Ab initio investigation of temperature dependent effects in magnetic shape memory Heusler alloys

SPP 1239的目标是研究有关材料性能和合金材料的加工条件的关键问题，这些材料在磁场诱导下发生形状变化，适用于磁力机械应用。然而，宏观行为源于微观结构的变化，这里将对其进行研究。预计这种相互依赖的具体知识为一方面研究材料性能，另一方面控制传感器/执行器系统所需的技术制造窗口提供了可能性。波恩的Forschungszentum Caesar和杜塞尔多夫的MPI für Eisenforschung的这项联合研究计划的目的是从实验和理论上为各自的组织-性能关系的关键问题做出贡献。这将包括对S材料的真实结构的考虑，包括缺陷、局部化学变化和原子有序效应。下面的实验研究是基于分子束外延生长的Heusler型三元和四元合金薄膜，显示出良好的晶格取向。只有这种条件才允许测试关于外部磁场方向的磁效应。此外，还将通过微压痕和局部结构表征来探讨其变形性能。实验结果将与Hickel/Neugebauer理论小组进行的模拟进行比较，反之亦然，进一步的理论结果有望刺激新的具体实验。

The goal of the SPP 1239 is to investigate the key questions regarding materials properties and processing conditions of alloy materials exhibiting magnetic-field induced shape changes, suitable for magnetomechanical applications. However, the macroscopic behavior is originating from microstructural changes which are to be investigated here. It is expected that the specific knowledge of this interdependence opens up the possibility for tayloring the materials properties on one hand and on the other hand to control the technical fabrication windows necessary for sensor / actuator systems. It is the aim of this joint research proposal of the Forschungszentrum caesar, Bonn, and the MPI für Eisenforschung, Düsseldorf, to contribute experimentally and theoretically to the key questions of the respective microstructure-property relationship. This will include the consideration of the material¿s real structure including defects, local chemical variations, and atomic ordering effects. The experimental study applied for below is based on MBE-growth of Heuslertype ternary and quaternary alloy films exhibiting a well defined crystal lattice orientation. Only this condition allows for testing the magnetic effects with regard to the external magnetic field direction. Additionally, the deformation properties will be probed with microindentation, accompanied by local structural characterization. The experimental results will be compared to simulations carried out by the theoretical group Hickel / Neugebauer and, vice versa, further theoretical results are expected to stimulate new specific experiments.