Synthesis and Real Structure Group

SPP 1239

Real and magnetic structure investigation of ferromagnetic shape memory alloys via transmission electron microscopy


Ferromagnetic shape memory alloys (FSMAs) have attained strong interest because of the large strain which can be obtained by the application of an external magnetic field. An applied magnetic field is not only an additional means to control the shape memory effect, but is also attractive because it is a much faster method of actuation than the more traditional method of heating and cooling a shape memory alloy. The mechanism of Magnetic Field-Induced Strain (MFIS) is based on the rearrangement of martensite variants by the magnetic field. The variants are separated by twin boundaries, which are formed as a result of the martensitic transformations.

The main scientific field of the project is the real structure analysis by advanced electron microscopy techniques. Particular prominence is on the crystallographic structure of complex, twinned, disordered and modulated phases and the magnetic structure of functional materials. In-situ studies of structural and magnetic changes of the samples by external stimuli, like variation of temperature and magnetic field at the sample position are also scheduled in the frame of this project.