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MA: Fachverband Magnetismus
MA 31: Poster II
MA 31.25: Poster
Wednesday, March 19, 2025, 17:00–19:30, P1
Ultrafast spin flop in Fe/Gd bilayers — Dominic Lawrenz1, Tim Amrhein1, Jonathan Weber1, Wibke Bronsch1, Niko Pontius2, Christian Schüßler-Langeheine2, Nele Thielemann-Kühn1, and •Martin Weinelt1 — 1Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin, Germany
Using time-resolved X-ray magnetic circular dichroism in reflection (XMCD-R) at the femtoslicing facility of BESSY II (Helmholtz-Zentrum Berlin) we studied ultrafast magnetization dynamics in an Fe(5 nm)/Gd(11 nm) bilayer on W(110). Structural and magnetic depth profiles of the bilayer were characterized by static Θ/2Θ XMCD-R scans. The magnetization M→ lies in-plane with antiparallel alignment of MFe→ and MGd→ at the Fe/Gd interface. At 300 K, Gd is magnetized only at the interface. Upon optical excitation Gd demagnetizes within 2 ps reaching a transient ferromagnetic state for ∼ 20 ps, comparable to simulations for Co/Gd in [1]. Close to the compensation temperature of 235 K, MFe→ = −MGd→ are oriented nearly perpendicular to the external field and twisted into the field direction with increasing distance to the interface. Upon optical excitation we observe a transient spin flop by 6∘ of the Gd magnetization within 300 fs. This is attributed to spin-transfer torque caused by ultrafast spin currents [2] and may hint to spin vacuum switching [3].
[1] M. Beens et al., Phys. Rev. B 100, 220409(R) (2019).
[2] B. Liu, H. Xiao, M. Weinelt, Sci. Adv. 9: eade0286 (2023).
[3] E. I. Harris-Lee et al., Sci. Adv. 10: eado6390 (2024).
Keywords: Fe/Gd bilayer; all-optical switching; ultrafast spip dynamics; XMCD