First-principles study of two-dimensional half-metallic ferromagnetism in NiXCl (X = S and Se) monolayer

Half-metallic ferromagnets with the character of making maximum use of spin polarization become the center of scientific research. Specifically, two-dimensional (2D) ferromagnetic materials, due to their 100% spin polarization at the Fermi level, are highly desirable for spintronic devices. Using first-principles calculations, we demonstrated that the NiSCl and NiSeCl monolayers are intrinsic 2D ferromagnetic half-metals. The predicted Curie temperatures of the NiSCl and NiSeCl monolayers are 311 and 180 K by Monte Carlo simulations, respectively. The calculated electronic structures using the Heyd–Scuseria–Ernzerhof hybrid functional showed that their half-metallic bandgaps are 1.06 and 0.53 eV, and 3.40 and 2.68 eV for NiSCl and NiSeCl monolayers, respectively. These results indicated that 2D NiSCl and NiSeCl are promising half-metallic materials.