Electrical control of metal–insulator transition and magnetism in asymmetric multiferroic InCrX3 (X = S, Se) monolayers

Electrical control of conductivity and magnetism in two-dimensional (2D) ferroelectric (FE) materials have attracted immense attention due to their fascinating properties and potential applications in designing field-effect transistors and high-density multistate data storage. Based on first-principles calculations and crystal field theory, we present an approach to obtain 2D intrinsic asymmetric multiferroics by replacing the In atom in the ferroelectric In2X3 monolayer (X = S, Se) with the Cr atom. Interestingly, it is found that the InCrX3 monolayers have two inequivalent polarized states, which are characterized by metal and semiconductor, respectively, which is related to the crystal field around Cr3+ ions. Thus, it provides a feasible way to realize electrical control of reversible metal–insulator transition induced by ferroelectric switching, indicating that the InCrX3 monolayers can be used as the channel materials in the FE memory technology. In addition, because of the existence of the Cr3+ ions, the InCrX3 monolayers also exhibit robust ferromagnetism with different Curie temperatures and magnetocrystalline anisotropy energies, which can provide a good platform for realizing the strong coupling between the magnetism and ferroelectricity. These interesting results provide a feasible way to design asymmetric FE materials with regulatable conductivity and magnetism that can enable a wide range of applications in nanodevices.