Dennis Meier

Technological evolution and revolution are both driven by the discovery of new functionalities, new materials and the design of yet smaller, faster, and more energy-efficient components. Progress is being made at a breathtaking pace, stimulated by the rapidly growing demand for more powerful and readily available information technology. High-speed internet and data-streaming, home automation, tablets and smartphones are now "necessities" for our everyday lives. Consumer expectations for progressively more data storage and exchange appear to be insatiable. Oxide electronics is a promising and relatively new field that has the potential to trigger major advances in information technology. Oxide interfaces are particularly intriguing. Here, low local symmetry combined with an increased susceptibility to external fields leads to unusual physical properties distinct from those of the homogeneous bulk. In this context, ferroic domain walls have attracted recent attention as a completely new type of oxide interface. In addition to their functional properties, such walls are spatially mobile and can be created, moved, and erased on demand. This unique degree of flexibility enables domain walls to take an active role in future devices and hold a great potential as multifunctional 2D systems for nanoelectronics. With domain walls as reconfigurable electronic 2D components, a new generation of adaptive nano-technology and flexible circuitry becomes possible, that can be altered and upgraded throughout the lifetime of the device. Thus, what started out as fundamental research, at the limit of accessibility, is finally maturing into a promising concept for next-generation technology.

The coexistence and coupling of magnetic and electric degrees of freedom in so-called multiferroics is not only the origin of new and unusual physical phenomena, these materials also have great potential for multifunctional spintronic applications or future data storage. A particularly interesting class of multiferroics are magnetically induced ferroelectrics. Unfortunately, their physics is currently far from being understood due to highly non-trivial correlation effects between spin, charge and lattice. Besides providing a comprehensive review on magnetically induced ferroelectricity, this work focuses on answering the key questions regarding correlated order parameters and associated domain structures in magnetically induced ferroelectrics. Optical second harmonic generation is applied to analyze the evolution of the symmetry breaking order parameters in the model systems MnWO4 and TbMn2O5. The nature and spatial distribution of domains are studied including correlation effects, their manipulation by thermal annealing procedures, as well as their control by external magnetic or electric fields.