1,261 research outputs found

    Effects of hydrogen/deuterium absorption on the magnetic properties of Co/Pd multilayers

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    The effects of hydrogen (H2) and deuterium (D2) absorption were studied in two Co/Pd multilayers with perpendicular magnetic anisotropy (PMA) using polarized neutron reflectivity (PNR). PNR was measured in an external magnetic field H applied in the plane of the sample with the magnetization M confined in the plane for {\mu}_o H= 6.0 T and partially out of plane at 0.65 T. Nominal thicknesses of the Co and Pd layers were 2.5 {\AA} and 21 {\AA}, respectively. Because of these small values, the actual layer chemical composition, thickness, and interface roughness parameters were determined from the nuclear scattering length density profile ({\rho}_n) and its derivative obtained from both x-ray reflectivity and PNR, and uncertainties were determined using Monte Carlo analysis. The PNR {\rho}_n showed that although D2 absorption occurred throughout the samples, absorption in the multilayer stack was modest (0.02 D per Pd atom) and thus did not expand. Direct magnetometry showed that H2 absorption decreased the total M at saturation and increased the component of M in the plane of the sample when not at saturation. The PNR magnetic scattering length density ({\rho}_m) revealed that the Pd layers in the multilayer stack were magnetized and that their magnetization was preferentially modified upon D2 absorption. In one sample, a modulation of M with twice the multilayer period was observed at {\mu}_o H= 0.65 T, which increased upon D2 absorption. These results indicate that H2 or D2 absorption decreases both the PMA and total magnetization of the samples. The lack of measurable expansion during absorption indicates that these changes are primarily governed by modification of the electronic structure of the material.Comment: to appear in Physics review B, 201

    Theoretical and Experimental Adsorption Studies of Polyelectrolytes on an Oppositely Charged Surface

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    Using self-assembly techniques, x-ray reflectivity measurements, and computer simulations, we study the effective interaction between charged polymer rods and surfaces. Long-time Brownian dynamics simulations are used to measure the effective adhesion force acting on the rods in a model consisting of a planar array of uniformly positively charged, stiff rods and a negatively charged planar substrate in the presence of explicit monovalent counterions and added monovalent salt ions in a continuous, isotropic dielectric medium. This electrostatic model predicts an attractive polymer-surface adhesion force that is weakly dependent on the bulk salt concentration and that shows fair agreement with a Debye-Huckel approximation for the macroion interaction at salt concentrations near 0.1 M. Complementary x-ray reflectivity experiments on poly(diallyldimethyl ammonium) chloride (PDDA) monolayer films on the native oxide of silicon show that monolayer structure, electron density, and surface roughness are likewise independent of the bulk ionic strength of the solution.Comment: Revtex, prb format; uses amssym

    Clergy Interest in Innovative Collaboration with Psychologists

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    What forms of innovative collaboration are possible between clergy and psychologists? A total of 117 clergypersons (63% response rate) rated 6 scenarios of collaboration, indicating their level of interest and the extent to which they would like to remain involved with the psychologist. The scenarios were derived from two categories of collaboration articulated by in previous research: mental health services and enhancing parish life. Overall, clergy expressed relatively modest levels of interest in innovative collaboration, though they were somewhat interested in mental health consultation services. Many clergy refer troubled parishioners to clinical or counseling psychologists for treatment, but appear less interested in more innovative forms of collaboration

    On the full scale and model scale cavitation comparisons of a Deep-V catamaran research vessel

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    In pushing for greener ships and more sustainable operations, designers and researchers are being challenged to increase vessel performance whilst reducing environmental impact. One topical, and a somewhat challenging aspect of this pursuit, is the reduction in Underwater Radiated Noise (URN). There are several European Collaborative Research Projects currently underway that aim to outline a framework for noise standards, amongst these projects is the Seventh Framework Project (FP7) “Suppression of Underwater Noise Induced by Cavitation” (SONIC) that has been tasked with concentrating on the URN from propeller cavitation; the main contributor to underwater noise generation. As one of the participants of the SONIC project the Newcastle University was involved in the full-scale trials and model-scale propeller testing campaign. The full-scale trial conducted on board Newcastle University’s catamaran research vessel R/V The Princess Royal involved cavitation observations though the dedicated observation windows above each propeller, Propeller Excited Vibration measurements as well as the off-board URN measurements. The model scale tests were made in The Emerson Cavitation Tunnel using a 1:3.5 scale dummy model of the starboard side demi-hull of the vessel. These tests tried to emulate, as best as possible, the full-scale trials in terms of measurement locations and viewing angles

    Correlation between microstructure and magnetotransport in organic semiconductor spin valve structures

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    We have studied magnetotransport in organic-inorganic hybrid multilayer junctions. In these devices, the organic semiconductor (OSC) Alq3_3 (tris(8-hydroxyquinoline) aluminum) formed a spacer layer between ferromagnetic (FM) Co and Fe layers. The thickness of the Alq3_3 layer was in the range of 50-150 nm. Positive magnetoresistance (MR) was observed at 4.2 K in a current perpendicular to plane geometry, and these effects persisted up to room temperature. The devices' microstructure was studied by X-ray reflectometry, Auger electron spectroscopy and polarized neutron reflectometry (PNR). The films show well-defined layers with modest average chemical roughness (3-5 nm) at the interface between the Alq3_3 and the surrounding FM layers. Reflectometry shows that larger MR effects are associated with smaller FM/Alq3_3 interface width (both chemical and magnetic) and a magnetically dead layer at the Alq3_3/Fe interface. The PNR data also show that the Co layer, which was deposited on top of the Alq3_3, adopts a multi-domain magnetic structure at low field and a perfect anti-parallel state is not obtained. The origins of the observed MR are discussed and attributed to spin coherent transport. A lower bound for the spin diffusion length in Alq3_3 was estimated as 43±543 \pm 5 nm at 80 K. However, the subtle correlations between microstructure and magnetotransport indicate the importance of interfacial effects in these systems.Comment: 21 pages, 11 figures and 2 table
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