Femtosecond spin current pulses generated by the non-thermal spin-dependent Seebeck effect and interacting with ferromagnets in spin valves

TL;DR

This paper demonstrates the generation of ultrashort femtosecond spin current pulses in spin valves via a non-thermal spin-dependent Seebeck effect, revealing insights into hot electron transport and spin interactions at interfaces.

Contribution

It provides experimental evidence of femtosecond spin current pulses generated by a non-thermal Seebeck effect in spin valves, highlighting hot electron dynamics and spin rotation at interfaces.

Findings

250 fs-long spin current pulses observed

Superdiffusive hot electron transport near ballistic limit

Hot electron spins rotate at Au/Fe interface

Abstract

Using the sensitivity of magneto-induced second harmonic generation to spin currents (SC), we demonstrate in Fe/Au/Fe/MgO(001) pseudo spin valves the generation of 250 fs-long SC pulses. Their temporal profile indicates that superdiffusive hot electron transport across a sub-100~nm Au layer is close to the ballistic limit and the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a non-thermal spin-dependent Seebeck effect is responsible for the generation of ultrashort SC pulses. We also show that hot electron spins rotate upon interaction with non-collinear magnetization at the Au/Fe interface, which holds high potential for future spintronic devices.