Tuning the magnetic moments in zigzag graphene nanoribbons: Effects of metal substrates

We report a systematic theoretical investigation of the effects of metal substrates on the local magnetic moments of zigzag graphene nanoribbons (ZGNRs). Representative metal surfaces of Au, Pt, Ni, Cu, Al, Ag, and Pd have been analyzed from atomic first principles. Results show that the local magnetic moments vanish when the nanoribbons are on top of the surfaces of Al, Ag, Pt, and Pd, while they are preserved for Au, Ni, and Cu. For s-dominated metals, the magnetic moments of the edge states of ZGNRs can be tuned by a bias voltage. For p- or d-dominated metals there is significant hybridization between the metal states and the nonbonding p orbital of the ZGNRs; thereby the tuning effect is reduced. We identify the microscopic physical reason behind the bias tuning of the magnetic properties of the ZGNRs.