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

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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.