Femtosecond time-resolved magneto-optical Kerr effect spectroscopy using a resistive 25 T magnet

Area of Science:

• Condensed Matter Physics
• Materials Science
• Ultrafast Magnetism

Background:

• Understanding magnetization dynamics is crucial for developing advanced magnetic materials and devices.
• High magnetic fields and ultrafast time resolution are essential for probing complex magnetic phenomena.

Purpose of the Study:

• To demonstrate a novel experimental technique for measuring magnetization dynamics at femtosecond timescales using high magnetic fields.
• To investigate the spin dynamics of (FeCo)1-xGdx ferrimagnetic alloys under various magnetic field orientations.

Main Methods:

• Utilized a split helix resistive magnet to generate magnetic fields up to 25 T.
• Employed time-resolved magneto-optic Kerr effect (TR-MOKE) spectroscopy with ultrafast lasers.
• Analyzed magnetization dynamics at magnetic field orientations perpendicular, parallel, and 20° off the sample plane.

Main Results:

• Observed distinct magnetization dynamics dependent on the external magnetic field alignment relative to the alloy's magnetization.
• Measured magnetization oscillation frequencies increasing linearly with magnetic field strength, reaching 500 GHz at 20 T.
• Identified a 180° phase shift in dynamics when reversing the magnetic field parallel to the sample plane.

Conclusions:

• The developed technique offers high frequency resolution and magnetic field strength for studying ultrafast spin dynamics.
• Different magnetic field orientations probe diverse magnetic properties, highlighting the versatility of the instrumentation.
• The findings provide insights into the complex magnetic behavior of rare-earth transition metal alloys.