Antiferromagnetic critical fluctuations in BaFe₂As₂

Magnetic correlations near the magnetostructural phase transition in the bilayer iron-pnictide parent compound, BaFe₂As₂, are measured. In close proximity to the antiferromagnetic phase transition in BaFe₂As₂, a crossover to three-dimensional critical behavior is anticipated and has been preliminarily observed. Here we report complementary measurements of two-dimensional magnetic fluctuations over a broad temperature range about TN. The potential role of two-dimensional critical fluctuations in the magnetic phase behavior of BaFe₂As₂ and their evolution near the anticipated crossover to three-dimensional critical behavior and long-range order are discussed.