The magnetostriction of FexMn1 − xS (x = 0.27) single crystals in strong magnetic fields up to 120 kOe has been investigated. It has been found that the magnetostriction
reaches colossal values (±3 × 10−4) atypical of compounds of 3d elements. It has been found that the magnetostriction changes sign when varying temperature and magnetic field; this behavior
indicates an important role of the spin-phonon interactions in the formation of the magnetic order in solid solutions of iron-manganese
sulfides. 相似文献
The structure of high-temperature SrFe1 − xMoxO3 − z (0 ≤ x ≤ 0.5) phases was studied. Such studies are necessary to understand the mechanism of oxygen transport in membrane materials
used for high-temperature oxygen separation. 相似文献
The electronic structure and ground state parameters of B2 RuAl-based refractory alloys have been investigated in the framework of the density functional theory using the exact muffin-tin
orbital method in combination with the coherent potential approximation. It has been demonstrated that the number of states
at the Fermi level for the Ru1 − xMexAl alloys as a function of the alloying metal content has a minimum, which indicates a change in the Fermi surface topology
and the presence of specific features in the behavior of elastic constants. It has been concluded that the electronic structure
of the alloys can be described in terms of the rigid band model. The nonlinear variations of the lattice parameters of the
alloys has been explained. 相似文献
The temperature dependence of the conductivity of the two-dimensional hole gas in an asymmetric GaAs/InxGa1 ? xAs/GaAs quantum well has been investigated. It is shown that fast spin relaxation leads to metallic-like behavior of the temperature dependence of the conductivity. 相似文献
The capacitance and dielectric loss tangent of GdxMn1–xS (x ≤ 0.2) solid solutions have been measured at a frequency of 10 kHz without magnetic field and in a magnetic field of 8 kOe in the temperature range of 90–450 K. An increase in the permittivity and a dielectric loss maximum have been detected in the low-temperature region. It has been found that the temperature of the maximum of the imaginary part of the permittivity shifts to higher temperatures with increasing concentration. The magnetocapacitance effect has been revealed for two compositions. The dielectric loss has been described in the Debye model with “freezing” dipole moments and in the orbital-charge ordering model. 相似文献
Results of an experimental study of MnS, FeS, and FexMn1?xS single crystals are presented. The phase composition, the lattice parameters, and the state of paramagnetic ions in FexMn1?xS have been determined by x-ray diffraction analysis and Mössbauer spectroscopy. A sequence of transitions have been found in iron manganese sulfide with x = 0.29 at temperatures T1 ≈ 25–50 K, T2 ≈ 125 K, and T3 ≈ 190 K with a change in kinetic properties and the formation of a metallic state at low temperatures T ≈ 2 K. The possibility of a Mott-Hubbard transition in FexMn1?xS sulfides with variation of the composition and the temperature is discussed. 相似文献
The results of experimental investigation of magnetic and electric properties of Fe1?xDyxSi crystals are reported. It is shown that the magnitude and position of the anomaly observed in the temperature dependences of magnetization are controlled to a considerable extent by the external magnetic field. It is found that the introduction of Dy ions leads to a weak magnetoresistive effect. 相似文献
The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths.
Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing
is fixed by known G/ψ−ηc(1S), ψ(2S)−ηc′(2S) splittings, which appears to be small, rss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed
in bottomonium. For nS b
states (n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3S and 4S charmonium states, the splittings 16(2) and 12(4) MeV are obtained.
The text was submitted by the authors in English. 相似文献
Orthovanadates Ce1–xBixVO4 (1 ≥ x ≥ 0) have been produced by solid-phase synthesis from initial oxides CeO2, Bi2O3, and V2O5 upon step-by-step burning. The high-temperature heat capacity of Ce1–xBixVO4 has been measured by differential scanning calorimetry. The experimental data on Cp = f(T) were used to calculate the thermodynamic properties (the enthalpy changes, the entropy changes, and the Gibbs energy). 相似文献
Charge density calculations and electronic band structures for GaxAl1 − xSb with x = 1.0, 0.5 and 0.0 are presented in this work. The calculations are performed using the empirical pseudopotential method.
