Density Functional Theory Study of Nonvolatile Electrical Control of Half-Metallicity in Multiferroic RuCl₂/Al₂S₃ Heterostructures: Implications for Spin Memory Devices

To overcome the volatility and high-power dissipation in conventional control approaches in spin-dependent devices, such as spin memory devices, there is an urgent need to realize nonvolatile all-electric spin manipulation in two-dimensional van der Waals (vdW) ferromagnetic (FM) semiconductors. Herein, we investigate the electronic and transport features of the multiferroic heterostructure (HS) RuCl 2 /Al 2 S 3 built by coupling the ferrovalley semiconductor RuCl 2 monolayer with the ferroelectric (FE) Al 2 S 3 monolayer by employing first-principles density functional theory plus nonequilibrium Green’s function transport theory. It is shown that the nonvolatile and reversible switching between the FM semiconductor and half-metallicity can be realized in the RuCl 2 /Al 2 S 3 HS by electrically controlling the FE polarization states of the Al 2 S 3 sublayer. Moreover, the large out-of-plane magnetic anisotropy and Curie temperature near room temperature of RuCl 2 can also survive in the vdW RuCl 2 /Al 2 S 3 HS, which is of practical importance. Notably, the FE sublayer Al 2 S 3 still retains its original semiconducting nature in different polarization states, which is beneficial to realize the polarization switching via an applied electric field. Furthermore, an all-electric controlled valve effect with an ultrahigh on/off ratio and pure spin-polarized current in the on state is confirmed in conceptual two-probe devices based on the RuCl 2 /Al 2 S 3 HS. These findings shed light on the potential applications of the all-electrically controlled vdW multiferroic HS RuCl 2 /Al 2 S 3 in compact and highly efficient information processing and data storage.