Tunable interface strain coupling and its impact on the electronic transport and magnetic properties of La₀.₅Ca₀.₅MnO₃/Pb(In₁/₂Nb₁/₂)O₃-Pb(Mg₁/₃Nb₂/₃)O₃-PbTiO₃ multiferroic heterostructures

Abstract

A comprehensive understanding of strain coupling across heterointerfaces and its impact on physical properties of oxide heterostructures is important for elucidating the mechanisms of certain novel physical phenomena occurring at heterointerfaces, such as magnetoelectric coupling, tunneling electroresistance effects, and strain-driven exchange bias. Using the La0.5Ca0.5MnO3/Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PINT) multiferroic heterostructure as a model system, we systematically investigated the influences of interface strain coupling on the electronic transport and magnetic properties as well as the electronic phase separation of charge-ordered La0.5Ca0.5MnO3 thin films through electric-field-induced ferroelectric domain switching. Upon the irreversible initial poling of the PMNT substrate, the induced in-plane compressive strain (Exx(film)=-0.045%) causes a decrease in TCO(ΔTCO=180K) and resistance [(ΔR/R)strain∼-99.4%], resulting in a gauge factor (ΔR/R)strain/xx(film)∼220800%. Such a large strain-tunability of resistance is unprecedented and magnetic-field tunable. This, together with the strain-tunable magnetoresistance (MR) and magnetization of the films, demonstrates strong coupling between the strain and the magnetic field. Further analysis indicates that this coupling is essentially mediated by the electronic phase separation, whose relative strength could be monitored by measuring (ΔR/R)strain against magnetic field and temperature. By combining 180° ferroelectric domain switching and x-ray diffraction and transport measurements, we identify that this electric-field modulation of the physical properties is strain-mediated but not interface charge-mediated. In addition, we observed that the non-180° ferroelastic domain switching-induced in-plane tensile strain (xx(film)=0.1%) induces a large increase in the resistance (up to ∼87.4%) and TCO and a drop in MR, signaling the stabilizing of the charge-ordered phase. Our findings provide further insight into the strain effect and essential physics of perovskite manganites, particularly the electronic phase separation.