Thickness-dependent of conduction mechanism and bias electric field modulation of transport properties for SrRuO3/PMN-PT heterostructures

Ultra-thin SrRuO₃ (SRO) films have been grown on ferroelectric and piezoelectric PMN-PT substrates. The structural properties of these films have been characterized by atomic force microscopy, x-ray diffraction and cross-sectional transmission electron microscopy. The nature of electric transport was analyzed in detail and the conduction mechanism of SRO films evolves through three regimes: from a three-dimensional (3D) metallic through a weakly localized to a strongly localized behavior as film thickness is reduced. The bias electric field modulations of transport properties and magnetic properties were explored for these films. We also demonstrate that ferroelectric (FE) domain switching induces a reversible tuning of the magnetic and electric properties in SRO/PMN-PT heterostructure. The FE domain switching in the substrate contributes to an in-plane strain that changes the spin exchange coupling in the SRO layer, and therefore results in a reversible resistance difference of up to 16%. This modulation effect on the electric properties by an electric field demonstrates great potential for the applications of all-oxides spintronics devices.