Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 22: Terahertz spintronics

MA 22.7: Vortrag

Dienstag, 2. April 2019, 15:30–15:45, H52

Exchange stiffness of terahertz spin waves in iron — •Liane Brandt¹, Niklas Liebing¹, Ilya Razdolski², Georg Woltersdorf¹, and Alexey Melnikov¹ — ¹Martin Luther University Halle-Wittenberg, Institute of Physics — ²Fritz Haber Institute of the Max Planck Society, Department of Physical Chemistry

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 (STT) 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 THz by continuously reducing the thickness of collector Fe layer from 17 to 1 nm. By analyzing the exchange stiffness of the first five PSSW modes we observe its decrease with decreasing collector thickness down to 50% for the thinnest collector, compared to the literature value of Fe. To model this stiffness behavior in Fe, we introduce modifications of the exchange interaction in the vicinity of the interfaces, and obtain important insights into the physics of itinerant ferromagnets by means of micromagnetic simulations using mumax3.

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

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