Tunable multiferroic properties of bilayer ScI2 via stacking engineering

Two-dimensional (2D) bilayer ScI2 demonstrates tunable multiferroic properties, including magnetic coupling, ferroelectricity, and valley polarization, controlled through interlayer sliding and rotation. Our first-principles calculations reveal that the AA stacking configuration induces antiferromagnetic (AFM) interlayer coupling, while a 180° rotation (AA* stacking) results in ferromagnetic (FM) coupling. Interlayer coupling switches to FM in the AB and BA stackings, while the AB* and BA* configurations favor AFM coupling. In the aligned stackings (AA, AB, and BA), interlayer sliding from AA induces ferroelectricity due to orbital hybridization and charge redistribution, with the strongest response predicted in the AB and BA configurations. Additionally, spontaneous valley polarization emerges in the AB/BA and AB*/BA* stackings, driven by inversion symmetry breaking and spin–orbit coupling. These results highlight the tunability of multiferroic properties in bilayer ScI2, offering insights for the design of 2D multiferroic devices for spintronic, electronic, and valleytronic applications.