Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

Abstract

X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L${}_{3,2}$-edges. This new ultrafast time-resolved capability is then applied to a fluence-dependent study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature. At the magnetic switching fuence, we corroborate the existence of a transient ferromagnetic-like state. The timescales of the dynamics, however, are longer than previously observed below the magnetization compensation temperature. Above and below the switching fluence range, we observe secondary demagnetization with about 5 ps timescales. This indicates that the spin thermalization takes longer than 5 ps.

arXiv comment5 pages, 4 figures

References in corpus (6)

• All-optical control of ferromagnetic thin films and nanostructures
• Band-selective Measurement of Electronic Dynamics in VO2 using Femtosecond Near Edge X-ray Absorption
• Statistical and coherence properties of radiation from X-ray free electron lasers
• Influence of laser-excited electron distributions on the x-ray magnetic circular dichroism spectra: Implications for femtosecond demagnetization in Ni
• Role of critical spin fluctuations in ultrafast demagnetization of transition-metal rare-earth alloys
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• Megahertz-rate Ultrafast X-ray Scattering and Holographic Imaging at the European XFEL
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• Laser induced ultrafast Gd 4f spin dynamics in Co100-xGdx alloys by means of time-resolved XMCD
• Time-Resolved XUV absorption spectroscopy and magnetic circular dichroism at the Ni $M_{2,3}$-edges
• Recent Progress in Ultrafast Dynamics of Transition-Metal Compounds Studied by Time-Resolved X-ray Techniques