关键词: first-principles calculations, 2D materials, magnetic properties, ferromagentic semiconductor

Abstract: The two-dimensional (2D) Janus monolayers are promising in spintronic device application due to their enhanced magnetic couplings and Curie temperatures. Van der Waals CrCl$_{3}$ monolayer has been experimentally proved to have an in-plane magnetic easy axis and a low Curie temperature of 17 K, which will limit its application in spintronic devices. In this work, we propose a new Janus monolayer Cr$_{2}$Cl$_{3}$S$_{3}$ based on the first principles calculations. The phonon dispersion and elastic constants confirm that Janus monolayer Cr$_{2}$Cl$_{3}$S$_{3}$ is dynamically and mechanically stable. Our Monte Carlo simulation results based on magnetic exchange constants reveal that Janus monolayer Cr$_{2}$Cl$_{3}$S$_{3}$ is an intrinsic ferromagnetic semiconductor with $T_{\rm C}$ of 180 K, which is much higher than that of CrCl$_{3}$ due to the enhanced ferromagnetic coupling caused by S substitution. Moreover, the magnetic easy axis of Janus Cr$_{2}$Cl$_{3}$S$_{3}$ can be tuned to the perpendicular direction with a large magnetic anisotropy energy (MAE) of 142 μeV/Cr. Furthermore, the effect of biaxial strain on the magnetic property of Janus monolayer Cr$_{2}$Cl$_{3}$S$_{3}$ is evaluated. It is found that the Curie temperature is more robust under tensile strain. This work indicates that the Janus monolayer Cr$_{2}$Cl$_{3}$S$_{3}$ presents increased Curie temperature and out-of-plane magnetic easy axis, suggesting greater application potential in 2D spintronic devices.

Key words: first-principles calculations, 2D materials, magnetic properties, ferromagentic semiconductor