Intrinsic two-dimensional multiferroicity in CrNCl2 monolayer*

Abstract

Two-dimensional multiferroics, which simultaneously possess ferroelectricity and magnetism in a single phase, are well-known to possess great potential applications in nanoscale memories and spintronics. On the basis of first-principles calculations, a CrNCl2 monolayer is reported as an intrinsic multiferroic. The CrNCl2 has an antiferromagnetic ground state, with a Néel temperature of about 88 K, and it exhibits an in-plane spontaneous polarization of 200 pC/m. The magnetic moments of CrNCl2 mainly come from the d5 xy orbital of the Cr cation, but the plane of the d xy orbital is perpendicular to the direction of the ferroelectric polarization, which hardly suppresses the occurrence of ferroelectricity. Therefore, the multiferroic exits in the CrNCl2. In addition, like CrNCl2, the CrNBr2 is an intrinsic multiferroic with antiferromagnetic-ferroelectric ground state while CrNI2 is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state. These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.