High-temperature ferromagnetism in monolayers MnGaX3 (X = Te, Se)

Two-dimensional (2D) ferromagnetic monolayers are highly desirable in the spintronic field owing to their atomic-thickness and controllable spin degree of freedom. We investigated the 2D transition-metal trichalcogenides MnGaX3 (X = Te, Se, S) as the promising candidate monolayer ferromagnets via first-principles calculations. Our calculations show that monolayer MnGaTe3 and MnGaSe3 are ferromagnetic (FM) metal and halfmetal with large magnetic moments and sizeable magneto-crystal anisotropy energy. Both the monolayers are mechanical and dynamical stable, and can be exfoliated from the corresponding layered crystals. More importantly, Monte Carlo simulations predict high Curie temperature for MnGaTe3 (720 K) and MnGaSe3 (910 K). Plus, their ferromagnetic configurations become more stable under the increasing biaxial tensile strain from 0 to 5%. Metallic MnGaTe3 converts into half-metal under biaxial tensile strain, and the band gap of semiconducting spinchannel of half-metallic MnGaSe3 increases under the increasing strain. The distinct half-metallic and robust intrinsic ferromagnetism at high temperature render the two monolayers attractive in spintronics.