High-throughput calculations of spintronic tetra-phase transition metal dinitrides

Two-dimensional (2D) transition metal dinitrides (TMN2) have attracted increasing attention owing to their diverse geometry configurations and versatile properties. Because of the large electrostatic repulsion between highly charged N3- ions, the TMN2 could show a low-coordination-number geometry different from the transition metal dichalcogenides (e.g. MoS2), which would bring high-temperature ferromagnetism and other unique properties. In this study, via high-throughput first-principles calculations, we systemically investigated the possible h-, t- and novel tetra-phases of 2D TMDNs (TM = all the 3d, 4d and 5d transition metals). The results show that, the 2D tetra-phases for several systems could be energetically preferred than their h- and t-phases. These 2D tetra-phases are dynamically and thermally stable with comparable mechanical properties to 2D MoS2 and germanene. The tetra-MoN2 and tetra-WN2 are semiconductors, while the tetra-MoN2, tetra-RuN2, tetra-ReN2, tetra-OsN2 and tetra-IrN2 are metals. In particular, the tetra-MnN2 exhibits ferromagnetic half-metallicity with Curie temperature (TC) up to ~590 K and out-of-plane magnetic anisotropy. These findings expand the family of 2D TMN2 and provide a material database for future theoretical and experimental studies for 2D spintronic materials.