New technique enables magnetic patterns to be mapped in 3D
Mapping of the captured magnetisation domains (right, red-blue patterns) in a sample 20 nanometres thick that had been wound in two layers into a tube. The tube has a diameter of 5 microns and a height of 50 microns. © F. Kronast/HZB
An international collaboration has succeeded in using synchrotron light to detect and record the complex 3D magnetisation in wound magnetic layers. This technique could be important in the development of devices that are highly sensitive to magnetic fields, such as in medical diagnostics for example. Their results are published now in Nature Communications.
3D structures in materials and biological samples can be investigated today using X-ray tomography. This is done by recording images layer-by-layer and assembling them on a computer into a three-dimensional mapping. But so far there has been no comparable technique for imaging 3D magnetic structures on nm length scales. Now teams from HZB and the Institut für Festkörperphysik / Technische Universität Dresden in collaboration with research partners from institutions in California (1) have developed a technique with which this is possible.
Mapping of rolled-up magnetic samples
They studied the magnetisation in rolled-up tubular magnetic nanomembranes (nickel or cobalt-palladium) about two layers thick. To obtain a 3D mapping of the magnetisation in the tubes, the samples were illuminated with circularly polarized X-rays. Using the X-ray microscope at the Advanced Light Source and the X-ray Photoemission Electron Microscopy (XPEEM) beamline at BESSY II, the samples were slightly rotated for each new image so that a series of 2D images was created. “The polarised light penetrated the magnetic layers from different angles. Using XPEEM, we were not only able to measure the magnetic features at the surface, but also obtained additional information from the “shadow”, explains Florian Kronast, who is responsible for the XPEEM beamline at HZB.
3D reconstruction of magnetic patterns
In the end, the physicists were successful in reconstructing the magnetic features on the computer in three dimensions.
“These samples displayed structures not smaller than 75 nanometres. But with this method we should be able to see even smaller structures and obtain a resolution of 20 nanometres”, explains Florian Kronast. However, so far only electron holography could be considered for mapping magnetic domains of three-dimensional objects at the nanometre scale. This required very complicated sample preparation and the magnetisation could only be indirectly determined through the resulting distribution of the magnetic field. “Our process enables you to map the magnetisation in directly in 3D. Knowledge of the magnetisation is prerequisite for improving the sensitivity of magnetic field detectors.”
Sensors for weak magnetic fields
The new method could be of interest to anyone involved with extremely small magnetic features within small volumes, such as those developing more sensitive devices for medical imaging, for example. Procedures like magnetoencephalography depend on externally detecting very weak magnetic fields created by the electrical activity of individual nerve cells – using appropriately sensitive detectors.
To the publication: Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Robert Streubel, Florian Kronast,Peter Fischer, Dula Parkinson, Oliver G. Schmidt & Denys Makarov. Nature Communications 6,7612, doi:10.1038/ncomms8612
(1): Advanced Light Source/Lawrence Berkeley National Laboratory, UC Santa Cruz
- Did marine life in the palaeocene use a compass?Some ancient marine organisms produced mysterious magnetic particles of unusually large size, which can now be found as fossils in marine sediments. An international team has succeeded in mapping the magnetic domains on one of such ‘giant magnetofossils’ using a sophisticated method at the Diamond X-ray source. Their analysis shows that these particles could have allowed these organisms to sense tiny variations in both the direction and intensity of the Earth’s magnetic field, enabling them to geolocate themselves and navigate across the ocean. The method offers a powerful tool for magnetically testing whether putative biological iron oxide particles in Mars samples have a biogenic origin.
- What vibrating molecules might reveal about cell biologyInfrared vibrational spectroscopy at BESSY II can be used to create high-resolution maps of molecules inside live cells and cell organelles in native aqueous environment, according to a new study by a team from HZB and Humboldt University in Berlin. Nano-IR spectroscopy with s-SNOM at the IRIS beamline is now suitable for examining tiny biological samples in liquid medium in the nanometre range and generating infrared images of molecular vibrations with nanometre resolution. It is even possible to obtain 3D information. To test the method, the team grew fibroblasts on a highly transparent SiC membrane and examined them in vivo. This method will provide new insights into cell biology.
- Technology Transfer Prize Ceremony 2025This year’s Technology Transfer Prize Ceremony will take place on October 13 at 2 pm in the Lecture Hall, BESSY II Building, Adlershof.