We investigate the electronic properties of $\text{Ba}{\left({\text{Fe}}_{1-x}{\text{Co}}_x\right)}_2{\text{As}}_2$ $\left(x=0.02,0.04\right)$ in the lightly electron-doped regime by ${}^{59}\text{C}\text{o}$ and ${}^{75}\text{A}\text{s}$ NMR. We demonstrate that Co doping significantly suppresses the magnetic ordering temperature to the SDW state, $T_{\text{SDW}}$. Furthermore, ordered moments below $T_{\text{SDW}}$ exhibit large distribution. Strong spin fluctuations remain even below $T_{\text{SDW}}$, 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.

• Received 10 February 2009

DOI:https://doi.org/10.1103/PhysRevB.79.140506