Two-Dimensional Multiferroic Tunnel Junctions Based on Janus Ferroelectric Materials

In recent years, two-dimensional (2D) multiferroic tunnel junctions (MFTJs) have attracted much attention due to their characteristics and potential application value. However, many current 2D MFTJs encounter the challenge that high tunneling electroresistance (TER) and high tunneling magnetoresistance (TMR) cannot coexist with a low resistance-area (RA) product simultaneously. Particularly, a high RA product tends to result in a low absolute variation in conductance, which limits the device's applicability. In addition, the phase transition temperature of the magnetic layer of some 2D MFTJs is not high enough. These have limited their practical applications to a certain extent. In this study, we theoretically constructed MFTJs using the Janus ferroelectric (FE) materials α-In₂S₂Se (ISS-1) and monolayer α-In₂SSe₂ (ISS-2) as the intermediate insulating layer, with the high Curie temperature ferromagnetic (FM) material Fe₃GaTe₂ (FGT) on both sides. This strategy concurrently achieved a maximum TER of 136%, a maximum TMR of 523%, and a minimum RA product of 0.06 Ω·μm² under zero bias. Meanwhile, the maximum conductance variation caused by polarization reversal ΔGP reached 1.02 μS and caused by magnetization configuration change ΔGM reached 1.70 μS. Furthermore, the variations in the corresponding properties under nonzero bias have been calculated. Our strategy not only provides a new means to realize the TER effect but also provides some theoretical guidance for realizing 2D MFTJs with better performance.