Revealing the dual nature of magnetism in iron pnictides and iron chalcogenides using x-ray emission spectroscopy

TL;DR

This study uses x-ray emission spectroscopy to reveal that local magnetic moments are present in various iron-based superconductors, with their size unaffected by doping or temperature, highlighting the dual nature of magnetism in these materials.

Contribution

It provides direct spectroscopic evidence of local magnetic moments across different iron-based superconductors, clarifying their magnetic properties in the paramagnetic phase.

Findings

Local magnetic moments are present in all studied samples.

Moment sizes vary significantly among different families.

Doping and temperature do not affect the local moment size.

Abstract

We report Fe K beta x-ray emission spectroscopy study of local magnetic moments in various iron based superconductors in their paramagnetic phases. Local magnetic moments are found in all samples studied: PrFeAsO, Ba(Fe,Co)2As2, LiFeAs, Fe1+x(Te,Se), and A2Fe4Se5 (A=K, Rb, and Cs). The moment size varies significantly across different families. Specifically, all iron pnictides samples have local moments of about 1 $\mu_B$/Fe, while FeTe and K2Fe4Se5 families have much larger local moments of ~2$\mu_B$/Fe, ~3.3$\mu_B$/Fe, respectively. In addition, we find that neither carrier doping nor temperature change affects the local moment size.