find robust discrete plateaus of integer magnetic moment as strain is varied in the defected ZGNRs, that we relate to changes in the band structure, namely, a half-metallic character or the opening of a gap. This behavior can be of interest for magnetic applications of carbon-based nanostructures