Theoretical Study on the Electronic Structure and Magnetic Properties Regulation of Janus Structure of M'MCO₂ 2D MXenes

Motivated by the recent successful synthesis of Janus monolayer of transition metal (TM) dichalcogenides, MXenes with Janus structures are worthy of further study, concerning its electronic structure and magnetic properties. Here, we study the effect of different transition metal atoms on the structure stability and magnetic and electronic properties of M'MCO₂ (M' and M = V, Cr and Mn). The result shows the output magnetic moment is contributed mainly by the d orbitals of the V, Cr, and Mn atoms. The total magnetic moments of ferromagnetic (FM) configuration and antiferromagnetic (AFM) configuration are affected by coupling types. FM has a large magnetic moment output, while the total magnetic moments of AFM2's (intralayer AFM/interlayer FM) configuration and AFM3's (interlayer AFM/intralayer AFM) configuration are close to 0. The band gap widths of VCrCO₂, VMnCO₂, CrMnCO₂, V₂CO₂, and Cr₂CO₂ are no more than 0.02 eV, showing metallic properties, while Mn₂CO₂ is a semiconductor with a 0.7071 eV band gap width. Janus MXenes can regulate the size of band gap, magnetic ground state, and output net magnetic moment. This work achieves the control of the magnetic properties of the available 2D materials, and provides theoretical guidance for the extensive design of novel Janus MXene materials.