EPITAXY, INTERFACES, AND DOMAIN BOUNDARIES OF ROOM TEMPERATURE MULTIFERROIC MAGNETOELECTRIC FILMS AND HETEROSTRUCTURES

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This research focuses on multiferroic materials exhibiting simultaneously magnetic and ferroelectric properties. Though a field of intense research, there are still very few known multiferroic materials at room temperature, and these materials still need a deeper understanding of their properties, in particular the coupling between the ferroelectric and magnetic properties, namely the magnetoelectric coupling. Recent investigations of ferroelectric and ferromagnetic thin films at a finer scale recently revealed that their domain walls have their own set of unique properties different from those of the domains, which can be controlled by external fields, opening the way to exploit these much localized functionalities to build true nanodevices. Understanding the domain wall properties, in particular their transport characteristics and associated physics, is essential in order to exploit their vast device potential, which could - in the long term - lead to truly reconfigurable nanoelectronics, where fully operational nanodevice circuits could be written, used and erased indefinitely. This research program will therefore study the fascinating properties of epitaxial thin films that do exhibit multiferroic and magnetoelectric properties at room temperature. In particular it will build on the body of work on the few epitaxial room temperature multiferroic thin films synthesized and investigated during the last 5 years, which exhibit a particular kind of domain walls, namely boundaries between in-plane orientation domains. The domain walls properties of these specific films will be studied, with a very strong emphasis on the local properties of the unique kind of domain walls they exhibit, which have never been studied before. Further building on the expertise acquired in growing epitaxial films of complex multiferroic films, the epitaxial growth of composite magnetoelectric thin films with various architecture will also be investigated and proof-of-concept devices will be fabricated using the room temperature magnetoelectric films produced. Finally, extending the knowledge acquired in epitaxial growth to a further class of materials, the epitaxial growth of multiferroic or magnetoelectric hybrid organic-inorganic materials, will be achieved and their properties, beyond photovoltaic features -including ferroelectric, piezoelectric, magnetic, possibly thermoelectric & electrochromic, properties will be investigated. This research program will result in a fundamental understanding of the mechanisms leading to the epitaxial growth of both inorganic and hybrid organic-inorganic functional materials, and will lay a solid physics and materials characterisation foundation for the vast device potential of epitaxial multiferroic magnetoelectric thin films and the unique local properties of their domain walls. It will also provide a very stimulating training environment for students and HQP in general, at the leading edge of today's research in the field.