Ferromagnetism triggered by nitrogen defects in graphitic carbon nitride

It remains a challenge to induce robust long-range ferromagnetism in graphene. Doping nitrogen in high concentration is considered as a potential approach. In this paper, three new graphitic carbon nitride structures with energetic stability in chemical formulae of C10N6, C(9)N(7)and C(7)N(9)are proposed and investigated by first-principles calculation. Both C(10)N(6)and C(9)N(7)are half-metals, and C(7)N(9)is a spin-polarized metal. The itinerantpelectrons occupy the spin-polarized narrow bands near the Fermi level, which induces Stoner ferromagnetism in the C(10)N(6)and C9N7. The direct exchange between the delocalized magnetic moment of the itinerant pi electrons is responsible for the ferromagnetism in the C7N9. The magnetic moment is determined by both spin-polarized electronic structures and long-range magnetic interaction. Intriguingly, besides the magnetic interactions between the itinerant pi electrons, we also find direct magnetic interaction between localized in-plane unpaired electrons. Our results will assist in understanding ferromagnetism and motivate new experiments to produce robust magnetism in graphene-like materials following the proposed synthesis strategy.