Intrinsic Ferromagnetic Semiconductors in Two-Dimensional Alkali-Based Chromium Chalcogenides

Two-dimensional (2D) intrinsic ferromagnetic semiconductors (FMSs) received huge attention due to their fascinating electron charge and spin properties, which are promising candidates for spintronic devices. In this work, we propose a class of monolayer FMS in alkali-based chromium chalcogenides (XCrY2, X = Li and Na; Y = S, Se, and Te). The proposed monolayer XCrY2 is expected to be exfoliated from their corresponding bulk counterparts, which are confirmed by first-principles calculations. Our calculations indicate that these monolayer FMS shows the ferromagnetic ground states possessing the high Curie temperatures using the Ising and Heisenberg models. The hybrid functional calculations show that LiCrSe2, NaCrSe2, and NaCrTe2 have desirable direct band gaps. In addition, it is found that the spin–orbit (SOC) effect can tremendously change the effective mass of the holes, resulting in higher hole mobility (up to 3 × 103 cm2 v–1 s–1). Our study provides a feasible way to realize 2D intrinsic FMS.