# Interplay of electronic and spin degrees in ferromagnetic SrRuO$_3$: anomalous softening of magnon gap and stiffness

## TL;DR

This study investigates how electronic and spin interactions in ferromagnetic SrRuO$_3$ influence magnon properties, revealing anomalous softening of magnon gap and stiffness linked to Weyl points and the anomalous Hall effect.

## Contribution

It demonstrates the direct influence of Weyl points and the anomalous Hall effect on spin dynamics in metallic ferromagnets, a novel insight into their interplay.

## Key findings

- Magnon modes exhibit broadening due to strong interaction with charge carriers.
- Magnon gap and stiffness soften upon cooling in the ferromagnetic phase.
- The temperature dependence of these effects correlates with the anomalous Hall effect.

## Abstract

The magnon dispersion of ferromagnetic SrRuO$_3$ was studied by inelastic neutron scattering experiments on single crystals as function of temperature. Even at low temperature the magnon modes exhibit substantial broadening pointing to strong interaction with charge carriers. We find an anomalous temperature dependence of both the magnon gap and the magnon stiffness, which soften upon cooling in the ferromagnetic phase. Both effects trace the temperature dependence of the anomalous Hall effect. We argue that these results show that Weyl points and the anomalous Hall effect can directly influence the spin dynamics in metallic ferromagnets.