Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 36: Focus Session: Ultrafast Spin, Lattice and Charge Dynamics of Solids

TT 36.4: Hauptvortrag

Freitag, 9. September 2022, 11:15–11:45, H10

Nanoscale transient magnetization dynamics: A comprehensive EUV TG study — •Laura Foglia — Elettra Sincrotrone Trieste, Trieste, Italy

The advent of X-ray free electron lasers (FELs) has allowed to overcome the wavelength limitations of optical radiation to manipulate and study magnetic phenomena on nanometer length- and femtosecond time-scale, which is paramount for light-controlled ultrafast magnetic data processing and storage applications. In this talk, we review the most recent advances on the EUV TG-based investigation of nanoscale transient magnetization dynamics, a technique pioneered at the FERMI FEL in Trieste, Italy. First, we show how EUV-TG is capable of inducing transient magnetization gratings which decay within tens of picoseconds via thermal diffusion. Building upon this first demonstration, we investigate the transition from ultrafast demagnetization to all-optical switching (AOS) by looking at the ratio between the first and the second order of diffraction as a function of excitation fluence. Indeed, the non-linear fluence dependence of AOS induces a non-uniform spacing of the magnetization pattern that results in the appearance of even diffraction orders. Finally, we compare the magnetization dynamics induced by intensity gratings with those launched by polarization gratings, obtained when the two excitation beams have orthogonal polarization. Here, the intensity distribution on the sample is uniform and ultrafast the formation of transient magnetization gratings has to be associated to the coupling of majority and minority spins with the electric field polarization.