P-Superdoped Graphene: Synthesis and Magnetic Properties

Phosphorus (P)-doping in vacancies of graphene sheets can significantly change graphene's physical and chemical properties. Generally, a high level for P-doping is difficult due to the low concentration of vacancy but is needed to synthesize graphene with the perfect properties. Herein, we synthesized the P-superdoped graphene with the very high P content of 6.40 at. % by thermal annealing of fluorographite (FGi) in P vapor. Moreover, we show that the P-doping level can be adjusted in the wide range from 2.86 to 6.40 at. % by changing the mass ratio of red phosphorus to FGi. The magnetic results show that (i) P-doping can effectively create localized magnetic moments in graphene; (ii) the higher the doping level of sp(3)-type PQ(x) groups, the higher the magnetization of P-superdoped graphene is; and (iii) the high P-doping levels can lead to the coexistence of antiferromagnetic and ferromagnetic behavior. It is proposed that the sp(3)-type POx groups are the major magnetic sources.