Transition Metal-Free Half-Metallicity in Two-Dimensional Gallium Nitride with a Quasi-Flat Band

Abstract

Two-dimensional half-metallicity without a transition metal is an attractive attribute for spintronics applications. On the basis of first-principles calculation, we revealed that a two-dimensional gallium nitride (2D-GaN), which was recently synthesized between graphene and SiC or wurtzite GaN substrate, exhibits half-metallicity due to its half-filled quasiflat band. We found that graphene plays a crucial role in stabilizing a local octahedral structure, whose unusually high density of states due to a flat band leads to a spontaneous phase transition to its half-metallic phase from normal metal. It was also found that its half-metallicity is strongly correlated to the in-plane lattice constants and thus subjected to substrate modification. To investigate the magnetic property, we simplified its magnetic structure with a two-dimensional Heisenberg model and performed Monte Carlo simulation. Our simulation estimated its Curie temperature (T C ) to be ∼165 K under a weak external magnetic field, suggesting that transition metal-free 2D-GaN exhibiting p orbital-based half-metallicity can be utilized in future spintronics.

Two-Dimensional Asymmetric Multiferroics: Unique Way toward Strong Magnetoelectric Coupling and Multistate Memory

“…On the basis of the ground states, the band structures of InTlNO 2 (Figure ) were studied with the HSE06 hybrid functional. We find that p1 and p2 are half-metallic because their spin-up states are n-type semiconducting as their conduction band minima (CBMs) are lower than the Fermi level at the Γ point by just 0.02 and 0.1 eV for p1 and p2, respectively, while the spin-down bands are metallic. − The projected densities of states (PDOSs) (Figure S4) demonstrate the strong coupling between the p x /p y orbitals of N ions and the p z orbital of the O ions near the Fermi level, leading to the magnetic moments. For p1 and p2, the ferromagnetic coupling can be explained by the Stoner effect.…”