Two‐Dimensional Altermagnetic Ti ₂ SSe, Ti ₂ SeTe, and Ti ₂ STe Monolayers

Altermagnetic materials represent an emerging magnetic phase characterized by a unique duality: antiferromagnetic‐like spin arrangements in real space coexist with ferromagnetic‐like spin splittings in momentum space. This intriguing duality places altermagnets at the forefront of condensed matter research. In this study, we propose a new class of 2D altermagnetic candidates–Ti 2 SSe, Ti 2 SeTe, and Ti 2 STe monolayers with square lattice structures. These compounds represent three Janus‐type configurations with asymmetrically arranged chalcogen atoms. Comprehensive first‐principles calculations, including molecular dynamics simulations, phonon dispersion analysis, and elastic constant evaluations, confirm that these monolayers are thermally, dynamically, and mechanically stable. The altermagnetic nature of these monolayers is evidenced by momentum‐resolved spin‐polarized band structures, which exhibit characteristic d‐wave spin‐splitting features. Remarkably, magnetic anisotropy energy calculations reveal that two of the compounds possess nearly isotropic in‐plane magnetism–an uncommon feature among two‐dimensional magnets. Furthermore, Monte–Carlo simulations based on the Heisenberg model predict that the Néel temperatures of these compounds exceed room temperature, indicating robust magnetic ordering at ambient conditions. These findings expand the landscape of 2D altermagnetic materials and provide a promising platform for future spintronic applications.