Antiferromagnetism of SrFe2As2 Studied by Single-Crystal 75As-NMR

We report results of As-75 nuclear magnetic resonance (NMR) experiments on a self-flux grown high-quality single crystal of SrFe(2)AS(2). The NMR spectra clearly show sharp first-order anti ferromagnetic (AF) and structural transitions occurring simultaneously. The behavior in the vicinity of the transition is compared with our previous study on BaFe(2)AS(2). No significant difference was observed in the temperature dependence of the static quantities such as the AF splitting and electric quadrupole splitting. However, the results of the NMR relaxation rate revealed difference in the dynamical spin fluctuations. The stripe-type AF fluctuations in the paramagnetic state appear to be more anisotropic in BaFe(2)AS(2) than in SrFe(2)AS(2).