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Light-matter interaction at the nanoscale in magnetic alloys and heterostructures is
a topic of intense research in view of potential applications in high-density magnetic recording. While the element-specific dynamics of electron spins is directly accessible to resonant x-ray pulses with femtosecond time structure, the possible element-specific atomic motion remains largely unexplored. We use ultrafast electron diffraction to probe the temporal evolution of lattice Bragg peaks of FePt nanoparticles embedded in a carbon matrix following excitation by an optical
femtosecond laser pulse. The diffraction interference between Fe and Pt sublattices enables us to demonstrate that the Fe mean-square vibration amplitudes are significantly larger that those of Pt as expected from their different atomic mass. Both are found to increase as energy is transferred from the laser-excited electrons to the lattice. Contrary to this intuitive behavior, we observe a laser-induced lattice expansion that is larger for Pt than for Fe atoms during the first picosecond
after laser excitation. This effect points to the strain-wave driven lattice expansion with the longitudinal acoustic Pt motion dominating that of Fe.

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• In Copyright
  

  This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Diego Turenne, Igor Vaskivskyi, Klaus Sokolowski-Tinten, Xijie J. Wang, Alexander H. Reid, Xiaozhe Shen, Ming-Fu Lin, Suji Park, Stephen Weathersby, Michael Kozina, Matthias C. Hoffmann, Jian Wang, Jakub Sebesta, Yukiko K. Takahashi, Oscar Grånäs, Peter M. Oppeneer, Hermann A. Dürr; Element-specific ultrafast lattice dynamics in FePt nanoparticles. Struct. Dyn. 1 November 2024; 11 (6): 064501 and may be found at https://doi.org/10.1063/4.0000260.

Keyword: ultra fast lattice dynamics, FePt, nanoparticles

Date published: 2024-11-01

Publisher: AIP Publishing

Journal:

• Structural Dynamics (ISSN: 23297778) vol. 11 issue. 6

Funding:

• Office of Science DE-AC02-76SF00515
• Vetenskapsrådet
• Deutsche Forschungsgemeinschaft 278162697
• Knut och Alice Wallenbergs Stiftelse 2022.0079
• Knut och Alice Wallenbergs Stiftelse 2023.336
• Knut och Alice Wallenbergs Stiftelse

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4948

First published URL: https://doi.org/10.1063/4.0000260

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Updated at: 2024-11-13 12:30:20 +0900

Published on MDR: 2024-11-13 12:30:20 +0900