Phase separation in superconducting and antiferromagnetic Rb0.8Fe1.6Se2 probed by M\"ossbauer spectroscopy

TL;DR

This study uses Mössbauer spectroscopy to investigate phase separation and magnetic properties in superconducting Rb0.8Fe1.6Se2, revealing coexistence of magnetic and non-magnetic phases at the nanoscale.

Contribution

It provides detailed Mössbauer evidence of phase separation and magnetic order in Rb0.8Fe1.6Se2, advancing understanding of its coexistence of superconductivity and magnetism.

Findings

88% magnetic and 12% non-magnetic Fe2+ species identified

Magnetic species linked to superstructure sites

Antiferromagnetic order confirmed in single crystals

Abstract

57Fe-M\"ossbauer studies of superconducting Rb0.8Fe1.6Se2.0 with TC = 32.4 K were performed on single-crystalline and polycrystalline samples in the temperature range 4.2 K to 295 K. They reveal the presence of 88% magnetic and 12% non-magnetic Fe2+ species with the same polarization dependence of their hyperfine spectra. The magnetic species are attributed to the 16i sites of the \surd5 x \surd5 x 1 superstructure, and non-magnetic species to a nano-sized phase postulated from recent studies of superconducting KxFe2-ySe2 systems. The 57Fe-spectrum of a single-crystalline sample in an external field of 50 kOe applied parallel to the crystallographic c-axis confirms the antiferromagnetic order between fourfold ferromagnetic Fe(16i) supermoments. The results are discussed with respect to the coexistence of superconductivity and magnetism as well as nano-scale phase separation in AxFe2-ySe2 systems.