Ferroelectricity-Driven Magnetism in a Metal Halide Monolayer

Electrical control of magnetism promises potential applications in low-cost, high-density spintronic devices; however, it remains a great challenge in traditional multiferroics. Here we propose that a type-III multiferroic material, where magnetism is driven by ferroelectricity, can be used to achieve effective electrical control of magnetism. We reveal that the emergence of ferroelectricity in a low-dimensional system could significantly reduce the interatomic orbital overlap and narrow the electronic bands, which increases the Stoner instability and, thus, results in a transition from nonmagnetic to ferromagnetic states. Based on first-principles calculations, the ferroelectricity-driven magnetism is demonstrated in a two-dimensional InI_{3} monolayer adsorbed by Cu single atoms (denoted as Cu-InI_{3}). When an out-of-plane shift of the Cu atom induces an out-of-plane ferroelectricity, the system is transferred from a nonmagnetic to a ferromagnetic phase. The revealed type-III multiferroics and electrical control of magnetism offer an innovative strategy for developing multiferroic and magnetoelectric devices.