Modulation of Electronic and Magnetic Properties for 2H–FeCl₂ Monolayer Using the Ferroelectric LiNbO₃(0001) Substrate

Using first-principles calculations, we systematically investigate the interfacial coupling and charge transfer mechanisms of the 2H–FeCl2/LiNbO3(0001) heterostructure, exploring the effect of the LiNbO3(0001) substrate on the magnetic and electronic properties of the 2H–FeCl2 overlayer. Our result reveals a ionic-van der Waals coupling between the 2H–FeCl2 monolayer and LiNbO3(0001) substrate, with predominately ionic bonding character. The interface charge transfer effect in the 2H–FeCl2/LiNbO3(0001) heterostructure is codetermined by both band alignment and interface local chemical environments and shows remarkable sensitivity to the ferroelectric polarization direction of the LiNbO3(0001) substrate, suggesting this system as a promising platform for developing ferroelectric field-effect transistors. Remarkably, the electronic and magnetic properties of the 2H–FeCl2 overlayer are significantly modified by the LiNbO3(0001) substrate. Although the pristine 2H–FeCl2 monolayer exhibits ferromagnetic order, the 2H–FeCl2 overlayer on both the negative and positive LiNbO3(0001) polarized substrate transforms into ferrimagnetism. Furthermore, the polarization reversal of the positive polarized LiNbO3(0001) substrate induces half-metal characteristics and p-type doping in the 2H–FeCl2 overlayer. These findings establish the 2H–FeCl2/LiNbO3(0001) heterostructure as a composite multiferroic material with an exceptional potential for spintronic and optoelectronic devices.