Atomic coexistence of superconductivity and incommensurate magnetic order in the Ba(Fe1-xCox)2As2 pnictide

TL;DR

This study reveals the coexistence of incommensurate magnetic order and superconductivity in Ba(Fe1-xCox)2As2, with detailed NMR analysis showing both phenomena occur simultaneously at the microscopic level.

Contribution

It provides the first direct evidence of atomic coexistence of superconductivity and incommensurate magnetic order in this pnictide compound.

Findings

Incommensurate magnetic order appears below 31K.

Superconductivity develops below 21.8K while magnetic order persists.

Magnetic moments are estimated at approximately 0.05 muB.

Abstract

75As NMR and susceptiblity were measured in a Ba(Fe1-xCox)2As2 single crystal for x=6%. Nuclear Magnetic Resonance (NMR) spectra and relaxation rates allow to show that all Fe sites experience an incommensurate magnetic ordering below T=31K. Comparison with undoped compound allows to estimate a typical moment of 0.05 muB. Anisotropy of the NMR widths can be interpreted using a model of incommensurability with a wavevector (1/2-eps,0,l) with eps of the order of 0.04. Below TC=21.8K, a full volume superconductivity develops as shown by susceptibility and relaxation rate, and magnetic order remains unaffected, demonstrating coexistence of both states on each Fe site.