Magnetic ground state in FeTe2,VS2, and NiTe2 monolayers: Antiparallel magnetic moments at chalcogen atoms

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 states of three transition-metal dichalcogenide monolayers, viz., ${\mathrm{FeTe}}_{2},{\mathrm{VS}}_{2}$, and ${\mathrm{NiTe}}_{2}$, 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 $p\text{\ensuremath{-}}d$ hybridization. The latter is found to be true for both $H$ and $T$ phases of ${\mathrm{FeTe}}_{2},{\mathrm{VS}}_{2}$, and ${\mathrm{NiTe}}_{2}$ monolayers. Our predictions show that the ${\mathrm{FeTe}}_{2}$ monolayer in its lowest-energy structure is a half metal, which prevails under both compressive and tensile strains. Half metallicity occurs also in the ${\mathrm{FeTe}}_{2}$ bilayer but disappears in thicker multilayers. The ${\mathrm{VS}}_{2}$ monolayer is a magnetic semiconductor; it has two different band gaps of different character and widths for different spin polarization. The ${\mathrm{NiTe}}_{2}$ 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.