Twist-angle programmable magnetism in graphene/CrI3 bilayers

Abstract

A graphene monolayer lacks an electronic bandgap and magnetism, which limits its application as components in electronic and spintronic devices. Proximity effects in graphene with other two-dimensional (2D) materials are a promising route to induce properties in van der Waals (vdW) heterostructures. Here, we build twisted vdW graphene/CrI₃ heterostructures and then study their electronic and magnetic properties using collinear spin-polarized density functional theory (DFT) calculations. Four twisted heterostructures were built with maximal biaxial strain to avoid renormalization of the band structures and possible expansion, shrinkage, or corrugation of the monolayers. We found the same electronic bandwidth in graphene with an induced magnetism by the ferromagnetic and semiconducting CrI₃ monolayer substrate. Fingerprints of moiré effects are observed in the calculated local spin density, spin-polarization ratio, orbital-resolved density of states, and unfolded band structures of graphene. Besides the twist-angle dependent Zeeman splitting found in graphene, we obtained an enhancement of magnetic exchange coupling in CrI₃. These results show that the interlayer rotation angle is an additional degree of freedom to compression and electric fields for programming magnetism density in graphene as well as in the CrI₃ monolayer.