Routes to magnetic graphene: from the decoration with nanoparticles to the symmetric broken bonds of its honeycomb lattice

Pristine graphene is nonmagnetic because the outer electrons in the rings of the honeycomb lattice are merged into its sigma- and pi- bonds. To have magnetic graphene, methods have been proposed to break the bond symmetry to obtain unpaired electrons and spins, so that spins interacting, magnetism in graphene is appearing. These methods are based on the intrinsic nature of graphene. Other methods are based on the extrinsic decoration of honeycomb graphene layers with magnetic nanoparticles. Here, we discuss the routes to have magnetic graphene magnetized in intrinsic and extrinsic manners, and some of its applications. In particular the nitrogen-doped graphene is considered. The Ruderman-Kittel-Kasuya-Yosida interaction is also proposed in a concise manner. Short discussion about graphene substitution with nitrogen-doped biochar and iron-decorated biochar is proposed too.