Magnetic and structural properties of Co-doped chalcogenide spinel Ga_0.67Cr₂S₄

Solid solutions of Ga_{(0.67–0.67x)}Co_xCr₂S₄ have been synthesized based on the cation-deficient spinel Ga_0.67Cr₂S₄ with x = 0–0.3. The structural properties of the synthesized compounds were analyzed by X-ray diffraction (XRD), which revealed that they are single-phase in spinel structure type. The surface morphology was examined using scanning electron microscopy (SEM), and it was determined that the average crystalline particle size is within the range of 0.6–1.0 µm. The EDX analysis confirmed that the composition was in compliance with the intended one and that the sample was homogeneous. A study of the structural properties revealed that the cationic vacancies and gallium ions in the spinel structure are ordered, resulting in the formation of a superstructure within the tetrahedral sublattice. Consequently, the solid solutions under investigation are classified within the \(\text{F}\overline{4}3\text{m }\) $\text{F}\overline{4}3\text{m}$ space group, rather than \(\text{Fd}\overline{3}\text{m }\) $\text{Fd}\overline{3}\text{m}$ . This study demonstrates how the magnetic properties of the investigated solid solutions are influenced by the presence of ordered vacancies. A change from paramagnetic to antiferromagnetic with weak ferromagnetism was observed for all compositions. The magnetic transition temperatures (T_N = 19–34 K for x = 0–0.3, respectively) have been determined. It has been demonstrated that the substitution of gallium by cobalt leads to an increase in the magnetic transition temperature. Furthermore, an increase in coercivity (H_C, from 1.41 to 2.62 kOe) and residual magnetization (M_R, from 0.007 to 0.034 μ_B) was observed in series with increasing cobalt concentration.