Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy

Observing nanoscale dynamics with soft X-rays

Scientists at the Max Born Institute have developed a new soft-X-ray instrument that can reveal  dynamics of magnetic domains on nanometer length and picosecond time scales. By bringing capabilities once exclusive to X-ray free-electron lasers into the laboratory, the work paves the way for routine investigations of ultrafast processes of emergent textures in magnetic materials and beyond.

A dropped fridge magnet offers a simple glimpse into a complex physical phenomenon: although it appears undamaged on the outside, its holding force can weaken because its internal magnetic structure has reorganized into countless tiny regions with opposing magnetization, so-called magnetic domains. These nanoscale textures are central to modern magnetism research, but observing them at very short time scales has long required access to large-scale X-ray free-electron laser (XFEL) facilities.

Researchers at the Max Born Institute (MBI) have now developed a laboratory-scale soft-X-ray instrument capable of seeing these hidden structures with nanometer (10-9 m) spatial and picosecond (10-12 s) temporal resolution. Their work, published in Light: Science & Applications, shows that the ultrafast dynamics of magnetic domains can be tracked in great detail directly in the lab.

Soft X-rays combine exceptional sensitivity to magnetic order with element specificity and high spatial resolution. In a small-angle X-ray scattering (SAXS) geometry, real-space magnetic domain patterns are translated into intensity distributions in reciprocal space, see Fig. 1d, providing rich information about the long- and short-range order of complex magnetic textures.

Sketch of the laser-driven plasma source and the scattering setup

Fig 1: a Sketch of the laser-driven plasma source and the scattering setup. The SAXS pattern detected by a fast-readout area detector together with the direct beam is shown in panel (d). b Magnetic force microscopy image of the magnetic domain pattern in the Fe/Gd multilayer. c, d The time-resolved SAXS signal detected at the Gd M5 absorption edge (1189 eV photon energy). The composite image in (d) shows the sum of detector frames taken before laser excitation (left) and frames taken after laser excitation (right). For data analysis, the 2D detector frames are azimuthally integrated as shown in (c). 

Until now, ultrafast resonant SAXS in the soft-X-ray regime was available only at XFELs. The new MBI setup overcomes this limitation by pairing a laser-driven plasma X-ray source, see Fig 1a, with a dedicated single-photon–sensitive area detector. Operating at 100 Hz with 9-ps temporal resolution, the instrument achieves the stability and sensitivity needed to capture extremely weak diffuse scattering signals.

To demonstrate its capabilities, the team studied a ferrimagnetic Fe/Gd multilayer hosting nanoscale magnetic maze domains. By tuning the soft X-rays to absorption edges of Fe and Gd around 700 and 1200 eV, respectively, they mapped element-specific magnetization dynamics and discovered a previously unobserved, complex reorganization of the domain pattern on picosecond to nanosecond timescales — likely driven by inhomogeneity of the optical excitation within the sample.

“This instrument lets us observe magnetic order with a level of detail that previously required a free-electron laser,” says Leonid Lunin, one of the study’s sharing first-authors. “Now we can do it every day, directly in the laboratory.”

Thanks to its flexibility and photon efficiency, the platform enables systematic studies involving variations in magnetic field, temperature, excitation fluence, or photon energy—measurements that are currently difficult or impossible at most large-scale facilities.

Looking ahead, the authors anticipate further increases in photon flux and sensitivity using next-generation laser and detector technology. Such upgrades could make multidimensional scans and advanced excitation schemes routine, opening new avenues for studying emergent phases, in a broad range of complex materials.

Original publication

Laser-driven resonant soft-X-ray scattering for probing picosecond dynamics of nanometre-scale order

L. Lunin,  M. Borchert,  N. Schneider,  K. Korell,  M. Schneider,  D. Engel,  Stefan Eisebitt,  B. Pfau,  D. Schick

 Light: Science & Applications 14 (2025) 394/1-9

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