Valence mediated tunable magnetism and electronic properties by ferroelectric polarization switching in 2D FeI2/In2Se3 van der Waals heterostructures

Exploring two-dimensional (2D) materials with both ferromagnetic and ferroelectric properties is scientifically interesting and of great technical importance to numerous functionalities in nanoscale devices. In this work, we have demonstrated a strong magnetoelectric coupling that appeared in the 2D FeI₂/In₂Se₃ van der Waals heterostructure. FeI₂ layers undergo a transition from ferromagnetic to antiferromagnetic by reversing the direction of ferroelectric polarization. First-principles calculation predicts a new magnetoelectronic coupling mechanism which is completely different from the Dzyaloshinskii-Moriya (DM) effect in multiferroic materials. Because of the polarization discontinuity at the interface, the valence states of Fe ions change between +2 and +3 for two different polarization directions, leading to the magnetic interaction variation between the direct exchange and I ion mediated superexchange. Moreover, metallic 2D electron gas (2DEG) transfers from the surface of FeI₂ to In₂Se₃ when the polarization reverses, which induces the spin polarization of the heterostructure varying from 93% to 0%. Our work is the first realization of manipulation magnetism by an electric field in full 2D van der Waals heterostructures.