Local defects and ferromagnetism in graphene layers
  We study the changes in the electronic structure induced by lattice defects in graphene planes. In many cases, lattice distortions give rise to localized states at the Fermi level. Electron-electron interactions lead to the existence of local moments. The RKKY interaction between these moments is always ferromagnetic, due to the semimetallic properties of graphene 
M. A. H. Vozmediano, M. P. Lopez-Sancho, T. Stauber, and F. Guinea