E. V. Busheva

New antiferromagnetic semiconductor CuCr1 5Sb0 5S4

Abstract The magnetic, electric and crystallographic properties of the new compound with the spinel structure CuCr 1.5 Sb 0.5 S 4 were studied. It appears that this compound, being a non-degenerate p-type semiconductor, has magnetic properties typical of antiferromagnets: a linear magnetic field dependence of the magnetization and a maximum of the magnetic susceptibility at temperature T N = 28 K. Also, the lattice parameter a , the anion parameter u and the temperature factors are presented. The distances between cations (both in the tetrahedral and octahedral positions) and anions show that between anions and cations in tetrahedral positions, the covalent bond dominates and between anions and cations in octahedral positions, the ionic bond dominates.

Synthesis and magnetic properties of CuCr1.5Sb0.5S4 − xSex solid solutions

CuCr1.5Sb0.5S4 − xSex (x = 0, 0.5, 3.5, 4) metal chalcogenides with spinel structure have been synthesized for the first time. Unit cell parameters have been calculated and magnetic properties have been measured for the samples prepared. These samples are nonuniform antiferromagnets having Neel temperatures of TN = 21–30 K.

CuCr2–xSbxS4 and Cu1–ySbyCr2S4 solid solutions

CuCr2–ySbxS4 and Cu1–ySbyCr2S4 solid solutions with the spinel structure were synthesized, and their magnetic and electrical properties were studied. The limits of solid solutions in these systems were found to bex = 0.5 andy = 0.22. Models of the cation distributions in the solid solutions are proposed. The CuCr2-xSbxS4 solid solutions with 0.10 <x < 0.15 are magnetic semiconductors with high ferromagnetic ordering temperatures.

Magnetic phase diagram of solid solutions in the CoCr2S4–Cu0.5In0.5Cr2S4 system

The magnetic properties of CoCr2S4–Cu0.5In0.5Cr2S4 solid solutions have been studied in the temperature range 5–300 K at different ac magnetic field frequencies (100, 500, and 1000 Hz) and an amplitude of 79.6 A/m. We have determined the temperatures of the magnetic transformations in the system, identified their nature, and constructed the magnetic phase diagram of the solid solutions.

Magnetic properties of solid solutions CuCr1.5 + x Sb0.5 – x S0.5Se3.5 (x = 0–0.5)

Magnetic properties of anion-substituted solid solutions CuCr1.5 + xSb0.5–xS0.5Se3.5 (x = 0–0.5) have been studied in the temperature range 5–300 K and in magnetic fields up to 10 kOe. Effective magnetic moments and Curie and Curie–Weiss constants have been determined. The increase in asymptotic Curie temperature with increasing x is explained by the increase in the content of Cr4+ ions generated through the Cr3+ ↔ Cr4+ valence redistribution.

Magnetic phase diagram of (1–x)CuCr1.5Sb0.5S0.5Se3.5–xCuCr2S0.5Se3.5 solid solutions

CuCr1.5 + xSb0.5–xS0.5Se3.5 (x = 0–0.5) mixed chromium chalcogenide spinels have been synthesized for the first time. Their magnetic properties have been studied, their magnetic transformations have been identified, and the magnetic phase diagram of the solid solution system has been mapped out. The CuCr2S0.5Se3.5-based ferromagnetic materials have the largest phase field in the system (0.23 ≤ x<0.5). With decreasing temperature, the materials undergo a reentrant transition to a spin glass state. In the composition range 0.12 ≤ x ≤ 0.23, the transition to a spin glass state occurs from the paramagnetic region. The antiferromagnetic materials have the smallest phase field (0 ≤ x ≤ 0.12).

Magnetic properties of CuCr2–хSbxSe4 (х = 0–0.5) solid solutions

Magnetic properties of spinel solid solutions CuCr2–хSbxSe4 (х = 0–0.5) were measured in the temperature range 5–300 K in a constant (50 Oe and 10 kOe) magnetic field. The results are interpreted in terms of the ionic model suggested earlier for CuCr2Х4 compounds.

Paramagnetism in CoxZn1–xCr2S4 solid solutions

The magnetic properties of CoxZn1–xCr2S4 solid solutions have been studied at temperatures from 5 to 300 K in static magnetic fields of 7.96 × 103 and 3.58 × 106 A/m. We have determined the Curie temperatures, Curie–Weiss constants, and effective magnetic moments of the solid solutions. The experimental data are discussed with allowance for the magnetic phase diagram of the system.

Magnetic properties of Cox(Cu0.5In0.5)1–xCr2S4 solid solutions

The magnetic properties of Cox(Cu0.5In0.5)1–xCr2S4 (х = 0, 0.2, 0.5, 0.6) solid solutions between ferrimagnet СоCr2S4 (TC = 223 K) and antiferromagnet Cu0.5In0.5Cr2S4 (TN = 28 K) have been measured over wide ranges of fields (up 40 kOe) and temperatures (5–300 K). The major magnetometric data have been determined. Transition from one end-member of the solid solutions to the other occurs through an intermediate spin-glass phase.

Interaction between Cr2Se3 and Cu2GeSe3

The interaction along the Cu2GeSe3-Cr2Se3 join has been investigated using differential thermal and X-ray powder diffraction analyses. It has been found that the join is quasi-binary with a degenerate eutectic based on the Cu2GeSe3 compound. Two new quaternary compounds have been found along the join, namely, Cu2GeCr6Se12 and the γ phase. The phase is formed at 915°C by the peritectic reaction L + β-Cr2Se3 = γ and has the primary crystallization region up to 9 mol % Cr2Se3 in the temperature range 758–915°C. The room-temperature homogeneity range of the γ phase is 65–70 mol % Cr2Se3. The Cu2GeCr6Se12 compound is formed by the peritectoid reaction γ + β-Cr2Se3=Cu2GeCr6Se12 at 880°C, and its homogeneity range is 73–79 mol %. The X-ray reflections of the γ phase are indexed for the tetragonal crystal system with the unit cell parameters a = 12.043 Å and c = 9.180 Å. Samples with ferromagnetic properties are found in the homogeneity regions of both compounds.