Abstract
We present a new type of two-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides MX 2 (M=V, Co; X = S, Se, Te, I, OH) via first-principles calculations. The obtained band gaps of monolayer (ML) VS 2 , VSe 2 , and VTe 2 in the H-phase given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μ B , while ML VI 2 and Co(OH) 2 in the T-phase exhibit energy gaps of 0.96 and 0.08 eV, respectively, with integer magnetic moments of 3.0 μ B . The GGA plus on-site Coulomb interaction U (GGA+U) scheme, which takes the electron-electron correlations in 3d orbitals into account, enhances the exchange splittings, and raises the energy gap of these MLs up to 0.4 to 3 eV. They agree very well with our calculated gaps based on the hybridized functional Heyd-Scuseria-Ernzerhof (HSE) of 0.6 to 3 eV. The wide range of energy gaps provides flexible applications in spintronics. All the calculations demonstrate 100% spin polarized bands around the Fermi level for these MLs. Combining the semiconducting energy gap and the fully spin polarized valence and conduction bands in a single-layer MX 2 , this new type 2D magnetic semiconductor shows great potential in future spintronics applications.