First 3D visualisation of magnetic material structures
For the very first time, three-dimensional (3D) imaging of magnetic material structures is now possible. Detailed information of these structures - also known as domains - is of enormous importance for the development of magnetic memory and charging units. If the arrangement of the domain walls is chosen in such a way that energy losses caused by resetting are reduced to a minimum, the magnetic memory becomes more efficient.
Magnetic domains are hidden in almost all magnetic materials. They are microscopically small, magnetized areas. The scientific term of these areas is "Weiss domain" after the physicist Pierre-Ernest Weiss, who, based on theoretical considerations, postulated their existence as early as 1907.
Scientists of the BAM Working Group "X-ray topography", together with colleagues of the HZB Helmholtz Centre Berlin, have developed a non-destructive visualisation technique for the micron- to millimetre-sized Weiss domains by combining a new measurement method and a new algorithm. They have devised an inverted Talbot-Lau neutron tomography which provides high-contrast images of the magnetic domains non-destructively.
However, a tomographic reconstruction algorithm, developed at BAM, was the prerequisite of being able to process the measured data into 3D images with sufficient accuracy. The physicist Axel Lange, collaborator of the Working Group and inventor of the "DIRECTT" reconstruction, pioneered this work. The domains are imaged exactly in their spatial arrangement and can be measured - a formerly unresolved problem in materials science for many decades.
In view of the significance of magnetic domains in our incomplete understanding of the physical properties of magnetic materials and their engineering applications e.g. in storage media or in vehicle construction, the obtained results and methods open new perspectives for research and development. They have been published in the "Nature Communications" magazine (DOI: 10.1038/ncomms1125 (2010))