Arsenic nuclear magnetic resonance in CaFe2As2

We present $^{75}$As nuclear magnetic resonance measurements in the paramagnetic and antiferromagnetic states of CaFe$_{2}$As$_{2}$. Single crystals were produced using a Sn flux method and characterized via powder X-Ray diffraction, susceptibility, and specific heat measurements. The NMR data show that the internal hyperfine field and the electric field gradient change discontinuously at T$_{0}$ = 169 K. The observed hyperfine field is consistent with stripe antiferromagnetic ordering of the Fe spins in the a-b plane. Spin lattice relaxation data show metallic T$_{1}$$^{-1}$ $\sim$ T for T $\leq$ T$_{0}$/3. However, T$_{1}$$^{-1}$ shows a small peak at 10 K attributed to slow spin fluctuations that could indicate the emergence of antiferromagnetic domain wall motion.