Design and application of a mechanical load frame for in situ investigation of ferromagnetic shape memory alloys by magnetic force microscopy.

An in situ mechanical load frame has been developed for a commercially available atomic force microscope. This frame allows examining changes in topography and magnetic domain configuration under a given constant load or strain. First results obtained on Ni-Mn-Ga ferromagnetic shape memory alloy single crystals are presented. The magnetic force microscopy (MFM) measurements under different strain levels confirm the one-to-one correspondence, i.e., the magnetomicrostructural coupling between the martensite twins and the magnetic domains. Additionally, the growth of the twin variant with favorable orientation to the compression axis during martensite detwinning was observed. It will be shown that this load frame can be used for the investigation of the relationship between the microstructure and the magnetic domain structure in ferromagnetic shape memory alloys by MFM.