Tuning the Electronic and Magnetic Properties of Double Transition Metal MCrCT$_2$ (M = Ti, Mo) Janus MXenes for Enhanced Spintronics and Nanoelectronics

Abstract: Janus MXenes, a new category of two-dimensional (2D) materials, shows promising potential for advances in optoelectronics, spintronics and nanoelectronics. Our theoretical investigations not only provide interesting insights but also highlight the promise of Janus MCrCT$_2$ (M = Ti, Mo; T = O, F, OH) MXenes for future spintronic applications and highlight the need for their synthesis. Electronic structure analysis shows different metallic and semi-metallic properties: MoCrCF$_2$ exhibits metallic properties, TiCrC(OH)$_2$ and MoCrCO$_2$ exhibit near semi-metallicity with spin polarization values of 61\% and 86\%, respectively, while TiCrCO$_2$ and TiCrCF$_2$ are completely half-metallic with 100\% spin polarization at the Fermi level. All studied Janus MXenes exhibit intrinsic ferromagnetism, which is mainly attributed to the chromium (Cr) atoms, as shown by the spin density difference plots. Among them, the TiCrCO$_2$ monolayer stands out with the highest exchange constant and ferromagnetic transition temperature (T$_c$). Notably, the O-terminated Janus MXenes exhibit weak perpendicular magnetic anisotropy, in contrast to the in-plane anisotropy observed for F and OH-terminated MXenes, making them particularly interesting for future spintronic applications which we further demonstrate with micromagnetic simulation which reveal distinct current-induced switching behaviors in these Janus MXenes with different surface terminations.