Characterization of the micro- and nanostructure of magnetic shape memory materials by Transmission Electron Microscopy (TEM).

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The project should unravel unknown features of the real structure of ferromagnetic shape memory alloys (FSMA) with particular focus on thin film materials. For this purpose, a combined approach of transmission electron microscopy (TEM) methods is selected including state of the art techniques of electron diffraction, high resolution imaging and electron- or X-ray spectroscopy. Particular emphasis is on the investigation of structure and composition with atomic resolution since the optimization of material properties can only be derived from a precise knowledge about nanostructure, defects and inhomogeneities. For FSMA the identification and chemical analysis of nanoscale precipitates are of particular importance, since they are critical for the function of the material. Moreover, the structures of FSMA are built from structural and magnetic domains calling for analyses by advanced imaging techniques, like high resolution TEM and Lorentz microscopy, respectively. These examinations range from the analysis of complex structures with nanoscale modulations up to the arrangement of atoms at interfaces. The influence of chemical substitutions and doping on the real structure should be analyzed thus revealing real structure-property relations of materials and devices. Moreover, chemical or structural changes of potential devices based on heating effects can be monitored close to atomic resolution by in-situ heating experiments. The interdisciplinary nature of the project is emphasized by the skill-intensive cooperation with selected groups of SPP 1239 which characterize the function of FSMA and provide the materials for the TEM analyses.