Defect stability and intriguing magnetic properties in Janus chromium trihalides monolayer

Monolayer CrI₃ with robust ferromagnetism has been extensively studied. Its Janus structures could further enhance its applications in spintronic devices. Here we investigate the intrinsic defects and their induced magnetic properties in Janus structures. We constructed the point defects in Janus CrX_1.5Y_1.5 (X, Y = Cl, Br, I; X ≠ Y) monolayer, and studied the structural stability and migration barriers by first-principles calculations. The single vacancy with one halogen atom missing, is the most stable defect in Cr-rich condition, while the Cr vacancy is preferred to form in halogen-rich condition. Our results revealed that the surface defects not only enhance the intrinsic ferromagnetism of the Janus structures, but also increase the Curie temperatures effectively. The intriguing properties induced by the surface defects make the Janus chromium trihalides monolayer promising for multifunctional nanodevices.