4,214 research outputs found
Josephson Junctions with a synthetic antiferromagnetic interlayer
We report measurements of the critical current vs. Co thickness in
Nb/Cu/Co/Ru/Co/Cu/Nb Josephson junctions, where the inner Co/Ru/Co trilayer is
a "synthetic antiferromagnet" with the magnetizations of the two Co layers
coupled antiparallel to each other via the 0.6 nm-thick Ru layer. Due to the
antiparallel magnetization alignment, the net intrinsic magnetic flux in the
junction is nearly zero, and such junctions exhibit excellent Fraunhofer
patterns in the critical current vs. applied magnetic field, even with total Co
thicknesses as large as 23 nm. There are no apparent oscillations in the
critical current vs. Co thickness, consistent with theoretical expectations for
this situation. The critical current of the junctions decays over 4 orders of
magnitude as the total Co thickness increases from 3 to 23 nm. These junctions
may serve as useful templates for future explorations of spin-triplet
superconducting correlations, which are predicted to occur in supercon-
ducting/ferromagnetic hybrid systems in the presence of certain types of
magnetic inhomogeneity.Comment: 4 pages, 5 figure
Human Security and Developmental Crisis in the Contemporary West Africa
The last two decades were characterized by severe conflicts in the West Africa subregion. The era of conflict resolution, management and peace building thus came to define theregion. The destruction left by long years of protracted conflicts and the present state of devel opment is reason enough to warrant attention both from within and beyond. The study expounds, operationalizes and clarifies the concept of human security and development, and how human security issues lead to underdevelopment. The paper investigates the human security concerns in the post-conflict period and also looks at the crisis of development in the sub-region. It highlights details on the developmental crises that have bedevilled the sub-region and at the same time exposes the threats these crises pose on national security and peace in the subregion. This paper concludes that there is no appreciable effort in operationalizing human security in West Africa and this will lead to instability. The paper maintains that human security issues now complicate the developmental crisis in the sub-region due to its ambiguity. The paper suggests that policy makers should address human security issues in order to tackle developmental crisis in the sub-region
Human Security and Developmental Crisis in the Contemporary West Africa
The last two decades were characterized by severe conflicts in the West Africa subregion. The era of conflict resolution, management and peace building thus came to define theregion. The destruction left by long years of protracted conflicts and the present state of devel opment is reason enough to warrant attention both from within and beyond. The study expounds, operationalizes and clarifies the concept of human security and development, and how human security issues lead to underdevelopment. The paper investigates the human security concerns in the post-conflict period and also looks at the crisis of development in the sub-region. It highlights details on the developmental crises that have bedevilled the sub-region and at the same time exposes the threats these crises pose on national security and peace in the subregion. This paper concludes that there is no appreciable effort in operationalizing human security in West Africa and this will lead to instability. The paper maintains that human security issues now complicate the developmental crisis in the sub-region due to its ambiguity. The paper suggests that policy makers should address human security issues in order to tackle developmental crisis in the sub-region
Spin-memory loss at Co/Ru interfaces
We have determined the spin-memory-loss parameter, , by
measuring the transmission of spin-triplet and spin-singlet Cooper pairs across
Co/Ru interfaces in Josephson junctions and by Current-Perpendicular-to-Plane
Giant Magnetoresistance (CPP-GMR) techniques. The probability of spin-memory
loss at the Co/Ru interface is . From the CPP-MR, we
obtain that is in good agreement with
obtained from spin-triplet transmission. For
spin-singlet transmission, we have that is
different from that obtained from CPP-GMR and spin-triplet transmission. The
source of this difference is not understood.Comment: 9 pages, 9 figure
Quantum corrections for pion correlations involving resonance decays
A method is presented to include quantum corrections into the calculation of
two-pion correlations for the case where particles originate from resonance
decays. The technique uses classical information regarding the space-time
points at which resonances are created. By evaluating a simple thermal model,
the method is compared to semiclassical techniques that assume exponential
decaying resonances moving along classical trajectories. Significant
improvements are noted when the resonance widths are broad as compared to the
temperature.Comment: 9 pages, 4 figure
Spin Triplet Supercurrent in Co/Ni Multilayer Josephson Junctions with Perpendicular Anisotropy
We have measured spin-triplet supercurrent in Josephson junctions of the form
S/F'/F/F'/S, where S is superconducting Nb, F' is a thin Ni layer with in-plane
magnetization, and F is a Ni/[Co/Ni]n multilayer with out-of-plane
magnetization. The supercurrent in these junctions decays very slowly with
F-layer thickness, and is much larger than in similar junctions not containing
the two F' layers. Those two features are the characteristic signatures of
spin-triplet supercurrent, which is maximized by the orthogonality of the
magnetizations in the F and F' layers. Magnetic measurements confirm the
out-of-plane anisotropy of the Co/Ni multilayers. These samples have their
critical current optimized in the as-prepared state, which will be useful for
future applications.Comment: 4 pages, 4 figures, formatted in RevTeX version 4. Submitted to
Physical Review B on August 13th, 201
Some forgotten features of the Bose Einstein Correlations
Notwithstanding the visible maturity of the subject of Bose-Einstein
Correlations (BEC), as witnessed nowadays, we would like to bring to ones
attention two points, which apparently did not received attention they deserve:
the problem of the choice of the form of correlation function when
effects of partial coherence of the hadronizing source are to be included and
the feasibility to model effects of Bose-Einstein statistics, in particular the
BEC, by direct numerical simulations.Comment: Talk delivered by G.Wilk at the International Workshop {\it
Relativistic Nuclear Physics: from Nuclotron to LHC energies}, Kiev, June
18-22, 2007, Ukraine; misprints correcte
Quantum-Statistical Correlations and Single Particle Distributions for Slowly Expanding Systems with Temperature Profile
Competition among particle evaporation, temperature gradient and flow is
investigated in a phenomenological manner, based on a simultaneous analysis of
quantum statistical correlations and momentum distributions for a
non-relativistic, spherically symmetric, three-dimensionally expanding, finite
source. The parameters of the model emission function are constrained by fits
to neutron and proton momentum distributions and correlation functions in
intermediate energy heavy-ion collisions. The temperature gradient is related
to the momentum dependence of the radius parameters of the two-particle
correlation function, as well as to the momentum-dependent temperature
parameter of the single particle spectrum, while a long duration of particle
evaporation is found to be responsible for the low relative momentum behavior
of the two-particle correlations.Comment: 20 pages + 5 ps figures, ReVTeX, uses psfig.sty, the description is
extended to include final state interactions, phenomenological evaporation
and to fit intermediate energy heavy ion proton and neutron spectrum and
correlation dat
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