Impact of C/N substitution on the local electronic structure of Cr-MAX phases

MAX phases have attracted increasing attention for their itinerant magnetism and potential in spintronic and magnetic device applications. A key step in understanding these properties is examining the interaction between the M- and X-sites in M_n+1AX_n compounds. In this study, we explore the local electronic structure and magnetic behavior of Cr-based MAX phases: Cr₂GaC, Cr₂GaN, and the hitherto unknown carbonitride Cr₂GaC_1−xN_x. Our results show that structural distortion introduced by C substitution drives changes in lattice symmetry, magnetic properties, and valence states. Chromium remains in the +3 oxidation state across all three phases, while Ga mediates a stabilizing role in maintaining charge balance without undergoing significant changes in its electronic configuration. Bi-magnon excitations are observed in our experiment and also supported by our theoretical calculations in the nitride phase. We determine the carbon to nitrogen ratio in the mixed carbonitride phase Cr₂GaC_1−xN_x (x = 0.4) to be 1.5:1.0 through both X-ray fluorescence and spectral calculations. Density functional theory calculations reproduce the experimental spectra without electron correlation, confirming the paramagnetic nature of these compounds at room temperature. Only the parent nitride phase exhibits a finite magnetic moment, consistent with magnetic measurements and supports that this material is a spin density wave candidate.