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 degrees , which indicates that the net magnetization is possible. Either FET doping or chemical doping is found to be possible.