▎ 摘　　要

Two-dimensional (2D) heterostructures based on graphene (Gr) and 2D magnetic materials have attracted much attention due to the unique properties, which have the potential applications in nano-electronics, optoelectronics and spintronics. Here, the electronic structure and magnetic properties of 2D Gr/Janus 2H-VSeX (X = S, Te) (Gr/VSeX) heterostructures are investigated systematically by density functional theory. The Dirac cones of graphene in Gr/VSeX heterostructures open a band gap, where the valley splitting appears at K and K' points by considering spin-orbit coupling effect. By comparing to Janus VSeTe monolayer, the valley splitting and Dzyaloshinskii-Moriya interaction (DMI) of Gr/VSeTe heterostructure are significantly enhanced. Meanwhile, the electronic structure and magnetic properties of Gr/VSeTe heterostructure can also be modulated by external electric field, interlayer distance and in-plane biaxial strain, where the in-plane biaxial strain effects on DMI is more pronounced. Moreover, the valley splitting of graphene (VSeTe) can be effectively enhanced by decreasing the interlayer distance of Gr/VSeTe heterostructure. These results show the potential applications of 2D magnetic heterostructures in nonoelectronics, spintronics and valleytronics. (C) 2020 Elsevier Ltd. All rights reserved.