Understanding of the spin dynamics in magnetic thin films and multilayers becomes quite important to develop ultra-high speed magnetic devices. Dynamics of the magnetization motion is widely known to follow the phenomenological Landau-Lifshitz-Gilbert (LLG) equation, which indicates that the magnetization precesses about the magnetic field and changes its direction to the field direction due to the damping of the precession. Such damping process can be measured by using so called optical pump-probe measurements using an ultra short pulsed laser.
    Our laboratory has studied the dynamics of the magnetization motion in various magnetic thin films by using the optical pump-probe measurements to control the precession of the magnetization and to develop ultra high speed magnetic devices. The figure shows typical result of the spin dynamics of GdFeCo amorphous films. The precession of the magnetization is triggered by the optical pump pulse and is monitored by the optically delayed probe pulse. By using the stable and high power ultra short pulse fiber layer, the precession motion of the spin is measured precisely with high signal to noise ratio.

Optical set up for pump-probe measurements
using an ultra short pulsed laser

 

Dynamic magnetization response of the GdFeCo film after the excitation of the pump beam

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