Magnetic ground state in FeTe_2, VS_2, and NiTe_2 monolayers: Antiparallel magnetic moments at chalcogen atoms

摘要

Our analysis based on the results of hybrid and semilocal density-functional calculations with and without Hubbard U correction for on-site Coulomb interactions reveals the true magnetic ground stales of three transition-metal dichalcogenide monolayers, viz., FeTe_2, VS_2, and NiTe_2, which comprise inhomogeneous magnetic moment configurations. In contrast to earlier studies considering only the magnetic moments of transition-metal atoms, the chalcogen atoms by themselves have significant, antiparallel magnetic moments owing to the spin polarization through p-d hybridization. The latter is found to be true for both H and T phases of FeTe_2, VS_2, and NiTe_2 monolayers. Our predictions show that the FeTe_2 monolayer in its lowest-energy structure is a half metal, which prevails under both compressive and tensile strains. Half metallicity occurs also in the FeTe_2 bilayer but disappears in thicker multilayers. The VS_2 monolayer is a magnetic semiconductor; it has two different band gaps of different character and widths for different spin polarization. The NiTei monolayer, which used to be known as a nonmagnetic metal, is indeed a magnetic metal with a small magnetic moment. These monolayers with intriguing electronic and magnetic properties can attain new functionalities for spintronic applications.