Micromagnetic view on ultrafast magnon generation by femtosecond spin current pulses

TL;DR

This paper presents a micromagnetic modeling approach to understand ultrafast magnon generation by femtosecond spin current pulses, aligning well with experimental data and proposing new experimental designs for nanoscale spin wave excitation.

Contribution

It introduces a micromagnetic model for femtosecond spin current-induced magnon excitation, demonstrating its effectiveness at ultrafast timescales and small spatial scales.

Findings

Reproduces experimental results of ultrafast magnon excitation.

Identifies factors influencing excitation efficiency of spin waves.

Proposes experimental design for sub-diffraction-limited spin wave excitation.

Abstract

In this Article we discuss a micromagnetic modelling approach to describe the ultrafast spin-transfer torque excitation of coherent and incoherent magnons on the nanoscale. Implementing the action of a femtosecond spin current pulse entering an orthogonally magnetized thin ferromagnetic film, we reproduce recent experimental results and reveal the factors responsible for the unequal excitation efficiency of various spin waves. Our findings are in an excellent agreement with the results of an analytical description of spin-wave excitation based on classical kinetic equations. Furthermore, we suggest an experimental design allowing for the excitation of laterally propagating spin waves beyond the optical diffraction limit. Our findings demonstrate that the classical micromagnetic picture retains its predictive and interpretative power on femtosecond temporal and nanometer spatial scales.