Anomalous quasielastic scattering contribution in the centrosymmetric multi-$\mathbf{q}$ helimagnet SrFeO$_3$

TL;DR

This study explores the magnetic properties and excitations in the centrosymmetric SrFeO$_3$, revealing a unique quasielastic scattering contribution linked to topological spin textures and phase transitions.

Contribution

It provides the first detailed investigation of static and dynamic magnetic properties, including spin excitations, in a centrosymmetric multi-$ extbf{q}$ helimagnet hosting topological spin textures.

Findings

Identification of quasielastic scattering dominating low-energy spin fluctuations.

Observation of phase transitions and domain selection in SrFeO$_3$.

High-energy magnons lose coherence in ordered phases.

Abstract

Centrosymmetric compounds which host three-dimensional topological spin structures comprise a distinct subclass of materials in which multiple-$\mathbf{q}$ magnetic order is stabilized by anisotropy and bond frustration in contrast to the more common path of antisymmetric exchange interactions. Here we investigate static and dynamic magnetic properties of the cubic perovskite SrFeO$_3$ $\unicode{x2013}$ a rare example of a centrosymmetric material hosting two types of topological spin textures: skyrmion- and hedgehog-lattice phases. Our detailed magnetization and dilatometry measurements describe the domain selection processes and phase transitions in SrFeO$_3$. Spin excitations are investigated using inelastic neutron scattering for all three zero-field phases. In the higher-temperature ordered phases, high-energy magnons increasingly lose coherence, so that spin fluctuations are dominated by a distinct quasielastic component at low energies. We anticipate that this could be generic to symmetric helimagnets in which the chiral symmetry is spontaneously broken by the magnetic order.