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MA: Fachverband Magnetismus

MA 31: Poster II

MA 31.21: Poster

Mittwoch, 19. März 2025, 17:00–19:30, P1

Ultrafast demagnetization via 4f-multiplet excitations in Terbium investigated by tr-ARPES — •Timo Dully, Gaurav Kshetry, Xinwei Zheng, Christian Strüber, and Martin Weinelt — Freie Universität Berlin

The magnetic properties of rare earth metals are governed by the localized electrons in the partially filled 4f electron shell and the interaction with the itinerant 3d electrons. Spin polarization of the 4f electrons decreases much faster in Terbium than in Gadolinium [1]. This has been attributed to enhanced coupling to the lattice caused by the anisotropic shape of the electronic wavefunction in Terbium. However, recent XMCD and RIXS experiments demonstrate an additional excitation pathway that is involved in drastically increasing the response of the magnetic system to optical excitation [2]. Scattering of optically excited 5d electrons with the 4f-subsystem allows for an efficient excitation of the 4f-multiplet.

In our time- and angle-resolved photoemission spectroscopy (tr-ARPES) setup using a hemispherical energy analyzer we measure the demagnetization of Tb as a function of time and fluence. We observe transient changes to the 4f photoemssion signal indicating a substantial excitation of the 4f-multiplet by energy transfer from the 5d valence electrons.

[1] B. Frietsch et al. Sci. Adv. 6(2020) eabb1601

[2] Nele Thielemann-Kühn et al., Sci. Adv. 10 (2024) eadk9522

Keywords: 4f-mulitplet; rare earth metal; ultrafast; magnetism; ARPES