Extreme Domain Wall Speeds under Ultrafast Optical Excitation

Area of Science:

• Condensed matter physics
• Ultrafast magnetism
• Materials science

Background:

• Domain walls in magnetic materials are crucial for data storage technologies.
• Theoretical predictions suggest domain wall speeds can exceed 10 km/s under specific conditions.
• Understanding ultrafast domain wall dynamics is key to advancing magnetic device performance.

Purpose of the Study:

• To experimentally investigate ultrafast domain wall speeds in magnetic materials.
• To test theoretical predictions of extreme domain wall velocities.
• To explore the mechanisms governing non-equilibrium domain wall motion.

Main Methods:

• Utilized time-resolved ultrafast extreme ultraviolet (EUV) magnetic scattering.
• Optically excited a magnetic sample with a nanoscale labyrinthine domain pattern.
• Analyzed diffraction pattern distortions and magnetization quenching dynamics.

Main Results:

• Observed ultrafast diffraction pattern distortion at distinct timescales from magnetization quenching.
• Diffraction pattern distortion exhibited a threshold dependence on laser fluence, unlike magnetization quenching.
• Experimental data, supported by simulations, indicated domain wall speeds of approximately 66 km/s for curved walls.

Conclusions:

• Experimental data support predictions of locally extreme, non-equilibrium domain wall speeds.
• Observed threshold dependence suggests the influence of pinning sites on domain wall motion.
• Discrepancies with theoretical details indicate the need for further investigation into underlying mechanisms.