Janus Cr 2 BN Monolayer with Ferroelectricity and Room-Temperature Ferromagnetism.

Janus monolayers, a special kind of two-dimensional materials, offer an exciting platform for the development of novel electronic/spintronic devices because of their out-of-plane asymmetry. Herein, we propose a sandwich liked Janus tetragonal Cr 2 BN monolayer with ferroelectricity and ferromagnetism through first-principles calculations. The predicted magnetic moment is up to ~3.0 μ B /Cr originating from the distorted square crystal field induced by out-of-plane asymmetry. The Cr 2 BN monolayer possesses an intrinsic ferromagnetism with a high Curie temperature of 383 K and a sizeable magnetic anisotropy energy of 171 μeV/Cr. Its robust ferromagnetism, dominating by the multi-anion mediated super-exchange interactions, can even resist -5 % ~5 % biaxial strain. Its large cohesive energy and high dynamical/thermal stability provide a strong feasibility for experimental synthesis. These intriguing properties render the Cr 2 BN monolayer a promising material for nanoscale spintronic devices.