The Deutsche Forschungsgemeinschaft (DFG) has funded the Collaborative Research Centre SFB 762 (project number 31047526) at Martin Luther University Halle‐Wittenberg from 2008 to 2019. SFB 762 was a collaboration of Martin Luther University Halle‐Wittenberg, Leipzig University, and the Max Planck Institute of Microstructure Physics in Halle.

Within the Collaborative Research Centre SFB 762 “Functionality of Oxide Interfaces”, a unique team of experts was focusing on the fabrication and characterisation of oxide heterostructures whose individual components are ferroelectric, magnetic, semiconducting, or insulating, thereby providing various degrees of freedom for designing functional elements. The investigated materials and structures are multifunctional, which means that based on the ferroelectric or magnetic state the electrical or optical properties are changed and determine the corresponding functionality. At the core of the functionality rests the interface and the coupling across the interface. More precisely, the interface's geometric structure as well as its charge and spin order can be manipulated by external electric or magnetic fields, causing by these means the functional effects. The couplings are of various kinds, for example electro‐optical, electric, piezoelectric, magneto‐elastic or magneto‐electric.

The focus of our activities was the investigation of multiferroic interfaces between ferroelectric and magnetic layers. The main goal was the design and microscopic understanding of multiferroic heterostructures with magnetoelectric coupling via the oxide interface. Magnetic response of the system to an external electric field was demonstrated as proof‐of‐principal by means of an epitaxial multiferroic tunnel junction consisting of ferromagnetic leads separated by a ferroelectric barrier. Closely related to this question is the cross‐talk of ferroelectric and magnetic domains across the interface which includes as well the mutual interaction of polarisation dynamics on the picosecond scale with magnetisation dynamics on the femtosecond scale.

A very important aspect of our research was dedicated to two‐dimensional (2D) oxide quasi‐crystals which have been discovered in our SFB. Besides fabrication and structural characterisation of this new oxide 2D material, we have been very much interested in the electronic properties of quasicrystals and their entropic stabilisation. Research in the field of oxide interfaces with quasi‐crystalline order was new ground.

A further aspect of our research was the formation of two‐dimensional electron or hole gases (2DEG) at oxide interfaces. Besides the existence of the phenomenon we concentrated to the manipulation of the 2DEG by ferroelectric and magnetic order of the adjacent components in the heterostructure. But we have as well been interested in the properties of the 2DEG itself, in particular the investigation of the topological character of the 2DEG, the electron‐phonon coupling, as well as the formation of magnetic order or superconductivity.

A further important question in our work was the investigation of defect‐induced magnetism in oxides. Stability and reproducibility of defect‐induced magnetism was the question to be answered, in particular under the focus whether a new type of magnetism could coexist with ferroelectricity.

The selection of ferroelectric and ferromagnetic oxides investigated in our SFB was very much triggered by nature's permission for and our accomplishment of their epitaxial growth and the fabrication of various heterostructures for further optimisation of the desired functional properties of the interface. The fact that the property should exist at finite temperatures was another very important aspect with regard to new concepts in sensor and information technologies.

The success of our concept was based on the combination of expertise in surface science, magnetism, semiconductor physics, solid state chemistry, material science, and theoretical physics. The locations Halle and Leipzig offered strong expertise and high‐end growth techniques for epitaxial growth of oxide layers and heterostructures. State‐of‐the‐art methods for structural, magnetic, ferroelectric, and electronic characterisation have been used and even further developed. The spectrum has been complemented by a variety of theoretical methods. Material‐specific description by ab initio methods based on time‐independent and time‐dependent density functional theory has been used. Properties of the ideal and defective oxide interfaces have been investigated for the ground‐state and at finite temperature. Influence of exchange and correlation at oxide interfaces was considered.

The overall scientific aim of SFB 762 was to understand all relevant processes of structural, electrical, and magnetic order at oxide interfaces on the atomic scale and their consequences for resulting meso‐ and macroscopic physical properties. Our investigations have yielded new insights into microscopic interactions at oxide interfaces which form the basis for new device concepts in the long term. Furthermore, the synthesis of oxide heterostructures demonstrated prototypically the functionality of interfaces with enormous relevance to applications and high potential for innovation with regard to new real world applications in sensor and information technologies.

The papers collected in the special issue of physica status solidi (b) in form of 2 Review Articles, 11 Feature Articles and 18 Original Papers mainly focus on our research described above and provide much more details and further outlooks. We hope that this collection of results demonstrates the beauty and attraction of this research area of solid state physics and the fun that we shared performing the research.

