75As NMR Study of Hole-Doped Superconductor Ba1-xKxFe2As2 (Tc ≃ 38 K)

We report the As-75 nuclear magnetic resonance (NMR) measurement of the hole doped superconductor Ba1-xKxFe2As2 with different lattice parameters and different superconducting volume fractions (T-c similar or equal to 38 K). As-75-NMR spectra revealed that the magnetically ordered and superconducting phases are microscopically separated. The spin-lattice relaxation rate 1/T-1 in the normal,late reflects the existence of a large two-dimensional antiferromagnetic spin fluctuation. The 1/T-1, in the Superconducting state down to the lowest measurement temperature T vailes close to T-3. In addition, it exhibits no coherence peak just below T-c. This shows a T dependence similar to those of other iron pnictides.