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arXiv · 2502.02240

Femtosecond charge and spin dynamics in CoPt alloys

Martin Pavelka·Simon Marotzke·Ru-Pan Wang·Mohamed F. Elhanoty·Günter Brenner·Siarhei Dziarzhytski·Somnath Jana·W. Dieter Engel·Clemens v. Korff Schmising·Deeksha Gupta·Igor Vaskivskyi·Tim Amrhein·Nele Thielemann-Kühn·Martin Weinelt·Ronny Knut·Juliane Rönsch-Schulenberg·Evgeny Schneidmiller·Christian Schüßler-Langeheine·Martin Beye·Niko Pontius·Oscar Grånäs·Hermann A. Dürr
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Abstract

The use of advanced X-ray sources plays a key role in the study of dynamic processes in magnetically ordered materials. The progress in X-ray free electron lasers enables the direct and simultaneous observation of the femtosecond evolution of electron and spin systems through transient X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD), respectively. Such experiments allow us to resolve the response seen in the population of the spin-split valence states upon optical excitation. Here, we utilize circularly polarized ultrashort soft X-ray pulses from the new helical afterburner undulator at the free-electron laser FLASH in Hamburg to study the femtosecond dynamics of a laser-excited CoPt alloy at the Co $L_{3}$ absorption edge. Despite employing a weaker electronic excitation level we find a comparable demagnetization for the Co $3d$-states in CoPt compared to previous measurements on CoPd. This is attributed to distinctly different orbital hybridization and spin-orbit coupling between $3d$ and $4d$ vs. $3d$ and $5d$ elements in the corresponding alloys and multilayers.

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Martin Pavelka, Simon Marotzke, Ru-Pan Wang, Mohamed F. Elhanoty, Günter Brenner, Siarhei Dziarzhytski, Somnath Jana, W. Dieter Engel, Clemens v. Korff Schmising, Deeksha Gupta, Igor Vaskivskyi, Tim Amrhein, Nele Thielemann-Kühn, Martin Weinelt, Ronny Knut, Juliane Rönsch-Schulenberg, Evgeny Schneidmiller, Christian Schüßler-Langeheine, Martin Beye, Niko Pontius, Oscar Grånäs, Hermann A. Dürr. 2025-02-04. Femtosecond charge and spin dynamics in CoPt alloys. https://doi.org/10.1063/4.0000297

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