Critical Behavior of Iron Above its Curie Temperature

High-resolution measurements of the energy distribution of neutrons critically scattered in Fe establish that the hydrodynamic region in which conventional theory is valid extends only to values of the scattering q≈K1, where K1 is the inverse of the spin correlation range. Analysis of data restricted to this region indicates that the susceptibility varies as (1-TcT)1.30±0.06. Contrary to expectations, the spin-diffusion constant Λ shows considerably less dependence on temperature, varying as (1-TcT)0.14±0.04.