Control of magnetism in bilayer CrI3 by an external electric field

Recently intrinsic ferromagnetism in two-dimensional(2D) van der Waals materials was discovered (Huang et al 2017 Nature 546 270-3; Gong et al 2017 Nature 546 265-9; O'Hara et al 2018 Nano Lett. 18 3125-31). A monolayer of Chromiun triiodide(CrI3) is ferromagnetic while a bilayer structure was reported to be anti-ferromagnetic, moreover an external electric field changes its magnetic phase (Jiang et al 2018 Nat. Mater. 17 406-10). We have studied the two found in nature stackings of CrI3 bilayers and found that indeed the magnetic phase of one of them can be tuned by an external electric field while the other remains ferromagnetic. We simulate those results with ab initio calculations and explain them with a simple model based on a rigid shift of the bands associated with different spins. The model can be applied to similar van der Waal stacked insulating bilayer anti-ferromagnets.