Local magnetic moment formation on edges of graphene

Local magnetic moment formation on edges of graphene is studied using the Hubbard model on a honeycomb lattice. The Coulomb interaction is treated with the mean field approximation. Realistic edges of graphene are composed of zigzag and armchair parts. It is found that, on a zigzag part of length na larger than 3a, where a is the lattice constant, local staggered moment whose magnitude is proportional to the length of the zigzag part, is developed, i.e., a zigzag part of length 3a is sufficient for generation of local magnetism. This also means that one has to get rid of zigzag parts of n >= 3 to suppress local edge magnetism of graphene.