The three signees had the pleasure to chair the SFB 762 during twelve fruitful years. We wish to thank all investigators involved in this project for their contributions, the Deutsche Forschungsgemeinschaft for their major support, the Martin Luther University Halle‐Wittenberg, and Leipzig University for additional and significant financial support and Wiley for the opportunity to publish this special issue.

On behalf of all participants in the SFB 762 over the years,

德意志联邦理工学院（DFG）于2008年至2019年资助了马丁·路德大学Halle-Wittenberg合作研究中心SFB 762（项目编号31047526）。SFB762是马丁·路德大学Halle-Wittenberg，莱比锡大学和麦克斯大学的合作哈雷普朗克微结构物理研究所。

在协作研究中心SFB 762“氧化物界面的功能”内，一个独特的专家团队专注于氧化物异质结构的制造和表征，这些氧化物异质结构的各个成分是铁电，磁，半导电或绝缘的，从而为设计提供了不同程度的自由度。功能元素。所研究的材料和结构是多功能的，这意味着基于铁电或磁性状态，可以更改电气或光学特性并确定相应的功能。功能的核心在于接口和跨接口的耦合。更确切地说，可以通过外部电场或磁场来控制界面的几何结构及其电荷和自旋顺序，通过这些方式引起功能上的影响。联轴器种类繁多，例如电光，电，压电，磁弹性或磁电。

我们活动的重点是研究铁电层和磁性层之间的多铁性界面。主要目标是通过氧化物界面进行磁电耦合的多铁异质结构的设计和微观理解。通过外延多铁隧道结由铁电势垒隔开的铁磁引线组成的外延原理证明了系统对外部电场的磁响应。与这个问题密切相关的是跨接口的铁电和磁畴的串扰，其中还包括皮秒级的极化动力学与飞秒级的磁化动力学之间的相互作用。

我们研究的一个非常重要的方面是致力于在我们的SFB中发现的二维（2D）氧化物准晶体。除了这种新型氧化物二维材料的制造和结构表征外，我们对准晶体的电子性质及其熵稳定也非常感兴趣。准晶序的氧化物界面领域的研究是新的领域。

我们研究的另一个方面是在氧化物界面处形成二维电子或空穴气体（2DEG）。除了该现象的存在外，我们还集中于通过异质结构中相邻组件的铁电和磁序操纵2DEG。但是我们也对2DEG本身的特性感兴趣，特别是对2DEG拓扑特性，电子-声子耦合以及磁阶或超导性形成的研究。

在我们的工作中，另一个重要的问题是对氧化物中由缺陷引起的磁性的研究。缺陷感应磁场的稳定性和可重复性是需要解决的问题，特别是在一种新型的磁场是否可以与铁电共存的问题上。

在我们的SFB中研究的铁电氧化物和铁磁氧化物的选择，很大程度上是由于自然界的许可以及我们对其外延生长的完成以及各种异质结构的制造，以进一步优化所需的界面功能特性。关于传感器和信息技术中的新概念，该特性应在有限的温度下存在这一事实是另一个非常重要的方面。

我们概念的成功是基于表面科学，磁性，半导体物理学，固态化学，材料科学和理论物理学方面的专业知识相结合。哈雷和莱比锡的所在地为氧化物层和异质结构的外延生长提供了强大的专业知识和高端的生长技术。结构，磁，铁电和电子表征的最新方法已得到使用，甚至得到了进一步发展。各种理论方法对光谱进行了补充。从头到尾的材料特定描述已经使用了基于时间独立和时间依赖的密度泛函理论的方法。已经研究了理想和有缺陷的氧化物界面在基态和有限温度下的特性。考虑了交换和相关对氧化物界面的影响。

SFB 762的总体科学目标是了解原子尺度上氧化物界面的结构，电和磁有序的所有相关过程，以及它们对所得介观和宏观物理性质的影响。我们的研究对氧化物界面的微观相互作用产生了新的见解，从长远来看，这些相互作用构成了新器件概念的基础。此外，氧化物异质结构的合成从根本上证明了界面的功能，这些界面与应用具有极大的关联性，并且对于传感器和信息技术中的新现实应用具有很大的创新潜力。

在专刊收集的论文物理学1.166（二）在2篇评论文章，11篇专题文章和18篇原始论文的形式主要集中在上述我们的研究和提供更多的细节和进一步的展望。我们希望这些结果集能够证明固态物理学这个研究领域的美丽和吸引力，以及我们共享的进行研究的乐趣。

在十二个硕果累累的三年中，三位签手很高兴担任了SFB 762的主席。我们要感谢所有参与此项目的研究人员所做的贡献，德国科学基金会的主要支持，马丁·路德大学的哈雷·威登伯格和莱比锡大学的额外和重要的财务支持，以及威利提供的机会出版此特别刊物。

多年来代表SFB 762的所有参与者，