Van der Waals Multiferroic Tunnel Junctions

Multiferroic tunnel junctions (MFTJs) have aroused significant interest due to their functional properties useful for nonvolatile memory devices. So far, however, all of the existing MFTJs have been based on perovskite-oxide heterostructures limited by a relatively high resistance-area (RA) product unfavorable for practical applications. Here, using first-principles calculations, we explore spin-dependent transport properties of van der Waals (vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic Fe_nGeTe₂ (n = 3, 4, 5) electrodes and 2D ferroelectric In₂Se₃ barrier layers. We demonstrate that such Fe_mGeTe₂/In₂Se₃/Fe_nGeTe₂ (m, n = 3, 4, 5; m ≠ n) MFTJs exhibit multiple nonvolatile resistance states associated with different polarization orientation of the ferroelectric In₂Se₃ layer and magnetization alignment of the two ferromagnetic Fe_nGeTe₂ layers. We find a remarkably low RA product (less than 1 Ω·μm²) which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms of their promise for nonvolatile memory applications.