Suppression of spin polarization in graphene nanoribbon by edge defects and impurities

We investigate the effect of edge defects (vacancies) and impurities (substitutional dopants) on the robustness of spin polarization in graphene nanoribbons (GNRs) with zigzag edges by using density-functional-theory calculations. The stability of the spin state and its magnetic moments is found to continuously decrease with increasing the concentration of the defects or impurities. The system generally becomes nonmagnetic at the concentration of one edge defect (impurity) per ~10 Å. The spin suppression is shown to be caused by the reduction and removal of edge states at the Fermi energy. Our analysis implies an important criterion on the GNR samples for spintronics applications.