Modeling of Field‑Tunable Spin Spirals and Skyrmions in Multiferroic NiI₂ Monolayers

This work was supported by the National Science Foundation through the Division of Materials Research under NSF Grant No. DMR-2213398 and the Department of Energy (DOE) under Grant DE-SC0024236.Controlling spins with large magnetic fields is impractical for real devices. Type-II multiferroics offer a compelling alternative: their magnetic order is tied to electric polarization, enabling electric-field control of magnetism. Monolayer NiI₂ is a prime example—its spin-spiral ground state breaks inversion symmetry and generates a spontaneous polarization intrinsically coupled to the spins. In this work, we leverage that magneto-electric coupling to steer spin textures in NiI₂ using applied electric fields. We build a spin Hamiltonian that explicitly includes the electric-field term and parameterize all couplings from density-functional theory to ensure quantitative fidelity. Large-scale Metropolis Monte Carlo simulations then explore field-tunable phases, stability of spirals, and pathways for switching between competing configurations. Our results outline design principles for low-power, electrically driven spin control in two-dimensional magnets and highlight NiI₂ as a realistic platform for spintronic functionalities without external magnetic fields.