Ultrafast magnetization dynamics in magnetically frustrated NiFe2O4 ferrimagnet

• NiFe2O4 shows complex dynamics between its elements after an ultrashort laser pulse excitation. The reflectivity shows oscillations, indicating either a reordering of the charge distribution several picoseconds after absorption of the laser pulse or a coherent phonon mode with a frequency of 0.5 THz. Also, the magnetic asymmetry exhibits oscillations that cannot be attributed to transverse magnetic excitations (magnons) but correspond to longitudinal excitations. The demagnetization shows different behavior depending on the excitation photon energy, for energies close to the band gap (1.55 eV) oscillations in the asymmetry are prominent, while for higher energies (3.1 eV) the demagnetization becomes dominant and the oscillations vanish. A fast demagnetization is observed when using 3.1 eV compared to 1.55 eV, while the electronic response remains similar, which indicates that the fast demagnetization dynamics is driven by holes created deeper in the valence band while the dynamics of electrons excited to d-states in the conduction band provides a smaller contribution to the demagnetization.The oscillations in the asymmetry can be a consequence of the competing exchange interactions that are antiferromagnetic between all three sublattices, but where a ferromagnetic alignment between octahedral Ni and octahedral Fe is the ground state.

Subject headings

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Keyword

Magnetic insulator

Time-resolved dynamics

ultrashort pulses

Physics with spec. in Atomic, Molecular and Condensed Matter Physics

Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik

Physics with spec. in Atomic, Molecular and Condensed Matter Physics

Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik

Physics with spec. in Atomic, Molecular and Condensed Matter Physics

Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik

Publication and Content Type

pop (subject category)

ovr (subject category)