Tailoring femtosecond hot-electron pulses for ultrafast spin manipulation

TL;DR

This study investigates how different capping layers influence hot-electron induced demagnetization in multilayer structures, revealing that platinum layers optimize photon-to-hot-electron conversion and demagnetization efficiency.

Contribution

It demonstrates that the capping layer material and thickness critically affect hot-electron generation and spin dynamics, providing insights for ultrafast spin manipulation.

Findings

Pt layers are more efficient than Co/Pt, Cu, or MgO in converting IR pulses to hot-electrons.

Maximum demagnetization occurs with a 7 nm Pt capping layer.

Experimental results align qualitatively with superdiffusive spin transport simulations.

Abstract

We have measured the hot-electron induced demagnetization of a [Co/Pt]2 multilayer in M(x nm)/Cu(100 nm)/[Co(0.6 nm)/Pt(1.1 nm)]2 samples depending on the nature of the capping layer M and its thickness x. We found out that a Pt layer is more efficient than [Co/Pt]X, Cu or MgO layers in converting IR photon pulses into hot-electron pulses at a given laser power. We also found out that the maximum relative demagnetization amplitude is reached for M(x) = Pt (7 nm). Our experimental results show qualitative agreement with numerical simulations based on the superdiffusive spin transport model. We concluded that the maximum relative demagnetization amplitude, which corresponds to the highest photon conversion into hot-electrons, is an interplay between the IR penetration depth and the hot-electron inelastic mean free path within the capping layer.