Element-specific ultrafast lattice dynamics in FePt nanoparticles
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 (UED) 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.
Authors
- Y. K. Takahashi (ORCID: https://orcid.org/0000-0001-9197-7236)
- Stephen Weathersby (ORCID: https://orcid.org/0000-0002-0253-4781)
- Matthias C. Hoffmann (ORCID: https://orcid.org/0000-0002-3596-9853)
- Jian Wang (ORCID: https://orcid.org/0000-0001-5553-303X)
- Ming‐Fu Lin (ORCID: https://orcid.org/0000-0001-8086-2484)
- Igor Vaskivskyi (ORCID: https://orcid.org/0000-0003-4090-1471)
- Xiaozhe Shen (ORCID: https://orcid.org/0000-0002-6844-608X)
- M. Kozina (ORCID: https://orcid.org/0000-0002-4747-345X)
- Jakub Šebesta (ORCID: https://orcid.org/0000-0002-8195-4353)
- Oscar Grånäs (ORCID: https://orcid.org/0000-0002-1482-2182)
- H. A. Dürr (ORCID: https://orcid.org/0000-0001-9680-8730)
- Diego Turenne (ORCID: https://orcid.org/0000-0001-5992-9699)
- Alexander H. Reid (ORCID: https://orcid.org/0000-0002-7587-295X)
- Peter M. Oppeneer (ORCID: https://orcid.org/0000-0002-9069-2631)
- Xijie Wang (ORCID: https://orcid.org/0000-0003-3324-4709)
- K. Sokolowski-Tinten (ORCID: https://orcid.org/0000-0002-7979-5357)
- Su Ji Park (ORCID: https://orcid.org/0000-0002-2269-7705)
Institutions
- Uppsala University (SE)
- TU Dortmund University (DE)
- National Institute for Materials Science (JP)
- SLAC National Accelerator Laboratory (US)
- Jožef Stefan Institute (SI)
- Linac Coherent Light Source (US)
- University of Duisburg-Essen (DE)
Publication Details
- Journal
- Structural Dynamics
- Published
- 2024-11-01
- DOI
- https://doi.org/10.1063/4.0000260
- Primary Topic
- Magnetic properties of thin films
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- U.S. Department of Energy
- Deutsche Forschungsgemeinschaft
- Knut och Alice Wallenbergs Stiftelse
- Vetenskapsrådet
- Office of Science
- Basic Energy Sciences
- SLAC National Accelerator Laboratory