Intrinsic large valley polarization, perpendicular magnetic anisotropy, and piezoelectric polarization in multiferroic two-dimensional ferrovalley semiconductors

first-principles calculations. Giant valley polarization (160-280 meV), perpendicular magnetic anisotropy (∼10 meV), high Curie temperatures, and the piezoelectric effect of OsClX (X = F, Br, I) monolayers are explored, and their mechanisms are elucidated through synergistic interactions of spin polarization, electric polarization, and strong SOC. Furthermore, we show that the layer-locked Berry curvature of ferroelectric bilayer OsClBr with AB and BA stacking switched by sliding can result in the unconventional layer-polarized anomalous Hall effect. Our approach applies to diverse two-dimensional Janus ferrovalley systems and is promising for application in valleytronics and magnetic storage devices.