Neutron-Scattering Observations of Critical Slowing Down of an Ising System

We have studied the dynamics of the order-disorder phase transition in ${\mathrm{Ni}}_3$Mn by neutron-scattering techniques. The relaxation time constant for the long-range order is about 90 min at a temperature 15°C below the critical temperature, but closer to the critical temperature it increases by more than an order of magnitude. This critical slowing down varies as the reduced temperature to a power of 1.04 ± 0.09.