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

Abstract

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 $\mathrm{Bi}/{\mathrm{CrI}}_{3}$ heterostructures using first-principles calculations. Results show that the easy-magnetization direction rotates from the easy axis in the ${\mathrm{CrI}}_{3}$ monolayer to the easy plane in the $\mathrm{Bi}/{\mathrm{CrI}}_{3}$ heterostructure. A built-in electric field in ${\mathrm{CrI}}_{3}$ introduced by the coupling between the ${\mathrm{CrI}}_{3}$ and Bi monolayers is found responsible for this spin reorientation. The Curie temperature of the $\mathrm{Bi}/{\mathrm{CrI}}_{3}$ heterostructure reaches 107 K, significantly larger than the Curie temperature (45 K) of the pristine ${\mathrm{CrI}}_{3}$ monolayer. The metal property of the heterostructure introduces a double exchangelike ferromagnetic (FM) coupling which promotes the Curie temperature. Moreover, in the Bi/bilayer ${\mathrm{CrI}}_{3}$ heterostructure, the coupling between ${\mathrm{CrI}}_{3}$ and Bi makes the interlayer ${\mathrm{CrI}}_{3}\ensuremath{-}{\mathrm{CrI}}_{3}$ exchange interaction become FM, and the ${\mathrm{CrI}}_{3}$ 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.