NMR investigation of spin correlations in BaCo2As2

TL;DR

This study uses NMR to explore magnetic properties of BaCo2As2, revealing enhanced low-temperature spin fluctuations and ferromagnetic correlations, with evidence of multiple electronic band contributions affecting its magnetic behavior.

Contribution

First NMR investigation of BaCo2As2 showing ferromagnetic spin fluctuations and multiple electronic band effects on its magnetic properties.

Findings

Enhanced low-frequency spin fluctuations below 100 K.

Presence of ferromagnetic correlations rather than antiferromagnetic.

Detection of two distinct components of spin susceptibility.

Abstract

We use NMR techniques to investigate the magnetic properties of BaCo2As2 single crystals, the non-superconducting end member of the Co-substituted iron-pnictide high Tc superconductor Ba(Fe1-xCox)2As2 with x = 1. We present 75As NMR evidence for enhancement of low frequency spin fluctuations below ~ 100 K. This enhancement is accompanied by that of static uniform spin susceptibility at the wave vector q = 0, suggesting that the primary channel of the spin correlations is ferromagnetic rather than antiferromagnetic. Comparison between the NMR Knight shift 75K and bulk susceptibility chi(bulk) data uncovers the presence of two separate components of spin susceptibility with distinct temperature dependences, presumably because multiple electronic bands crossing the Fermi energy play different roles in the electronic properties of BaCo2As2.