Interplay of heating and helicity in all-optical magnetization switching

Contrasting hypotheses have been made about the role played by laser heating and photon helicity in all-optical switching. Here we present an experiment that distinguishes between heating- and helicity-driven effects. We show that even though a minimum amount of circularity is needed to switch, heating contributes to the process. Moreover, we show that the helicity information carried by the exciting laser pulses is more easily transferred into the magnetic material at lower temperatures and that it persists in GdFeCo for at least some picoseconds after optical excitation.