Strain-tunable effective mass and magnetic phase transition in two-dimensional NiI2 monolayer

Recently, extensive efforts have been directed toward the exploration of two-dimensional (2D) van der Waals ferromagnets. In this study, we systematically investigate the effects of in-plane homogeneous strain on the magnetic properties and electronic structure of the NiI2 monolayer through first-principles calculations. Our results suggest that the NiI2 monolayer is a 2D ferromagnetic (FM) semiconductor with out-of-plane magnetic easy axis. Notably, biaxial strain exerts profound control over multiple fundamental properties: compressive strain simultaneously induces a complete transition from ferromagnetic to antiferromagnetic ordering while driving bandgap closure and metallic conversion, with both phenomena governed by competing exchange mechanisms. Furthermore, the strain-dependent reduction in carrier effective masses, particularly under compressive conditions, further suggests promising p-type transport characteristics. These findings establish NiI2 as a highly responsive platform where spin configuration, electronic structures, and carrier dynamics can be coherently engineered through lattice deformation, advancing prospects for tailored spintronic applications.