C 59 o and A 75 s NMR investigation of lightly doped Ba(Fe1−xCox)2As2 (x=0.02,0.04)

We investigate the electronic properties of Ba(Fe1−xCox)2As2 (x=0.02,0.04) in the lightly electron-doped regime by C 59 o and A 75 s NMR. We demonstrate that Co doping significantly suppresses the magnetic ordering temperature to the SDW state, TSDW. Furthermore, ordered moments below TSDW exhibit large distribution. Strong spin fluctuations remain even below TSDW, 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.