Interplay between spin density wave and superconductivity in '122' iron pnictides: 57Fe M\"ossbauer study

TL;DR

This study uses 57Fe Mössbauer spectroscopy to explore the coexistence of spin density wave magnetism and superconductivity in '122' iron pnictides, revealing that superconductivity occurs in regions with non-magnetic phases due to dopant variation.

Contribution

It provides new insights into the microscopic coexistence of SDW and superconductivity in '122' iron pnictides using Mössbauer spectroscopy.

Findings

Superconductivity coexists with SDW in these compounds.

Superconducting regions are non-magnetic despite the sample being single phase.

Dopant concentration variation causes phase separation at microscopic level.

Abstract

Iron-based superconductors Ba0.7Rb0.3Fe2As2 and CaFe1.92Co0.08As2 of the '122' family have been investigated by means of the 14.41-keV Moessbauer transition in 57Fe versus temperature ranging from the room temperature till 4.2 K. A comparison is made with the previously investigated parent compounds BaFe2As2 and CaFe2As2. It has been found that Moessbauer spectra of these superconductors are composed of the magnetically split component due to development of spin density wave (SDW) and non-magnetic component surviving even at lowest temperatures. The latter component is responsible for superconductivity. Hence, the superconductivity occurs in the part of the sample despite the sample is single phase. This phenomenon is caused by the slight variation of the dopant concentration across the sample (crystal).