The origin and understanding of coupling phenomena between different physical properties is a central subject of solid state science and related applications. It has fascinated physicists, chemists and materials scientists for decades and becomes increasingly important for Multifunctional Materials.Multiferroics possess several so-called ferroic properties: ferromagnetism, ferroelectricity, and/or ferroelasticity. The understanding of cross-coupling between ferroic orders and external parameters presents both profound fundamental questions and great potential for innovative applications. The overall objective of this proposal is to acquire a broad knowledge of coupling phenomena in multiferroic materials with an aim of discovering new general concepts, clearing the way for both understanding and applications. For this, we intend to embrace the whole range from fundamental research to industrial collaborations.A material is generally considered functional if it possesses a physical property that is usable in applications. A smart material is one that serves this function smartly i.e. by responding adaptively in a pre-designed useful and efficient manner to changing environmental conditions. A large amount of research currently concentrates on multifunctional materials in which several functions can potentially be used simultaneously. One of the key questions for the future development of multifunctional or smart materials concerns the mutual coupling between the properties, its underlying mechanism and whether it can be used in applications.Multiferroics are multifunctional materials par excellence, because they simultaneously possess several so-called ferroic orders such as ferromagnetism, ferroelectricity or ferroelasticity. The prefix ferro refers historically to iron (ferrum in Latin), which shows a spontaneous magnetization M that can be controlled (and critically reversed) by the application of a magnetic field. In analogy, the electrical polarization P of a ferroelectric material can be controlled by the application of an electric field, and the ferroelastic deformation e by a mechanical strain (see information box next page for more details on ferroic materials).The field of (multi)ferroic materials is extremely active with an important number of research axes. We believe devoutly that only a broad approach and thus a profound knowledge of ferroic materials will allow both a fundamental understanding and innovative applications. Within this broad approach we will focus our main efforts on four lines of research, which are briefly introduced below. Depending on the line of research, our research will have a more application-related focus with a publs-private-partnership, as on piezoelectric materials, or be more at the forefront of science in emerging fields such as domain engineering.1) Piezoelectric materials (coupling of deformation & ferroelectricity)2) Magnetoelectric Multiferroics (coupling of electric & magnetic orders)3) Photoferroelectrics / Photoferroics (coupling of light with ferroic orders)4) Domain Boundary engineering (multiple coupling)This proposed PEARL project will be integrated into the “Science and Analysis of Materials” (SAM) department of the CRP Lippmann. The project has a high strategic value for the CRP with the aim to reinforce the field of high knowledge-content materials, which provide new functionalities and improved performances and which will be critical drivers of innovation in technologies. This strategy stands in the wider context of the announced merger of CRP Gabriel Lippmann and CRP Henri Tudor into a single research centre focused on applied research and innovation, in which materials science will be one of the main focus areas.