Magnetoelectric Multiferroics with P-Orbital-Induced <i>d</i>⁰ Ferromagnetism Above Room Temperature in Monolayer XN (X = Ge and Sn)

Intrinsic multiferroics with the coexistence of ferromagnetism and ferroelectricity in a single phase have attracted extensive attention in recent decades due to their potential applications in multifunctional spintronics and nonvolatile memory devices, and two-dimensional (2D) multiferroics with intrinsic ferro-type properties are even more attractive for miniaturization of devices beyond Moore’s laws. In this work, using first-principles calculations, we investigated the stability, band structure, and magnetic and ferroelectric properties of buckled monolayer XN (X = Ge and Sn), as well as the effects of biaxial strain on their magnetic and ferroelectric properties. It was found that monolayer GeN and SnN are dynamically stable. Intriguingly, monolayer XN (X = Ge and Sn) is an intrinsic multiferroic semiconductor, in which robust ferroelectricity and d0 ferromagnetism with a Curie temperature above room temperature and large magnetic anisotropy are simultaneously achieved, and the magnetic moments of monolayer XN (X = Ge and Sn) are provided by the partially filled p orbits of the N and X atoms. Moreover, the ferroelectricity and p-orbital-induced d0 ferromagnetism of monolayer XN (X = Ge and Sn) can be effectively modulated by strains. Our results present a promising route for exploring 2D multiferroics with the coexistence of robust ferroelectricity and d0 ferromagnetism above room temperature in a single phase.