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) RuCl2/Al2S3 built by coupling the ferrovalley semiconductor RuCl2 monolayer with the ferroelectric (FE) Al2S3 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 RuCl2/Al2S3 HS by electrically controlling the FE polarization states of the Al2S3 sublayer. Moreover, the large out-of-plane magnetic anisotropy and Curie temperature near room temperature of RuCl2 can also survive in the vdW RuCl2/Al2S3 HS, which is of practical importance. Notably, the FE sublayer Al2S3 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 RuCl2/Al2S3 HS. These findings shed light on the potential applications of the all-electrically controlled vdW multiferroic HS RuCl2/Al2S3 in compact and highly efficient information processing and data storage.