Observation of Coherent Helimagnons and Gilbert damping in an Itinerant Magnet

TL;DR

This study investigates magnetic excitations in an itinerant helimagnet using time-resolved spectroscopy, revealing helimagnons and quantifying Gilbert damping, thus advancing understanding of spin dynamics in chiral magnetic materials.

Contribution

It provides the first direct measurement of helimagnons and Gilbert damping in an itinerant helimagnet using optical spectroscopy.

Findings

Observation of dispersing helimagnons with magnetic field

Quantification of Gilbert damping in Fe0.8Co0.2Si

Demonstration of spin dynamics versatility in chiral magnets

Abstract

We study the magnetic excitations of itinerant helimagnets by applying time-resolved optical spectroscopy to Fe0.8Co0.2Si. Optically excited oscillations of the magnetization in the helical state are found to disperse to lower frequency as the applied magnetic field is increased; the fingerprint of collective modes unique to helimagnets, known as helimagnons. The use of time-resolved spectroscopy allows us to address the fundamental magnetic relaxation processes by directly measuring the Gilbert damping, revealing the versatility of spin dynamics in chiral magnets. (*These authors contributed equally to this work)