Field-dependent ultrafast dynamics and mechanism of magnetization reversal across ferrimagnetic compensation points in GdFeCo amorphous alloy films

Abstract

Ultrafast dynamics of genuine magneto-optical recording across ferrimagnetic compensation points is demonstrated in GdFeCo films using time-resolved polar Kerr spectroscopy combined with a laser-synchronized sinusoidal alternating magnetic field which can reinitialize irreversible initial magnetization state to laser radiating. The external field dependence of magnetization reversal dynamics is measured and shows that reversal rate accelerates with increasing external fields. Analysis of the magnetization reversal dynamics with Bloch equation shows the magnetization reversal rate is linearly dependent on the external fields within experimental errors, which supports quantitatively that the mechanism of magneto-optical recording in rare earth-transition metal ferromagnetic films is related to the formation and growth of the reversed domains. It is also shown that nucleation field is obviously larger than hot coercivity shown in the anomalous hysteresis loop.