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MA: Fachverband Magnetismus

MA 9: Ultrafast Magnetization Effects II

MA 9.2: Talk

Monday, March 18, 2024, 15:30–15:45, H 2013

Ultrafast demagnetization dynamics in Fe studied by tr-ARPES — •Xinwei Zheng, Christian Strüber, and Martin Weinelt — Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin

We investigate the ultrafast magnetization dynamics of Fe(110) on W(110) by time- and angle-resolved photoemission spectroscopy (tr-ARPES) with an IR pump pulse and a high-order harmonic XUV probe pulse. After laser excitation, transient changes to the band structure with tr-ARPES are observed. In contrast to a small reduction of the exchange splitting by only 3%, the magnetic linear dichroism signal calculated from the asymmetry between spectra for two opposite in-plane magnetization directions drops by 60% within 150 fs. This result proves that spin-mixing dominates the ultrafast demagnetization dynamics in Fe [1]. Moreover, we measure a stronger reduction of the asymmetry in the minority spin band close below the Fermi level compared to that in the majority spin band at a binding energy of 0.3 eV. This indicates that the spin system in Fe is out of equilibrium for about 1-2 ps after laser excitation [2]. The pump-fluence dependence of the MLD signal and the electronic temperature implies that a significant amount of energy is transferred into the spin system within 150 fs, leading to spin excitations particularly within the minority spin band.

[1] E. Carpene et al., Phys. Rev. B. 78, 174422 (2008)

[2] R. Gort et al., Phys. Rev. Lett. 121, 087206 (2018)

Keywords: tr-ARPES; Iron