Theory of Vacancy-Induced Intrinsic Magnetic Impurity with   Quasi-Localized Spin Moment in Graphene
  In this paper, by considering the Hubbard model on a honeycomb lattice, we developed a theory for the intrinsic magnetic impurities (MIs) with the quasi-localized spin moments induced by the vacancies in graphene. Because the intrinsic MIs are characterized by the zero modes that are rthotropic to the itinerant electrons, their properties are much different from those of Anderson MIs with the well-localized spin moments. 
Yang Li, Jing He, and Su-Peng Kou
cond-mat.mes-hall cond-mat.str-el