First-principles study on p-orbital Half-Metallicity in Two-Dimensional Gallium Nitride

Based on the first-principles calculation, we revealed that a two-dimensional gallium nitride (2D-GaN), which was recently synthesized in-between graphene and SiC or wurtzite GaN substrate, exhibits itinerant ferromagnetism. We found that graphene stabilizes a local octahedral structure of 2D-GaN, whose unusual half-filled quasi-flat bands lead to a spontaneous phase transition to its ferromagnetic phase from normal metal. More intriguingly, its magnetic property is closely related to in-plane lattice constant, and thus under tensile strain, 2D-GaN eventually exhibits p-orbital half-metallicity. To investigate its magnetic property, we simplified its magnetic structure with a 2D Heisenberg model and performed a Monte Carlo simulation. Our simulation revealed that its half-metallicity could be stabilized with a small amount of external magnetic field, and its Curie transition temperature is estimated to be T_C ~ 160K.