Ferroelectricity coexisted with p-orbital ferromagnetism and metallicity in two-dimensional metal oxynitrides

Abstract Two-dimensional (2D) multiferroics have attracted increasing interests in basic science and technological fields in recent years. However, most reported 2D magnetic ferroelectrics are based on the d -electron magnetism, which makes them rather rare due to the empirical d 0 rule and limits their applications for low magnetic phase transition temperature. In this work, we demonstrate that the ferroelectricity can coexist with the p -electron-induced ferromagnetism without the limitation of d 0 rule and metallicity in a family of stable 2D MXene-analogous oxynitrides, X 2 NO 2 ( X = In, Tl). Remarkably, the itinerant character of p electrons can lead to the strong ferromagnetic metallic states. Furthermore, a possible magnetoelectric effect is manifested in a Tl 2 NO 2 /WTe 2 heterostructure through the interface engineering. Our findings provide an alternative possible route toward 2D multiferroics and enrich the concept of ferroelectric metals.