The gradual destruction of magnetism in the superconducting family NaFe(1-x)CoxAs

TL;DR

This study investigates how Co doping in NaFeAs gradually suppresses magnetic and structural order, leading to a robust superconducting phase, using multiple advanced experimental techniques to reveal the interplay of these states.

Contribution

It provides detailed experimental evidence of the gradual suppression of magnetism and structural distortion with Co doping in NaFeAs, elucidating their relationship with superconductivity.

Findings

Magnetic order weakens and disappears around a specific Co concentration.

Structural distortion diminishes concurrently with magnetic suppression.

Superconductivity emerges as magnetism and structural order are destroyed.

Abstract

The interplay and coexistence of superconducting, magnetic and structural order parameters in NaFe{1-x}Co{x}As has been studied using SQUID magnetometry, muon-spin rotation and synchrotron x-ray powder diffraction. Substituting Fe by Co weakens the ordered magnetic state through both a suppression of T_N and a reduction in the size of the ordered moment. Upon further substitution of Fe by Co the high sensitivity of the muon as a local magnetic probe reveals a magnetically disordered phase, in which the size of the moment continues to decrease and falls to zero around the same point at which the magnetically-driven structural distortion is no longer resolvable. Both magnetism and the structural distortion are weakened as the robust superconducting state is established.