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arXiv · 2310.18289

Non-thermal electrons open the non-equilibrium pathway of the phase transition in FeRh

Maximilian Mattern·Steffen Peer Zeuschner·Matthias Rössle·Jon Ander Arregi·Vojtěch Uhlíř·Matias Bargheer
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Abstract

We use ultrafast x-ray diffraction to study non-equilibrium pathways of the phase transition in FeRh parametrized by the structural response. By increasing the pump-pulse duration beyond the electron-phonon coupling time, we suppress the electron-phonon non-equilibrium present upon femtosecond laser excitation but still photoexcite electrons to non-thermal states. Irrespective of the pump pulse duration, we find an optically induced nucleation of ferromagnetic domains on an $8\,\text{ps}$ timescale that starts as soon as the successively deposited energy surpasses the site-specific threshold energy. If in contrast, FeRh is only indirectly excited by diffusion of thermalized electrons from an opaque Pt cap layer, the ferromagnetic phase rises on a $50\,\text{ps}$ timescale. These findings unambiguously identify the photo-excitation of non-thermal electrons and not electron-phonon non-equilibria to enable the non-equilibrium pathway of the phase transition in FeRh.

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Maximilian Mattern, Steffen Peer Zeuschner, Matthias Rössle, Jon Ander Arregi, Vojtěch Uhlíř, Matias Bargheer. 2023-10-27. Non-thermal electrons open the non-equilibrium pathway of the phase transition in FeRh. https://doi.org/10.1038/s42005-025-02066-5

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