Magnetic phase diagram of Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript>2</Subscript>S<Subscript>4</Subscript> solid solutions

Using experimental data, we have constructed a magnetic phase diagram of Co _x Zn_1–x Cr₂S₄ spinel solid solutions. According to the phase diagram, the Co _x Zn_1–x Cr₂S₄ system has four magnetically active regions: paramagnetic, ferrimagnetic, antiferromagnetic, and spin glass. The CoCr₂S₄-based ferrimagnetic thiochromite solid solutions exist in the widest composition range (not counting the paramagnetic region): 0.31 ≤ x < 1.0. Lowering the temperature leads to a reentrant and a spin-glass transition of these materials. The next in area is a metastable region: 0.12 ≤ x ≤ 0.31. In this composition range, a pure spin glass transition occurs from the paramagnetic region. ZnCr₂S₄-based antiferromagnetic thiochromite materials exist in the narrowest composition range: 0 ≤ x ≤ 0.12.     

Magnetic Properties of CuTi<Subscript>2−2<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>4</Subscript> Materials

The magnetic properties of semi-conductor CuTi_2−2x Cr_2x S₄ systems have been studied. The nearest neighbour J ₁(x) and the next-neighbour super-exchange J ₂(x) interactions are evaluated by using the mean field theory for this spinel CuTi_2−2x Cr_2x S₄ system. The magnetic energy, the intraplanar and the interplanar interactions are deduced. The high-temperature series expansion (HTSE) combined with the Padé approximants method (PA) is applied to this spinel system to determinate the magnetic phase diagrams, i.e. T _C versus dilution x. The critical exponents associated with the magnetic susceptibility (γ) and with the correlation length (ν) are deduced in order phase.     

Structural and magnetic properties of Cr<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te (<Emphasis Type="Italic">x</Emphasis> = 0−0.4) solid solutions

Cr_1?x V _x Te solid solutions with a hexagonal structure (NiAs type) have been obtained in the composition range x = 0?0.4 by direct melting of elemental mixtures, followed by annealing and quenching. The 80-K magnetic moment is found to decrease from 2.4μ_B in CrTe to 1.52μ_B in Cr_0.6V_0.4Te. The Curie temperature varies from 342 K to 321 K, respectively.     

Thermal conductivity of Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Se (<Emphasis Type="Italic">x</Emphasis> ≤ 0.025) solid solutions

The thermal conductivity of Er _x Sn_{1 ? x} Se solid solutions has been measured at temperatures from 80 to 360 K. The results have been used to evaluate the electronic and lattice components of thermal conductivity for elastic carrier scattering, parabolic bands, and arbitrary degeneracy. With increasing erbium content and temperature, both the electronic and lattice components decrease considerably. Long-term annealing increases both components. It follows from the present experimental data that heat conduction in Er _x Sn_{1 ? x} Se is mainly due to phonons and that the observed rise in thermal resistance with Er content is due to phonon-phonon and paramagnetic-ion scattering.     

Formation of interfacial CdTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> solid solutions in CdTe/CdS heterojunctions

Experimental evidence is presented that interfacial CdTe_1?x S _x solid solutions graded in composition can be formed in CdTe/CdS heterojunctions.     

Dominancy of antiferromagnetism in Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O diluted magnetic semiconductors

The outline of magnetic interactions in DMSs was determined using Zn_1−x Co _x O particles, where “x” was changed as 0.01, 0.05, 0.10, 0.15, and 0.20. The syntheses were accomplished though mechanical milling and thermal treatment, known as solid state reaction. The formation of each synthesis was monitored by differential thermal and thermo gravimetric methods (DT-TGA). Substitution of Co²⁺ ions with Zn²⁺ host atoms in a ZnO lattice was analyzed using X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectrometry (EDS) data, transmission electron microscopy (TEM) figures, scanning area electron diffraction (SAED) patterns, and X-ray photo spectroscopy (XPS) spectrum. The measured Co contents in ZnO lattice were found to be ~0.7% less than the expected result. In addition to Zn_1−x Co _x O particles, tungsten (W) contaminations were noticed in the variations of 1.5 ± 0.2%, as originating from the abrasion between the miller and balls. The progressive replacement of Co²⁺ with Zn²⁺ host ions in ZnO lattice from 1% to 20% decreased the band edge from 3.03 ± 0.01 eV to 2.95 ± 0.01 eV, respectively. Co doping has also changed the magnetic nature of the ZnO. Although having both interactions (ferromagnetic and antiferromagnetic), dominance of ferromagnetic behavior was only observed for Zn_0.99Co_0.01O with the coercivity of ~154 ± 50 Oe and positive Curie–Weiss temperature as 79 ± 1 K. However, the calculated \frac2J_\textex k_\textB {\frac{{2J_{\text{ex}} }}{{k_{\text{B}} }}} values have proved that the higher Co²⁺ concentrations in ZnO lattice have increased the efficiency of antiferromagnetic interactions. Surprisingly, there was no rapid change at \frac2J_\textex k_\textB {\frac{{2J_{\text{ex}} }}{{k_{\text{B}} }}} values as mentioned in previous works.     

