Low Energy, Coherent, Stoner-like Excitations in CaFe$_{2}$As$_{2}$

TL;DR

This paper uses density-functional theory to identify a new type of low-energy, coherent Stoner-like excitations in CaFe₂As₂, revealing complex magnetic dynamics beyond localized spin models.

Contribution

It uncovers sharp itinerant excitations coexisting with spin waves, emphasizing the importance of itinerant electron effects in magnetic excitations of CaFe₂As₂.

Findings

Discovery of sharp Stoner-like resonances at energies near the N{\'e}el temperature.

Coexistence of localized spin waves and itinerant excitations.

Multiple excitation branches indicating complex magnetic behavior.

Abstract

Using linear-response density-functional theory, magnetic excitations in the striped phase of CaFe$_{2}$As$_{2}$ are studied as a function of local moment amplitude. We find a new kind of excitation: sharp resonances of Stoner-like (itinerant) excitations at energies comparable to the N{\'{e}}el temperature, originating largely from a narrow band of Fe $d$ states near the Fermi level, and coexist with more conventional (localized) spin waves. Both kinds of excitations can show multiple branches, highlighting the inadequacy of a description based on a localized spin model.