Magnetic excitations in underdoped Ba(Fe1-xCox)2As2 with x=0.047

TL;DR

This study uses inelastic neutron scattering to analyze magnetic excitations in underdoped Ba(Fe1-xCox)2As2, revealing diffusive spin dynamics and anisotropic damping effects that shape the magnetic spectrum.

Contribution

It provides a phenomenological model describing magnetic excitations in underdoped Ba(Fe1-xCox)2As2, highlighting the role of anisotropies in damping and correlation length.

Findings

Magnetic excitations are well described by diffusive spin dynamics.

High-energy peak splitting is due to anisotropic damping, not incommensurability.

Magnetic spectrum remains similar across paramagnetic and ordered phases.

Abstract

The magnetic excitations in the paramagnetic-tetragonal phase of underdoped Ba(Fe0.953Co0.047)2As2, as measured by inelastic neutron scattering, can be well described by a phenomenological model with purely diffusive spin dynamics. At low energies, the spectrum around the magnetic ordering vector Q_AFM consists of a single peak with elliptical shape in momentum space. At high energies, this inelastic peak is split into two peaks across the direction perpendicular to Q_AFM. We use our fittings to argue that such a splitting is not due to incommensurability or propagating spin-wave excitations, but is rather a consequence of the anisotropies in the Landau damping and in the magnetic correlation length, both of which are allowed by the tetragonal symmetry of the system. We also measure the magnetic spectrum deep inside the magnetically-ordered phase, and find that it is remarkably similar to the spectrum of the paramagnetic phase, revealing the strongly overdamped character of the magnetic excitations.