Nodal-Loop Half Metallicity in Two-Dimensional Fe4N2 Pentagon Crystal with Room-Temperature Ferromagnetism

Two-dimensional (2D) materials with fully spin-polarized nodal-loop band crossing are a class of topological magnetic materials, holding promise for high-speed low-dissipation spintronic devices. Recently, several 2D nodal-loop materials have been reported in theory and experiment, such as Cu2Si, Be2C, CuSe, and Cr2S3 monolayers, adopting a triangular, tetragonal, hexagonal, or complex lattice. However, 2D nodal-loop half metal with room-temperature magnetism is still little reported. Here, we report that 2D Fe4N2 pentagon crystal is a nodal-loop half metal with room-temperature magnetism over 428 K and a global minimum structure by using first-principles calculations and global structure search. The Dirac nodal-lines in Fe4N2 form a flat nodal-loop at Fermi level and a spin-polarized type-II nodal-loop above Fermi level, which are protected by mirror symmetry. Our results establish Fe4N2 as a platform to obtain nodal-loop half metallicity in 2D pentagon lattice and provide opportunities to build high-speed low-dissipation spintronics in the nanoscale.