Giant enhancement of perpendicular magnetic anisotropy and induced quantum anomalous Hall effect in graphene/NiI2 heterostructures via tuning the van der Waals interlayer distance

Using first-principles calculations, we reveal that the perpendicular magnetic anisotropy of ${\mathrm{NiI}}_{2}$ monolayer can be effectively enhanced via decreasing the interlayer distance of graphene/${\mathrm{NiI}}_{2}$ (Gr/${\mathrm{NiI}}_{2}$) van der Waals (vdW) heterostructures. Furthermore, by analyzing the atomic-resolved magnetocrystalline anisotropy energy (MAE), orbital hybridization-resolved MAE and the density of states we elucidate that this magnetic anisotropy enhancement mainly originated from the electronic states change of $5p$ orbitals of interfacial I atoms. At the same time, we find that the ${\mathrm{NiI}}_{2}$ substrate induces strong magnetic proximity effects on graphene and the quantum anomalous Hall effect (QAHE) can be acquired by decreasing the interlayer spacing. Our work demonstrates the control of magnetic anisotropy of two-dimensional ferromagnetic materials via tuning vdW interlayer distance, and provides a van der Waals system to realize the QAHE.