Two-dimensional stable Fe-based ferromagnetic semiconductors: FeI₃ and FeI_1.5Cl_1.5 monolayers

Two-dimensional (2D) ferromagnetic (FM) semiconductors are highly desirable in next generation spintronic devices. Herein, we report an intrinsic FM semiconductor, an FeI3 monolayer which can be exfoliated from its bulk crystal owing to the small cleavage energy and the high in-plane stiffness. The FeI3 monolayer is dynamically and mechanically stable. Additionally, the FeI3 monolayer has sizable magneto-crystalline anisotropy energy (MAE) and the Curie temperature is higher than the liquid-nitrogen temperature (77 K), and there is a big discrepancy (Δcbm) between the conduction band minimum of the two spin-channels and negligible thermally induced hop. Carrier doping less than 0.1 e per unit cell further improves the relevant properties by modulating the MAE, Curie temperature, and Δcbm. Moreover, the isoelectronic analogue FeI1.5Cl1.5 monolayer is a bipolar FM semiconductor with a high Curie temperature (260 K). Our results demonstrate promising applications of the FeI3 monolayer in next-generation spintronic devices owing to its robust intrinsic ferromagnetism and novel semiconducting properties.