First experiments with ultrashort, circularly polarized soft x-ray pulses at FLASH2
/ Authors
S. Marotzke, D. Gupta, R.-P. Wang, M. Pavelka, S. Dziarzhytski, C. von Korff Schmising, S. Jana, N. Thielemann-Kühn, T. Amrhein, M. Weinelt
and 16 more authors
I. Vaskivskyi, R. Knut, D. Engel, M. Braune, M. Ilchen, S. Savio, T. Otto, K. Tiedtke, V. Scheppe, J. Rönsch-Schulenberg, E. Schneidmiller, C. Schüßler-Langeheine, H. Dürr, M. Beye, G. Brenner, N. Pontius
/ Abstract
Time-resolved absorption spectroscopy and magnetic circular dichroism with circularly polarized soft x-rays (XAS and XMCD) are powerful tools to probe electronic and magnetic dynamics in magnetic materials element- and site-selectively. By employing these methods, groundbreaking results have been obtained, for instance, for magnetic alloys, which helped to fundamentally advance the field of ultrafast magnetization dynamics. At the free-electron laser facility FLASH, key capabilities for ultrafast XAS and XMCD experiments have recently improved. In an upgrade, an APPLE-III helical afterburner undulator was installed at FLASH2 in September 2023. This installation allows for the generation of circularly polarized soft x-ray pulses with a duration of a few tens of femtoseconds covering the L3,2-edges of the important 3d transition metal elements with pulse energies of several μJ. Here, we present first experimental results with such ultrashort x-ray pulses from the FL23 beamline employing XMCD at the L3,2-edges of the 3d metals, Co, Fe, and Ni. We obtain significant dichroic difference signals indicating a degree of circular polarization close to 100%. With the pulse-length preserving monochromator at beamline FL23 and an improved pump-laser setup, FLASH can offer important and efficient experimental instrumentation for ultrafast demagnetization studies and other investigations of ultrafast spin dynamics in 3d transition metals, multilayers, and alloys.
Journal: Structural Dynamics
DOI: 10.1063/4.0000298