Mechanism for Reversible Electrical Switching of Spin Polarization in Co/PbZr0.2Ti0.8O3La0.7Sr0.3MnO3 Tunnel Junctions

The possibility of switching the sign of the tunneling electrons' spin polarization by an electric field could introduce dramatic and technologically promising changes in the way spin transport is controlled in spintronic devices. Recently, such switching was observed experimentally in Co/PbZr0.2Ti0.8O3 (PZT)/La0.7Sr0.3MnO3 multiferroic tunnel junctions. Using ab initio calculations, we identify a micro-scopic mechanism that can explain this effect. Following an extensive search, we single out a Co/PZT-interface atomic configuration, including an oxygen-related defect complex, which can account for the experimental spin-polarization switching trend. For this configuration, we find that inversion of the PZT ferroelectric polarization induces drastic reversible changes in the reactivity and chemical binding of the interfacial O with Co. This ferroelectric-controllable reactivity of O leads virtually to an on-off switchable O-Co hybridization and a swappable spin polarization in the PZT barrier.