Solid solutions of Ga(0.67–0.67x)CoxCr2S4 have been synthesized based on the cation-deficient spinel Ga0.67Cr2S4 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 F43m space group, rather than Fd3m . 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 (TN = 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 (HC, from 1.41 to 2.62 kOe) and residual magnetization (MR, from 0.007 to 0.034 μB) was observed in series with increasing cobalt concentration.

The magnetic properties of the Co1-xFexCr2S4 solid solutions for compositions adjacent to CoCr2S4 were investigated using various techniques, including magnetization measurements and AC susceptibility. The results revealed that substituting Fe for Co in the CoCr2S4 compound led to changes in the magnetic behavior, such as the presence of ferrimagnetic ordering and the emergence of a cluster spin glass phase. The study found that the temperature of the ferrimagnetic transition (TC) decreased with increasing Fe concentration, indicating the influence of iron on the magnetic properties of the solid solutions. Additionally, the discovery of a cluster spin glass phase for specific compositions (x = 0, 0.1, 0.2, 0.4) suggests complex magnetic behavior in these materials. In summary, the study offers valuable insights into the magnetic properties of Co1-xFexCr2S4 solid solutions and highlights the potential for tuning their magnetic behavior through compositional variations.

The magnetic susceptibility of Fe1 – xCoxCr2S4 solid solutions in the FeCr2S4-rich part of the FeCr2S4–CoCr2S4 system has been studied by static and dynamic methods. The magnetic measurements were performed at temperatures from 5 to 300 K in static (50 Oe and 45 kOe) and ac magnetic fields (field amplitude Hac = 1 Oe; ac field frequencies ν = 100, 1000, and 10 000 Hz). We have determined the temperatures of the magnetic transformations in the system and identified their nature. The results demonstrate that the temperature of the ferrimagnetic phase transition (TC) in Fe1 – xCoxCr2S4 increases with increasing cobalt content. The materials with x = 0–0.5 have been shown to undergo a transition to a spin glass state, evidenced by a shift of maxima in temperature dependences of the imaginary part of their dynamic susceptibility.

— The magnetic susceptibility of Fe 1 – x Co x Cr 2 S 4 solid solutions in the FeCr 2 S 4 -rich part of the FeCr 2 S 4 –CoCr 2 S 4 system has been studied by static and dynamic methods. The magnetic measurements were performed at temperatures from 5 to 300 K in static (50 Oe and 45 kOe) and ac magnetic fields (field amplitude H ac = 1 Oe; ac field frequencies ν = 100, 1000, and 10 000 Hz). We have determined the temperatures of the magnetic transformations in the system and identified their nature. The results demonstrate that the temperature of the ferrimagnetic phase transition ( T C ) in Fe 1 – x Co x Cr 2 S 4 increases with increasing cobalt content. The materials with x = 0–0.5 have been shown to undergo a transition to a spin glass state, evidenced by a shift of maxima in temperature dependences of the imaginary part of their dynamic susceptibility.

Detailed dynamic magnetic susceptibility measurements for Fe1 – xAgxCr2S4 (x = 0–0.15) solid solutions have shown that polycrystalline silver-doped iron thiochromite undergoes paramagnetic-to-ferrimagnetic phase transitions with transition temperatures dependent on the degree of silver substitution for iron, TC = 194–212 K at x = 0.05–0.15, and spin glass transitions at Tf = 80–115 K for x = 0.05–0.15. The increase in the transition temperatures with increasing silver concentration is attributable to the diamagnetic dilution effect. The cusp observed around 50 K, due to the low-temperature structural anomaly in the Fe1 – xAgxCr2S4 solid solutions, has been confirmed by measuring the imaginary part of their dynamic magnetic susceptibility as a function of temperature, χ''(T), at an increased field modulation amplitude of 15 Oe. An effect related to long-range orbital ordering as a consequence of a Jahn–Teller transition has been found at temperatures TOO = 10–15 K.

The CoCr0.5Ga1.5S4 compound has been synthesized and shown to crystallize in trigonal symmetry (P3m1) with unit-cell parameters а = 3.639 Å and с = 12.016 Å. Its magnetic properties have been measured in the temperature range 4–300 K in static magnetic fields of 50 Oe and 45 kOe and in an ac magnetic field (10, 100 and 1000 Hz) with a modulation amplitude of 1 Oe. According to the results obtained by measuring its magnetic properties, the compound is a ferrimagnet with an ordering temperature TC = 205 K. Temperature dependences of the imaginary part of its dynamic magnetic susceptibility obtained during cooling show a cusp with a frequency dependence indicative of a transition to a reentrant spin glass state at Tf ~ 12 K.

