59Co and 75As NMR Investigation of the Lightly Doped Ba[Fe(1-x)Co(x)]2As2 (x =0.02, 0.04)

TL;DR

This study uses 59Co and 75As NMR to explore how light electron doping affects magnetic order and spin fluctuations in Ba[Fe(1-x)Co(x)]2As2, revealing suppressed magnetic ordering and persistent spin dynamics.

Contribution

It provides new insights into the magnetic and electronic behavior of lightly electron-doped BaFe2As2 using NMR techniques, highlighting differences from hole-doped cuprates.

Findings

Co doping suppresses the SDW transition temperature

Large distribution of ordered magnetic moments below T_SDW

Persistent spin fluctuations down to 4.2 K

Abstract

We investigate the electronic properties of Ba[Fe(1-x)Co(x)]2As2 (x =0.02, 0.04) in the lightly electron-doped regime by 59Co and 75As NMR. We demonstrate that Co doping significantly suppresses the magnetic ordering temperature to the SDW state, T_{SDW}. Furthermore, ordered moments below T_{SDW} exhibit large distribution. Strong spin fluctuations remain even below T_{SDW}, persisting all the way down to 4.2 K. We find no signature of additional freezing of spin degrees of freedom unlike the case of the lightly hole-doped stripe phase of the cuprates.