Quantitative Aberration-Corrected Observations of Magnetic Domain Walls in Multi-Ferroic Materials

技术概述：像差校正洛伦兹透射电子显微镜（LTEM）将用于研究许多多铁性材料的磁畴壁行为，即表现出多个相变的材料，每个相变都会产生精细尺度的畴微观结构。本研究的重点是研究畴壁与孪晶和反相边界之间的相互作用。选择的合金是成分接近Ni2MnGa的铁磁形状记忆合金和成分约为30 at的Fe-Pd合金。% Pd。研究将主要包括静态和动态条件下的畴壁实验观测，并辅以基于微磁模型的图像模拟。这项研究将在像差校正的泰坦80-300透射电子显微镜上进行，并将包括对样品施加的原位磁场。一种新开发的实验方法，矢量场电子断层扫描，将首次应用于这些材料，以产生详细的磁化结构的三维视图。非技术概述：该项目旨在应用先进的显微镜方法来研究磁性材料，以提高对这类重要材料的理解水平。磁铁在当今社会中无处不在，对其行为的更好理解将影响广泛的工程应用，包括在计算机硬盘驱动器中使用的磁性记录介质，以及利用磁铁的微观机械系统。该项目的外展部分被称为“在当地学校教授高级表征工具”，通过为当地学校提供便携式电子显微镜，将影响匹兹堡地区几所学校的初中和高中科学教育。科学教师将有机会了解这些仪器，并随后在自己的课堂上向学生传达这些新知识。

TECHNICAL SUMMARY: Aberration-corrected Lorentz Transmission Electron Microscopy (LTEM) will be used to study magnetic domain wall behavior in a number of multi-ferroic materials, i.e. materials that exhibit multiple phase transitions, each giving rise to a fine-scale domain microstructure. The main focus of this research is on the interactions between the domain walls and other boundaries, such as twins and anti-phase boundaries. The alloys of choice are the ferromagnetic shape memory alloys with compositions near Ni2MnGa, and Fe-Pd alloys with around 30 at. % Pd. The research will consist mainly of experimental observations of domain walls under static and dynamic conditions, supported by image simulations based on micro-magnetic models. The research will be carried out on an aberration-corrected Titan 80-300 transmission electron microscope and will include in-situ magnetic fields applied to the samples. A newly developed experimental approach, vector-field electron tomography, will be applied to these materials to generate, for the first time, detailed three-dimensional views of the magnetization configurations.NON-TECHNICAL SUMMARY: This project seeks to apply advanced microscopy methods to the study of magnetic materials, in order to improve the level of understanding of this important class of materials. Magnets are ubiquitous in today's society, and an improved understanding of their behavior will impact a wide range of engineering applications, including magnetic recording media used in computer hard drives, and microscopic mechanical systems that make use of magnets. The outreach component of this project is called TACTILS (Teaching Advanced Characterization Tools In Local Schools), and will impact middle and high school science education in several schools in the Pittsburgh area by making portable electron microscopes available for use in local schools. Science teachers will have an opportunity to learn about these instruments and subsequently convey this new knowledge to the students in their own classrooms.