Electrically Tunable Antiferromagnetic Multiferroic Tunnel Junctions

Abstract

Antiferromagnetic multiferroic tunnel junctions (AFM-MFTJs) based on two-dimensional (2D) van der Waals materials hold promise for low-power spintronic devices. However, their microscopic magnetoelectric coupling mechanisms remain unclear. Here, by combining first-principles calculations with nonequilibrium Green’s function (NEGF) theory, we propose a model 2D AFM-MFTJ composed of CuInP2S6 (CIPS) and bilayer ScCl2, which enables full electrical control of magnetic states and multiple nonvolatile resistance states. Ferroelectric polarization reversal in CIPS switches the interlayer magnetic configuration of bilayer ScCl2 between ferromagnetic and antiferromagnetic states. Crucially, this transition is governed by a change in the exchange mechanism from super-double exchange (SDE) to super-superexchange (SSE). The SDE interaction, mediated by spin-conserving hopping through multi-anion pathways, stabilizes ferromagnetic coupling. In contrast, the SSE mechanism, arising from long-range virtual hopping across the van der Waals gap, favors antiferromagnetic alignment. This SDE–SSE transition reveals a previously overlooked magnetoelectric coupling mechanism driven by polarization-induced reconstruction of exchange pathways. The AFM-MFTJ of the Au/CIPS/DL-ScCl2/Au device exhibits a tunneling magnetoresistance of 498% at zero bias, which increases to 2 × 103% at 0.15 V. These findings highlight exchange-mechanism engineering as a key strategy for electrically controlling antiferromagnetism in 2D spintronic devices.