The role of electron and phonon temperatures in the helicity-independent all-optical switching of GdFeCo

TL;DR

This study investigates the roles of electron and phonon temperatures in helicity-independent all-optical switching of GdFeCo, revealing that non-equilibrium phenomena are essential and peak electron temperature is not critical.

Contribution

It provides quantitative measurements of temperature dynamics during AOS and highlights the importance of non-equilibrium effects in the switching process.

Findings

Critical switching fluences depend on initial temperature and pulse duration.

Switching time increases with pulse duration, reaching ~13 ps for 10 ps pulses.

Peak electron temperature is not the key factor for switching.

Abstract

Ultrafast optical heating of the electrons in ferrimagnetic metals can result in all-optical switching (AOS) of the magnetization. Here we report quantitative measurements of the temperature rise of GdFeCo thin films during helicity-independent AOS. Critical switching fluences are obtained as a function of the initial temperature of the sample and for laser pulse durations from 55 fs to 15 ps. We conclude that non-equilibrium phenomena are necessary for helicity-independent AOS, although the peak electron temperature does not play a critical role. Pump-probe time-resolved experiments show that the switching time increases as the pulse duration increases, with 10 ps pulses resulting in switching times of ~sim 13 ps. These results raise new questions about the fundamental mechanism of helicity-independent AOS.