Interstitial iron tuning of the spin fluctuations in Fe1+xTe

TL;DR

This study uses neutron scattering to explore how interstitial iron affects low-energy spin fluctuations in Fe1+xTe, revealing tunable magnetic properties that depend on iron concentration and temperature.

Contribution

It demonstrates that interstitial iron concentration can modulate spin fluctuations in Fe1+xTe, expanding understanding beyond selenium doping effects.

Findings

Fe1.057(7)Te exhibits gapped, three-dimensional spin fluctuations.

Fe1.141(5)Te shows gapless, two-dimensional fluctuations with a different wavevector.

Spin fluctuations can be tuned by interstitial iron, affecting magnetic and superconducting properties.

Abstract

Using neutron inelastic scattering, we investigate the low-energy spin fluctuations in Fe1+xTe as a function of both temperature and interstitial iron concentration. For Fe1.057(7)Te the magnetic structure is defined by a commensurate wavevector of (1/2,0,1/2). The spin fluctuations are gapped with a sharp onset at 7 meV and are three dimensional in momentum transfer, becoming two dimensional at higher energy transfers. On doping with interstitial iron, we find in Fe1.141(5)Te the ordering wavevector is located at the (0.38, 0, 1/2) position and the fluctuations are gapless with the intensity peaked at an energy transfer of 4 meV. These results show that the spin fluctuations in the Fe1+xTe system a can be tuned not only through selenium doping, but also with interstitial iron. We also compare these results with superconducting concentrations and in particular the resonance mode in the Fe_1+xTe_1-ySe_y system.