Strain-induced magnetic transition and exchange competition in a metallic Cr₂SbS monolayer with high Néel temperature

Two-dimensional magnetic materials hold great promise for spintronic applications but often suffer from low Néel temperatures and limited tunability. Here, based on first-principles calculations, we identify a previously unexplored orthorhombic Cr₂SbS monolayer with robust structural stability. The material is confirmed to be dynamically, thermally, thermodynamically, and mechanically stable. The Cr₂SbS monolayer exhibits an antiferromagnetic (AFM) metallic ground state with a sizable magnetic anisotropy energy of 80 µeV per Cr atom favoring the out-of-plane direction. Monte Carlo simulations based on the Heisenberg model predict a Néel temperature as high as ∼908 K, far exceeding room temperature, establishing it as one of the rare high-T_N 2D magnets. Under biaxial strain from -4% to 4%, the system undergoes a transition from AFM to ferromagnetic (FM) ordering, accompanied by a reorientation of the easy magnetization axis from out-of-plane to in-plane. At -3% strain, one magnetic configuration converges to a nonmagnetic state, indicating strong competition among exchange interactions. Notably, the metallic nature is preserved across the entire strain range, while the critical temperature remains above room temperature. When a tensile strain is applied, the critical temperature can even exceed 1000 K. These combined features, including ultrahigh Néel temperature, robust metallicity, and strain-tunable magnetism, make the Cr₂SbS monolayer a promising platform for next-generation spintronic devices.