Janus-enhanced magnetic modulation under strain engineering and carrier doping in Fe₃GaTe₂ monolayers

Two-dimensional (2D) intrinsic Fe₃GaTe₂ ferromagnets have attracted considerable interest owing to their high Curie temperature (T_C) and strong perpendicular magnetic anisotropy. Intrinsic manipulations, like Janus functionalization, offer a powerful approach to tune the magnetic properties for enhanced performance and flexibility. Here, we systematically investigated the electronic and magnetic properties of monolayer Fe₃GaTe₂ and its Janus derivatives (Fe₃GaXTe) under biaxial strain and electrostatic doping via first-principles calculations. As demonstrated, Janus functionalization substantially modifies the atomic magnetic moments, magnetic anisotropy energy (MAE), Dzyaloshinskii-Moriya interaction (DMI), exchange coupling, and T_C by altering the geometric configuration, charge redistribution, and electronic states. Exchange interactions of the metallic Fe₃GaXTe systems in response to mechanical strain and carrier doping were explored. A remarkable enhancement of exchange coupling was achieved under compressive strain and electron doping, resulting in a pronounced increase in T_C. These behaviors originate from strain-induced modulation of super-exchange pathways and electric-field-driven redistribution of electronic states. Meanwhile, the MAE exhibits a tunable sign and magnitude, indicating a controllable manipulation of the easy magnetization axis. All these results highlight the effectiveness of Janus engineering in optimizing and tailoring the magnetic functionality of 2D ferromagnets and portray a promising roadmap for the applications of spintronic devices.