Ferroelectric phase transitions induced by a strain gradient

In perovskite oxide ferroelectrics, gradients of lattice strain are known to induce nanoscale topological structures, leading novel or enhanced functionality. Here, we experimentally detect and theoretically analyze thickness distribution structural properties in epitaxial ${\mathrm{Pb}}_{0.5}{\mathrm{Sr}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}$ films grown on (001) $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrates. We show that the relaxation substrate-imposed stress produces a gradient, which leads formation distinct ferroelectric phases as function distance from film-substrate interface within same film. Charge carriers trapped at phase boundaries stabilize induced manifest themselves under electric field. Crosstalk between phases, where polarization may rotate one invert other one, opens perspectives for advanced thin film devices.