Uncovering two-dimensional intrinsic ferromagnetism from host antiferromagnet via super-exchange interaction modulation*

Two-dimensional ferromagnetic semiconductors have been gaining great attention as they incorporate low-dimensionality, ferromagnetism and semiconductivity, which are promising for next-generation multifunctional spintronics. Here, we report an effective strategy to design ferromagnetic single crystals based on our previous extended super-exchange theory for polyvalent anion materials, e.g. CrOCl. We reveal that the magnetic order of one specific super-exchange cation-anion-cation path in CrOCl prototype is directly related to all anions' valence state. Choosing suitable anions (A₁=VIIA, A₂=VA element) in sites, all super-exchange paths are tuned into strongly ferromagnetic, leading to designed materials are intrinsic ferromagnets companied with high Curie temperatures. On the basis of the explored strategy and first-principles calculations, two stable monolayers CrIP and CrIAs are predicted to be ferromagnetic half-metal and semiconductor, respectively. The Curie temperature, estimated by Monte Carlo simulation using Heisenberg model, is as high as 1050 K and 655 K.