From single to multiple pulse all-optical switching in GdFeCo thin films

All-optical switching refers to the magnetization reversal induced by ultrashort laser pulses. Both single-pulse all-optical helicity-independent switching and multiple pulses all-optical helicity-dependent switching have been reported for GdFeCo thin films. In this paper, we demonstrate that for two GdFeCo compositions, the transition between these two behaviors can appear by increasing the thickness of the Pt capping or by tuning the laser fluence. The two types of switching cannot be observed for the same set of parameters, which supports that their mechanisms are uncorrelated. Our calculations indicate that the transition may be induced by a strong inhomogeneity of the electronic temperature within the thickness of the GdFeCo layer in the subpicosecond timescale.