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Element-specific ultrafast lattice dynamics in FePt nanoparticles

Journal Article · · Structural Dynamics
DOI:https://doi.org/10.1063/4.0000260· OSTI ID:2565517
 [1];  [2];  [3];  [4];  [5];  [5];  [5];  [5];  [6];  [5];  [5];  [7];  [1];  [7];  [1];  [1];  [1]
  1. Uppsala University (Sweden)
  2. Uppsala University, (Sweden); Jozef Stefan Institute (IJS), Ljubljana (Slovenia)
  3. University of Duisburg-Essen (Germany)
  4. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); University of Duisburg-Essen (Germany); Technische Universität of Dortmund (Germany)
  5. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Linac Coherent Light Source (LCLS)
  6. SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
  7. National Institute for Materials Science (NIMS), Tsukuba (Japan)
+ Show Author Affiliations
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.
Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
Knut and Alice Wallenberg Foundation (KAW); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
2565517
Alternate ID(s):
OSTI ID: 2566331
Journal Information:
Structural Dynamics, Journal Name: Structural Dynamics Journal Issue: 6 Vol. 11; ISSN 2329-7778
Publisher:
American Crystallographic Association/AIPCopyright Statement
Country of Publication:
United States
Language:
English

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36 MATERIALS SCIENCE