High Curie temperature and intrinsic ferromagnetic half-metallicity in two-dimensional Cr3X4 (X = S, Se, Te) nanosheets
Two-dimensional (2D) intrinsic magnetic materials with room temperature ferromagnetism and complete spin-polarization are highly desirable for realizing advanced spintronic devices. However owing to the weak d–p–d super-exchange interaction, many recently realized 2D ferromagnetic (FM) materials present a very low Curie temperature (TC). Here, based on first principles calculations, we report a series of Cr3X4 (X = S, Se, Te) monolayers, in which the coexistence of two oxidation states of Cr atoms results in double-exchange interaction and thereby enhances FM coupling greatly and improves TC up to 370 K for Cr3Se4 and 460 K for Cr3Te4, respectively. Spin-polarized calculations further demonstrate that Cr3Se4 and Cr3Te4 monolayers are FM half-metals, which ideally could achieve 100% spin-polarized currents. Meanwhile, excellent dynamical and thermal stabilities are identified, and a possible synthetic strategy is proposed. Our work not only provides two competitive ferromagnetic candidate materials for nanoscale spintronic applications, but also shows that double-exchange interaction may be a way to realize 2D room temperature FM half-metals.