Magnetism of substitutional Co impurities in graphene: Realization of single π vacancies

We report ab initio calculations of the structural, electronic, and magnetic properties of a graphene monolayer substitutionally doped with Co (Co-sub) atoms. These calculations are done within density-functional theory using the generalized gradient approximation. We focus in Co because among traditional ferromagnetic elements (Fe, Co, and Ni), only Co-sub atoms induce spin polarization in graphene. Our results show the complex magnetism of Co substitutional impurities in graphene, which is mapped into simple models such as the pi-vacancy and Heisenberg model. The links established in our work can be used to bring into contact the engineering of nanostructures with the results of pi models in defective graphene. In principle, the structures considered here can be fabricated using electron irradiation to create defects and depositing Co at the same time.