Kerr microscopy with machine learning domain detection for in-situ magnetic materials analysis (MaKerr)

本项目建议书涉及一种高分辨率光-光学克尔显微镜，专门设计用于在汽车应用中发现的真实的生活条件（温度、磁场和机械负载）下对硬磁和软磁材料的磁化进行原位表征，例如电动汽车的牵引电机。关键要素是原位显微镜与数字显微镜、自动量化工具和机器学习方法的智能结合，以基于对其微观结构的有效分析，在其应用环境中获得对这些材料的更深入了解。这就需要一个整体的方法来考虑系统，然后是可视化过程：样品制备-显微镜-相机-软件。样品制备的一个重要因素是通过介电抗反射涂层增强对比度和表面保护。显微镜概念的核心元素是在高真空室中操作的多个测试模块的实现，包括热台，机械显微操作器（例如拉伸应力），用于产生均匀和可调磁场的电磁铁以及快速和高分辨率的数码相机技术。灵活的设计允许测试模块的同时操作，例如，在高温和磁场存在的情况下，在拉伸应力的作用下对软磁电工钢进行研究。使用具有高数值孔径的透镜保证了显微镜的高光学分辨率，也可以与真空室结合使用（不使用时高达230 nm，使用真空室时高达430 nm）。最先进的高速数码相机允许分析的物理过程的时间分辨率高达10毫秒。专门设计的机器学习软件例程能够高度准确地检测磁畴模式，即使在材料与不太有利的信号噪声比，例如材料与弱内在磁对比度或在快速时间流逝获取的图像。因此，自动检测和量化在大样本区域内获得的畴图案可以作为时间和/或温度的函数。应用显微镜系统非常适合有效地研究可持续的强大电能转换器开发中出现的重要科学问题，例如在永磁体中的磁反转和退磁过程或软磁部件中的磁损耗的深入分析中。此外，通过实验高通量筛选发现的新的硬磁相的磁势可以被评估，分析畴结构。在这里，磁畴图案的对比度和大小及其运动具有特殊的意义。

This project proposal concerns a high resolution light-optical Kerr microscope specifically designed for insitu characterization of the magnetization of hard- and soft magnetic materials under real life conditions (temperature, magnetic fields, and mechanical loads) as found in automotive applications, e.g. traction motors for electric cars. Key element is the intelligent combination of in-situ microscopy with digital microscopy, automated quantification tools and machine learning approaches to obtain a deeper knowledge of these materials in their application environment based on efficient analysis of their microstructures. This requires a holistic approach to consider the system and then the visualization process: sample preparation – microscope – camera – software.An important element of sample preparation is contrast enhancement and surface preservation by dielectric anti-reflection coatings. Core element of the microscope concept is the implementation of multiple testing modules operated in a high vacuum chamber, including a hot stage, mechanical micromanipulator (e.g. tensile stress), electromagnets for generation of homogenous and tunable magnetic fields as well as fast and high resolution digital camera technology. The flexible design allows the concurrent operation of the testing modules, e.g. investigation of soft magnetic electrical steel under application of tensile stress at elevated temperatures in the presence of magnetic fields. Usage of lenses with high numerical aperture guarantees high optical resolution of the microscope also when operated in combination with the vacuum chamber (up to 230 nm without, 430 nm with vacuum chamber). State of the art high speed digital cameras allow analysis of physical processes with time resolutions of up to 10 ms. Specifically designed machine learning software routines enable highly accurate detection of magnetic domain patterns even in materials with less favorable signal to noise ratio, e.g. materials with weak intrinsic magnetic contrast or images acquired in fast time lapses. Thus, automated detection and quantification of domain patterns acquired over a large sample area is possible as a function of time and/or temperature.The applied for microscope system is exceptionally well suited to efficiently investigate important scientific questions arising in the development of sustainable powerful electric energy converters, such as in depth analysis of magnetic reversal and demagnetization processes in permanent magnets or magnetic losses in soft magnetic components. In addition, the magnetic potential of novel hard magnetic phases found by experimental high throughput screening can be evaluated, analyzing the domain structure. Here, the contrast and size of the domain pattern and its movement are of special significance.