Achieving large six nonvolatile states via monolayer homologous multiferroic MoPtGe₂S₆ in van der Waals tunnel junctions

Multiferroic tunnel junctions (MFTJs), which combine tunneling magnetoresistance (TMR) and electroresistance (TER) effects, have emerged as key candidates for data storage. Two-dimensional van der Waals (vdW) MFTJs, in particular, are promising spintronic devices for the post-Moore era. However, these vdW MFTJs are typically based on multiferroics composed of ferromagnetic and ferroelectric materials or multilayer magnetic materials with sliding ferroelectricity, which increases device fabrication complexity. In this work, we design a vdW MFTJ using bilayer MoPtGe₂S₆, a material with homologous multiferroicity in each monolayer, combined with symmetric PtTe₂ electrodes. Using first-principles calculations based on density functional theory and nonequilibrium Green’s functions, we theoretically explore the spin-polarized electronic transport properties of this MFTJ. By controlling the ferroelectric and ferromagnetic polarization directions of bilayer MoPtGe₂S₆, the MFTJ can exhibit six distinct non-volatile resistance states, with maximum TMR (137%) and TER (1943%) ratios. Under biaxial strain, TMR and TER can increase to 265% and 4210%, respectively. The TER ratio also increases to 2186% under a 0.1V bias voltage. Remarkably, the MFTJ exhibits a pronounced spin-filtering and a significant negative differential resistance (NDR) effect. These findings not only highlight the potential of monolayer multiferroic MoPtGe₂S₆ for MFTJs but also offer valuable theoretical insights for future experimental investigations.