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

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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.