Numerical studies of the magnetism in graphene nanoribbons and graphene dot

Within determinant quantum Monte Carlo simulation, the magnetic properties of graphene nanoribbons and graphene dot are studied. It is predicted that the armchair graphene nanoribbons show carrier mediated ferromagnetism as electron filling is lower than 0.8. The uniform magnetic susceptibility increase as the width of nanoribbons decrease, and it increases greatly as the next-nearest-neighbor hopping energy increases. It is also shown that strain may induce magnetism in doped square graphene dot having zigzag edge. The resultant ferromagnetism in graphene-based system may facilitate the development of spintronics.