Ferroelectricity and multiferroicity in two-dimensional ScPSe and ScCrPSe 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, ScPSe and ScCrPSe monolayers with ferroelectric (FE) and multiferroic properties, respectively. The ScPSe 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 ScCrPSe monolayer formed by substituting half of the Sc atoms of ScPSe with Cr exhibits multiferroic properties. The magnetic ground state of the ScCrPSe 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 ScCrPSe monolayer. Our theoretical results offer a new platform for the further study of 2D multiferroicity and nonvolatile magnetoelectric nanodevices.