Electrical properties of epitaxial PZT-LSMO magnetoelectric heterostructures: the effect of the interface with the electrodes

Abstract Ferroelectric–ferromagnetic heterostructures with well-defined polarization orientation are the focus of many research studies owing to their interesting interface-driven phenomena such as magnetoelectric coupling. In most practical electronic applications, capacitor geometry is often used, and in the case of ferroelectric–ferromagnetic heterostructures this can bring additional challenges regarding the overall functionality due to the physical phenomena from the ferroelectric-electrode interface. In this study, it is presented the influence of the top and bottom electrode on the electrical properties of Pb(Zr 0,2 Ti 0,8 )O 3 –La 1− x Sr x MnO 3 /SrTiO 3 (001) epitaxial heterostructures. This was done by growing the thin films with different layer stacking sequences by changing the Sr doping level from the bottom electrode. It was found that both the ferroelectric polarization orientation and tetragonality of the PZT films were significantly affected by the layer stacking sequence and Sr doping level of the bottom electrode. The ferroelectric polarization was oriented either towards or away from the Pb(Zr 0,2 Ti 0,8 )O 3 –La 1− x Sr x MnO 3 interface depending on the layer stacking sequence, and the tetragonality increased when the Sr doping increases from x = 0.3 to x = 0.33. The materials used as the top electrode were Pt and Au/SrRuO 3 . Electric measurements performed in capacitor geometry show that the hysteresis curves start to be affected by leakage currents, which have a direct impact on the estimation of the ferroelectric polarization values and on the internal built in field. The most severely affected were the measurements performed with top Pt electrodes. The conduction mechanisms and leakage current values obtained by using the top Au/SrRuO 3 electrode were found to be dependent on the Sr doping level, despite the fact that the electrical resistivity values and microstructures of the individual La 1− x Sr x MnO 3 films were similar.