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X-ray detection of ultrashort spin current pulses in synthetic antiferromagnets

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Stamm C., Murer C., Wörnle M. S., Acremann Y., Gort R., Däster S., Reid A. H., Higley D. J., Wandel S. F., Schlotter W. F., Gambardella P.,
Project Spin-orbitronics in ferromagnets and antiferromagnets
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Original article (peer-reviewed)

Journal Journal of Applied Physics
Volume (Issue) 127(22)
Page(s) 223902 - 223902
Title of proceedings Journal of Applied Physics
DOI 10.1063/5.0006095

Open Access

URL https://arxiv.org/abs/2006.11030
Type of Open Access Repository (Green Open Access)

Abstract

We explore the ultrafast generation of spin currents in magnetic multilayer samples by applying fs laser pulses to one layer and measuring the magnetic response in the other layer by element-resolved x-ray spectroscopy. In Ni(5 nm)/Ru(2 nm)/Fe(4 nm), the Ni and Fe magnetization directions couple antiferromagnetically due to the Ruderman–Kittel–Kasuya–Yosida interaction but may be oriented parallel through an applied magnetic field. After exciting the top Ni layer with a fs laser pulse, we also find that the Fe layer underneath demagnetizes, with a 4.1±1.9% amplitude difference between parallel and antiparallel orientation of the Ni and Fe magnetizations. We attribute this difference to the influence of a spin current generated by the fs laser pulse that transfers angular momentum from the Ni into the Fe layer. Our results confirm that superdiffusive spin transport plays a role in determining the sub-ps demagnetization dynamics of synthetic antiferromagnetic layers, but also evidence large depolarization effects due to hot electron dynamics, which are independent of the relative alignment of the magnetization in Ni and Fe.
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