Reversibly controlled ternary polar states and ferroelectric bias promoted by boosting square???tensile???strain

Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in multifunctional heterostructures. However, the defect-dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, we report deterministic switching between the ferroelectric and the pinched states by exploiting a new substrate of cubic perovskite, BaZrO3, which boosts square-tensile-strain to BaTiO3 and promotes four-variants in-plane spontaneous polarization with oxygen vacancy creation. First-principles calculations propose a complex of an oxygen vacancy and two Ti3+ ions coins a charge-neutral defect-dipole. Cooperative control of the defect-dipole and the spontaneous polarization reveals ternary in-plane polar states characterized by biased/pinched hysteresis loops. Furthermore, we experimentally demonstrate that three electrically controlled polar-ordering states lead to switchable and non-volatile dielectric states for application of non-destructive electro-dielectric memory. This discovery opens a new route to develop functional materials via manipulating defect-dipoles and offers a novel platform to advance heteroepitaxy beyond the prevalent perovskite substrates

Switchable bias-field effect in large tensile strained BaTiO3 epitaxy film on lab-made BaZrO3 substrate

Strain engineering for the heteroepitaxy film is a technique to apply strain on the oxide film through the lattice mismatch between the film and substrate[1]. The applied strain often leads to enhancement of their physical properties or sometimes creates new physical phenomena. Magnitude and symmetry of the applied strain strongly depend on the chosen substrate. However, the prevalent perovskite substrates have been limited in the well-known perovskite oxides system, such as SrTiO3, scadates, aluminates, etc. Recently, we have developed a new perovskite oxide substrate BaZrO3 and successfully grown BaTiO3 film on the lab-made BaZrO3 substrate. In this presentation, we introduce and discuss emerging physical phenomena in the epitaxial BaTiO3 film on the BaZrO3 single crystal substrate. [1] R. Ramesh and D. G. Schlom, Nature Reviews Materials 4, 257 (2019