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arXiv · 1511.07372

Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

Daniel J. Higley·Konstantin Hirsch·Georgi L. Dakovski·Emmanuelle Jal·Edwin Yuan·Tianmin Liu·Alberto A. Lutman·James P. MacArthur·Elke Arenholz·Zhao Chen·Giacomo Coslovich·Peter Denes·Patrick W. Granitzka·Philip Hart·Matthias C. Hoffmann·John Joseph·Loïc Le Guyader·Ankush Mitra·Stefan Moeller·Hendrik Ohldag·Matthew Seaberg·Padraic Shafer·Joachim Stöhr·Arata Tsukamoto·Heinz-Dieter Nuhn·Alex H. Reid·Hermann A. Dürr·William F. Schlotter
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Abstract

X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L$_{3,2}$-edges. This new ultrafast time-resolved capability is then applied to a fluence-dependent study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature. At the magnetic switching fuence, we corroborate the existence of a transient ferromagnetic-like state. The timescales of the dynamics, however, are longer than previously observed below the magnetization compensation temperature. Above and below the switching fluence range, we observe secondary demagnetization with about 5 ps timescales. This indicates that the spin thermalization takes longer than 5 ps.

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Daniel J. Higley, Konstantin Hirsch, Georgi L. Dakovski, Emmanuelle Jal, Edwin Yuan, Tianmin Liu, Alberto A. Lutman, James P. MacArthur, Elke Arenholz, Zhao Chen, Giacomo Coslovich, Peter Denes, Patrick W. Granitzka, Philip Hart, Matthias C. Hoffmann, John Joseph, Loïc Le Guyader, Ankush Mitra, Stefan Moeller, Hendrik Ohldag, Matthew Seaberg, Padraic Shafer, Joachim Stöhr, Arata Tsukamoto, Heinz-Dieter Nuhn, Alex H. Reid, Hermann A. Dürr, William F. Schlotter. 2015-11-23. Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser. https://doi.org/10.1063/1.4944410

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