Two-dimensional intrinsic ferromagnetic half-metals: monolayers Mn₃X₄ (X = Te, Se, S)

Inspired by the recent progress on the intrinsic two-dimensional (2D) ferromagnetism, we studied three potential 2D magnets (Mn₃X₄; X = Te, Se, S) by performing the first-principles calculation based on the density functional theory and Monte Carlo simulations. We predicted intrinsic ferromagnetism in monolayers Mn₃Te₄ and Mn₃Se₄, which are half-metallic with 100% spin polarization at the Fermi level. The half-metal band gap of monolayers Mn₃Te₄ and Mn₃Se₄ is 0.62 and 0.83 eV, respectively. More importantly, the Curie temperatures of Mn₃Te₄ and Mn₃Se₄ were estimated to be above the room temperature by performing the Monte Carlo simulations, suggesting ferromagnetic ordering at room temperature. Additionally, we calculated the phonon spectrum, elastic modulus, and performed the ab initio molecular dynamics simulation which proves that monolayers Mn₃Te₄ and Mn₃Se₄ are thermally, dynamically and mechanically stable. Plus, mechanical stripping method was proven to be the feasible way to obtain single-layer Mn₃X₄.