Nanoscale Transient Magnetization Gratings Created and Probed by Femtosecond Extreme Ultraviolet Pulses

Area of Science:

• Ultrafast magnetism
• Nanoscale science
• Materials science

Background:

• Understanding ultrafast magnetic dynamics is crucial for developing advanced magnetic storage and spintronic devices.
• Probing magnetic phenomena at the nanoscale requires advanced techniques capable of high spatial and temporal resolution.

Purpose of the Study:

• To develop and demonstrate a novel method for generating and probing transient magnetic gratings with nanometer periods.
• To investigate the ultrafast dynamics of electronic and magnetic excitations in a CoGd alloy using coherent extreme ultraviolet (EUV) pulses.

Main Methods:

• Utilized coherent femtosecond extreme ultraviolet (EUV) pulses from a free electron laser (FEL).
• Generated transient periodic magnetization patterns with periods as short as 44 nm.
• Employed resonant probing at the M-edge of cobalt to study electronic and magnetic excitations.

Main Results:

• Observed electronic excitation with a ~0.5 ps decay time in a demagnetized sample, indicating electron-phonon relaxation.
• Detected a magnetization grating appearing on a subpicosecond timescale in a magnetized sample.
• Demonstrated demagnetization at EUV intensity maxima, followed by decay via thermal diffusion over tens of picoseconds.

Conclusions:

• The developed technique enables the study of ultrafast magnetic phenomena on nanometer length scales.
• This approach provides new avenues for investigating the dynamics of magnetic materials with high spatial and temporal resolution.