Two series of manganese-doped chalcopyrites Cu 1 – x /2 Ga 1 – x /2 Mn x Se 2 and CuGa 1 – x Mn x Se 2 have been prepared by solid-phase synthesis. Manganese-containing impurities have been found in all samples because of low solubility of manganese in chalcopyrite CuGaSe 2 . Nevertheless, manganese is incorporated into the chalcopyrite structure in a noticeable amount. All manganese-containing chalcopyrites have mainly paramagnetic properties; however, a ferromagnetic contribution has been found for all samples.

Single crystals of chalcogenide chromium spinel CdCr 2 S 4 (ferromagnet, T C ≈ 80 K) have been grown from a solution in a melt. The morphology, local elemental composition, and microstructure elements of the crystals are studied by scanning electron microscopy. All crystals have a composition close to stoichiometric. A study of their magnetic properties in the temperature range of 5–300 K in a constant (100 Oe) and/or alternating (100, 1000, and 10000 Hz) magnetic field show that CdCr 2 S 4 has a number of features that are considered a hallmark of spin glasses.

— We have synthesized Fe 1 – x Ag x Cr 2 S 4 (0 < x < 0.5) solid solutions via doping of the FeCr 2 S 4 thiochromite with silver. From a break in the composition dependence of the unit-cell parameter for the synthesized materials, the solid solution series has been shown to be limited by x = 0.22. The magnetic properties of the solid solutions have been studied at temperatures from 4 to 300 K in a magnetic field H = 3980 A/m (50 Oe). All of the materials have been shown to be ferrimagnets with a Curie temperature rising with silver concentration: from 185 K at x = 0 to 203 K at x = 0.22. We have determined saturation magnetic moments of the solid solutions and proposed a model that accounts for their observed magnetic properties.

— We have synthesized Fe x (Cu 0.5 In 0.5 ) 1 – x Cr 2 S 4 solid solutions and measured their magnetic properties in the temperature range 4.2–300 K in a static magnetic field of 0.1 and 45 kOe. The main magnetostatic parameters of the synthesized materials have been determined: saturation magnetization, effective and spin magnetic moments, Curie and Néel temperatures, Curie constants, and Curie–Weiss constants. The results thus obtained, including the properties of magnetic clusters and the composition dependence of the asymptotic Curie temperature, have been interpreted using a previously reported magnetic phase diagram of the Fe x (Cu 0.5 In 0.5 ) 1 – x Cr 2 S 4 solid solutions, which provides insight into the nature of the phase transformations involved.

We have synthesized Fe x (Cu 0.5 In 0.5 ) 1 – x Cr 2 S 4 solid solutions and measured their magnetization and dynamic magnetic susceptibility as functions of temperature between room temperature and liquid helium temperature in weak magnetic fields H = 100 Oe and Н ~ = 1 Oe at frequencies of 10, 100, 1000, and 10 000 Hz. The results have been used to construct the magnetic phase diagram of the FeCr 2 S 4 –(Cu 0.5 In 0.5 )Cr 2 S 4 system. The largest area in the phase diagram is occupied by the FeCr 2 S 4 ferrimagnet field ( x = 0.28–1), in which there are two types of reentrant spin glass: RSG 1 and RSG 2 . The phase field second in area in the phase diagram is that of spin glass, SG 1 ( x ≈ 0.03–0.28). Antiferromagnet-based compositions have the smallest area in the phase diagram ( x = 0–0.2).

The magnetic susceptibility of the ferrimagnet FeCr2S4 was studied by a dynamic method in order to highlight the nature of a magnetic transition in the region of T = 60 K. The properties of the compound were measured in zeroth DC magnetic field НDC = 0 in the temperature range 4–230 K at the modulation amplitudes НАC = 1 and 17 Oe and the AC frequencies ν = 10, 100, 1000, and 10 000 Hz. At T > 60 K, the properties of FeCr2S4 correspond to the long-range ferrimagnetic order with local spin disorder. Spin lattice distortions (microareas or magnetic clusters) strongly increase in the region of 150 K, where a local spin glass appears with the spin freezing temperature Tf = 155 K. The flat maximum of the impurity spin glass in FeCr2S4 at T = 155 K can be considered as a mere assembly or conglomerate of especially large magnetic clusters with the effective Curie temperature T = 155 K.