Halogen-driven magnetic properties of two-dimensional binary and Janus Cr ₂ XYSe ₂ (X, Y = F, Cl, Br, I) monolayers

In this study, we investigate the structural, electronic, and magnetic properties of the orthorhombic phase of Cr₂XYSe₂ (X, Y = F, Cl, Br, I) two-dimensional monolayers using first-principles calculations based on density functional theory. The calculated exchange interaction parameters and magnetic anisotropies exhibit a strong dependence on both the chemical composition of the monolayers and the Hubbard parameter U. This finding indicates that the interplay between spin-orbit coupling and electron localization is crucial for stabilizing long-range magnetic order in these systems. Furthermore, the renormalized magnon spectrum derived from our calculations yields Curie temperatures of approximately 200 K for the iodine-based monolayers, the highest among the compositions studied, indicating the maximum thermal stability. The results of this investigation provide a comprehensive understanding of how chemical substitution, electron correlations, and symmetry reduction interact to control magnetism in two-dimensional materials. This study advances the understanding of magnetism in Cr₂XYSe₂ monolayers and establishes a distinct materials design framework for two-dimensional van der Waals magnetic systems.