Engineering of two-dimensional half-metallic CoAl2Se4 with intrinsic ferromagnetism and high Curie temperature

Abstract

Half-metallic magnets with high Curie temperatures ($T_c$) are essential for the advancement of next-generation spintronic technologies. In this study, we perform a comprehensive first-principles investigation of the CoAl${}_2$Se${}_4$ monolayer, an $A{M}_2{X}_4$-type material that has remained largely unexplored. Our findings confirm its energetic, mechanical, and dynamical stability, as evidenced by cohesive and formation energy calculations, elastic constants, and phonon dispersion analysis. The observed ferromagnetic behavior arises from Co-Se-Co bond superexchange interactions, in agreement with the Goodenough–Kanamori rules. The monolayer exhibits robust half-metallicity, characterized by a substantial half-metallic gap of 2.76 eV, enabling fully spin-polarized electronic conduction. Magnetic anisotropy energy calculations indicate an easy-plane magnetization, while Monte Carlo simulations predict a high Curie temperature of 431 K, well above room temperature, ensuring stable magnetic ordering under ambient conditions. These outstanding properties position the CoAl${}_2$Se${}_4$ monolayer as a promising candidate for spin filtering devices, magnetoresistive sensors, and next-generation magnetic memory technologies.