Time-resolved splitting of magnons into vortex gyration and Floquet spin waves

TL;DR

This paper investigates the time dynamics of magnon splitting in a magnetic vortex, revealing how Floquet spin waves and vortex gyration emerge synchronously after a delay that depends on the excitation frequency and power.

Contribution

It provides the first time-resolved measurements of magnon splitting, demonstrating the three-wave splitting mechanism into vortex gyration and Floquet spin waves.

Findings

Floquet spin waves emerge synchronously with vortex gyration.

The incubation delay diverges at the scattering threshold.

Maximum delay observed is as short as 3 ns at resonance.

Abstract

Forced excitations at frequencies in the range of the first order azimuthal spin waves of a magnetic disk in the vortex state are known to scatter into the vortex gyration mode, thereby allowing the growth of Floquet spin waves forming a frequency comb. We study the temporal emergence of this dynamical state using time-resolved microwave electrical measurements. The most intense Floquet mode emerges synchronously with the gyration mode after a common incubation delay which diverges at the scattering threshold. This delay is minimal when the drive is resonant with one of the first order azimuthal spin waves. It can be as short as 3 ns for the maximum investigated power. We conclude that the first-to-occur scattering mechanism is the three-wave splitting of a regular azimuthal eigenmode into a coherent pair formed by a gyration magnon and a Floquet spin wave.