Ferroelectricity and multiferroicity in two-dimensional Sc₂P₂Se₆ and ScCrP₂Se₆ monolayers

Two-dimensional (2D) multiferroic materials with coexistence of ferroelectricity and ferromagnetism have attracted extensive research interest due to novel physical properties and potential applications, such as in non-volatile storage nanodevices. Here, using first-principles calculations, we predicted two types of 2D materials, Sc₂P₂Se₆ and ScCrP₂Se₆ monolayers with ferroelectric (FE) and multiferroic properties, respectively. The Sc₂P₂Se₆ monolayer has out-of-plane FE polarization originating from the asymmetrical arrangement of P atoms. The FE phase is separated from the antiferroelectric (AFE) phase by an energy barrier of 0.13 eV, ensuring the stability of the FE state at room temperature. The ScCrP₂Se₆ monolayer formed by substituting half of the Sc atoms of Sc₂P₂Se₆ with Cr exhibits multiferroic properties. The magnetic ground state of the ScCrP₂Se₆ monolayer is tunable, due to the disparity of an indirect exchange interaction between the FE and AFE phases. A reversible electrical switching between the ferromagnetic and antiferromagnetic states can be achieved in a multiferroic ScCrP₂Se₆ monolayer. Our theoretical results offer a new platform for the further study of 2D multiferroicity and nonvolatile magnetoelectric nanodevices.