Graphitic-nitrogen-enhanced ferromagnetic couplings in nitrogen-doped graphene

Nitrogen doping is a promising approach to induce the basal-plane localized magnetic moments in sp -electron-only graphene sheets. Enhancing the magnetic couplings among the moments can contribute to the high Curie temperature TC and large ratio of ferromagnetism (FM), which is vital for real applications in spintronic devices; however, it is still challenging. Here, we experimentally demonstrate that graphitic nitrogen (N-Q) could enhance the ferromagnetic couplings of localized magnetic moments provided by the defective N in nitrogen-doped graphene (NG). Nearly pure FM at 2 K is obtained in NG16.04 (N-Q/N = 16.04 at. %) with a TC up to 397.5 K, while the room-temperature saturated magnetization is high as ∼ 0.4 emu/g. The rich C → N electrons contributed by the high ratio of the N-Q complex dominantly devote itinerant magnetism and enhance the interactions among the pyrrolic N (N-5) and/or pyridinic N complexes. Our density functional theory simulation results provide the configurations of (trimerized N-5)-triazinic N-Q along certain directions with enhanced sublattice-independent FM, which are proposed to be the magnetic structures in NG16.04 . Our investigation reveals that introducing the N-Q can serve as an ideal route for the long-range spin correlations and thus full ferromagnetic couplings in graphene.