Double-Exchange Magnetic Interactions in High-Temperature Ferromagnetic Iron Chalcogenide Monolayer.

Smythite (Fe3S4) is an iron-based chalcogenide, having a lamellar structure compared to compositionally same another iron-based chalcogenide mineral greigite (Fe3S4). Because of the abundance of such transition metal based chalcogenides, they offer the low-cost productivity of spintronic-based devices. Here, we have studied the charge transfer processes and complex magnetic ordering in a two dimensional (2D) smythite lattice. We find that Fe2+/Fe3+ redox couple and complex magnetic ordering govern these charge transfer processes. A very strong ferromagnetic in-lattice coupling is also observed due to the presence of three Fe-centers. To describe the magnetic behavior; (i) molecular, and (ii) periodic approaches have been considered. We have observed a substantial increase in Curie temperature with applied mechanical stress due to the opening of the double exchange interaction angle. We have observed an in-plane Jahn-Teller distortion, which is further confirmed by the spin-orbit counter plot. Thereby, our study provides an insight on double exchange mechanism favours by the Fe2+/Fe3+ redox couple and results in a strong ferromagnetic ordering.