On the crystal structure of the defective ternary compound ZnGa2Se4

In order to resolve the crystal structure and the corresponding space group of the tetrahedrally coordinated II–III2–V I4 defective semiconductor ZnGa2Se4, a study of the magnetic susceptibility of the alloy system Zn1−zMnzGa2Se4 is performed. The analysis of the Curie–Weiss temperature confirms, consistently with the phase diagram previously reported, that the room temperature crystal structure of the alloy system Zn1−zMnzGa2Se4 in all the composition ranges (0≤z≤1)(0≤z≤1) is of defect chalcopyrite type with space group I4̄ while samples obtained at temperatures higher than about 500 °C, which are rapidly cooled to room temperature, crystallizes in the partially disordered stannite-type structure I4̄2m. Hence, a careful process of crystal growth of this system, including a study of the phase diagram, annealing at adequate temperature, and slow cooling of the samples is necessary in order to obtain specimens in the ordered phase.

Research highlights
► Crystal structure of present alloys is of defect chalcopyrite type, space group I4̄.
► Samples obtained at T>800 K fast cooled to 300 K present stannite-type structure.
► A careful crystal growth procedure allow us to obtain ZnGa2Se4 in the ordered phase.
► Zn1−zMnzGa2Se4 samples slowly cooled down to 300 K are antiferromagnetic.
► Zn1−zMnzGa2Se4 samples quenched from 970 to 300 K exhibit spin-glass behavior.