Interface engineering and strain-tuned half-metallicity, magnetic anisotropy and spin transport in VI3-based van der Waals heterostructures.

Two-dimensional van der Waals (vdW) magnetic heterostructures provide a versatile platform for engineering spin-dependent phenomena. Despite growing interest in intrinsic 2D magnets, VI3-based vdW heterostructures remain largely unexplored. Using first-principles calculations, we demonstrate that interlayer coupling in VI3-based heterostructures induces intrinsic half-metallicity, enhances magnetic anisotropy, and enables strain-tunable spin transport. Among the considered stacking configurations, AB-stacked VI3/CrGeTe3 is the most stable, whereas AB-stacked VI3/FeI3 is the least stable. Phonon spectra, elastic constants, and ab initio molecular dynamics simulations confirm the stability of all systems except VI3/FeI3, which is thermally stable only at cryogenic temperatures. Interlayer hybridization and charge redistribution drive intrinsic half-metallicity in VI3/CrI3, VI3/CrGeTe3, and VI3/FeGeTe3, while VI3/FeI3 remains a spin-polarized semiconductor. Under biaxial strain, VI3/CrI3 retains half-metallicity throughout the investigated ± 10% strain range, whereas VI3/FeI3 undergoes a semiconductor-to-half-metal transition and the telluride-based heterostructures become metallic. Heterostructure formation enhances magnetic anisotropy and reorients the magnetic easy axis of VI3 from in-plane to out-of-plane, with strain enabling controllable easy-axis switching. Spin-transport calculations predict tunneling magnetoresistance exceeding 250%, reaching approximately 340% in Co(111)-based VI3/CrI3 magnetic tunnel junctions. These results identify VI3-based vdW heterostructures as promising platforms for strain-engineered spintronic devices, with VI3/CrI3 emerging as the most promising candidate owing to its persistent half-metallicity, enhanced magnetic anisotropy, and exceptionally high tunneling magnetoresistance.