Defect-Property Relations at Charged Interfaces in Ferroic Oxides

Oxide materials exhibit a broad range of tunable phenomena, including magnetism, multiferroicity, and superconductivity. Oxide interfaces are particularly intriguing, giving a new dimension to property engineering of functional materials. The low local symmetry at the interfaces, combined with their sensitivity to electrostatics and strain, leads to unusual physical effects, offering amazing opportunities for fundamental and applied research.<br/><br/>In my talk, I will discuss the unique electronic properties that arise at natural and artificially designed charged interfaces in ferroelectric and multiferroic oxides. To give an overview and demonstrate how structural, electric, and compositional degrees of freedom at such interfaces control the material’s behavior, I will present three examples: (i) ferroelectric domain walls in BiFeO₃, (ii) grain boundaries in ferroelectric ErMnO₃ polycrystals, and (iii) epitaxial heterointerfaces in multiferroic (LuFeO₃)₉/(LuFe₂O₄)₁ superlattices. To characterize the different types of interfaces, we perform correlated microscopy measurements, combining scanning probe microscopy, electron microscopy, and atom probe tomography. The imaging experiments provide new insight into the atomic-scale structure and chemical composition at charged oxide interfaces, clarifying the key role polar discontinuities and point defects play for their emergent physical properties.