A new way to control the magnetic properties of rare earth elements

The image shows the terbium orbitals between which the excitation takes placeand a schematic sketch of the excitation process.

The image shows the terbium orbitals between which the excitation takes placeand a schematic sketch of the excitation process. © HZB

The special properties of rare earth magnetic materials are due to the electrons in the 4f shell. Until now, the magnetic properties of 4f electrons were considered almost impossible to control. Now, a team from HZB, Freie Universität Berlin and other institutions has shown for the first time that laser pulses can influence 4f electrons- and thus change their magnetic properties. The discovery, which was made through experiments at EuXFEL and FLASH, opens up a new way to data storage with rare earth elements.

 

The strongest magnets we know of are based on rare earths. Their 4f electrons are responsible for their magnetic properties: they generate a large magnetic moment that is maintained even when their chemical environment changes. This means that rare earths can be used in very different compounds and alloys without changing their special magnetic properties. Until now, it was assumed that the magnetic properties of 4f electrons could not be changed even if the material was excited with a laser pulse. But indeed, this is possible, as a team from HZB, Freie Universität Berlin, DESY, the European X-ray laser XFEL and other institutions has now shown: The spatial arrangement of the 4f electrons can be briefly switched by laser excitation. This also changes their magnetism. This effect opens up new possibilities for the fast and energy-efficient control of magnetic rare-earth materials. The work has now been published in the journal Science Advances.

Terbium studied at the X-ray lasers EuXFEL and FLASH

The team carried out experiments at the X-ray lasers EuXFEL and FLASH and analysed samples of terbium, a rare earth element with atomic number 65 and a total of 8 electrons in 4f orbitals. The sample was excited with an ultrashort laser pulse and analysed by X-ray spectroscopy. The soft X-ray radiation used in the study is able to determine the electronic structure of a material very sensitively. The experiment shows that after laser excitation, 4f electrons briefly switch to an orbital with a different spatial distribution. This is due to a scattering process with 5d electrons, which had not been considered before. The redistribution of the 4f electrons by the laser excitation causes a brief switch in their magnetic properties.

Rare earth materials as data storage devices

This controlled switching opens up new applications for rare earth materials, such as energy-efficient and fast information storage devices. Until now, rare earths have not been used in magnetic storage media. The latest storage media are so-called HAMR (Heat-Assisted Magnetic Recording) data storage devices, in which magnetic structures are heated by a laser pulse in order to be switched by a magnet. With the much stronger rare-earth magnets, an ultrashort laser pulse could now excite the 4f electrons and enable switching - an electronic effect that would be even faster and more efficient than the heating mechanism in HAMR memory.

High-resolution spectroscopy with ultrashort X-ray pulses at BESSY II

This research has been made possible by the development of accelerator-based X-ray sources for generating ultrashort X-ray pulses in recent decades. These X-ray sources allow to observe elementary processes in magnetic materials on time scales of a few femtoseconds. A femtosecond (10-15 s) is one millionth of a billionth of a second. Light travels by about a hair's breadth in 300 femtoseconds.

The work was carried out at the European X-ray laser EuXFEL and at FLASH in Hamburg. The HZB also operates a short-pulse X-ray source, which will be expanded by the end of this year specifically for experiments with high spectroscopic resolution. BESSY II will then also offer optimal conditions for this type of experiment. Berlin is one of the world's leading centres for research into ultrafast magnetic effects.

Note: The work at Freie Universität, Technische Universität, HZB, Fritz-Haber-Institut and Max-Born-Institut together with partners in Halle is funded by the German Research Foundation as part of a Transregional Collaborative Research Centre (Transregio-SFB 227 "Ultrafast Spin Dynamics").

C. Schüssler-Langeheine/red.

  • Copy link

You might also be interested in

  • What vibrating molecules might reveal about cell biology
    Science Highlight
    16.10.2025
    What vibrating molecules might reveal about cell biology
    Infrared 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.
  • Perovskite solar cells from Germany are competing with China's PV technology - HZB 2025 Technology Transfer Award
    News
    15.10.2025
    Perovskite solar cells from Germany are competing with China's PV technology - HZB 2025 Technology Transfer Award
    Photovoltaics is the leading technology in the transition to clean energy. However, traditional silicon-based solar technology has reached its efficiency limit. Therefore, a HZB-team has developed a perovskite-based multi-junction cell architecture. For this, Kevin J. Prince and Siddhartha Garud received the Helmholtz-Zentrum Berlin's (HZB) Technology Transfer Prize of 5,000 euros.

  • Sasol and HZB deepen collaboration with strategic focus on digitalisation
    News
    08.10.2025
    Sasol and HZB deepen collaboration with strategic focus on digitalisation
    Sasol Research & Technology and Helmholtz Zentrum Berlin (HZB) are expanding their partnership into the realm of digitalisation, building on their joint efforts in the CARE-O-SENE project and an Industrial Fellowship launched earlier this year. This new initiative marks a significant step forward in leveraging digital technologies to accelerate catalyst innovation and deepen scientific collaboration.