Electrically tunable 2D ferromagnetic semiconductors CrSBr and CrSeBr with high Curie temperature

Identifying 2D ferromagnets with high transition temperature is crucial for the development of miniaturized spintronics and magnetoelectrics. Here we present our theoretical study of van der Waals layered magnetic semiconductors CrSBr and CrSeBr. Using first-principles DFT and renormalized spin-wave theory, we show that monolayer CrSBr and CrSeBr exhibit highly anisotropic electronic structure with a sizable bandgap. More importantly, monolayer CrSBr and CrSeBr possess high Curie temperature of ~150K which was recently verified by experiments, beyond that of CrI₃ and Cr₂Ge₂Te₆. The origin of the high Curie temperature is attributed to strong anion-mediated superexchange interaction and sizable spin-wave excitation gap due to large exchange and single-ion anisotropy. It was shown that electrostatic doping can switch magnetization easy axis, realizing spin field effect transistor. Monolayer CrSBr and CrSeBr semiconducting ferromagnets offer long-desired alternatives to dilute magnetic semiconductors and provide unprecedented opportunities for 2D spintronics such as spin valves and spin FETs. Reference: APL 117, 083102 (2020).