Sliding Ferroelectric Metal with Ferrimagnetism

Two-dimensional (2D) sliding ferroelectric (FE) metals with ferrimagnetism represent a previously unexplored class of spintronic materials, featuring out-of-plane FE polarization, metallic conductivity, and a finite net magnetization, which together enable electrically tunable spintronic functionalities via FE switching. Here, based on antiferromagnetic (AFM) metallic bilayers, we propose a general strategy for constructing 2D sliding FE ferrimagnetic (FiM) metals that can achieve triply-coupled switching, in which the FE polarization, spin splitting, and net magnetization are reversed simultaneously through FE switching. As a prototypical realization, we design a bilayer sliding FE metal with FiM order, derived from monolayer Fe$_5$GeTe$_2$ -- a van der Waals metal with intrinsic ferromagnetic order close to room temperature. The system exhibits a FE transition from a nonpolar (NP) AFM phase to a FE FiM phase via interlayer sliding. The in-plane mirror symmetry breaking in FE metallic states lifts the nonrelativistic spin degeneracy that exists in the NP phase, leading to a sizable net magnetic moment. Furthermore, the interplay between metallicity, ferroelectricity, and ferrimagnetism gives rise to pronounced sign-reversible transport responses near the Fermi level, all of which can be electrically controlled by FE switching. Our results establish sliding FE metals with FiM as a promising platform for electrically reconfigurable, high-speed, and low-dissipation spintronic devices.