Tuning of electronic structure, magnetic phase, and transition temperature in two-dimensional Cr-based Janus MXenes

Abstract

Two-dimensional (2D) transition metal carbides and nitrides, called as MXenes, displaying astonishing properties are emerged as a new class of 2D layered materials. In this study, we have studied the structural, electronic, and magnetic properties of 2D bare M2C and Janus Cr-based MM'C metal carbides (M not equal M' = Cr, Ti, Sc, V) based on density functional theory. We found that 2D Janus MM'C MXenes are dynamically and thermally stable and show unique electronic and magnetic properties which are not seen in their individual bare cases. Our calculated electronic band structures indicate that the Janus MM'C MXenes have Dirac-type band dispersion as seen in stanene with tiny band gaps. In addition, all considered bare M2C MXenes show metallic property. However, Janus CrScC has dilute magnetic semiconducting property, CrVC shows half-metallicity, and CrTiC shows metallic property which can easily turn to half-metallicity by external effects. Our extensive density functional theory and Monte Carlo calculations indicate that Janus MM'C MXenes also show different magnetic properties than their bare cases. While Cr2C and Sc2\C have ferromagnetic spin orientations with T-C = 2000 and 226 K Curie temperatures, respectively, CrScC shows ferrimagnetic character with antiferromagnetic Neel spin orientation and has T-N = 1120 K magnetic phase transition temperature between ferrimagnetic and paramagnetic phases. Finally, external magnetic field effects on each crystal have also been elucidated in detail. The numerical outcomes reveal that Janus Cr-based MM'C metal carbides have some unusual and interesting hysteresis characters. Our investigations presented here are not only interesting from a theoretical perspective, but also they show that Janus MM'C MXenes are promising candidates for future spintronic applications, which should encourage their synthesis.