Substrate-induced magnetism in epitaxial graphene buffer layers

Abstract

Magnetism in graphene is of fundamental as well as technological interest, with potentialapplications in molecular magnets and spintronic devices. While defects and/oradsorbates in freestanding graphene nanoribbons and graphene sheets have beenshown to cause itinerant magnetism, controlling the density and distributionof defects and adsorbates is in general difficult. We show from first principlescalculations that graphene buffer layers on SiC(0001) can also show intrinsicmagnetism. The formation of graphene–substrate chemical bonds disrupts the grapheneπ-bonds and causes localization of graphene states near the Fermi level. Exchangeinteractions between these states lead to itinerant magnetism in the graphene buffer layer.We demonstrate the occurrence of magnetism in graphene buffer layers on bothbulk-terminated as well as more realistic adatom-terminated SiC(0001) surfaces. Ourcalculations show that adatom density has a profound effect on the spin distribution in thegraphene buffer layer, thereby providing a means of engineering magnetism in epitaxialgraphene.