Spin reorientation and Curie temperature promotion in CrI3-Bi van der Waals heterostructures

Promoting the Curie temperature and tunning the magnetocrystalline anisotropy have been key issues in two-dimensional (2D) magnetic materials. Here, we address this issue by studying Bi/CrI3 heterostructures using first-principles calculations. Results show that the easy-magnetization direction rotates from the easy axis in the CrI3 monolayer to the easy plane in the Bi/CrI3 heterostructure. A built-in electric field in CrI3 introduced by the coupling between the CrI3 and Bi monolayers is found responsible for this spin reorientation. The Curie temperature of the Bi/CrI3 heterostructure reaches 107 K, significantly larger than the Curie temperature (45 K) of the pristine CrI3 monolayer. The metal property of the heterostructure introduces a double exchangelike ferromagnetic (FM) coupling which promotes the Curie temperature. Moreover, in the Bi/bilayer CrI3 heterostructure, the coupling between CrI3 and Bi makes the interlayer CrI3-CrI3 exchange interaction become FM, and the CrI3 bilayer has a FM ground state. Our work provides a way to modulate the magnetic properties of 2D materials and may be used for designing 2D spintronic devices.