Results 1 - 10 of 25358
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[en] The functionalization of fine primary particles by atomic layer deposition (particle ALD) provides for nearly perfect nanothick films to be deposited conformally on both external and internal particle surfaces, including nanoparticle surfaces. Film thickness is easily controlled from several angstroms to nanometers by the number of self-limiting surface reactions that are carried out sequentially. Films can be continuous or semi-continuous. This review starts with a short early history of particle ALD. The discussion includes agitated reactor processing, both atomic and molecular layer deposition (MLD), coating of both inorganic and polymer particles, nanoparticles, and nanotubes. A number of applications are presented, and a path forward, including likely near-term commercial products, is given.
[en] The precessional switching process in magnetic recording thin films is investigated by means of micromagnetic simulations. The uniform mode theory is used to predict the right time instant to switch off the field and the time tolerance which still allows successful switching. This analysis is performed for different values of applied field and anisotropy constant. We verified that the uniform mode theory provides accurate information about the tolerance on the switching time for moderately soft materials
[en] When reducing the size of array elements and interelement separations to the nanoscale, long-range magnetostatic interactions become important. A methodology that extends the study of conventional single-element magnetostatics is presented, adding the effect of stacking nanoelements into close proximity in arrays and the consequent interaction effects. This would be very time consuming to model by micromagnetic simulations that are also very vulnerable to artifacts due to cell or boundary condition selection. The proposed method considers an analytical expression valid for short interelement separations and not very costly to evaluate by computational means. This approach allows the quantitative study of shape anisotropy in non-square-shaped arrays. It is also shown how it can be used to find anisotropy compensation conditions, where an anisotropy due to a magnetic element shape can be compensated by the shape anisotropy due to the array. The obtained results can be used to establish a criterion for the minimum number of elements to be considered for a micromagnetic simulation of an array to be realistic depending on the element size and separation
[en] The giant magnetoimpedance (GMI) effect of controlled-inclination magnetic stripe domain for a thin-film GMI sensor is investigated. The inclined stripe domain structure has an inclined angle of domain walls against the transverse direction of the rectangular-strip element. It is obtained that GMI profile changes from a profile with a dip point at the zero magnetic field to a profile with one maximum impedance only at the zero field at an angle of 70 deg. . In the case of GMI profile with a dip point, increasing the inclination angle decreases the bias field. This reduction of the bias field more than triples the sensor gain. An excellent linear property extending for wide range is obtained. A steplike impedance change property is also realized by this method
[en] The relaxation dynamics of Preisach superpositions of thermally activated, bistable elements are shown to exhibit aging and memory effects in response to certain field- and temperature-cycling protocols, which are reminiscent of those observed in spin glasses, but which are not a consequence of collective freezing. Model simulations are able to replicate memory effects observed in a thin film of Fe nanoparticles embedded in glass
[en] Highlights: • Shear horizontal wave dispersion in nanolayers with surface effects is examined. • Wave velocity is dependent on the layer thickness and surface elastic constants. • Surface elastic constants can be analytically derived from the wave velocity. - Abstract: In this work, the shear horizontal (SH) wave dispersion in two dissimilar nanolayers is investigated by using the surface elasticity theory in which the surface effects are featured by surface elastic constants. It is found that the SH wave dispersion shows distinct dependence on the nanolayer thickness as well as the surface elastic constants. The larger the surface elastic modulus and/or the smaller the thickness, the higher the phase velocity. In particular, as the wave frequency approaches zero, the analytical relation between the phase velocity in the first mode dispersion and the surface elastic constants is deduced. Thereby, a facile method is suggested to determine the surface elastic constants from the phase velocity of SH waves scattered in nanolayers.
[en] We study theoretically the behavior of vortices in a thin film superconductor placed close to a soft magnetic film. It is shown that the field from the vortex induces a magnetization distribution in the soft magnetic film, thus modifying the fields and vortex interactions. We suggest that the interaction between two otherwise identical vortices is attractive at short distances, but repulsive at larger distances. This is in contrast to the case without the soft magnetic film, where the force is always repulsive
[en] In usual dry laser cleaning of opaque samples, short laser pulses are projected onto the sample surface to be cleaned. Energy transferred from light ejects extraneous particles away from the surface. Laser beam fluence is limited by the damage reached by high temperature that the sample surface can produce. We have experimentally shown that for thin samples, the thermo-elastic wave propagates within the whole sample thickness, thus also the rear surface, while temperature effects are limited to the front surface. Therefore, the proposed 'verso' laser cleaning technique (the pulsed laser beam impinges on rear sample surface) can be applied to any opaque 'mechanically thin' film and is useful for samples having delicate treatments on the surface to be cleaned (e.g. written paper, painted tiles, magnetic films). We have applied our technique to paper sheets showing that it is possible to efficiently clean the surface without damaging ink marks on it. Using a probe beam deflection (PBD) technique in both direct and reverse configuration we have shown that the 'verso' cleaning effect is due to the higher penetration depth of the thermo-elastic wave with respect to the temperature profile propagation
[en] We present an experimental study of transport properties of a large two-dimensional array of superconductor-normal-metal-superconductor (SNS) junctions comprised of the nanopatterned superconducting film, ensuring that NS interfaces of our SNS junctions are highly transparent. We find the anomalously high charge transmission at certain applied voltages commensurate with the magnitude of the gap in superconducting islands. This indicates the nonlocal nature of the charge transfer in multiply connected SNS systems. We propose the mechanism of the correlated transmission of Cooper pairs in large arrays of SNS junctions based on the combined action of the proximity effect and the simultaneous Andreev conversion processes at many NS-interfaces.
[en] There is considerable experimental evidence that the microstructure has important consequences for polymer-based electronic and optoelectronic applications, but few theoretical and computational models account for it. We produced several realisations of polymer networks exhibiting specific arrangements of C4n+2 H2n+4 molecules at the mesoscopic scale and we carried out computer experiments in which bipolar charge carriers were injected in the polymer system from the appropriate electrodes. Our results show that polymer microstructures resulting from different arrangements of polymer molecules have significant effects on the competition between charge trapping, current transport and recombination within the polymer layer. It was found that current efficiency increases non-linearly with the external applied electric field, the effect being more pronounced for molecular orientations parallel to the electrode surface. In contrast, recombination efficiency shows an opposite behaviour since no significant charge accumulation within the polymer layer is predicted. However, the space-charge effects due to electrons and holes are responsible for most of the recombination events not occurring in neither long or short chains