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

该建议是与S.Fähler博士、L.Schultz教授(IFW Dresden)、Dr.-ing一起提出的一揽子建议的一部分。H.-H.Gatzen(汉诺威大学)和PD M.Kohl博士(Uni Karlsruhe)在SPP 1239磁性形状中。本文重点研究了磁性形状记忆合金薄膜的生长形态，包括晶体织构和机械应力对磁场诱导晶体相变的影响。我们建议在我们的超高真空系统中，在盐或软衬底上用电子束蒸发制备合金薄膜，然后对原始的非晶层进行退火热处理，以获得织构薄膜。在外加磁场作用下，研究了部分自支撑薄膜的形状记忆相变与其微观结构(颗粒尺寸、形貌、织构)、薄膜的机械应力状态及其弹性模数之间的关系。我们感兴趣的是这些薄膜的磁畴结构和晶体微结构之间的关系。由于孪生过程的细节尚不清楚，我们正在寻找合作剪切事件与位错运动的组合。为此，我们建议使用扫描探针技术，如扫描隧道显微镜、原子力显微镜和磁力显微镜来分析上述相关性。随后，我们建议使用Göttingen提供的在准静态到kHz(不久的将来为MHz)的频率范围内的机械光谱来更详细地研究引起形状记忆效应的特征弛豫模。

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.