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1.
Pressure effects on the Curie temperature and the crystallographic phase transition temperature of CeAg were determined from an electrical resistivity measurement from 4.2 to 300 K at hydrostatic pressures up to 5 kb. Results correspond to the alloying effect in Ce(Ag,In).  相似文献   

2.
Magnetization measurements for CeAg under hydrostatic pressures up to 4.0 kbar and CeAg1?xInx compounds (0.01 ? x ? 0.20) at normal pressure were made at 4.2 K in magnetic fields up to 50 kOe. It was found that the magnetization of CeAg under pressure and of CeAg1?xInx were larger than that of CeAg at normal pressure.  相似文献   

3.
We show that in a metal the magnetic field effect on the longitudinal acoustic sound propagation is drastically enhanced by the exchange interaction between electrons, and that observed large magnetic field effects in A15 compounds as well as in itinerant electron ferromagnets can be qualitatively understood from such results.  相似文献   

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The structural stability of CeAg has been studied by self-consistent full-potential linearized augmented plane wave method (FP_LAPW) based on the density functional theory (DFT). The result shows that the low-temperature phase of CeAg is not a simple tetragonal structure. The degenerate d states at the Fermi level are split because of atomic shifts, which result in the cubic-to-tetragonal transition.  相似文献   

7.
The role of elastic stress in statistical and scaling properties of elastic turbulence in a polymer solution flow between two disks is discussed. The analogy with a small-scale magnetodynamics and a passive scalar turbulent advection in the Batchelor regime is used to explain the experimentally observed statistical properties, the flow structure, and the scaling of elastic turbulence. The emergence of a new length scale, namely, the boundary layer thickness, is observed and studied.  相似文献   

8.
The present study aims at providing insight into the acceleration mechanism of a bubble chain rising in shear-thinning viscoelastic fluids. The experimental investigation by the Particle Image Velocimetry (PIV), birefringence visualisation and rheological simulation shows that two aspects are central to bubble interactions in such media: the stress creation by the passage of bubbles, and their relaxation due to the fluids memory forming an evanescent corridor of reduced viscosity. Interactions between bubbles were taken into account mainly through a linear superposition of the stress evolution behind each bubble. An analytical approach together with the rheological consideration was developed to compute the rise velocity of a bubble chain in function of the injection period and bubble volume. The model predictions compare satisfactorily with the experimental investigation.  相似文献   

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Density functional theory(DFT) is applied to investigate the stability and mechanical properties of NbxCy compounds.The structures of NbxCy compounds are optimized, and the results are in good agreement with previous work. The calculated results of the cohesive energy and the formation enthalpy of NbxCy show that they are thermodynamically stable structures, except for Pmc21-Nb2 C. The mechanical properties such as the bulk modulus, Young’s modulus, the shear modulus, and Poisson’s ratio are obtained by Voigt–Reuss–Hill approximation. The results show that the Young’s modulus and shear modulus of NbC are larger than other NbxCy compounds. The mechanical anisotropy is characterized by calculating several different anisotropic indexes and factors, such as universal anisotropic index(AU), shear anisotropic factors(A1, A2,A3), and percent anisotropy(ABand AG). The surface constructions of bulk and Young’s moduli are illustrated to indicate the mechanical anisotropy. The hardness of NbxCy compounds is also discussed in this paper. The estimated hardness for all NbxCy compounds is less than 20 GPa.  相似文献   

11.
A survey is made of pairs of heteronormal planar elastic waves, which can propagate in an unlimited crystal medium and have equal theoretical values of the phase velocity, using Voigt elastic moduli. Such pairs are chosen for which it is possible that the theoretical equality of velocities will be disturbed when using another theory of the elastic properties of crystals with generally different tensors of material constants (for example Kuvshinskij J. V., Aero E. L.: Fiz. tv. tela5 (1963), 2591). In such a case, a comparison of the measured velocities of a suitable pair of waves can help to decide between the two theories. Pairs of waves are found for 12 non-piezoelectric crystal classes. Among such pairs it is easy to find pairs of waves of the same properties for piezoelectric crystal classes.  相似文献   

