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 T-N. 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.