FEATURE ARTICLE Magnetic X-ray tomography: 3D mapping with nanoscale resolution The experimental technique of magnetic X-ray tomography employed in this study draws on a basic principle from computer tomography (CT). Similar to medical CT scans, many X-ray images of the sample are taken one after the other from many different directions with a small angle in-between adjacent images. The measurements were carried out at the cSAXS beamline of the synchrotron light source SLS at PSI using advanced instrumentation for X-ray nanotomography under the OMNY project and a recently developed imaging technique called ptychography. Employing computer calculations and a novel reconstruction algorithm developed at PSI, all of the data collected this way was combined to form the final 3D map of the magnetisation. The scientists employed so-called 'hard' X-rays from the SLS at PSI. In comparison with 'soft' X-rays, hard X-rays have higher energy. Lower energy soft X-rays have already very successfully been used to achieve a similar map of the magnetic moments, Claire Donnelly explains. But soft X-rays hardly penetrate such samples so you can only use them to see the magnetisation of a thin film or at the surface of a bulk object. In order to really dive inside their magnet, the PSI scientists chose hard X-rays of higher energy, at the price of obtaining a much weaker signal: Many people did not believe that we would be able to achieve this 3D magnetic imaging with hard X-rays, Laura Heyderman recalls. Representation of a Bloch point which the scientists found in their data. A Bloch point contains a magnetic singularity at which the magnetisation abruptly changes its direction. Within the Bloch point shown here, this change of direction is from upward pointing magnetic needles - visualised by arrows - to downward pointing ones. This singularity is surrounded by a swirling magnetisation pattern which is analogous to the structure of a tornado. (Graphics: Paul Scherrer Institute/Claire Donnelly) (Right) Laura Heyderman, Claire Donnelly and Sebastian Gliga are part of a team of scientists who for the first time have succeeded in imaging the internal magnetic structure of a 3D object. (Photo: Paul Scherrer Institute/Markus Fischer) www.MagneticsMag.com Winter 2017 * Magnetics Business & Technology 13http://www.newenglandwire.com http://www.MagneticsMag.com