Hydrochemical synthesis of AgCl<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Br<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> solid solutions

A phase-component model is proposed for the hydrochemical conversion of silver chloride to AgCl _x Br_{1 − x} solid solutions, and the corresponding quantitative relations are derived. Experimental data are used to obtain a relation between the equilibrium composition of solid solutions and that of the liquid phase at different temperatures. The possible mechanisms of solid-solution formation are considered.     

Lattice parameter of PbTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cl<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> solid solutions

The lattice parameter of PbTe_1?x Cl _x solid solutions is shown to be a nonmonotonic function of chlorine content, with a minimum at x = 0.005. The results are interpreted in terms of a self-compensation model.     

Enhanced Superconductivity in Double-Doping Cu<Subscript>0.15</Subscript>TaSe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript><Emphasis Type="Italic">S</Emphasis><Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Superconducting Cu _x TaSe₂(x=0.05, 0.15) and Cu_0.15TaSe_2?x S _x (x=0, 0.5, 1, 1.5) single crystals have been systematically fabricated by a chemical vapor transport method. It is found that the double doping in TaSe₂, i.e., the simultaneous intercalation of Cu and substitution of Se by S, can substantially enhance the superconducting transition temperature. Transport property measurements give evidence of the coexistence and competition of charge density wave state and superconductivity in Cu _x TaSe₂ which provide meaningful information to understand the complex electronic states in this system. The parallel shift and the fan-shape broadening behaviors are observed in the superconducting transition curves under magnetic fields of Cu_0.15TaSeS and TaSeS, respectively, indicating an increase of coherence length and suppression of superconducting fluctuation induced by copper intercalation.     

Magnetic Behaviors of Ferromagnetic Semiconductor Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te Grown by MBE

The magnetic and structural properties of MBE-grown films of Zn_1?xCr _x Te were investigated. The magnetization versus magnetic field (M–H) measurement of Zn_1?xCr _x Te (x = 0.01–0.17) showed clear hysteresis loop at low temperatures. The ferromagnetic transition temperature (T_C) estimated from the Arrott-plot analysis increased almost linearly with the Cr composition (x) up to 275 K at x = 0.17. However, in the magnetization versus temperature (M–T) measurement, the irreversibility between the zero-field-cooled (ZFC) and field-cooled (FC) processes was observed. This is typically observed in the magnetic random system such as spin-glass or superparamagnetic phase. In the high resolution transmission microscopy (HRTEM) observations, structural defects such as stacking faults and polycrystalline-like structure were observed at high Cr compositions, whereas any apparent precipitates of different phases were not seen in all the range of Cr compositions examined. The correlation of the observed magnetic randomness with the local structural defects was discussed.     

Magnetic Phase Diagram of CuCr<Subscript>2–<Emphasis Type="Italic">x</Emphasis></Subscript>Sb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>4</Subscript> Solid Solutions

The magnetization of CuCr_2–xSb _x S₄ solid solutions has been measured as a function of temperature between 300 and 5 K in a weak (3980 A/m) and a strong (7960 A/m) magnetic field. We have identified the type and character of the magnetic transformations observed in the system and determined the temperature and composition limits of the stability regions of the magnetically active phases involved and the cation and valence distributions in them. A magnetic phase diagram of the synthesized materials has been mapped out, where the largest area (0 < x < 0.23) after the paramagnetic region is occupied by solid solutions based on the CuCr₂S₄ ferromagnet. In the composition range (0.23 < x < 0.40) adjacent to the infinite clusters—CuCr₂S₄ ferromagnet and CuCr_1.5Sb_0.5S₄ antiferromagnet—the phase diagram contains medium and small finite ferro- and antiferromagnetic clusters forming a short-range magnetic order or spin glass. The compositions based on the CuCr_1.5Sb_0.5S₄ antiferromagnet lie in the composition range 0.4 < x < 0.5.     

Synthesis and structural properties of AgCl<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Br<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0.5–0.8) solid solutions

The properties of AgCl_{1 - x} Br_x ( x = 0.5-0.8) solid solutions prepared by the Bridgman-Stockbarger method are studied using a variety of techniques (x-ray diffraction, microstructural examination, chemical analysis, and x-ray microanalysis). The lattice parameter of the solid solutions is found to exhibit a negative deviation from additivity. The effects of composition and preparation conditions on the structural properties of the solid solutions are discussed. The structural characteristics of abrasively polished surfaces of the samples are shown to be influenced by the preparation conditions.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 78–87. Original Russian Text Copyright © 2005 by Artjushenko, Baskov, Golovanov, Kuzmicheva, Lisitskii, Musina, Polyakova, Sakharov, Sakharova.     

