Magnetic and Superconducting Properties of Underdoped Ba(Fe1-xCox)2As2 Measured with Muon Spin Relaxation/Rotation

TL;DR

This study uses muon spin relaxation/rotation to investigate the coexistence of magnetism and superconductivity in underdoped Ba(Fe1-xCox)2As2, revealing how magnetic order diminishes with increased doping.

Contribution

It provides detailed measurements of magnetic and superconducting properties in underdoped Ba(Fe1-xCox)2As2, highlighting the interplay between magnetism and superconductivity.

Findings

Magnetic fields decrease with increased Co doping.

Presence of weak magnetism in a low-temperature volume fraction.

Magnetic inhomogeneities increase with doping.

Abstract

We report muon spin relaxation/rotation (uSR) measurements of single crystal Ba(Fe1-xCox)2As2 with x=0.038 and 0.047. Zero field (ZF)-uSR and Transverse field (TF)-iSR measurements of these underdoped samples find the presence of magnetism and superconductivity. We find internal fields along the c-axis whose magnitude decreases with increasing doping. We find evidence for a low-temperature volume fraction that is only weakly magnetic, where that volume fraction increases with increasing Co doping of the sample. TF-uSR measurements show slight changes in the spectra that indicate magnetic inhomogeneities due to the loss of Fe moments in the system, the effect of which is larger in the higher Co doping. We discuss the existence of superconductivity in these samples in close proximity to strong magnetic order.