1,493 research outputs found
Effects of hydrogen/deuterium absorption on the magnetic properties of Co/Pd multilayers
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
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
Magnetically asymmetric interfaces in a (LaMnO)/(SrMnO) superlattice due to structural asymmetries
Polarized neutron reflectivity measurements of a ferromagnetic
[(LaMnO)/(SrMnO)] superlattice reveal a modulated
magnetic structure with an enhanced magnetization at the interfaces where
LaMnO was deposited on SrMnO (LMO/SMO). However, the opposite
interfaces (SMO/LMO) are found to have a reduced ferromagnetic moment. The
magnetic asymmetry arises from the difference in lateral structural roughness
of the two interfaces observed via electron microscopy, with strong
ferromagnetism present at the interfaces that are atomically smooth over tens
of nanometers. This result demonstrates that atomic-scale roughness can
destabilize interfacial phases in complex oxide heterostructures.Comment: 5 pages, 4 figure
Suppressed magnetization in LaCaMnO/YBaCuO superlattices
We studied the magnetic properties of LaCaMnO /
YBaCuO superlattices. Magnetometry showed that with
increasing YBaCuO layer thickness the saturation
magnetization per LaCaMnO layer decreases. From polarized
neutron reflectometry we determined that this magnetization reduction is due to
an inhomogenous magnetization depth profile arising from the suppression of
magnetization near the LaCaMnO /
YBaCuO interface. Electron energy loss spectroscopy
indicates an increased 3d band occupation of the Mn atoms in the
LaCaMnO layers at the interface. Thus, the suppression of
ferromagnetic order at the LaCaMnO /
YBaCuO interface is most likely due to charge transfer
between the two materials.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Clergy Interest in Innovative Collaboration with Psychologists
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
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Fabrication of boron-phosphide neutron detectors
Boron phosphide is a potentially viable candidate for high neutron flux neutron detectors. The authors have explored chemical vapor deposition methods to produce such detectors and have not been able to produce good boron phosphide coatings on silicon carbide substrates. However, semi-conducting quality films have been produced. Further testing is required
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