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arXiv · 2103.06029

Probing optical spin-currents using THz spin-waves in noncollinear magnetic bilayers

Tom Lichtenberg·Maarten Beens·Menno H. Jansen·Rembert A. Duine·Bert Koopmans
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Abstract

Optically induced spin currents have proven to be useful in spintronics applications, allowing for sub-ps all-optical control of magnetization. However, the mechanism responsible for their generation is still heavily debated. Here we use the excitation of spin-current induced THz spin-waves in noncollinear bilayer structures to directly study optical spin-currents in the time domain. We measure a significant laser-fluence dependence of the spin-wave phase, which can quantitatively be explained assuming the spin current is proportional to the time derivative of the magnetization. Measurements of the absolute spin-wave phase, supported by theoretical calculations and micromagnetic simulations, suggest that a simple ballistic transport picture is sufficient to properly explain spin transport in our experiments and that the damping-like optical STT dominates THz spin-wave generation. Our findings suggest laser-induced demagnetization and spin-current generation share the same microscopic origin.

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Tom Lichtenberg, Maarten Beens, Menno H. Jansen, Rembert A. Duine, Bert Koopmans. 2021-03-10. Probing optical spin-currents using THz spin-waves in noncollinear magnetic bilayers. https://doi.org/10.1103/physrevb.105.144416

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