Keywords: BESSY II (269) spintronics (93) HZB own research (99)

News    07.07.2015

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.
Copyright: 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



You might also be interested in
  • <p>Experiments at the femtoslicing facility of BESSY II revealed the ultrafast angular momentum flow from Gd and Fe spins to the lattice via orbital moment during demagnetization of GdFe alloy.</p>SCIENCE HIGHLIGHT      10.05.2019

    Laser-driven Spin Dynamics in Ferrimagnets: How does the Angular Momentum flow?

    When exposed to intense laser pulses, the magnetization of a material can be manipulated very fast. Fundamentally, magnetization is connected to the angular momentum of the electrons in the material. A team of researchers led by scientists from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) has now been able to follow the flow of angular momentum during ultrafast optical demagnetization in a ferrimagnetic iron-gadolinium alloy at the femtoslicing facility of BESSY II. Their results are helpful to understand the fundamental processes and their speed limits. The study is published in Physical Review Letters. [...]

  • <p>A green laser pulse initially excites the electrons in the Cu<sub>2</sub>O; just fractions of a second later, a second laser pulse (UV light) probes the energy of the excited electron.</p>SCIENCE HIGHLIGHT      09.05.2019

    Copper oxide photocathodes: laser experiment reveals location of efficiency loss

    Solar cells and photocathodes made of copper oxide might in theory attain high efficiencies for solar energy conversion. In practice, however, large losses occur. Now a team at the HZB has been able to use a sophisticated femtosecond laser experiment to determine where these losses take place: not so much at the interfaces, but instead far more in the interior of the crystalline material. These results provide indications on how to improve copper oxide and other metal oxides for applications as energy materials. [...]

  • <p>Tomography of a lithium electrode in its initial condition.</p>SCIENCE HIGHLIGHT      06.05.2019

    3D tomographic imagery reveals how lithium batteries age

    Lithium batteries lose amp-hour capacity over time. Microstructures can form on the electrodes with each new charge cycle, which further reduces battery capacity. Now an HZB team together with battery researchers from Forschungszentrum Jülich, the University of Munster, and partners in China have documented the degradation process of lithium electrodes in detail for the first time. They achieved this with the aid of a 3D tomography process using synchrotron radiation at BESSY II (HZB) as well at the Helmholtz-Zentrum Geesthacht (HZG). Their results have been published open access in the scientific journal "Materials Today". [...]