Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity

Area of Science:

• Ultrafast magnetism
• Materials science
• X-ray physics

Background:

• Models for ultrafast demagnetization involve local or non-local angular momentum transfer.
• Distinguishing these effects requires high-resolution magnetic depth profiling.

Purpose of the Study:

• To demonstrate time-resolved x-ray resonant magnetic reflectivity for femtosecond magnetic depth profiling.
• To investigate ultrafast demagnetization dynamics in magnetic thin films.

Main Methods:

• Utilized a pump-probe setup with a custom reflectometer at the FLASH2 free-electron laser (FEL).
• Employed the third harmonic of the FEL to probe near the Fe L3 edge of a magnetic thin film.
• Applied time-resolved x-ray resonant magnetic reflectivity to capture magnetic depth profiles.

Main Results:

• Observed two distinct dynamics on different timescales.
• Revealed non-homogeneous loss of magnetization.
• Detected a significant layer dilation (2 Å) followed by oscillations.

Conclusions:

• The technique is feasible for studying ultrafast demagnetization.
• Results indicate complex, non-homogeneous dynamics govern magnetization quenching.
• Future analysis will provide quantitative transient magnetic depth profiles.