57 research outputs found
Domain wall effects in ferromagnet-superconductor structures
We investigate how domain structure of the ferromagnet in
superconductor-ferromagnet heterostructures may change their transport
properties. We calculate the distribution of current in the superconductor
induced by magnetic field of Bloch domain walls, find the ``lower critical''
magnetization of the ferromagnet that provides vortices in the superconductor
Hypoxic Preconditioning: The Multiplicity of Central Neurotransmitter Mechanisms and Method of Predicting Its Efficiency
In rats, a single moderate hypobaric hypoxia (HBH) increased the resistance to severe hypoxia (SHBH). The HBH efficiency and neurotransmitter mechanisms of its preconditioning action were investigated by biochemical and pharmacological methods. It will be substantiated in the chapter: (1) HBH preconditioning has its own mechanisms that do not depend on an innate resistance to SHBH and prior hypoxic experience of rats; (2) the same preconditioning effect can be achieved by diverse neuronal pathways and synaptic plasticity means; (3) cholinergic and, presumably, serotoninergic, GABAergic and/or glutamatergic systems of the caudal brainstem, cortex and some other brain structures are involved in HBH realisation; (4) the rate of sensorimotor gating estimated in the model of acoustic startle pre-pulse inhibition (PPI) predicts the efficiency of hypoxic preconditioning and (5) the cholinergic system, including α7 nicotinic receptors, is involved in the mechanisms of HBH-PPI-dependent preconditioning effects
Experimental Simulation of the Radionuclide Behaviour in the Process of Creating Additional Safety Barriers in Solid Radioactive Waste Repositories Containing Irradiated Graphite
Results of the experimental modeling of radionuclide behavior when creating additional safety barriers in solid radioactive waste repositories are presented. The experiments were run on the repository mockup containing solid radioactive waste fragments including irradiated graphite. The repository mockup layout is given; the processes with radionuclides that occur during the barrier creation with a clayey solution and during the following barrier operation are investigated. The results obtained confirm high anti-migration and anti-filtration properties of clay used for the barrier creation even under the long-term excessive water saturation of rocks confining the repository
Critical temperature of superconductor/ferromagnet bilayers
Superconductor/ferromagnet bilayers are known to exhibit nontrivial
dependence of the critical temperature T_c on the thickness d_f of the
ferromagnetic layer. We develop a general method for investigation of T_c as a
function of the bilayer's parameters. It is shown that interference of
quasiparticles makes T_c(d_f) a nonmonotonic function. The results are in good
agreement with experiment. Our method also applies to multilayered structures.Comment: 4 pages, 2 EPS figures; the style file jetpl.cls is included. Version
2: typos correcte
Layered ferromagnet-superconductor structures: the state and proximity effects
We investigate clean mutilayered structures of the SFS and SFSFS type, (where
the S layer is intrinsically superconducting and the F layer is ferromagnetic)
through numerical solution of the self-consistent Bogoliubov-de Gennes
equations for these systems. We obtain results for the pair amplitude, the
local density of states, and the local magnetic moment. We find that as a
function of the thickness of the magnetic layers separating adjacent
superconductors, the ground state energy varies periodically between two stable
states. The first state is an ordinary "0-state", in which the order parameter
has a phase difference of zero between consecutive S layers, and the second is
a "-state", where the sign alternates, corresponding to a phase difference
of between adjacent S layers. This behavior can be understood from simple
arguments. The density of states and the local magnetic moment reflect also
this periodicity.Comment: 12 pages, 10 Figure
Proximity effects in superconductor-ferromagnet heterostructures
The very special characteristic of the proximity effect in
superconductor-ferromagnet systems is the damped oscillatory behavior of the
Cooper pair wave function in a ferromagnet. In some sense, this is analogous to
the inhomogeneous superconductivity, predicted long time ago by Larkin and
Ovchinnikov (1964), and Fulde and Ferrell (1964), and constantly searched since
that. After the qualitative analysis of the peculiarities of the proximity
effect in the presence of the exchange field, the author provides a unified
description of the properties of the superconductor-ferromagnet
heterostructures. Special attention is paid to the striking non-monotonous
dependance of the critical temperature of the multilayers and bilayers on the
ferromagnetic layer thickness and conditions of the realization of the "Pi"-
Josephson junctions. The recent progress in the preparation of the high quality
hybrid systems permitted to observe on experiments many interesting effects,
which are also discussed in the article. Finally, the author analyzes the
phenomenon of the domain-wall superconductivity and the influence of
superconductivity on the magnetic structure in superconductor-ferromagnet
bilayers.Comment: Submitted to Reviews of Modern Physic
Adjustment of superconductivity and ferromagnetism in few-layered ferromagnet-superconductor nanostructures
The phase diagrams of the few-layered nanosystems consisting of dirty superconducting (S) and
ferromagnetic (F) metals are investigated within the framework of the modern theory of the proximity
effect taking into account the boundary conditions. The F/S tetralayer and pentalayer are
shown to have considerably richer physics than the F/S bi- and trilayer (due to the interplay between
the 0 and π phase superconductivity and the 0 and π phase magnetism and nonequivalence of
layers) and even the F/S superlattices. It is proven that these systems can have different critical
temperatures and fields for different S layers. This predicted decoupled superconductivity is found
to manifest itself in its most striking way for F/S tetralayer. It is shown that F/S/F/S
tetralayer is the most perspective candidate for use in superconducting spin nanoelectronics
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