Soft X-ray ptychography of magnetic domains – promises and limitations

We report on recent experimental work performed at the Advanced Photon Source (ALS) of an attempt to image in 3D a range of magnetic nanostructured thin films (~100nm thickness) including skyrmions, stripe and worm domains at nanometer resolution, with the aim to obtain maps of their domain wall structures at as high a resolution as possible. This experiment was motivated by the recent work of Donnelly et al, where hard X-ray vector tomography was performed to 100nm resolution on a micrometer thick sample. Our work was unfortunately limited by a lower than optimal source brightness, reducing the maximum resolution obtainable to the 20-40nm range, outside of what would be necessary to satisfactorily study the domain wall morphology. The Advanced Light Source however is a fairly mature instrument, and had this work been performed at SIRIUS, higher performance would have been expected due to diffraction limited coherent flux. A series of simulations will be presented to evaluate the expected possibilities of such an experiment at SIRIUS, looking at expected scattered photon counts for different magnetic samples and the resulting sample heating from high photon incidence, thus providing a realistic evaluation of experimental possibilities in the near future. (author)