Strain-Tunable Interlayer Magnetic Coupling in van der Waals Ferromagnet Fe₃GaTe₂ Nanoflakes

Interlayer magnetic coupling plays vital roles in the 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-antiferromagnetic coupling in Fe_3GaTe_2, an above-room-temperature vdW ferromagnet, can be largely enhanced by in-plane tensile strain implemented via a flexible substrate, leading to a large zero-field-cooled exchange bias (EB) with a maximal EB field H_\rm EB up to 1.7 kOe at 50 K. A positive correlation between the EB field H_\rm EB and coercivity H_\rm c is further revealed in strained Fe_3GaTe_2 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 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, enabling tailoring of magnetism and other correlated states at interfaces.