Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 26: Ultrafast Magnetization Effects I

MA 26.9: Talk

Wednesday, March 19, 2025, 17:15–17:30, H16

Ultrafast energy-resolved spin dynamics in nickel — Christopher Seibel, Tobias Held, Markus Uehlein, •Sebastian T. Weber, and Baerbel Rethfeld — Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau

Magneto-optical methods were used when ultrafast magnetization dynamics were discovered and are still used intensively. Recent experiments show a strongly energy-dependent magneto-optic response and indicate spin transfer processes on the timescale of the pulse duration in a pure metallic ferromagnet [1].

We investigate the non-equilibrium spin dynamics on these early timescales by full spin-resolved Boltzmann collision integrals [2]. We trace the temporal evolution of the individual distribution functions of up and down electrons, where spin-flips due to electron-electron and electron-phonon collisions are taken into account.

From the dynamics of the distributions, we extract the spin-resolved densities of both, electrons and holes, at various energies. The energy-resolved spin polarization can vary significantly depending on the considered energy range. It can deviate from the overall magnetization dynamics, both in terms of the qualitative behavior and the timescales involved. Additionally, we present results on the non-equilibrium magneto-optic response calculated from the distribution functions.

[1] H. Probst et al., Phys. Rev. Res. 6, 013107 (2024)
[2] B. Müller et al., Phys. Rev. Lett. 111, 167204 (2013)

Keywords: ultrashort laser-excitation; non-equilibrium