Asymmetric Janus functionalization induced magnetization and switchable out-of-plane polarization in 2D MXene Mo2CXX′

Abstract

Exploring two-dimensional (2D) van der Waals materials with out-of-plane polarization and electromagnetic coupling is essential for the development of next-generation nano-memory devices. A novel class of 2D monolayer materials with predicted spin-polarized semi-conductivity, partially compensated antiferromagnetic (AFM) order, fairly high Curie temperature, and out-of-plane polarization is analyzed in this work for the first time. Based on density functional theory calculations, we systematically studied these properties in asymmetrically functionalized MXenes (Janus Mo₂C)-Mo₂CXX′ (X, X′ = F, O, and OH). Using ab initio molecular dynamics (AIMD) and phonon spectrum calculations, the thermal and dynamic stabilities of six functionalized Mo₂CXX′ were identified. Our DFT+U calculation results also provided a switching path for out-of-plane polarizations, where the reverse of electric polarization is driven by terminal-layer atom flipping. More importantly, strong coupling between magnetization and electric polarization originating from spin-charge interactions was observed in this system. Our results confirm that Mo₂C-FO would be a novel monolayer electromagnetic material, and its magnetization can be modulated by electric polarization.