Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 35: Poster 2

MA 35.29: Poster

Thursday, September 8, 2022, 16:00–18:00, P4

Spin-transport-driven ultrafast magnetization dynamics in a ferrimagnetic Gd/Fe bilayer — •Huijuan Xiao, Bo Liu, and Martin Weinelt — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195, Berlin

Laser-induced spin transport has been proven to be a key ingredient in ultrafast spin dynamics, such as femtosecond demagnetization and all-optical switching (AOS). We use time- and spin-resolved photoemission spectroscopy of the gadolinium surface state to study spin dynamics in a ferrimagnetic Gd/Fe bilayer. This prototype system for AOS was epitaxially grown on W(110). Our findings suggest that spin transport between the antiferromagnetically coupled gadolinium and iron layers leads to an ultrafast drop of the spin polarization and an increased exchange splitting at the Gd surface. The Gd surface state shows an ultrafast decrease of the spin polarization by 20% within the first ∼100 fs and a subsequent slower decrease by about 5% on the picosecond timescale. The increase of the exchange splitting counterbalances the overall demagnetization of the Gd layer. In contrast, the pure Gd/W(110) film shows a constant spin polarization and a reduced exchange splitting of the surface state upon optical excitation. These findings are corroborated by the transient electron temperature. Our results provide clear evidence that magnetization dynamics in the Gd/Fe bilayer can be driven by spin transport. We see distinct signatures in the spin-dependent electronic structure that allow us to gain microscopic insights into ultrafast spin dynamics (supported by SFB/TRR 227 Ultrafast Spin Dynamics).