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MA: Fachverband Magnetismus

MA 49: Terahertz dynamics

MA 49.5: Vortrag

Donnerstag, 15. März 2018, 16:00–16:15, EB 202

Terahertz laser-induced spin waves in metallic multilayers: tuning the frequencies — •Liane Brandt¹, Mirko Ribow¹, Niklas Liebing¹, Ilya Razdolski², Georg Woltersdorf¹, and Alexey Melnikov^1,2 — ¹Martin Luther University Halle-Wittenberg, Institute of Physics — ²Fritz Haber Institute of the Max Planck Society, Department of Physical Chemistry

Recently, in Fe/Au/Fe tri-layers we have demonstrated the excitation of sub-THz perpendicular standing spin waves (PSSW) in the 14 nm-thick Fe layer studied by the time-resolved magneto-optical Kerr effect in a back pump-front probe scheme [1]. This high-frequency spin dynamic is driven by interface-confined spin transfer torque (STT) exerted by 250 fs-short spin current pulses generated in the optically excited opposite Fe layer [2]. To tune the PSSW frequencies, we fabricated an epitaxial Fe/Au/Fe structure with continuously varying Fe collector thickness from 1 to 17 nm. We demonstrate efficient STT-driven excitation of PSSWs with frequencies up to 2 THz corresponding to spin-wavelengths of 2 nm. Signatures of the higher-order PSSWs with even higher frequencies (up to 5 THz) are also observed. We analyze the PSSW dispersion, damping, and amplitudes in the time domain as well as their dependence on the collector thickness and discuss new insights into the STT-induced THz spin dynamics.

[1] I. Razdolski et al., Nature Commun. 8, 15007 (2017)

[2] A. Alekhin et al., PRL 119, 017202 (2017)