Correlated trends of coexisting magnetism and superconductivity in optimally electron-doped oxy-pnictides

TL;DR

This study explores how magnetism and superconductivity coexist and influence each other in electron-doped oxy-pnictides, revealing their correlated suppression and the role of local electronic environments.

Contribution

It demonstrates the coexistence of magnetic order and superconductivity within nanometer domains and links their behavior to local electronic environments in doped oxy-pnictides.

Findings

Magnetic order and superconductivity coexist within nanometer domains.

Both order parameters disappear around a critical doping level x_c=0.6.

Superconductivity is linked to magnetic fluctuations and local electronic environments.

Abstract

We report on the recovery of the short-range static magnetic order and on the concomitant degradation of the superconducting state in optimally F-doped SmFe_(1-x)Ru_(x)AsO_0.85F_0.15 for 0.1< x<0.6. The two reduced order parameters coexist within nanometer-size domains in the FeAs layers and finally disappear around a common critical threshold x_c=0.6. Superconductivity and magnetism are shown to be closely related to two distinct well-defined local electronic environments of the FeAs layers. The two transition temperatures, controlled by the isoelectronic and diamagnetic Ru substitution, scale with the volume fraction of the corresponding environments. This fact indicates that superconductivity is assisted by magnetic fluctuations, which are frozen whenever a short-range static order appears, and totally vanish above the magnetic dilution threshold x_c.