Investigating magnetic properties and Curie temperatures of FeX2 (X=S, Se, Te) monolayers

Abstract

In recent years, there has been a growing interest in two-dimensional magnetic materials. With their unique properties and tunable characteristics, magnetic monolayers hold significant potential for the next-generation devices. This study employs the first principles calculations to examine the electronic, structural, and magnetic properties of the hexagonal and trigonal FeX2 (X=S, Se, Te) monolayers. The calculations show that only two configurations are dynamically stable which are hexagonal FeS2 and FeTe2. Both H-FeS2 and H-FeTe2 monolayers exhibit metallic behavior in PBE calculations. Furthermore, the results indicate that these monolayers also exhibit ferromagnetic behavior. This ferromagnetic ordering suggests significant interactions between the magnetic moments. The magnetic exchange constants are determined by using 2D Ising model. After determining the magnetic exchange constants, a Monte Carlo simulation is performed to obtain the Curie temperature. Furthermore, the influence of the Hubbard U parameter on the electronic and magnetic structure was also examined, revealing significant modifications in the band structure and magnetic moments. Additionally, magnetic exchange constants were calculated for the PBE+U case, as well as using the TB2J method, to provide a comprehensive understanding of the magnetic properties of the stable structures.