Twist-Induced Flat Bands and Magnetic Phase Transitions in 1T-FeCl ₂ Bilayers: A First-Principles Study

Using first-principles calculations, we systematically explore the synergistic interplay between twist angle (θ) and stacking registry in governing the magnetic and electronic landscapes of 1T-FeCl 2 bilayers. Our results demonstrate that twist engineering serves as a robust mechanism for tuning interlayer magnetic coupling, enabling a deterministic transition between antiferromagnetic and ferromagnetic orders. Furthermore, θ is identified as a governing parameter for modulating magnetic anisotropy. Specific θ not only stabilizes a perpendicular easy axis, but also induces highly isotropic in-plane characteristics. Notably, in certain moiré configurations, the formation of persistent flat bands can lead to strong electronic correlations. All investigated twisted bilayers exhibit high thermal stability, underscoring their experimental feasibility. This work establishes twisted 1T-FeCl 2 as a fertile platform for exploring Moiré-engineered magnetism and provides a computational blueprint for next-generation 2D spintronic devices.