Magnetic monolayer Li$_{2}$N: Density Functional Theory Calculations (1710.04440v1)

Abstract: Density functional theory (DFT) calculations are used to investigate the electronic and magnetic structures of a two-dimensional (2D) monolayer Li${2}$N. It is shown that bulk Li${3}$N is a non-magnetic semiconductor. The non-spinpolarized DFT calculations show that $p$ electrons of N in 2D Li${2}$N form a narrow band at the Fermi energy $E{\rm{F}}$ due to a low coordination number, and the density of states at the Fermi energy ($g(E_{\rm{F}}$)) is increased as compared with bulk Li${3}$N. The large $g(E{\rm{F}}$) shows instability towards magnetism in Stoner's mean field model. The spin-polarized calculations reveal that 2D Li${2}$N is magnetic without intrinsic or impurity defects. The magnetic moment of 1.0\,$\mu{\rm{B}}$ in 2D Li${2}$N is mainly contributed by the $p{z}$ electrons of N, and the band structure shows half-metallic behavior. {Dynamic instability in planar Li${2}$N monolayer is observed, but a buckled Li${2}$N monolayer is found to be dynamically stable.} The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms is also investigated to access the exchange field strength. {We found that planar (buckled) 2D Li${2}$N is a ferromagnetic material with Curie temperature $T{c}$ of 161 (572) K.}