Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 63: Spin: Transport, Orbitronics and Hall Effects III
MA 63.9: Talk
Friday, March 20, 2020, 11:45–12:00, HSZ 403
Effective damping of terahertz spin-wave modes in iron — •Liane Brandt1, Niklas Liebing1, Ilya Razdolski2, Roman Verba3, Vasyl Tyberkevych4, Andrei Slavin4, Georg Woltersdorf1, and Alexey Melnikov1 — 1Martin Luther University Halle-Wittenberg, Institute of Physics, Halle (Saale), Germany — 2Fritz Haber Institute of the Max Planck Society, Department of Physical Chemistry, Berlin, Germany — 3Institute of Magnetism, Kyiv, Ukraine — 4Oakland University, Department of Physics, Rochester, USA
Recently, we have demonstrated the excitation of perpendicular standing spin waves (PSSW) in Fe/Au/Fe tri-layers 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 exerted by 250 fs-short spin current pulses generated in the optically excited emitter Fe layer [2]. The frequency of the PSSWs is tuned up to 2.5 THz by continuously reducing the thickness of collector Fe layer from 17 to 1 nm.
By analyzing the effective damping of the PSSW modes we observe an increase by two orders of magnitude in effective damping with increasing wave number. While the Gilbert damping is independent on the wave number, we can describe the increase in effective damping by the k-dependent spin diffusion term. Additional effects due to interfaces, defects in the volume and spin pumping appear to be small.
[1] I. Razdolski et al., Nat. Comm. 8, 15007 (2017)
[2] A. Alekhin et al., PRL 119, 017202 (2017)