Transient magnetic gratings on the nanometer scale

Area of Science:

• Condensed matter physics
• Ultrafast magnetism
• Nanoscale science

Background:

• Laser-driven electron dynamics in ultrathin magnetic films are crucial for ultrafast magnetism.
• Experimental investigation of these nanoscopic, femtosecond processes remains challenging.

Purpose of the Study:

• To develop and demonstrate a new scattering-based technique for investigating non-local magnetization dynamics.
• To probe electron and spin transport on nanometer length and femtosecond timescales.

Main Methods:

• Utilized a laser-induced electro- and magneto-optical grating in a Co/Pd ferromagnetic multilayer.
• Employed tailored Al near-field masks with nanometer periodicities for spatially modulated excitation.
• Performed x-ray scattering experiments with magnetic circular dichroism contrast at the FERMI free-electron laser.

Main Results:

• Achieved sub-wavelength in-plane sensitivity for magnetic structures using a periodic excitation mask.
• Observed a strongly enhanced and characteristic transient scattering response.
• Inferred confinement of ultrafast lateral expansion to below three nanometers.

Conclusions:

• The developed scattering technique provides unprecedented access to ultrafast non-local dynamics.
• Hot-electron and spin transport in these systems are highly localized.
• This method opens new avenues for studying nanoscale phenomena in magnetic materials.