Influence of Nitrogen and Boron on the magnetization of nanoporous graphene : A first-principle investigation

Spin-polarized density functional theory (DFT) calculations with the generalized gradient approximation (GGA) of the Perdew–Burke–Ernzerhof (PBE) flavour, i.e., GGA-PBE has been performed to study the interactions of nitrogen (N) and boron (B) dopants with model graphene nanopores. We study the formation energy, magnetic and electronic properties of nanoporous graphene containing varying concentration of N and B as dopants. Magnetism in nanoporous graphene is induced by σ and π dangling bonds due to missing carbon atoms following the creation of the nanopores. Here, we show that progressive substitution of carbon atoms carrying dangling bonds, with either B or N atoms, results to the progressive decrease in the magnetic moment of the doped nanopore defect structures. In the N doped nanopore, for every single N substituting the C atom carrying dangling bonds at the perimeter of the nanopore, the magnetic moment reduces by about 1 μB. The magnetization of the nanopore is completely annihilated after full substitution of the carbon atoms carrying dangling bonds. In the case of B doped nanopore however, the magnetic moment decreases rapidly and vanishes before all the C atoms carrying dangling bonds are substituted. Löwdin charge analysis shows that N doping leads to charge transfer from the C to the N atom while B doping leads to charge transfer from B to the neighbouring C atoms. Thus, the electron withdrawing characteristics of N atom contributes to reduce the magnetization. On the other hand, B atom donates its charges which contribute to saturate the C dangling bonds and thus reduces the magnetization. Our work shows the possibility of achieving finite magnetic moment in graphene via a combination of nanopore engineering, B or N doping. Such nanoscale control of magnetization in a low-dimensional structure such as graphene, has important consequence for spintronics and related applications.