A Janus CrSSe monolayer with interesting ferromagnetism†

The search for intrinsic half-metallic ferromagnetic (FM) monolayers with a high Curie temperature (T_C), considerable magnetic anisotropy energy (MAE), and multiferroic coupling is key for the development of ultra-compact spintronics. Here, we have identified a new stable FM Janus monolayer, the tetrahedral CrSSe, through first-principles structural search calculations, which not only exhibits very interesting magnetoelectric properties with a high T_C of 790 K, a large MAE of 0.622 meV per Cr, and robust half-metallicity, but also shows obvious ferroelasticity with a modest energy barrier of 0.31 eV per atom. Additionally, there appears to be interesting multiferroic coupling between in-plane magnetization and ferroelasticity. Furthermore, by replacing the Se/S atoms in the CrSSe monolayer with S/Se atoms, we obtained two new half-metallic FM CrS₂ and CrSe₂ monolayers, which also exhibit excellent magnetoelectric properties. Therefore, our findings provide a pathway to design novel multiferroic materials and enrich the understanding of 2D transition metal chalcogenides.