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.
Using the density functional theory and the direct method, phonon dispersion relations and phonon density spectra have been calculated for two slabs with Fe(100) and Fe(110) surfaces. A drastic difference between phon...
Using the density functional theory and the direct method, phonon dispersion relations and phonon density spectra have been calculated for two slabs with Fe(100) and Fe(110) surfaces. A drastic difference between phonon state distributions for both surfaces has been found. The magnetic moments of surface Fe atoms are enhanced by 30% and 14% for (100) and (110) surfaces, respectively.
We have investigated the formation of gold nanoclusters during submonolayer deposition on atomically flat KBr and RbI (001) ionic-crystal substrates, as well as on substrates patterned with two-dimensional (2D) nanosc...
We have investigated the formation of gold nanoclusters during submonolayer deposition on atomically flat KBr and RbI (001) ionic-crystal substrates, as well as on substrates patterned with two-dimensional (2D) nanoscale pits produced by electron stimulated desorption. In this way, it is possible to produce atomic steps free from stress and local charging, which are normally considered the reason for enhanced cluster nucleation. Easy nucleation of the Au clusters inside the pits at the lower side of the atomic step edge is not observed, while nucleation of the Au nanoclusters is found to occur preferentially at the upper step edges. Moreover, we observe that gold atoms landing inside the bottom of the pits are able to escape from them by means of thermally activated upward diffusion at the step edges. We propose that the preferential Au nucleation sites at the edges of 2D pits are activated by F centers produced in electronic processes used for nanopatterning of the ionic crystals.
We have carried out first principles, all-electron computations of the magnetic momentum density ρmag(p) and magnetic Compton profiles (MCPs) for momentum transfer along the [100], [001], and [110] directions in LaSr...
We have carried out first principles, all-electron computations of the magnetic momentum density ρmag(p) and magnetic Compton profiles (MCPs) for momentum transfer along the [100], [001], and [110] directions in LaSr2Mn2O7 and La1.2Sr1.8Mn2O7 within the local spin density approximation (LSDA) based band theory framework. Parallel measurements of these three MCPs from a single crystal of La1.2Sr1.8Mn2O7 at 5K in a magnetic field of 7T are also reported. ρmag(p) is shown to contain distinct peaks arising from the occupied majority-spin t2g electrons and to display images of the Fermi surface (FS) in the first and higher Brillouin zones (BZs). The overall shape of the MCPs, Jmag(pz), obtained by integrating ρmag(p) over px and py, is found to be dominated by the majority-spin t2g states. The FS-related fine structure in the MCPs is, however, substantial only in the [100] MCP, which contains features arising from the large majority-spin hole sheets. The overall shapes and widths of the experimental MCPs along all three directions investigated are in reasonably good accord with theoretical predictions, although some discrepancies indicating inadequacy of the LSDA in treating the magnetic states can be identified. We discuss details of the FS-related signatures in the first and higher BZs in the [100] MCP and show that high resolution magnetic Compton scattering experiments with a momentum resolution of 0.1a.u. full-width-at-half-maximum or better will be necessary to observe this fine structure. We comment also on the feasibility of using positron annihilation spectroscopy in this connection.
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.
A multichannel ASIC for digital X-ray imaging requires one or more discriminators in each recording channel. The critical parameters of these discriminators are low power consumption and low offset spreads from channe...
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This paper presents the design and results of first measurements of a fast binary readout architecture ASIC aimed for digital X-ray imaging. The ASIC called DEDIX includes 64 readout channels, a number of DACs for dif...
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