Coupling of polarization orientations of the ferroelectric layers in an oxide sandwich structure

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Mediated by the intrinsic polarization field, ferroelectric materials induce rich lattice and electronic responses associated with remarkable physical properties in their heterointerface structures. In this work, we investigate the coupling of polarization orientations of the ferroelectric BaTiO3 layers sandwiching the metallic SrRuO3 layer with different thicknesses. Measured by the electric field for switching the polarization orientation of the upper BaTiO3, it is found that the coupling of the polarization orientations increases as the SrRuO3 thickness decreases and the interaction length is determined to be 8 monolayers of SrRuO3. The transport properties of the SrRuO3 layer sensitively depend on the parallel/antiparallel orientation configuration of BaTiO3, with the resistivity changing by as much as 250% for the 6-monolayer sample. This work provides the fundamental knowledge of ferroelectric interactions in oxide sandwich structures toward their potential applications of nonvolatile memory devices.