Artificial Multiferroics and Enhanced Magnetoelectric Effect in van der Waals Heterostructures.

Multiferroic materials with coupled ferroelectric (FE) and ferromagnetic (FM) properties are important for multifunctional devices because of their potential ability of controlling magnetism via electric field and vice versa. The recent discoveries of two-dimensional (2D) FM and FE materials have ignited tremendous research interest and aroused hope to search for 2D multiferroics. However, intrinsic 2D multiferroic materials and, particularly, those with strong magnetoelectric couplings are still rare to date. In this paper, using first-principles simulations, we propose artificial 2D multiferroics via a van der Waals (vdW) heterostructure formed by FM bilayer chromium triiodide (CrI) and FE monolayer ScCO. In addition to the coexistence of ferromagnetism and ferroelectricity, our calculations show that, by switching the electric polarization of ScCO, we can tune the interlayer magnetic couplings of bilayer CrI between the FM and antiferromagnetic states. We further reveal that such a strong magnetoelectric effect is from a dramatic change of the band alignment induced by the strong built-in electric polarization in ScCO and the subsequent change of the interlayer magnetic coupling of bilayer CrI. These artificial multiferroics and enhanced magnetoelectric effect give rise to realizing multifunctional nanoelectronics by vdW heterostructures.