Engineering Spintronic devices to observe ferromagnetic layer switching induced by a single- femto-second current pulse INVITED

Abstract

The magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse in a GdFeCo/Cu/[Co/Pt] spin-valve structure was first demonstrated in 2018 [1]. This work has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not fully understood.The single GdFeCo layer demonstrate all-optical helicity-independent switching (AO-HIS). In that case, the magnetization of this Rare-earth – Transition Metal alloy can be switched with one single femto-second pulse whatever light helicity is used. AO_HIS was attributed to the presence of two exchange coupled magnetic sublattices (the Rare Earth and the Transition Metal one) showing different relaxation times after the ultrafast laser excitation [2]in the GdFeCo/Cu/[Co/Pt] spin-valve studied in ref [1]. the switching of the [Co/Pt] ferromagnetic layer is observed after a single femto-second laser pulse. It has been carefully checked that no exchange coupling between the two magnetic layers exist. The [Co/Pt] switching would then result from the combined effect of the spin current generated by the AO-HIS of the GdFeCo layer [3] and the laser-induced heating of the ferromagnet.More recently single-shot all-optical magnetization switching was investigated in a GdFeCo/Cu/[CoxNi1-x/Pt] spin-valve structure. It was demonstrated that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temperature of the ferromagnetic layer. We were able to explain most of the experimental results using a phenomenological model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching [4,5]. **