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 d0 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 d0 rule and metallicity in a family of stable 2D MXene-analogous oxynitrides, X2NO2 (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 Tl2NO2/WTe2 heterostructure through the interface engineering. Our findings provide an alternative possible route toward 2D multiferroics and enrich the concept of ferroelectric metals.