First principles electron transport in magnetoelectric SrRuO₃/BaTiO₃/SrTiO₃/SrRuO₃ interfaces

Recently, all-oxide ferroelectric tunnel junctions, with single or composite potential barriers based on SrRuO₃/BaTiO₃/SrTiO₃(SRO/BTO/STO) perovskites, have drawn a particular interest for high density low power applications, due to their highly tunable transport properties and device scaling down possibility to atomic size. Here, using first principles calculations and the non-equilibrium Green's functions formalism, we explore the electronic structure and tunneling transport properties in magnetoelectric SRO/BTO/<i>m</i>STO/SRO interfaces, (<i>m</i>= 0, 2, or 4 unit cells), considering both the RuO₆octahedra tilts and magnetic SRO electrodes. Our main results may be summarized as follows: (i) the band alignment schemes predict that polarization direction may determine both Schottky barrier or Ohmic contacts for<i>m</i>(STO) = 0, but only Schottky contacts for<i>m</i>(STO) = 2 and 4 junctions; (ii) the tunnel electroresistance and tunnel magnetoresistance ratios are evaluated at 0 and 300 K; (iii) the most magnetoelectric responsive interfaces are obtained for the<i>m</i>(STO) = 2 heterostructure, this system also showing co-existent giant tunnel electroresistance and tunnel magnetoresistance effects; (iv) the interfacial magnetoelectric coupling is not strong enough to control the tunnel magnetoresistance by polarization switching, in spite of significant SRO ferromagnetism.