Evolution of the spin Hall effect in Pt nanowires: Size and temperature effects

We have studied the evolution of the Spin Hall Effect in the regime where the material size responsible for the spin accumulation is either smaller or larger than the spin diffusion length. Lateral spin valve structures with Pt insertions were successfully used to measure the spin absorption efficiency as well as the spin accumulation in Pt induced through the spin Hall effect. Under a constant applied current the results show a decrease of the spin accumulation signal is more pronounced as the Pt thickness exceeds the spin diffusion length. This implies that the spin accumulation originates from bulk scattering inside the Pt wire and the spin diffusion length limits the SHE. We have also analyzed the temperature variation of the spin hall conductivity to identify the dominant scattering mechanism.Comment: 4 pages, 4 figure

Gestion Électronique des Documents iconographiques au SICD de Strasbourg

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Switching probability sub-distributions and asymmetric magnetization reversal in FePt nanostructures

International audienceThe coercive field statistics in FePt nanostructures reveals the existence of multiple switching probability sub-distributions that can be asymmetric with respect to the field orientation. Each sub-distribution is correlated with an individual magnetization reversal path whose selection cannot happen at the magnetization reversal in negative (positive) field but rather at the moment of applying the initial positive (negative) magnetic field. This serves to determine the reference magnetic state from which reversal in negative (positive) field will develop. The disappearance of the asymmetric sub-distributions upon increasing the initial magnetic field μ0Hmax supports this model. However, the sub-distributions remaining at high μ0Hmax are not necessarily those characterized by the highest coercive field. This is attributed to the fact that the initial magnetization state hierarchy and the coercive field hierarchy are essentially decorrelated

Electric-field effect on coercivity distributions in FePt magneto-electric devices

International audienceWe have investigated the contribution of stochastic thermally activated processes to the electric-field effects on coercivity in FePt. Coercive field distributions were measured under different gate voltages in solid-state field-effect structures. For low voltages a shift in the coercive field distribution can be observed, however, it is not larger than the width of the distribution. Higher oltages are needed to obtain the splitting from the negative (zero) voltage distribution allowing for the unambiguous characterization of the electric-field effect. A virtual unipolarity in the electric-field effect has been identified as a feature introduced by the dielectric layer that disappears upon annealing

Simulation numérique du comportement thermo-hydro-mécanique des assemblages bois réalisés avec des organes métalliques

Le matériau bois est constitué de polymères sensibles à la température et à l’humidité. L’étude de son comportement thermo-hydro-mécanique est donc indispensable au développement de son usage dans le domaine de la construction. Dans cette étude, le comportement thermo-hydro-mécanique du matériau bois est analysé dans le cadre de la théorie de la mécanique non-linéaire des milieux continus. Une modélisation théorique basée sur la thermodynamique des processus irréversibles est utilisée pour traduire le couplage du comportement mécanique orthotrope avec effet de l’humidité sous l’action de hautes températures. L’intégration locale des équations constitutives est réalisée par un schéma implicite itératif utilisant des corrections plastiques. La validation de la procédure de calcul implémentée dans le code ABAQUS/Explicit est faite sur la simulation des assemblages bois réalisés avec organes métallique

Spin-orbit torques for current parallel and perpendicular to a domain wall

We report field- and current-induced domain wall (DW) depinning experiments in Ta/Co20Fe60B20/MgO nanowires through a Hall cross geometry. While purely field-induced depinning shows no angular dependence on in-plane fields, the effect of the current depends crucially on the internal DW structure, which we manipulate by an external magnetic in-plane field. We show for the first time depinning measurements for a current sent parallel to the DW and compare its depinning efficiency with the conventional case of current flowing perpendicularly to the DW. We find that the maximum efficiency is similar for both current directions within the error bars, which is in line with a dominating damping-like spin-orbit torque (SOT) and indicates that no large additional torques arise for currents parallel to the DW. Finally, we find a varying dependence of the maximum depinning efficiency angle for different DWs and pinning levels. This emphasizes the importance of our full angular scans compared to previously used measurements for just two field directions (parallel and perpendicular to the DW) and shows the sensitivity of the spin-orbit torque to the precise DW structure and pinning sites.Comment: 11 pages, 3 figure