The charge density is computed for a number of planes, i.e. z = 0.0, 0.125 and 0.25 A0 by generating the potential through a number of potential parameters available in the literature. The virtual crystal approximation
was applied for the semiconducting alloy. The characteristics of the band structure and charge density are observed to be
affected by the potential parameters. Calculated band gaps and the nature of gaps are in good agreement with the experimental
data reported. The ionicity is also reasonably in good agreement with other scales proposed in the literature; however the
formulation needs to be improved. The present work also demands indirect experimental band gap for the alloy.
相似文献
Nano-octahedra of cobalt ferrite CoxFe3???xO4 (1?≤?x?<?2), with a broad size distribution around 15–20 nm, were synthesized by a hydrothermal method using nitrates as precursors. For the first time, single-phased nano-octahedra of cobalt-rich ferrite CoxFe3???xO4 (x?=?1.5) were synthesized. The nano-octahedra are crystallized in a normal spinel structure, with tetrahedral sites occupied by Co2+. This specific octahedral shape was obtained with anionic, cationic, and nonionic surfactants. The nature of the surfactant influenced the chemical composition of the powder and the size of the nano-octahedra. The {100} truncation of the octahedra is more pronounced for the small particles. For the first time, single-phased nanoparticles with as much as x?=?1.8 cobalt were synthesized with ethylene glycol as solvent. These nanoparticles, around 8 nm in size, have no specific shape and possess a lacunar spinel structure similar to maghemite. The samples were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy.
New Rb3PO4-based ceramic materials with high rubidium-cation conductivity in the Rb3–2xPbxPO4 system have been synthesized and studied. Introduction of Pb2+ cations leads to a sharp increase in the conductivity of rubidium orthophosphate due to formation of cation vacancies and, at temperatures 350–550°C, also due to the stabilization of high-temperature cubic modification Rb3PO4. At high temperatures, the electrolytes prepared have very high ion conductivity higher than 10–1 S cm–1 at 700°C, which is higher than the values previously obtained in similar systems with additions of tin and cadmium ions. The factors influencing the transport properties of the materials under study are discussed. 相似文献
Previously, iron—silicon alloys were investigated using X-ray diffraction and Mössbauer spectroscopy. It was demonstrated that, at low silicon concentrations, the alloys undergo a local separation into regions of the α iron phase depleted in silicon and silicon-rich clusters with a B2 ordering. The structure of locally ordered regions of the B2 phase is characterized by a pair ordering of silicon atoms: the Si—Si pairs are formed by next-nearest neighbors, and the axes of pairs are oriented along the 〈100〉 directions, which are the easy-magnetization axes. The thermomagnetic treatment in a constant magnetic field applied along the 〈100〉 axis induces an axial magnetic anisotropy, results in the formation of an anisotropic distribution of the B2 phase, and leads to a slight decrease in the volume fraction of the coordination 6: 2 with two silicon atoms in the first coordination shell of the iron atom. Therefore, the formation of an anisotropic local order of pairs of silicon atoms occurs as a result of their reorientation. 相似文献
A technology for obtaining single-phase ceramic samples of La1 − xKxMnO3 manganites, as well as the dependence of their structure parameters on the potassium content, is described. The magnetocaloric
effect in the samples has been measured by two direct methods, the classical method and the magnetic field modulation method,
and has been calculated from the specific heat data. The values of the magnetocaloric effect obtained by these methods are
significantly different. The observed discrepancies have been explained. Correlation between the doping level and the value
of the effect has been found. It has been shown that the magnetic-field dependence of variation of the magnetic entropy near
TC in weak fields corresponds to theoretical calculations and that the value of the magnetocaloric effect in high magnetic fields
can be predicted using this dependence. 相似文献
