Commensurate Itinerant Antiferromagnetism in BaFe₂As₂:
⁷⁵As-NMR Studies on a Self-Flux Grown Single Crystal

Abstract

We report results of ⁷⁵As nuclear magnetic resonance (NMR) experiments on a self-flux grown single crystal of BaFe₂As₂. A first-order antiferromagnetic (AF) transition near 135 K was detected by the splitting of NMR lines, which is accompanied by simultaneous structural transition as evidenced by a sudden large change of the electric field gradient tensor at the As site. The NMR results lead almost uniquely to the stripe spin structure in the AF phase. The data of spin–lattice relaxation rate indicate development of anisotropic spin fluctuations of the stripe-type with decreasing temperature in the paramagnetic phase.