Strain-tunable interlayer magnetic coupling in van der Waals ferromagnet Fe₃GaTe₂ nanoflakes

Interlayer magnetic coupling plays vital roles in physical properties of van der Waals (vdW) magnets and in engineering functionally optimized spintronics. So far, however, few avenues are available to control the magnetic coupling at interfaces. Here, we report that the interlayer ferromagnetic (FM)-antiferromagnetic (AFM) coupling in Fe₃GaTe₂, an above-room-temperature vdW ferromagnet, can be largely enhanced by in-plane tensile strain implemented by a flexible substrate, leading to a large zero-field cooling (ZFC) exchange bias (EB) with a maximal EB field H_EB up to 1.7 kOe at 50 K. A positive correlation between EB field H_EB and coercivity H_C is further revealed in strained Fe₃GaTe₂ nanoflakes. Theoretical analysis combining micromagnetic simulation and density functional theory (DFT) reveals that strain enhances interlayer exchange coupling, giving rise to EB effects. A nonmonotonic evolution of coercivity with respect to the tensile strain along a general crystallographic direction within the ab-plane is further demonstrated by DFT calculations, aligning qualitatively with experimental findings. Our work provides an alternative knob to tune interlayer coupling in vdW materials, allowing for the tailoring of magnetism and other correlated states at interfaces.