The elastic order-disorder transformations and related hysteresis effects in alkali-metal halide cyanide double-mixed crystals are studied by monitoring as a function of temperature the changes in optical transmission produced by light scattering of their multidomain elastically ordered structures. The studies are performed in the double-mixed crystals ${\mathrm{K}}_{1\mathrm{-}\mathit{y}}$${\mathrm{Na}}_{\mathit{y}}$${\mathrm{Br}}_{1\mathrm{-}\mathit{x}}$${\mathrm{CN}}_{\mathit{x}}$ and ${\mathrm{K}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Rb}}_{\mathit{y}}$${\mathrm{Br}}_{1\mathrm{-}\mathit{x}}$${\mathrm{CN}}_{\mathit{x}}$ in which cyanide and cationic sublattices are disordered simultaneously by varying (x,y) concentration parameters. The results allow us to determine approximately the regions of the concentration plane (x,y) for which elastic ordering is achieved. Some features of the complete three-dimensional (x,y;T) phase diagrams are discussed.

• Received 11 January 1990

DOI:https://doi.org/10.1103/PhysRevB.41.11422