A symmetry analysis of ordering in lithium nickelite Li1?x?zNi1+xO2 (Li1?x?z□yNi1+xO2) was performed with regard to the substitution of Li and Ni atoms and the occurrence of structural vacancies □ in the metal sublattice. For all the ordered phases, the k9(3) ray of the Lifshitz {k9} star is present in the order-disorder transition channel. This ray determines the consecutive alternation of atomic planes filled with only Ni atoms or only Li atoms and vacancies in the \([1\bar 11]_{B1} \) direction. It was shown that the rhombohedral ordered LiNiO2 phase is formed in the defect-free lithium nickelite, whereas a family of three monoclinic Li3□Ni4O8 (C2/m space group) and Li2□Ni3O6 (C2/m and C2 space groups) superstructures arises as the concentration of structural vacancies increases. For all the superstructures, the order-disorder phase-transition channels were determined and the distribution functions of Li and Ni atoms have been calculated. The long-range order parameters describing each superstructure were found as functions of the Li1?x? zNi1+xO2 composition. 相似文献
The isothermal changes in the magnetic entropy and the lattice entropy and the adiabatic temperature change in La(Fe0.88Si0.12)13 and La(Fe0.86Si0.14)13 ferromagnets in a magnetic field are calculated. The calculations are performed with a generalized magnetostriction model
of a ferromagnet; the calculation results are compared to experimental data. It is shown that the change in the lattice entropy
decreases the magnetocaloric effect and makes it possible to explain the experimental data obtained for La(FexSi1 − x)13 (x = 0.86, 0.88) ferromagnets. The temperature dependences of the bulk compression moduli of these ferromagnets are calculated,
and these dependences indicate a strong lattice softening in the vicinity of the magnetic phase transition in them. The thermal
expansion coefficient and some magnetic properties of the ferromagnet with x = 0.86 are measured to determine the numerical values of the parameters entering into calculation formulas. 相似文献
We investigate the inclusive photoproduction of J/ψ mesons at HERA within the framework of the kT-factorization QCD approach. Our study is based on the color singlet model supplemented with the relevant off-shell matrix
elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon
contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS
collaborations. Special attention is put on the J/ψ polarization parameters λ and ν, which are sensitive to the production dynamics. 相似文献
The structure, the magnetic and magnetotransport properties of perovskite Sr0.9Y0.1CoO2.63 have been studied. The sample is shown to have a two-phase structure. The main phase has a tetragonally distorted unit cell and is described by space group I4/mmm. The broadening of the reflections with indices corresponding to doubling unit cell parameter c indicates the absence of the rigorous translation symmetry along axis c. The existence of the broadened superstructure reflection observed in the diffraction pattern at small angles at temperature lower than 400 K is explained by the existence of the monoclinic phase whose content is significantly lower than that of the tetragonal phase, but is dominant in the Sr0.8Y0.2CoO3–δ composition. The spontaneous magnetization appears as the monoclinic phase forms. The magnetic structure is mainly G-type antiferromagnetic with magnetic moments 1.5μB in the layers of CoO6 octahedra and 2μB in the anion-deficit CoO4 + γ layers. The conduction of the Sr0.9Y0.1CoO2.63 composition has a semiconducting character. The magnetoresistance is 57% in a field of 14 T at a temperature of 5 K and strongly decreases with the temperature increase. 相似文献
We report Eu-local-spin magnetism and Ni-doping-induced superconductivity (SC) in a 112-type ferroarsenide system Eu(Fe1?xNix)As2. The non-doped EuFeAs2 exhibits two primary magnetic transitions at ~100 and ~40 K, probably associated with a spin-density-wave (SDW) transition and an antiferromagnetic ordering in the Fe and Eu sublattices, respectively. Two additional successive transitions possibly related to Eu-spin modulations appear at 15.5 and 6.5 K. For the Ni-doped sample with x = 0.04, the SDW transition disappears, and SC emerges at Tc = 17.5 K. The Eu-spin ordering remains at around 40 K, followed by the possible reentrant magnetic modulations with enhanced spin canting. Consequently, SC coexists with a weak spontaneous magnetization below 6.2 K in Eu(Fe0.96Ni0.04)As2, which provides a complementary playground for the study of the interplay between SC and magnetism. 相似文献