Phase Control of Graphene Nanoribbon by Carrier Doping: Appearance of Noncollinear Magnetism

The zigzag graphene nanoribbon (ZGNR) has an antiferromagnetic property, that is, the relative spin angle theta between the two edges is 180 degrees. By using noncollinear first-principles calculations, we find that the magnetic phase of the ZGNR can be controlled by injecting either electrons or holes: as the carrier density increases, theta continuously decreases from 180 to 0, which indicates that the net magnetization is possible. Either FET doping or chemical doping is found to be possible.