The iron pnictides have attracted great interest following the

discovery of superconductivity up to 50K and because of their superficial
similarities with the cuprate superconductors. In both systems,
superconductivity emerges when long range antiferromagnetic order is
suppressed by doping or pressure. This indicates that spin correlations are
intimately connected with superconductivity and may be involved in the
pairing mechanism, in contrast to ordinary superconductors where the pairing
is provided by phonons.  Elastic and inelastic neutron scattering provides a
most direct probe of both the long range spin order as well as the strong
spin fluctuations remaining when the long range order has been suppressed,
allowing detailed studies of how these spin correlations evolve as the
superconducting state is approached and entered as a function of doping and
temperature.