Nanoscale investigation of coupling phenomena in bismuth ferrite under continuously varied mechanical stress

铋铁氧体(BFO)是为数不多的常温多铁单相化合物之一，是目前固体研究的热点领域。除了它在无铅压电、磁电、光伏或多电平存储方面的潜在应用外，对BFO强耦合铁性对外场的微妙响应的基本了解定义了多铁性物理学的一个重要目标。深入研究如何通过连续可变的外部单轴弯曲产生机械应力来调节BFO的电子、铁电和磁性组态，是当前项目的重点。在原位基片弯曲过程中，将分析宏观关键性质--如电子结构、导电性、电极化和磁极化及其相互耦合--以及相应的纳米指纹。其中一个主要问题是通过同时应用电磁和磁敏扫描探头方法来研究不同铁性磁畴类型及其边界的纳米尺度应力诱导行为。此外，目的是通过可调的外应力来系统地优化铁性参数。

Being one of the very few multiferroic single-phase compounds at room temperature, bismuth ferrite (BFO) is currently a highly topical field of solid-state research. Apart from its potential for lead-free piezoelectric, magnetoelectric, photovoltaic or multilevel memory applications, the fundamental understanding of the subtle response of the strongly coupled ferroic properties of BFO to external fields defines an important goal in the physics of multiferroics. The in-depth study of how the electronic, ferroelectric, and magnetic configuration of BFO can be tuned, especially in thin films, by inducing mechanical stress via continuously variable external uniaxial sample bending stands in the focus of the current project. During in-situ substrate bending, macroscopic key properties – such as electronic structure, conductivity, electric and magnetic polarization and their mutual coupling – as well as the corresponding nanoscopic fingerprints will be analyzed. One main issue is the investigation of the nanoscale stress-induced behavior of the different ferroic domain types and their boundaries by the simultaneous application of electrically and magnetically sensitive scanning probe methods. Moreover, the aim is to optimize the ferroic parameters via the tunable external stress systematically.