NMR study of nematic spin fluctuations in a detwinned single crystal of   underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$
  We report the experimental details of how mechanical detwinning can be implemented in tandem with high sensitivity nuclear magnetic resonance measurements and use this setup to measure the in-plane anisotropy of the spin-lattice relaxation rate in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ with $x=0.048$. The anisotropy reaches a maximum of 30\% at $T_{N}$, and the recovery data reveal that the glassy behavior of the spin fluctuations present in the twinned state persist in the fully detwinned crystal. A theoretical model is presented to describe the spin-lattice relaxation rate in terms of anisotropic nematic spin fluctuations. 
T. Kissikov, A. P. Dioguardi, E. I. Timmons, M. A. Tanatar, R.   Prozorov, S. L. Bud'ko, P. C. Canfield, R. M. Fernandes, an...
cond-mat.str-el