Intrinsic two-dimensional multiferroicity in CrNCl2 monolayer*

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 CrNCl 2 monolayer is reported as an intrinsic multiferroic. The CrNCl 2 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 CrNCl 2 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 CrNCl 2 . In addition, like CrNCl 2 , the CrNBr 2 is an intrinsic multiferroic with antiferromagnetic-ferroelectric ground state while CrNI 2 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.