The order-disorder phase transition in KSCN near 142 °C, which is connected with the head-tail orientation of the linear SCN molecules, is investigated by diffuse-neutron-scattering techniques. The results show a transition from a long-range-ordered structure to a short-range-ordered state which persists up to temperatures near the melting point. Above ${\mathit{T}}_{\mathit{c}}$ near the (100) superlattice point, a Lorentzian intensity distribution is observed whose temperature dependence shows a mean-field behavior. The short-range-ordered state is described by an ensemble of ordered microdomains.

• Received 13 May 1991

DOI:https://doi.org/10.1103/PhysRevB.44.9159