Scientific Reports (May 2022)

Determination of sub-ps lattice dynamics in FeRh thin films

  • Michael Grimes,
  • Hiroki Ueda,
  • Dmitry Ozerov,
  • Federico Pressacco,
  • Sergii Parchenko,
  • Andreas Apseros,
  • Markus Scholz,
  • Yuya Kubota,
  • Tadashi Togashi,
  • Yoshikazu Tanaka,
  • Laura Heyderman,
  • Thomas Thomson,
  • Valerio Scagnoli

DOI
https://doi.org/10.1038/s41598-022-12602-w
Journal volume & issue
Vol. 12, no. 1
pp. 1 – 11

Abstract

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Abstract Understanding the ultrashort time scale structural dynamics of the FeRh metamagnetic phase transition is a key element in developing a complete explanation of the mechanism driving the evolution from an antiferromagnetic to ferromagnetic state. Using an X-ray free electron laser we determine, with sub-ps time resolution, the time evolution of the (–101) lattice diffraction peak following excitation using a 35 fs laser pulse. The dynamics at higher laser fluence indicates the existence of a transient lattice state distinct from the high temperature ferromagnetic phase. By extracting the lattice temperature and comparing it with values obtained in a quasi-static diffraction measurement, we estimate the electron–phonon coupling in FeRh thin films as a function of laser excitation fluence. A model is presented which demonstrates that the transient state is paramagnetic and can be reached by a subset of the phonon bands. A complete description of the FeRh structural dynamics requires consideration of coupling strength variation across the phonon frequencies.