12.
The magnetic properties of a sample of synthetic ferrihydrite have been investigated by use of Mössbauer spectroscopy. The area ratios of the Mössbauer lines are not significantly changed by application of magnetic fields at 5 K, indicating an amorphous magnetic structure. An average magnetic moment per particle of 3.1×10?21 JT?1 was estimated from the dependence of the hyperfine splitting of the Mössbauer spectra on external magnetic fields at 80 K.  相似文献   

13.
The lattice constants at room temperature and the magnetic properties of several members of the series GdχLa1-χMg were studied in the temperature range 4.2–300 K with applied fields up to 340 kG. Several of the pseudo-binary compounds were found to give rise to antiferromagnetic ordering in low applied fields. In their magnetic isotherms at 4.2 K critical fields occur which are associated with the destruction of the antiferromagnetic ground state. These critical fields were found to increase with La concentration. It is shown that in GdχLa1-χMg the antiferromagnetic interaction between the Gd spins decreases with increasing χ whereas the ferromagnetic interaction increases in the same sense. In GdMg the antiferromagnetic interaction has almost completely vanished, so that superficially this compound looks like a normal ferromagnet.  相似文献   

14.
Elastic scattering through 180° from 9Be, 12C and 13C targets has been observed for electrons of 35 to 90 MeV. Magnetic scattering cross sections for 9Be and 13C have been obtained by subtracting charge scattering as deduced from the scattering from the spin-zero nucleus 12C. Theoretical shell model predictions for the magnetic cross sections are derived for (1s)4(1p)A?4 configurations and various coupling schemes. Both harmonic oscillator and Woods-Saxon radial wave functions are used. A comparison of our results with magnetic cross sections calculated in DWBA yields magnetic rms radii 〈r2M12 = 3.2 ± 0.3 fm and 〈r2M12 = 3.3 ± 0.3 fm for 9Be and 13C. For 13C a combined flt to our low-q data and to earlier high-q data, yields 〈r2M12 = 3.4 ± 0.1 fm and a strong preference for intermediate coupling (IC) wave functions. Magnetic dipole scattering from 9Be is also close to the IC prediction, as deduced from a fit to our data and earlier high-q data. The fitted value of the octupole moment Ω = 5±1 μNfm1 can only be explained by a deformation of the average nuclear potential. The radial size 〈r21p12 = 2.85 ± 0.05 fm for the 1p radial wave function is in agreement with both the 9Be and 13C data.  相似文献   

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Expressions for the effective elastic constants of two-phase composites in the form of series obtained with Fourier transforms have been analyzed. In certain cases, such series are shown to be fully summed up; as a result, one can directly obtain exact expressions for the effective bulk modulus of a composite. It is found that the symmetry of the coefficients in series for the shear modulus and Young’s modulus and the corresponding reciprocal quantities can be used to relate these series to each other. Thus, all well-known exact relations for the effective elastic constants can be derived. A set of equations is proposed to compute the effective constants of a two-dimensional isotropic symmetrical composite with arbitrary properties of its phases.  相似文献   

17.
The general approach to study the properties of the mechanical deformations of solid nematics, which are the macroscopic homogeneous elastic media having the rotational symmetry of the nematic liquid crystals is proposed. The stress tensor, the Young modulus and the Poisson ratios for the parallel and perpendicular homogeneous orientations of nematic molecules relative to the axis of external forces influence are obtained by the varying of the free energy of mechanical deformation. It is shown that these constants have the anisotropic character and the experiments for the direct measurement of five elasticity coefficients entering the free energy expression are proposed.  相似文献   

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The structural phase transformations in various phases (monoclinic, ortho I, ortho II, and tetragonal) of zirconia (ZrO2) have been investigated using an effective interionic interaction potential. The cohesive energy, the equation of state, and the elastic properties of these phases have also been studied and found to reproduce well the experimentally observed data for almost all the phases of zirconia ceramics.  相似文献   

20.
Elastic moduli of transition metal nitrides, TiN, ZrN and HfN, have been evaluated using electrostatic and Born repulsive potentials. Acoustical dissipation due to phonon-phonon (p-p) interaction, thermoelastic mechanism and dislocation damping due to screw and edge dislocations has been evaluated in the temperature range 50-500 K along the three crystallographic directions of propagation, viz. [1 0 0], [1 1 0] and [1 1 1] for longitudinal and shear modes. Grüneisen numbers, acoustic coupling constants and their ratios have been evaluated for the longitudinal and shear waves. Results are in good agreement with available data.  相似文献   

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