Ultrafast Spin Accumulations Drive Magnetization Reversal in Multilayers

TL;DR

This paper reveals how ultrafast spin accumulations influence magnetization reversal in multilayer spintronic devices, providing insights into non-equilibrium spin dynamics and guiding future device design.

Contribution

It demonstrates that magneto-optical experiments can track ultrafast spin accumulation dynamics, elucidating the mechanisms behind all-optical switching in magnetic multilayers.

Findings

Ultrafast laser excitation generates measurable spin accumulation.

The final magnetic state is mainly influenced by reference-layer dynamics.

Demagnetization and remagnetization-driven spin accumulation are key to switching.

Abstract

Engineering and controlling heat and spin transport on the femtosecond time-scale in spintronic devices opens up new ways to manipulate magnetization with unprecedented speed. Yet the underlying reversal mechanisms remain poorly understood due to the challenges of probing ultrafast, non-equilibrium spin dynamics. In this study, we demonstrate that typical magneto-optical experiments can be leveraged to access the time evolution of the spin accumulation generated within a magnetic multilayer following an ultrafast laser excitation. Furthermore, our analysis shows that the final magnetic state of the free-layer in a spin-valve is mainly dictated by the ultrafast dynamics of the reference-layer magnetization. Our results disentangle magnetization and spin transport dynamics within a multilayer stack and identify demagnetization and remagnetization-driven spin accumulation as the key mechanism for all-optical switching. These findings establish new design principles for ultrafast spintronic devices based on tailored spin current engineering.