Spin waves in the $(\pi,0)$ magnetically ordered iron chalcogenide Fe$_{1.05}$Te

TL;DR

This study investigates the spin wave dispersion in Fe$_{1.05}$Te using inelastic neutron scattering, revealing unique magnetic interactions that differ from theoretical predictions and related compounds, hinting at a shared magnetic origin for superconductivity.

Contribution

The paper provides the first detailed experimental characterization of spin waves in Fe$_{1.05}$Te and compares magnetic exchange couplings with theoretical models and other iron-based superconductors.

Findings

Spin waves in Fe$_{1.05}$Te show novel dispersion patterns.

Magnetic exchange couplings differ significantly from density functional predictions.

Next-nearest-neighbor couplings are similar in Fe$_{1.05}$Te and CaFe$_2$As$_2$.

Abstract

We use inelastic neutron scattering to show that the spin waves in the iron chalcogenide Fe$_{1.05}$Te display novel dispersion clearly different from those in the related iron pnictide systems. By fitting the spin waves to a Heisenberg Hamiltonian, we extract magnetic exchange couplings that are dramatically different from both predictions by density functional calculations and measurements on the iron pnictide CaFe$_2$As$_2$. While the nearest-neighbor exchange couplings in CaFe$_2$As$_2$ and Fe$_{1.05}$Te are quite different, their next-nearest-neighbor exchange couplings are similar. These results suggest that superconductivity in the pnictides and chalcogenides share a common magnetic origin that is intimately associated with the next-nearest-neighbor magnetic coupling between the irons.