First-Principles Study on Valley Polarization of Ferromagnetic PrBr2 Monolayer under Strain

Two-dimensional (2D) magnetic ferrovalley materials, with both spontaneous spin and valley polarization properties, have attracted significant attention due to their potential applications in spintronics and valley electronics. Herein, using first-principles calculation, we predict a new stable ferromagnetic (FM) semiconductor, PrBr2 monolayer (ML), which is demonstrated as a ferrovalley material. PrBr2 ML has excellent mechanical, dynamic, and thermal stabilities. Its intrinsic FM ground state has a large magnetic anisotropy energy (MAE) of 130 mu eV and a higher Curie temperature (T-C) of 101 K compared to those of the synthesized FM 2D materials. Owing to the interplay of magnetic exchange and spin-orbit coupling, it has sizable valley polarization, reaching up to 55 meV. The values of Berry curvature between the K and -K valleys are opposite, giving rise to an anomalous valley Hall effect. Furthermore, an enhancement of both MAE and valley polarization can be induced by applying modest tensile biaxial strains. Remarkably, the magnetization easy axis can translate from in-plane to out-of-plane orientation as the compressive strain is less than -5%. These findings not only highlight the significant role of strains in tuning the spin- and valley-relevant properties but also establish a promising FM ferrovalley semiconducting candidate for spintronic and valleytronic devices.