We predict the giant ferroelectric control of interfacial properties of Ni/HfO2, namely, (i) the magnetocrystalline

anisotropy and (ii) the inverse spin and orbital Rashba effects. The reversible control of magnetic

properties using electric gating is a promising route to low-energy consumption magnetic devices, including

memories and logic gates. Synthetic multiferroics, composed of a ferroelectric in proximity to a magnet, stand

out as a promising platform for such devices. Using a combination of ab initio simulations and transport

calculations, we demonstrate that reversing the electric polarization modulates the interface magnetocrystalline

anisotropy from in-plane to out-of-plane. This modulation compares favorably with recent reports obtained upon

electromigration induced by ionic gating. In addition, we find that the current-driven spin and orbital densities

at the interface can be modulated by about 50% and 30%, respectively. This giant modulation of the spin-charge

and orbit-charge conversion efficiencies opens appealing avenues for voltage-controlled spin- and orbitronics

devices.

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