Modeling electronic structure and magnetic properties of Cr and Ti based Carbide and Nitride Mxenes.

Two-dimensional (2D) magnetic and semiconducting materials, in particular carbide- and nitride-based MXenes, are attracting considerable interest for emerging magneto-electronic and advanced technological applications. In this work, we present a comprehensive first-principles investigation of the structural, electronic, and magnetic properties of pristine, defect-engineered, and strain-modified Cr- and Ti-based carbide and nitride MXenes with various surface terminations (-F, -O, -H, and -OH). The calculated formation and cohesive energies confirm their chemical stability, while the dynamical stability of the Ti- and Cr-based monolayers is further validated through phonon dispersion analyses. All MAX-phase-derived and defect-free functionalized MXenes exhibit metallic behavior, except for the oxygen-terminated systems, which emerge as 100% spin-polarized half-metallic ferromagnets. Spin–orbit coupling (SOC) plays a crucial role in these systems, particularly in the bare nitride MXenes (X₂N; X = Ti, Cr), where it induces Dirac-like topological features and band inversion near high-symmetry points. The half-metallicity is highly sensitive to external perturbations: it evolves into a semi-metallic state under 1% compressive strain and is completely suppressed under 2% compression. Furthermore, transition-metal doping (V, Cr, Mn, and Co) at appropriate lattice sites causes substantial modifications in the electronic structure, transforming half-metallic characteristics into semiconducting behavior with sizable band gaps at specific doping concentrations. In short, the insightful study regarding structural stability, electronic band characteristics, magnetic mechanisms, and topological behavior highlight the potential of Ti-/Cr-derived MXenes as promising candidates for experimental synthesis. These materials hold significant prospects for applications in spintronics, magnetic data-storage technologies, water purification, energy conversion, and biomedicine. The origin of magnetism, associated structural and magnetic phase transitions, and pathways toward experimental realization of these 2D MXenes will also be discussed comprehensively.