Interface‐Engineered Giant Multistate Resistance Switching in Altermagnetic Multiferroic Tunnel Junctions

ABSTRACT Altermagnets enable spin–split transport without stray magnetic fields, yet converting their momentum‐dependent spin splitting into a strong tunnel‐junction response requires interface‐selected tunneling channels. Here, using density functional theory combined with nonequilibrium Green's function calculations, we demonstrate giant multistate resistance switching in CrSb/‐ altermagnetic multiferroic tunnel junctions. The response is governed not by the bulk spin splitting of CrSb alone, but by a symmetry‐selected interfacial mechanism in which Cr/Sb terminations and h ‐BN or graphene insertion layers determine spin‐channel matching, while ferroelectric polarization reshapes the electrostatic barrier. Symmetric and asymmetric terminations reverse the correspondence between parallel/antiparallel Néel‐vector configurations and high‐/low‐resistance states, showing that the actual alignment of interfacial Cr moments selects the dominant tunneling channels. Monolayer‐ junctions exhibit four nonvolatile resistance states, with tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) reaching 1626% and 2206%, respectively, and increasing to 9576% and 4144% upon Fermi‐level shifting. Finite‐bias calculations further reveal robust spin filtering and tunable spin‐polarized currents. Extending the barrier to bilayer introduces interlayer polarization coupling, enabling eight resistance states with maximum TMR and TER values of and , respectively. These results establish interface symmetry, spin‐channel matching, and ferroelectric barrier reconstruction as design principles for stray‐field‐free multistate spintronic tunnel devices.