Unusual magnetic properties of functionalized graphene nanoribbons

The edge-induced magnetism of graphene nanoribbons (GNRs) has been found to be highly unstable at room temperature, thus making it difficult for spintronics applications under ambient conditions. Using first-principles calculations, we propose a way to overcome this problem by embedding transition-metal atoms into functionalized GNRs. We show that due to low or vanishing reaction barriers, 3d transition-metal atoms can be easily embedded into GNR once they are functionalized by -F or -CN groups. A systematic study of these materials shows fascinating magnetic properties; Co-embedded systems not only have high magnetic anisotropy energies hundreds of times larger than that of pure GNR and bulk Co, but also, the magnetic preferential directions can be switched by an electric field. Mn-embedded systems exhibit giant magnetic moments and half-metallicity with greatly enhanced stability. Under a small amount of biaxial strain, the magnetic moment of every Mn atom in such a Mn-embedded system can be increased by 2.1 μ_B due to a change in the d_xy orbital occupancy, and its Curie temperature is estimated to be over 1000 K. © 2013 American Chemical Society.