Spin wave stiffness and damping in a frustrated chiral helimagnet Co$_8$Zn$_8$Mn$_4$ as measured by small-angle neutron scattering

TL;DR

This study investigates temperature-dependent spin wave properties in the frustrated chiral helimagnet Co$_8$Zn$_8$Mn$_4$ using small-angle neutron scattering, revealing complex behaviors linked to magnetic frustration and anisotropy.

Contribution

First application of spin wave small-angle neutron scattering to measure temperature-dependent stiffness and damping in Co$_8$Zn$_8$Mn$_4$, providing new insights into magnetic frustration effects.

Findings

Quantitative estimates of spin wave stiffness and damping across 70-250 K.

Identification of non-trivial temperature dependencies due to magnetic frustration.

Evidence of continuous variation in exchange and Dzyaloshinskii-Moriya interactions.

Abstract

Multiple intriguing low temperature phenomena have recently been discovered in the family of chiral cubic Co-Zn-Mn compounds with $\beta-$Mn-type structure. In particular, Co$_8$Zn$_8$Mn$_4$ displays a reduction of the helical spiral pitch on cooling, along with lattice shape transformations of metastable skyrmions and the manifestation of peculiar magnetic textures due to strong magnetocrystalline anisotropy. Here we report on temperature-dependent measurements of helimagnon excitations in the field polarized regime Co$_8$Zn$_8$Mn$_4$ using the spin wave small-angle neutron scattering (SWSANS) technique. By applying a new analytical expression to interpret the data, quantitative estimates for both spin wave stiffness and damping are extracted across a wide temperature range between 70 K and 250 K. We speculate that their non-trivial temperature-dependencies arise due to the effects of magnetic frustration arising from Mn magnetic moments, which is further reflected in continuous variations of both exchange and Dzyaloshinskii-Moriya interactions.