Magnetism in graphene nanoribbons on Ni(111): First-principles density functional study

Abstract

We study magnetism of zigzag graphene nanoribbons (ZGNRs) whose ribbon widths are 1.8--2.2 nm by performing first-principles density functional theory calculations. In contrast with freestanding ZGNRs, ZGNRs directly adsorbed on Ni(111) do not show flat-band magnetism due to strong orbital hybridization between edge-localized $\text{C}\text{ }p$ orbitals and $\text{Ni}\text{ }d$ orbitals. The flat-band magnetism of the ZGNR is recovered by introduction of a graphene sheet between the ZGNR and Ni(111) as a buffer layer which weakened the orbital hybridization. In this case, a parallel configuration of spin moments at the two edges has lower energy than the antiparallel spin configuration whereas the magnetic ground state of the freestanding ZGNR has an antiparallel spin configuration. We explore the effects of orbital hybridization and charge transfer on the magnetic stability of ZGNRs on graphene/Ni(111).