The first-principles calculations on the magnetic properties of 2D materials CrXY (X = S, Se; Y = Cl, Br, I)

Two-dimensional (2D) magnetic materials have emerged as promising candidates for spintronic applications, enhancing their magnetic phase transition temperature and magnetic anisotropy energy (MAE) remains a critical challenge. Here, using first-principles calculations, we systematically investigate the Curie temperature (T_C) and MAE of CrXY (X = S, Se; Y = Cl, Br, I) monolayers under under x and xy-strain. We identify the Cr-Y-Cr superexchange pathway along the a-axis as the core mechanism governing magnetic properties, a previously unreported finding. Heavier Y-site halogens, especially iodine, enhance Cr-Cr exchange coupling via p-orbital spin-polarization. Notably, CrSeI exhibits high T_C (184.4 K) and MAE (336 μeV/Cr). Applying 6 % tensile uniaxial strain further boosts these to T_C = 220.2 K and MAE = 759 μeV/Cr, highlighting its potential for next-generation magnetic memory devices. Our work provides a comprehensive analysis of element substitution and strain engineering effects on the CrXY family.