First-principles prediction of two-dimensional Rare-earth intrinsic ferrovalley materials: Non-Janus GdXY (X≠Y=Cl,Br,I) monolayers

Two-dimensional ferrovalley magnetic materials have attracted much attention due to the applications in valley-based nonvolatile random access memories and valley filters. In this work, using first-principles calculations, we predict a promising class of bipolar magnetic semiconductors, namely non-Janus GdXY(X≠Y=Cl,Br,I) monolayers, which exhibit excellent mechanical and thermal stability, large magnetic moment (8 μ_B/Gd), and high Curie temperature (above 450 K). When magnetized along the ±z direction, a spontaneous valley polarization can be observed in non-Janus GdXY. Due to the non-zero Berry curvature, the anomalous Hall effect will be able to be observed in non-Janus GdXY. In addition, the system transforms into a semi-semiconductor from a bipolar magnetic semiconductor with increasing biaxial tensile strain. Under the strain of -4%∼+4%, the ferrovalley characteristics can be well maintained. Our findings not only reveal that non-Janus GdXY is a novel room-temperature ferrovalley semiconductor material, but also provide a new platform for designing spintronics and valley electronics devices.