The Routes to Magnetic Graphene, from Decorations with Nanoparticles to the Broken Symmetry of its Honeycomb Lattice Bonds

Pristine graphene is nonmagnetic because the outer electrons in the rings of its honeycomb lattice are merged into 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 their interaction can turn on the graphene magnetism. These methods are therefore based on the intrinsic nature of graphene. Other methods are based on the extrinsic decoration of graphene layers with magnetic nanoparticles. Here, we discuss the routes to have 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 very concise manner. Short discussion about graphene substitution with nitrogen-doped biochar and iron-decorated biochar is proposed too.