Ultrafast electron-phonon-magnon interactions at noble metal-ferromagnet interfaces

TL;DR

This study investigates ultrafast interactions between electrons, phonons, and magnons at noble metal-ferromagnet interfaces, revealing how laser-induced heating affects thermal boundary resistance and generates acoustic pulses and magnons.

Contribution

It provides new insights into ultrafast electron-phonon-magnon dynamics at metal-ferromagnet interfaces using time-resolved optical techniques and analytical modeling.

Findings

Kapitza resistance influences transient lattice overheating.

Ultrafast laser excitation generates acoustic pulses and magnons.

Measured hot electron diffusion length in cobalt.

Abstract

Ultrafast optical excitation of gold-cobalt bilayers triggers the nontrivial interplay between the electronic, acoustic, and magnetic degrees of freedom. Laser-heated electrons generated at the gold-air interface diffuse through the layer of gold and strongly overheat the lattice in cobalt resulting in the emission of ultrashort acoustic pulses and generation of exchange-coupled magnons. Time-resolved optical measurements allow for extracting the thermal boundary (Kapitza) resistances at metal/metal interfaces and the hot electron diffusion length in ferromagnetic materials. Both the experimental data and the analytical treatment of the two-temperature model reveal the role of the Kapitza resistance in transient lattice overheating.