Monolayer Fe₃GaX₂ (X = I, Br, Sb): High-Temperature Two-Dimensional Magnets and a Novel Partially Ordered Spin State

We systematically investigated the effects of charge doping and strain on monolayer Fe₃GaTe₂ and proposed three new novel two-dimensional magnetic materials: monolayer Fe₃GaX₂ (X = I, Br, Sb). We found that both strain and charge doping can tune the magnetic interactions, and tuning by charge doping is more significant. Differential charge analysis revealed that the doped charges predominantly accumulate around the Te atoms. Based on this insight, we introduced Fe₃GaI₂, Fe₃GaBr₂, and Fe₃GaSb₂ monolayers. The Fe₃GaI₂ and Fe₃GaBr₂ monolayers contain I and Br atoms rather than Te atoms and emulate an electron-doped Fe₃GaTe₂ monolayer, resulting in notably high T_c values of 867 and 844 K, respectively. In contrast, the Fe₃GaSb₂ monolayer mimics a hole-doped Fe₃GaTe₂ monolayer and presents a mix of ferromagnetic and antiferromagnetic interactions, manifesting a distinctive partially ordered magnetic state. Our study demonstrates that substitution atoms based on the charge-doping effect offer a promising approach for predicting new magnetic materials. The proposed Fe₃GaI₂, Fe₃GaBr₂, and Fe₃GaSb₂ monolayers hold great potential for spintronics applications and may stimulate the pursuit of new types of spin liquid.