Transition metal ad-atoms on graphene: Influence of local Coulomb interactions on chemical bonding and magnetic moments

TL;DR

This study uses first-principles calculations to explore how local Coulomb interactions influence the electronic and magnetic properties of transition metal adatoms on graphene, revealing the importance of U in determining configurations and magnetic moments.

Contribution

It demonstrates the significant impact of local Coulomb interactions U on the electronic configurations and magnetic moments of transition metal adatoms on graphene, including chemical control via hydrogenation.

Findings

High-spin configurations for Cr and Mn adatoms are stable.

Electronic configurations of Fe, Co, Ni depend on Coulomb U.

Hydrogenation allows control of adatom spin states.

Abstract

We address the interaction of graphene with 3d transition metal adatoms and the formation of localized magnetic moments by means of first-principles calculations. By comparing calculations within the generalized gradient approximation (GGA) to GGA+U we find that the electronic configuration and the adsorption geometries can be very sensitive to effects of local Coulomb interactions U in the transition metal d-orbitals. We find high-spin configurations being favorable for Cr and Mn adatoms independent of the functional. For Fe, Co and Ni different electronic configurations are realized depending on the value of the local Coulomb interaction strength U. Chemical control over the spin of the adatoms by hydrogenation is demonstrated: NiH and CoH adsorbed to graphene exhibit spin S=1/2 and S=1, respectively.