Tunable Magnetic Properties And Electronic Structures Of Two-dimensional 2H-VS₂ Monolayer And Its Heterostructure

Two-dimensional(2D)transition metal dichalcogenides(TMDs)due to its excellent properties have been successfully applied in optoelectronics,spintronics and logic devices.However,most TMDs materials are nonmagnetic,which limits their applications in magnetic storage devices.Although a large number of studies have reported that magnetic doping,adsorption and defect can induce magnetism in TMDs,there are still many problems.Therefore,searching for a new class of 2D magnetic materials is crucial,which is also an interesting topic in the field of 2D semiconductor materials.In recent years,2D intrinsic room temperature ferromagnetic material vanadium disulfide(VS₂)due to its extraordinary intrinsic room temperature ferromagnetic ordering and semiconductor characters receives intensive attention.The magnetic properties,electronic structure and valley polarization of 2H-VS₂ monolayer and its heterostructure are systematically investigated by first-principle calculations in this paper.1.Based on the first-principle of density functional theory and Mede A-VASP software package,the effects of in-plane strain and interlayer coupling on the valley polarization,magnetocrystalline anisotropy and electronic structure of 2H-VS₂monolayer with stable room-temperature ferromagnetism are systematically investigated.The results show that the pristine 2H-VS₂ monolayer exhibits obvious room temperature ferromagnetism,high Curie temperature(512K),in-plane magnetocrystalline anisotropy and large spontaneous valley polarization(71.1 me V).By incorporating spin-orbit coupling(SOC)effect and magnetic exchange interaction into two-band k·p model,the valley polarization of 2H-VS₂ monolayer is more caused by the intrinsic magnetic exchange interaction of V 3d electrons.The 3d orbital of V atoms resolved magnetocrystalline anisotropy energy(MAE)reveals that d_xy and d²²_x-yorbitals contribute to in-plane MAE which firstly increases and then decreases with increasing strain.For the van der Waals layered 2H-VS₂,the AB stacking order retains the space inversion symmetry,resulting that the valley polarization decreases or even disappears.On the contrary,the AA stacking order induces a larger valley polarization with breaking the space inversion symmetry.2.The effects of different atoms terminated and switching the different ferroelectric polarization on magnetic,electronic structure and valley polarization of2H-VS₂ monolayer by the YMnO₃/2H-VS₂ heterostructures are systematically investigated by first-principles calculations.The results show that the interlayer distance of Y heterostructure model are slightly smaller than those ofO and MnO models,implying a strong interfacial hybridization,and the interlayer distance is sensitive to the ferroelectric polarization switching.It is clear that the band structures of YMnO₃ changes significantly with the terminal change and the reversal of ferroelectric polarization,while the valley characteristic of 2H-VS₂ monolayer are retained in all heterostructure models.Furthermore,owing to the exchange interaction between 2H-VS₂ monolayer and surface atoms of YMnO₃,the magnetism of 2H-VS₂monolayer inO and MnO terminated models can be effectively modulated with polarization switching,which is of great significance to the development of information storage devices and nonvolatile devices.