Thermal conductivity of TlIn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Dy<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>2</Subscript> solid solutions

The thermal conductivity of TlIn_{1 ? x} Dy _x Te₂ solid solutions, based on the compound semiconductor TlInTe₂, has been measured as a function of temperature (80–350 K). The results have been used to assess the effects of phonon-phonon and impurity scattering on the thermal conductivity of the solid solutions. Phonon scattering by the isovalent impurity Dy is shown to be significant above the Debye characteristic temperature of the materials.     

The thermovoltaic effect in variband solid solution Si<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 1)

The thermovoltaic effect in films of variband solid solution Si_1–x Ge _x (0 ≤ x ≤ 1) has been observed for the first time. The samples comprised n-Si–p-Si_1–x Ge _x (0 ≤ x ≤ 1) heterostructures grown by liquid phase epitaxy. An electromotive force within 0.05–0.3 mV and a current of 0.0025–0.0035 μA appeared on heating samples in a temperature range from 40 to 250°C.     

Inhomogeneous magnetic states in Mn<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sb (0.6 ≤ x ≤ 1.0) solid solutions

Mn_{2 ? x} Zn _x Sb (0.6 ≤ x ≤ 1.0) solid solutions are shown to undergo magnetic phase separation (coexistence of two magnetic phases in a structurally homogeneous material) using a combination of characterization techniques (magnetometry, X-ray diffraction, neutron diffraction, Mössbauer spectroscopy, and resistivity measurements). A model is presented for the coexistence of two magnetic phases in the two-sublattice ferrimagnet Mn₂Sb diamagnetically diluted with zinc.     

Low-temperature heat capacity of Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> solid solutions

The heat capacity of Li _x Ni_{2 − x} O₂ (x = 0.40–0.76) oxides has been measured using an adiabatic calorimeter, and their thermodynamic functions have been determined. The results indicate that the lithium nickelate solid-solution series contains a two-phase region and that near-stoichiometric LiNiO₂ has a layered structure, in accordance with earlier results.     

Structural Defects in Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>As<Subscript>2</Subscript> Solid Solutions

The impurity photoconductivity spectra of undoped Cd_{1 ? x} Zn _x As₂ single crystals with x ≤ 0.06 are measured in the range 85–300 K. The results are used to determine the ionization energies of donor and acceptor levels produced in the crystals by structural defects: ?_d ≈ 0.019, 0.26, and 0.42 eV; ?_a = 0.24 and 0.34 eV, respectively. The nature of the structural defects responsible for these levels is discussed.     

Heat capacity of Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> solid solutions

We have synthesized Li _x Ni_{2 − x} O₂ oxides in the range x = 0.1–0.84 and showed that the solid-solution system contains a two-phase region. The heat capacity of Li _x Ni_{2 − x} O₂ has been determined by differential scanning calorimetry.     

Mechanism of AC charge transport in TlSb<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>2</Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0 and 0.03)

The dielectric properties and ac electrical conductivity of TlSb_1–xGa _x S₂ (x = 0, 0.03) single-crystals have been measured in the frequency range 5 × 10⁴ to 3.5 × 10⁷ Hz. Experimental data on the frequency dispersion of the dielectric coefficients and electrical conductivity of the TlSb_1–xGa _x S₂ (x = 0, 0.03) single crystals have allowed us to identify the nature of the dielectric loss and the mechanism of charge transport and evaluate parameters of localized states in the band gap. The incorporation of gallium atoms into the crystal lattice of TlSbS₂ crystals has been shown to lead to an increase in the Fermi-level density of states and mean hop time and distance.     

Structure of Cs<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Rb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>H<Subscript>2</Subscript>PO<Subscript>4</Subscript> solid solutions

Cs_{1 − x} Rb _x H₂PO₄ solid solutions have been synthesized for the first time in a broad composition range, x = 0.03–0.9. At room temperature, the Cs_{1 − x} Rb _x H₂PO₄ solid solutions are isostructural with the low-temperature phase of CsH₂PO₄ over the entire composition range studied. In the CsH₂PO₄-based solid-solution series, the unit-cell parameters and volume decrease with increasing Rb content. At high temperatures, the Cs_{1 − x} Rb _x H₂PO₄ solid solutions exist in the range x = 0–0.4, are isostructural with cubic CsH₂PO₄, and have a smaller unit-cell parameter.