Magnetic Correlations at Graphene Edges: Basis for Novel Spintronics Devices

Magnetic zigzag edges of graphene are considered as a basis for novel spintronics devices despite the fact that no true long-range magnetic order is possible in one dimension. We study the transverse and longitudinal fluctuations of magnetic moments at zigzag edges of graphene from first principles. We find a high value for the spin wave stiffness D=2100  meV Ų and a spin-collinear domain wall creation energy E_dw=114  meV accompanied by low magnetic anisotropy. Above the crossover temperature T_x≈10  K, the spin correlation length ξ∝T^-1 limits the long-range magnetic order to ∼1  nm at 300 K while below T_x, it grows exponentially with decreasing temperature. We discuss possible ways of increasing the range of magnetic order and effects of edge roughness on it.