PAK 5: "Integrated Microactuator Systems Emphasizing Ni-Mn-Ga Films with a Tailored Microstructure" INTACT - Mechanical, magnetic and morphological properties of vapor desposited magnetic shape memory alloy thin films

• Antragsteller: Professor Dr. Stefan Mayr
• Fachliche Zuordnung: Mechanische Eigenschaften von metallischen Werkstoffen und ihre mikrostrukturellen Ursachen
• Förderung: Förderung von 2006 bis 2011
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 28340798

This proposal is part of a packet proposal together with Dr. S. Fähler, Prof. Dr. L. Schultz (IFW Dresden), Prof. Dr.-Ing. H.-H. Gatzen (Uni Hannover) and PD Dr. M. Kohl (Uni Karlsruhe) within the SPP 1239 ¿Magnetic Shape¿. Here we focus on the influence of the growth morphology including crystallographic texture and the mechanical stresses in magnetic shape memory alloy films on the magnetic field induced crystallographic phase transition. We propose to prepare thin alloy films by e-beam evaporation in our UHV-system on salt or soft substrates followed by an annealing procedure to obtain textured films in case of originally amorphous layers. The shape memory phase transition of partly freestanding films will be explored in an external magnetic field as a function of the microstructure (grain size, morphology, texture), the mechanical stress state of the films and its elastic modules. We are interested in the correlation between the magnetic domain structure and the crystallographic microstructure in these films. Since the details of the twinning process are unknown, we are looking for cooperative shearing events versus a combination of dislocation movements. For this we propose to use scanning probe technology like STM, AFM and MFM to analyse the correlation mentioned above. Later on we propose to use mechanical spectroscopy, which is available in Göttingen in the frequency range from the quasi static to kHz (MHz in the near future), to study the characteristic relaxation modes responsible for the shape memory effect in more detail.

• DFG-Verfahren: Schwerpunktprogramme
• Teilprojekt zu: SPP 1239: Änderung von Mikrostruktur und Form fester Werkstoffe durch äußere Magnetfelder
• Beteiligte Person: Professor Dr. Konrad Samwer