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Unraveling ultrafast spin dynamics in optically excited multicomponent metallic systems using femtosecond XUV radiation - Marcel Hennes - Mercredi 22 septembre 2021 à 11 h

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-32, 2e étage, salle 201

Marcel Hennes, maître de conférences à l’INSP

Abstract

The discovery of ultrafast laser-induced magnetization quenching in ferromagnetic thin films [1] has laid the groundwork for a vibrant research field, femtomagnetism, which aims at understanding - and ultimately controlling - magnetization dynamics on sub-ps timescales. With the advent of new research facilities providing fs-pulses with wavelengths in the XUV and x-ray domain, pump-probe approaches have turned into element-selective tools that allow to unravel the ultrafast evolution of magnetic systems with nm resolution. While this has led to stunning advances, many results remain contradictory, which calls for additional systematic investigations.

In my talk, I will show recent data gathered at the free electron laser FERMI as well as experiments performed on high harmonic generation (HHG) setups. In the first part of my presentation, I will describe a novel streaking approach [2], which was employed to simultaneously analyze the evolution of charge and magnetic degrees of freedom in optically excited Ni/Fe thin films [3,4]. The second part of my talk will be devoted to amorphous CoTb and multilayered Co/Pt thin films, systems with large perpendicular magnetic anisotropy, exhibiting magnetic stripe structures. Using x-ray resonant magnetic scattering (XRMS) experiments, we studied the domain modification following ultrafast laser irradiation in an element selective fashion [5]. Our results challenge existing data and shed new light on the spatio-temporal evolution of spin structures in these multicomponent thin films that have been proposed as future building blocks for ultrafast data storage devices.

[1] E. Beaurepaire et al., Phys. Rev. Lett. 76 (1996) 4250 [2] E. Jal et al., Phys. Rev. B 99 (2019) 144305 [3] B. Roesner et al., Struct. Dyn. 7 (2020) 054302 [4] M. Hennes et al., Appl. Sci. 11 (2021) 325 [5] M. Hennes et al., Phys. Rev. B 102, (2020) 174437