Growth of Acinetobacter baumannii in Pellicle Enhanced the Expression of Potential Virulence Factors

BACKGROUND: Interestingly, Acinetobacter baumannii presents an enhanced capacity to form biofilms (also named pellicles) at the air-liquid interface as compared to the other Acinetobacter species. This characteristic questions the contribution of this phenotype to an increased risk of clinical infections by this pathogen. METHODOLOGY/PRINCIPAL FINDINGS: By a proteomic approach using 2-D gel electrophoresis-LC-MS/MS mass spectrometry, we compared the membrane protein patterns of A. baumannii 77, a pellicle-forming clinical isolate, grown in planktonic and in sessile modes. We identified 52 proteins with a differential expression, including 32 up-regulated and 20 down-regulated in the pellicle state. Several proteins, differentially expressed during pellicle development, were of particular interest. We determined the over-expression of four siderophore iron uptake systems including the acinetobactin and enterobactin receptors and confirmed that the development of this type of biofilm is promoted by ferric ions. Two over-expressed proteins, CarO and an OprD-homologue, putative carbapenem-resistance associated porins, would be involved in the transport of specific compounds, like ornithine, a biosynthesis precursor of a siderophore from the hydroxamate family. We evidenced the overexpression of a lipase and a transporter of LCFA that may be involved in the recycling of lipids inside the pellicle matrix. Finally, we demonstrated both by proteomic and by AFM studies that this particular type of biofilm required multiple pili systems to maintain this cohesive structure at the air-liquid interface; two of these systems have never been described in A. baumannii. CONCLUSIONS/SIGNIFICANCE: Our study demonstrated that several proteins, overexpressed at a late state of pellicle development, could be potentially involved in virulence processes. Therefore, regarding the number of potential virulence factors that are over-expressed in this growth mode, the pellicle-forming clinical isolates should be kept under survey

Study of the dynamics of thin liquid films sheared by gas flows

We investigate the long-wave instability of a thin liquid film sheared by a concurrent gas flow. The film flows down an inclined plane and is driven by a constant shear stress and a pressure gradient. The height of the film is small compared to the wavelength, which justifies a long-wave approach. We adopt this procedure to approximate the Saint-Venant (or shallow water) equations. A linear stability analysis is thus developed and the limit between stable and unstable conditions is analyzed in terms of a critical Reynolds number. It comes out that the constant shear stress, applied at the free surface of the film, tends to stabilize the liquid layer to long waves. This is true when the mass flow of the film is kept unaltered. On the other side, the role of the pressure gradient is the same as the longitudinal component of gravity, which is known to be a destabilizing factor for the liquid film

Pulse wave velocity distribution in a cohort study: from arterial stiffness to early vascular aging

BACKGROUND: By contrast with other southern European people, north Portuguese population registers an especially high prevalence of hypertension and stroke incidence. We designed a cohort study to identify individuals presenting accelerated and premature arterial aging in the Portuguese population. METHOD: Pulse wave velocity (PWV) was measured in randomly sampled population dwellers aged 18-96 years from northern Portugal, and used as a marker of early vascular aging (EVA). Of the 3038 individuals enrolled, 2542 completed the evaluation. RESULTS: Mean PWV value for the entire population was 8.4?m/s (men: 8.6?m/s; women: 8.2?m/s; P??10?m/s). Logistic regression models indicated gender differences concerning the risk of developing large artery damage, with women having the same odds of PWV above 10?m/s 10 years later than men. CONCLUSION: The population PWV values were higher than expected in a low cardiovascular risk area (Portugal). High prevalence rates of EVA and noteworthy large artery damage in young ages were found.Funded by the Life and Health Research Institute, Minho University, Guimarães, Portugal