Carrier localization due to local magnetic order induced by magnetic impurities in Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM = Mn and Cr) as seen via optical spectra

TL;DR

This study uses optical spectroscopy to reveal how magnetic impurities Mn and Cr induce carrier localization in Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$, highlighting their non-conventional magnetic effects above the antiferromagnetic transition.

Contribution

It uncovers a novel spectral feature linked to magnetic impurity-induced local magnetic order affecting charge dynamics in iron pnictides.

Findings

Magnetic impurities cause carrier localization observable in optical spectra.

Suppression of coherent charge transport due to magnetic impurities.

Mn and Cr act as non-conventional magnetic pair-breakers.

Abstract

The charge dynamics of Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM = Mn and Cr) has been investigated by optical spectroscopy. It was found that in addition to the strong suppression of the coherent charge transport, the magnetic impurity induces a novel spectral feature related to the carrier localization in the far-infrared region above the antiferromagnetic transition temperature. We attribute it to the cooperative effect between conduction electrons and local magnetic order induced by magnetic impurities. The present results demonstrate that Mn and Cr are not conventional magnetic pair-breakers in iron pnictides.