Element Selective Probe of the Ultra-Fast Magnetic Response to an Element Selective Excitation in Fe-Ni Compounds Using a Two-Color FEL Source

  • Ferrari Eugenio
  • Spezzani Carlo
  • Fortuna Franck
  • Delaunay Renaud
  • Vidal Franck
  • Nikolov Ivaylo
  • Cinquegrana Paolo
  • Diviacco Bruno
  • Gauthier David
  • Penco Giuseppe
  • Ribič Rebernik
  • Roussel Eléonore
  • Trovò M
  • Moussy Jean-Baptiste
  • Pincelli Tommaso
  • Lounis Lounès
  • Svetina Cristian
  • Zangrando M
  • Mahne M
  • Raimondi Lorenzo
  • Manfredda M
  • Pedersoli Emanuele
  • Capotondi Flavio
  • Demidovich Alexander
  • Giannessi Luca
  • Kiskinova M
  • de Ninno Giovanni
  • Danailov Miltcho
  • Allaria Enrico
  • Sacchi Maurizio

  • Ultra-fast dynamics
  • Two-color source
  • Free electron laser

ART

The potential of the two-color mode implemented at the FERMI free-electron laser (FEL) source for pumping and probing selectively different atomic species has been demonstrated by time-resolved scattering experiments with permalloy (FeNi alloy) and NiFe$_2$O$_4$ samples. We monitored the ultra-fast demagnetization of Ni induced by the pump FEL pulse, by tuning the linearly-polarized FEL probe pulse to the Ni-3p resonance and measuring the scattered intensity in the transverse magneto-optical Kerr effect geometry. The measurements were performed by varying the intensity of the FEL pump pulse, tuning its wavelength to and off of the Fe-3p resonance, and by spanning the FEL probe pulse delays across the 300–900 fs range. The obtained results have evidenced that for the case of NiFe$_2$O$_4$, there is a sensible difference in the magnetic response at the Ni site when the pump pulse causes electronic excitations at the Fe site.