Engineering half-valley-metal and ferrovalley phases with a robust anomalous valley Hall effect in a ScI2/InSe heterostructure.

Ferrovalley van der Waals heterostructures (vdWHs) have drawn growing attention owing to their special spin-valley coupling and potential applications in next-generation electronic devices. Here, the valley polarization and ferromagnetism of ScI2/InSe vdWH are studied via first-principles methods, with particular emphasis on the tunability provided by electric field and vertical strain. Our results demonstrate that the thermally and dynamically stable ScI2/InSe vdWH exhibits intrinsic ferromagnetic half-metallicity with unconventional V-type band alignment. Including spin-orbit coupling lifts the valley degeneracy, yielding a spontaneous valley polarization of 90.87 meV and enabling the anomalous valley Hall effect (AVHE). An in-plane magnetic easy axis is identified, accompanied by an elevated Curie temperature of 274 K compared to 138 K for a ScI2 monolayer. Additionally, an electric field drives a reversible transition from quasi-half-valley-metal to ferrovalley semiconductor and back, with the AVHE preserved at 0.3 V Å-1. Vertical strain induces a reconfiguration of both electronic and magnetic properties, leading to an unconventional VI-type band alignment, together with a simultaneous rotation of the magnetic easy axis from in-plane to out-of-plane. A compressive strain of -0.8 Å leads to an enhancement of the Curie temperature, which surpasses room temperature and reaches 386 K.