Stacking-dependent magnetism in bilayer CrI3*

We report the connection between the stacking order and magnetic properties of bilayer CrI3 using first-principles calculations. We show that the stacking order defines the magnetic ground state. By changing the interlayer stacking order one can tune the interlayer magnetism between antiferromagnetism and ferromagnetism. To measure the predicted stacking-dependent magnetism, we propose using a linear magnetoelectric effect. Our results not only gives a possible explanation for the observed antiferromagnetism in bilayer CrI3 but also have direct implications in heterostructures made of two-dimensional magnets.