Magnetic and electrical properties of cation-substituted sulfides MexMn1 ? xS (Me = Co, Gd)

The temperature dependences of the specific magnetization σ and the electrical resistivity ρ of Me _x Mn_{1 − x} S single crystals (Me= Co, Gd; x= 0.05) have been studied in the temperature range 80 K < T < 1000 K. The samples under study have revealed the presence of a spontaneous magnetic moment below the Néel temperature (T _N) and ferromagnetic clusters in Gd_0.05Mn_0.95S in the temperature range 146 K < T < 680 K. Substitution of gadolinium for manganese initiates a transition from p-type to n-type conduction. The change in the conduction type is accompanied by an increase in the electrical resistivity at 300 K by approximately one order of magnitude and, accordingly, by a decrease in the activation energy. The magnetic and electrical properties of the crystals under study have been interpreted in terms of the cluster model with temperature-dependent ferromagnetic exchange and an electron localized in this cluster. Original Russian Text ? S.S. Aplesnin, L.I. Ryabinkina, O.B. Romanova, V.V. Sokolov, A.Yu. Pichugin, A.I. Galyas, O.F. Demidenko, G.I. Makovetskiĭ, K.I. Yanushkevich, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 4, pp. 661–664.     

Thermodynamics of mixtures and solutions of hydroxypropylcellulose with poly(ethylene glycol)

Differential scanning calorimetry, X-ray diffraction analysis, polarization microscopy, methods of cloud points and static sorption, and a polarization-photoelectric installation were used to make a thermodynamic analysis of systems constituted by hydroxypropylcellulose, poly(ethylene glycols), and water. The thermodynamic parameters obtained were correlated with phase diagrams of these systems.     

Correlation between the magnetic and electrical properties of MnSe1-x Te x chalcogenides

The coefficients of thermal expansion, lattice constant, and magnetization of anion-substituted MnSe_{1 - x}Te_x chalcogenides were measured upon cooling in zero and nonzero magnetic fields in the temperature range 4.2–600 K. Resistivity as a function of magnetic field up to 1 T was measured. The dynamic properties of the materials were studied by the ESR method. Magnetoresistance and temperature hysteresis were found in MnSe_{1 - x}Te_x solid solutions.     

Magnetic properties and the metal–insulator transition in GdXMn1−XS solid solutions

The structural, magnetic, electrical, and thermoelectric properties of Gd_XMn_1?XS ($0.01\le X\le 0.3$) solid solutions synthesized for the first time on the basis of $\alpha$-MnS have been studied experimentally in the temperature range 77–1000 K in magnetic fields up to 10 kOe. The synthesized samples are antiferromagnetic semiconductors with an NaCl-type cubic lattice typical of $\alpha$-MnS. Both concentration ($X_c=0.3$) and temperature ($T_c=450K$) metal–insulator phase transitions have been observed. The concentration metal–insulator transition is accompanied by a decrease in resistivity and thermopower by twelve and two orders of magnitude, respectively, with the change in conductivity from p-type to n-type.     

Electrical conductivity and thermopower in Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Mn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> S sulfides

This paper reports on the results of investigations into the structural, electrical, and thermoelectrical properties of sulfides Co _x Mn_{1 ? x} S (0 ≤ x ≤ 0.4) in the temperature range 80–950 K. It is established that the thermopower coefficient α decreases significantly with an increase in the cobalt concentration in the lattice of the α-MnS compound. The Co _x Mn_{1 ? x} S compounds with cobalt concentrations in the range 0 ≤ x ≤ 0.3 are semiconductors with hole conduction (α > 0), whereas the compound with x = 0.4 exhibits metallic conduction (α < 0). It is found that the band gap E _g of the compounds under investigation varies in the range from 1.46 eV for α-MnS (x = 0) to 0.26 eV for Co _x Mn_{1 ? x} S (x = 0.4).     

Correlation of the magnetic and transport properties with polymorphic transitions in bismuth pyrostannate Bi2(Sn1 − x Cr x )2O7

Physics of the Solid State - The correlation of the electrical, magnetic, and structural properties of Bi2(Sn1 − x Cr x )2O7 solid solutions has been investigated for two compositions with x...     

Thermodynamics of liquid-crystalline solutions of hydroxypropyl cellulose in water and ethanol

Phase diagrams were constructed and comprehensive thermodynamic analysis was performed for hydroxypropyl cellulose-water and hydroxypropyl cellulose-ethanol systems with the use of the static sorption, calorimetry, cloud-point, polarization microscopy, and X-ray diffraction analysis techniques and the measurement of transmitted polarized light intensity. The concentration dependences of the enthalpy, entropy, and Gibbs energy of the formation of liquid-crystalline phases in the systems were determined. It was found that the formation of liquid-crystalline solutions of hydroxypropyl cellulose in water is associated with the energy term of interaction between the components and that in ethanol solutions is due to changes in combinatorial entropy.     

Transmission spectra of films of Mn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se solid solutions

Films of Mn_1−x Fe _x Se (x = 0–0.45) solid solutions were flash-sputtered. We measured the transmission spectra of the films in the wavelength range 200–1000 nm at room temperature. From these spectra, we calculated the absorption coefficients and determined the fundamental absorption edge, the position of which is shifted from 2.65 eV in MnSe to 2.30 eV in solid solutions of compositions x = 0.20–0.45. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 136–138, January–February, 2007.     

Weak ferromagnetism and spin density distributions in thin films of Gd x Bi1 − x FeO3 solid solutions

Polycrystalline thin-film Gd _x Bi_{1 ? x} FeO₃ (x = 0, 0.05, 0.10, 0.15, or 0.20) samples are synthesized by means of thermal vacuum deposition. The concentrations, temperatures, and magnetic field dependences of specific magnetization are studied. Self-consistent calculations of the spin density distribution are performed for R3c BiFeO₃ and Pnma Gd_0.25Bi_0.75FeO₃ using the density functional theory in the LSDA approximation.