Berlin 2024 – scientific programme
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MA: Fachverband Magnetismus
MA 24: Terahertz Spintronics I
MA 24.2: Talk
Wednesday, March 20, 2024, 09:45–10:00, EB 202
Accessing ultrafast spin-transport dynamics in copper using broadband terahertz spectroscopy — •Reza Rouzegar1,3, Jiri Jechumtal2, Oliver Gueckstock1,3, Wolfgang Hoppe5, Quentin Remy1, Tom Seifert1, Georg Woltersdorf5, Piet Brouwer1, Markus Münzenberg4, Tobias Kampfrath1, and Lukas Nadvornik2 — 1Freie Universität Berlin — 2Charles University, Prague — 3Fritz-Haber-Institute, Berlin — 4Universität Greifswald — 5Martin-Luther-Universität Halle
We study femtosecond spin currents through Cu in CoFeB(2 nm)|Cu(d)| Pt(2 nm) stacks by terahertz emission spectroscopy. In our approach, spin currents are transmitted through a Cu(d) interlayer with thickness d and converted into a measurable charge current in Pt. The spin current jsd(t) vs time t behind the Cu layer exhibits an increasing delay and stronger dispersion when d increases [1]. Using an analytical dynamic-diffusion model, we can describe the spin current propagation for a spin velocity of 1.1 nm/fs, which agrees well with the Fermi velocity of Cu, and an electron scattering time of τ=4 ± 2 fs. In the framework of our model, we can separate ballistic and diffusive components of the spin current [1]. We conclude that, for thicknesses of d≥ 2 nm, the spin current is dominated by diffusive transport.
[1] J. Jechumtal, R. Rouzegar, et.al., arXiv:2310.12082 (2023).
Keywords: Spin transport; Diffusive and ballistic transport; Terahertz spectroscopy