Abstract Compositions of the Cd (1– x ) Mn ( x ) In 2 S 4 system (0.5 ≤ x ≤ 1.0) were synthesized by the melt and annealing technique and grown by the chemical vapor transport method. The magnetic cation distributions have been estimated by X‐ray powder diffraction structure refinements using the Rietveld method. These alloys form a solid solution in all the range of compositions and crystallize with cubic symmetry in the space group Fd 3m. All phases show a spinel structure with a random arrangement of cations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)