Electrically Controlled Spin Valve at a Complex Oxide Interface

Since the discovery of giant magnetoresistance exploration of spin-dependent electronic transport has proved promising for applications. To avoid the costly generation of magnetic fields in these devices there have been recent efforts toward manipulating magnetization by \textit{electric} fields. Such magnetoelectric effects can be induced at the surfaces and interfaces of many ferromagnetic metals. Ferroelectric materials are especially helpful in this because their spontaneous electrical polarization can induce a large response at the interface with a magnetic metal. One example is the ferroelectric control of magnetic order at the interface between La$_{1-x}A_{x}$MnO$_{3}$ (where $A$ is a divalent cation), and the ferroelectric BaTiO$_{3}$ [1]. Importantly, ferroelectric films can now be made thin enough (less than a few nm) to allow measurable electron tunneling while still maintaining a stable and switchable polarization [2]. Here we show that those few atomic layers near the interface sensitive to the ferroelectric polarization can act as an atomic scale spin-valve in series with the ferroelectric tunnel barrier. Switching the ferroelectric barrier induces more than an order of magnitude change in the conductance due to the interfacial spin-valve, constituting a substantial spin-dependent transport phenomenon controlled by an electric field alone.\\[0pt] [1] J. D. Burton and E. Y. Tsymbal, Phys. Rev. B \textbf{80}, 174406 (2009).\\[0pt] [2] A. Gruverman\textit{ et al.}, Nano Lett. \textbf{9}, 3539 (2009).