Domain Walls and Twin Boundaries in Ferromagnetic Shape Memory Alloys

这项由材料研究部授予卡内基-梅隆大学的续展奖项是将电子显微镜技术应用于铁磁形状记忆合金(FSMA)和金属间化合物，特别是试图了解花呢结构的本质。获得这一奖项后，De Graef教授将研究镍-锰-镓和钴-镍-镓合金的物理和磁性微结构，重点是具有近室温相变的成分。研究人员开发的显微技术将用于同时对FSMA驱动过程中移动的孪晶和其他晶体缺陷以及驱动孪晶边界运动的磁畴壁进行成像。所提出的研究将有助于从根本上理解铁磁形状记忆合金中磁场与与激励相关的原子位移的耦合机制。FSMA领域对它们的潜在应用具有相当大的兴趣，因为该奖项开发的高应变、中频致动器和传感器科学将有助于我们理解磁畴和孪晶边界的运动。本项目为铁磁形状记忆合金开发的表征工具和方法也将对表征磁记录介质的能力产生积极影响。拟议的研究将对研究生教育、课程开发和高级材料表征的教学做出重大贡献。在材料科学和工程系以及计算机系的本科生的帮助下，为结晶学和衍射学的本科生教科书开发一个互动式网站将是该项目的一部分。

This renewal award by the Division of Materials Research to Carnegie-Mellon University is to apply electron microscopic techniques to ferromagnetic shape memory alloys (FSMA) and intermetallics, and in particular to try to understand the nature of the tweed structures. With this award, Professor De Graef will study the physical and magnetic microstructure of alloys of Nickel-Manganese-Gallium and Cobalt-Nickel-Gallium, with an emphasis on compositions with near room temperature phase transformations. The microscopy techniques, which were developed by the investigator, will be used for simultaneously imaging twins and other crystal defects that move during FSMA actuation, and the magnetic domain walls that drive the twin boundary motion. Proposed research would contribute significantly to the fundamental understanding of the mechanisms that couple the magnetic field to the atomic displacements associated with the actuation in ferromagnetic shape memory alloys. FSMA area is of considerable interest for potential applications of them as high-strain, moderate-frequency actuators and sensors Science developed by this award would shed light into our understanding of the motion of magnetic domains and twin boundaries. The characterization tools and methods developed by this project for ferromagnetic shape memory alloys will also have a positive impact on the ability to characterize magnetic recording media. There would be significant contributions for graduate education, course development, and teaching of advanced materials characterization by the proposed studies. Development of an interactive web-based site with the help of undergraduate students from both Materials Science and Engineering and Computer departments for an undergraduate textbook on crystallography and diffraction would be part of this project.