In addition, these distortions are distinctly nonlinear in pump fluence with a threshold, reminiscent of the threshold behavior for driven domain wall motion. Specifically, we observe nontrivial distortions in the shape of magnetic diffraction patterns depending on the symmetry of the magnetic domain pattern. Surprisingly, we found that the spatial symmetry of spin textures affects ultrafast spatial dynamics at the nm length scale. I will focus on some of our recent results obtained at the European XFEL and FERMI that demonstrate how spin textures are spatially perturbed under ultrafast optical pumping conditions. I will highlight some of the intriguing data obtained in the recent years with x-ray/EUV free electron lasers (FELs) that hint at the rich variety of magnetic behavior at the frontier of the ultrafast and ultra-small. These and many other experimental findings in ultrafast spin dynamics are now possible due to emerging coherent x-ray/EUV sources that combine the power of x-rays with fs time resolution. However, it has been recently recognized that spatial domain pattern and nanoscale heterogeneities can play a critical role in dictating the ultrafast behavior.
There is an explosive increase in studies that aim to understand the mechanisms of photon-driven spin dynamics at such short time-scales.
Ultrafast control of magnetization with light holds the promise of being a new paradigm for the next generation memory and data storage devices.
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