T. G. Aminov

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.

A new High-Tc ferromagnet: Manganese-doped CdGeAs2 chalcopyrite

New ferromagnets with high Curie temperatures, reaching 355 K, have been obtained by doping a GdGeAs2 semiconductor compound with manganese. The obtained compounds are magnetically inhomogeneous, comprising a mixture of ferromagnetic (FM) and paramagnetic phases. The volume fraction of the FM phase increases with the degree of doping. The development of ferromagnetism in this system is probably related to the presence of vacancies of the (Cd, VC, Mn)GeAs2 type or to a nonstoichiometry of the (Cd, Ge, Mn)GeAs2 type, since theoretical estimates show that the FM state is energetically more favorable than the spin glass state only in these cases.

Physical Chemistry of the Magnetic Semiconductor CdCr2Se4

The magnetic semiconductor CdCr2Se4 is the best known chalcogenide spinel. This article reviews the available information about this compound: phase diagrams, homogeneity region, vapor pressure, crystal growth, doping of crystals, and defect chemistry. A large body of data in this field have been obtained by the authors.

Superparamagnetism in Mn-doped CuGaTe2

We have established conditions for the preparation of CuGaTe2〈Mn〉 chalcopyrite solid solutions containing manganese on one or two cation sites, which are expected to be suitable for spintronic applications. Models for the formation of the solid solutions have been proposed, and the cation and valence distributions have been inferred from experimental data. The magnetic and electrical properties of CuGaTe2〈Mn〉 can be accounted for by the presence of Mn2+-containing superparamagnetic clusters.

Spin glasses in CdCr2S4-ZnCr2S4 solid solutions

Magnetic properties of the continuous series of the solid solutions formed by the ferromagnet CdCr2S4 and antiferromagnet ZnCr2S4 compounds have been studied. The concentration and temperature boundaries of the magnetically active phases coexisting in the Cd1 − xZnxCr2S4 system have been determined. It has been established that the ferromagnetic samples based on CdCr2S4 lie in the interval of concentrations 0 < x < 0.20, and the antiferromagnetic samples based on ZnCr2S4 are located in the interval of 0.9 < x < 1.0. The widest concentration interval (0.2 < x < 0.9) corresponds to spin glasses. The results obtained are discussed based on the percolation model.

Magnetic properties of Cu0.5Fe0.5 − xGaxCr2S4 solid solutions

Solid solutions between ferrimagnet Cu0.5Fe0.5Cr2S4 (TC = 347 K) and antiferromagnet Cu0.5Ga0.5Cr2S4 (TN = 31 K) have been synthesized, and their magnetic properties studied. Both compounds belong to the A0.5+A0.53+Cr2X4 group with the 1 : 1 order of A+ and A3+ ions in the tetrahedral spinel sites. Measurements on a SQUID magnetometer over wide ranges of fields (0.05–40 kOe) and temperatures (5–300 K) provided a deeper insight into the nature of magnetism and cation distribution in the studied samples.

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.

Magnetic properties of Cu0.5Fe0.5Cr2S4-based solid solutions

Different models are used to analyze the magnetic properties of solid solutions of the Cu0.5Fe0.5Cr2S4 ferrimagnet in the ZnCr2S4, Cu0.5In0.5Cr2S4, and Cu0.5Ga0.5Cr2S4 antiferromagnets. The composition dependences of the saturation magnetic moment and Curie temperature for the solid solutions are determined.

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.

Synthesis and magnetic properties of Cu0.5Fe0.5 − xInxCr2S4 (x = 0−0.4) solid solutions

Multistep synthesis with X-ray diffraction monitoring of the phase composition has been carried out, optimal synthesis parameters have been determined, and the magnetic properties of solid solutions between thiospinels with ordered tetrahedral A lattices (ferrimagnet Cu0.5Fe0.5Cr2S4 (TC = 347 K) and anti-ferromagnet Cu0.5In0.5Cr2S4 (TN = 35 K) have been studied. Both compounds crystallize in F