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

技术概要：像差校正洛伦兹透射电子显微镜（LTEM）将用于研究多铁性材料中的磁畴壁行为，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结构。本研究的主要焦点是畴壁与其他边界（如孪晶和反相边界）之间的相互作用。所选择的合金是具有接近Ni 2 MnGa的组成的铁磁形状记忆合金和具有约30 at. % Pd。这项研究将主要包括静态和动态条件下磁畴壁的实验观察，并得到基于微磁模型的图像模拟的支持。这项研究将在一台像差校正的Titan 80-300透射电子显微镜上进行，并将包括对样品施加的现场磁场。一个新开发的实验方法，矢量场电子断层扫描，将被应用到这些材料产生，第一次，详细的三维视图的磁化configurations.Non-Technical摘要：该项目旨在应用先进的显微镜方法的磁性材料的研究，以提高这一重要类别的材料的理解水平。 磁体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，包括计算机硬盘驱动器中使用的磁记录介质，以及使用磁体的微观机械系统。该项目的推广部分被称为TACTILS（在当地学校教授先进的表征工具），将通过在当地学校提供便携式电子显微镜来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，并随后在自己的教室里向学生传授这些新知识。

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.