Antiferromagnetic Critical Fluctuations in BaFe$_2$As$_2$

Magnetic correlations near the magnetostructural phase transition in the bilayer iron-pnictide parent compound, BaFe{sub 2}As{sub 2}, are measured. In close proximity to the antiferromagnetic phase transition in BaFe{sub 2}As{sub 2}, 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{sub N}. The potential role of two-dimensional critical fluctuations in the magnetic phase behavior of BaFe{sub 2}As{sub 2} and their evolution near the anticipated crossover to three-dimensional critical behavior and long-range order are discussed.