Magnetic response and electronic states of well defined Graphene/Fe/Ir(111) heterostructure

TL;DR

This study explores the electronic and magnetic properties of a graphene/Fe/Ir(111) heterostructure, revealing how Fe intercalation affects the Dirac cone, induces spin splitting, and alters magnetic orientation.

Contribution

It provides atomic-level control of Fe intercalation in graphene/Ir(111), demonstrating the impact on electronic structure and magnetic properties with first-principles calculations and magnetic measurements.

Findings

Fe intercalation breaks Dirac cone symmetry and shifts energy by 3 eV.

Fe states exhibit large spin splitting with hybridization to graphene.

Magnetic orientation switches from perpendicular to parallel depending on Fe lattice matching.

Abstract

We investigate a well defined heterostructure constituted by magnetic Fe layers sandwiched between graphene (Gr) and Ir(111). The challenging task to avoid Fe-C solubility and Fe-Ir intermixing has been achieved with atomic controlled Fe intercalation at moderate temperature below 500 K. Upon intercalation of a single ordered Fe layer in registry with the Ir substrate, an intermixing of the Gr bands and Fe d states breaks the symmetry of the Dirac cone, with a downshift in energy of the apex by about 3 eV, and well-localized Fe intermixed states induced in the energy region just below the Fermi level. First principles electronic structure calculations show a large spin splitting of the Fe states, resulting in a majority spin channel almost fully occupied and strongly hybridized with Gr {\pi} states. X-ray magnetic circular dichroism on the Gr/Fe/Ir heterostructure reveals an ordered spin configuration with a ferromagnetic response of Fe layer(s), with enhanced spin and orbital configurations with respect to the bcc-Fe bulk values. The magnetization switches from a perpendicular easy magnetization axis when the Fe single layer is lattice matched with the Ir(111) surface to a parallel one when the Fe thin film is almost commensurate with graphene.