Laser-induced Spin Dynamics in Metallic Multilayers

TL;DR

This paper investigates ultrafast spin dynamics in metallic multilayers induced by femtosecond laser pulses, focusing on hot electron-driven demagnetization and spin transfer torque effects in Au/Fe systems.

Contribution

It introduces a model system of Au and Fe layers to study the mechanisms of laser-induced ultrafast spin dynamics and spin transfer torque in metallic multilayers.

Findings

Ultrafast demagnetization observed in Fe layers.

Femtosecond laser pulses generate hot electrons causing spin transfer torque.

Time-resolved magneto-optics reveals dynamics on femtosecond timescales.

Abstract

Electronic excitations in a ferromagnet can trigger ultrafast spin dynamics with potential applications in a speed increase in magnetic recording. The project investigates ultrafast magnetization dynamics, which is driven in metallic layers by ballistic hot electrons. In a ferromagnet these electrons induce a change in the absolute value of the magnetization M through spin-dependent scattering. If the electrons are spin-polarized, scattering at the interface of a noble metal and a ferromagnet results in spin-transfer torque and hence modifies the direction of M. To reveal the underlying mechanisms, we study model systems, which are realized by layers of Au with its large ballistic mean free path and Fe as an itinerant ferromagnet. We aim at understanding ultrafast demagnetization and femtosecond all-optical generation of spin transfer torque effects (excitation of hot electrons with a femtosecond laser). The launched dynamics are probed by magneto-optics in a time-resolved experiment.