Control of ultrashort spin current pulses in metallic multilayers

TL;DR

This paper investigates how to control and understand ultrashort spin current pulses emitted from Fe/Au interfaces, revealing the roles of hot electron dynamics, diffusive transport, and carrier multiplication.

Contribution

It introduces a method to control spin pulse shape and duration via emitter thickness and develops a model for superdiffusive spin transport in gold.

Findings

Pulse shape and duration depend on emitter thickness.

Hot electron emission and diffusion parameters govern pulse characteristics.

Carrier multiplication significantly influences spin current emission.

Abstract

We study the emission of femtosecond spin current pulses at Fe/Au interfaces. Using optical second harmonic generation we demonstrate the control of pulse shape and duration by varying the emitter thickness and show that it is determined by the parameters of hot electrons emission and the diffusive transport. Using a simple model of electron emission we develop a description of superdiffusive spin transport in Au allowing to extract electron velocity and scattering rates from the experimental data. The importance of carrier multiplication in Fe is demonstrated.