Revealing the Underlying Mechanisms of the Stacking Order and Interlayer Magnetism of Bilayer CrBr3

Aiming to clarify the mechanisms governing the interlayer magnetic coupling, we have investigated the stacking energy and interlayer magnetism of bilayer CrBr3 systemically. The magnetic ground states of bilayer CrBr3 with different R-type and H-type stacking orders are established, which are found to be in good agreement with recent experiments [Science 2019, 366, 983]. Further analyses indicate that the stacking energy is mainly determined by the Coulomb interaction between the interlayer nearest-neighbor Br-Br atoms, while interlayer magnetism can be understood by a competition between super-superexchange interactions involving t(2g)-t(2g) and t(2g)-e(g) orbitals and semicovalent exchange interactions of e(g)-e(g) orbitals. Our studies give an insightful understanding of the stacking order and interlayer magnetism of bilayer CrBr3, which should be useful to understand the quantum confinement effect of other van der Waals magnetic materials.