We have studied the effects of Sr replacement by different lanthanides in Sr2CrReO6. Our attempts at electron doping of Sr2CrReO6 led to multiphasic systems. Single phases are only obtained with the stoichiometric for...
We have studied the effects of Sr replacement by different lanthanides in Sr2CrReO6. Our attempts at electron doping of Sr2CrReO6 led to multiphasic systems. Single phases are only obtained with the stoichiometric formula Sr2−xLnxCr1+x∕2Re1−x∕2O6. We have studied the properties of these compounds with x⩽0.5 and Ln=La, Nd, or Sm. All of these samples crystallize in a face-centered cubic cell, which shrinks as Ln-size decreases. The distribution of Re and Cr atoms has been solved using x-ray diffraction. The samples show spontaneous magnetization at room temperature with large coercive fields. The Ln addition slightly affects the Curie temperature although the saturated magnetic moment decreases, owing to the increase of antisite defects. We have also studied Sr2−xNdxCr1+x∕2Re1−x∕2O6 and Sr2−xSmxCr1+x∕2Re1−x∕2O6 (x⩽0.5) by means of x-ray absorption spectroscopy. The spectra at the CrK edge agree with the presence of Cr3+ for all compounds although changes with increasing the rare-earth content are visible at the preedge features. These changes suggest a change in the Cr-O covalency of the samples with increasing Ln content. Measurements at the ReL1,2,3 edges reveal the presence of Re5+ in all compounds. This implies that replacing Sr by Ln does not affect the electronic state of both Cr3+ and Re5+.
The confinement of materials in low-dimensional structures has significant impact on propagating excitations like phonons. Using the isotope-specific Fe57 nuclear resonant vibrational spectroscopy we were able to dete...
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The confinement of materials in low-dimensional structures has significant impact on propagating excitations like phonons. Using the isotope-specific Fe57 nuclear resonant vibrational spectroscopy we were able to determine elastic and thermodynamic properties of ultrathin Fe films on W(110). With decreasing thickness one observes a significant increase of the mean atomic displacement that goes along with an enhancement of vibrational modes at low energies as compared to the bulk. The analysis reveals that these deviations result from atomic vibrations of the single atomic layers at the two boundaries of the film, while the atoms inside the films vibrate almost bulklike.
The Ho3Cu4Si4 compound crystallizes with the orthorhombic Gd3Cu4Ge4-type crystal structure, in which the rare earth ions occupy two different crystallographic sites: 2d and 4e. Its complex magnetic properties have bee...
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The Ho3Cu4Si4 compound crystallizes with the orthorhombic Gd3Cu4Ge4-type crystal structure, in which the rare earth ions occupy two different crystallographic sites: 2d and 4e. Its complex magnetic properties have been studied by means of magnetization, heat capacity, electrical resistivity and neutron diffraction measurements. The results reveal that the two magnetic sublattices order independently at 19.5 and 5 K for the 2d and the 4e sublattice, respectively. Moreover, the magnetic ordering of the 4e sublattice changes with the temperature, while the ordering of the 2d sublattice remains unperturbed. These findings hint at local interactions being the more probable origin of the observed magnetic orderings than long-range (RKKY) ones.
We report results of conductivity and Seebeck coefficient calculations for TiCo1-xCuxSb alloys, as well as their comparison with experimental data. TiCoSb crystallizes in a half-Heusler crystal structure. As revealed ...
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Topology of exponential and scale-free trees and simple graphs is investigated numerically. The numbers of the nearest neighbors, the next-nearest neighbors, the next-next-nearest neighbors, the 4-th and the 5-th neig...
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Topology of exponential and scale-free trees and simple graphs is investigated numerically. The numbers of the nearest neighbors, the next-nearest neighbors, the next-next-nearest neighbors, the 4-th and the 5-th neighbors are calculated. The functional dependence [A.E. Motter, T. Hishikawa, Y.-Ch. Lai, Phys. Rev. E66, 065103(R) (2002)] of the node-to-node distance dij on the product of connectivities kikj has been studied numerically. The results of simulations for exponential networks agree with the existing analytical predictions.
The diffusive motion of quasi-two-dimensional electron gas through an ultra-thin system of disordered potentials is considered. In such a system, the Fermi sphere splits into a set of independent sheets due to a small...
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The diffusive motion of quasi-two-dimensional electron gas through an ultra-thin system of disordered potentials is considered. In such a system, the Fermi sphere splits into a set of independent sheets due to a small thickness of the system. Each sheet can be seen as an electron subband. Electron transport goes through these subbands independently. The sum of electrical conductivities over the subbands determines the total current, which is calculated for ultra-thin films of cesium. We also present the relation between our approach and the Landauer formalism based on the notion of the transmission coefficient.
Electron transport through a disordered two-dimensional array of potentials has been investigated. The resistivity was calculated according to the Faber-Ziman diffraction model, suitably modified for a two-dimensional...
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Electron transport through a disordered two-dimensional array of potentials has been investigated. The resistivity was calculated according to the Faber-Ziman diffraction model, suitably modified for a two-dimensional electron gas. The structure factor is obtained by means of numerical simulations. The pseudopotentials are assumed to be Shaw potentials with appropriate screening. The resistivities of disordered monolayers of alkali metals have been calculated in this model using parameters that allowed us to explain the experimental data for bulk materials.
This paper presents the new framework for visual computational design in which emergence is a key to creativity. Visual shape grammar computations proceeded with the use of diagrams are situated in a design context in...
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The measurements and calculations have aimed at the verification of codes and data bases applied in modeling of transmutations in the spallation target and the resulting radioactivity. In experiments cylindrical Pb ta...
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The measurements and calculations have aimed at the verification of codes and data bases applied in modeling of transmutations in the spallation target and the resulting radioactivity. In experiments cylindrical Pb targets were exposed to the beam of 660 MeV protons. Using gamma-spectrometry, a number of radionuclides were identified in Pb and Bi samples irradiated in the targets. Axial and radial distributions of several nuclides production rates were determined. Three types of the distribution shapes were distinguished: Bi isotopes, medium and heavier nuclides. The distributions of Bi isotopes reveal a sharp characteristic peak about 30cm inside the target. The comparison of experimental results with calculations (MCNPX, FLUKA and LAHET) shows agreement within one order of magnitude, at the worst. Almost always the C/E ratio is between 3 and 1/3. However, no single code and/or reaction model yields good results for all examined nuclides. (c) 2006 Elsevier B.V. All rights reserved.
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