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

本研究主要研究同时具有磁性和铁电性的多铁性材料。虽然这是一个密集的研究领域，但已知的常温多铁材料仍然很少，这些材料仍然需要更深入地了解它们的性质，特别是铁电和磁性之间的耦合，即磁电耦合。最近对更精细规模的铁电和铁磁薄膜的研究表明，它们的磁区壁具有一系列不同于磁区的独特性质，可以通过外场控制，从而为开发这些非常局域的功能来构建真正的纳米器件开辟了道路。要开发其巨大的器件潜力，从长远来看，这可能导致真正可重构的纳米电子学，在这种情况下，完全可操作的纳米器件电路可以被无限期地写入、使用和擦除，因此了解域壁特性，特别是它们的传输特性和相关物理特性，是至关重要的。 因此，这项研究计划将研究在室温下确实表现出多铁性和磁电性质的外延薄膜的迷人特性。特别是，它将建立在过去5年中合成和研究的少数几种外延室温多铁性薄膜的工作基础上，这些薄膜表现出一种特殊的磁畴壁，即平面取向磁畴之间的边界。我们将研究这些特定薄膜的磁区壁特性，重点放在它们所展示的独特的磁区壁的局部特性上，这是以前从未研究过的。 在复杂的多铁性薄膜外延生长技术的基础上，还将研究各种结构的复合磁电薄膜的外延生长，并将使用所生产的室温磁电薄膜来制造概念验证器件。 最后，将在外延生长中获得的知识扩展到另一类材料，即多铁性或磁电混合有机-无机材料的外延生长，以及它们的性能，超越了光伏特性，包括铁电、压电、磁性，可能是学生和HQP的热电NT，处于当今该领域研究的前沿。

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 nt for students and HQP in general, at the leading edge of today's research in the field.