5,408 research outputs found
Peculiarities of neutron waveguides with thin Gd layer
Peculiarities of the formation of a neutron enhanced standing wave in the
structure with a thin highly absorbing layer of gadolinium are considered in
the article. An analogue of the poisoning effect well known in reactor physics
was found. The effect is stronger for the Nb/Gd/Nb system. Despite of this
effect, for a Nb/Gd bilayer and a Nb/Gd/Nb trilayer placed between Al2O3
substrate and Cu layer, it is shown theoretically and experimentally that one
order of magnitude enhancement of neutron density is possible in the vicinity
of the Gd layer. This enhancement makes it possible to study domain formation
in the Gd layer under transition of the Nb layer(s) into the superconducting
state (cryptoferromagnetic phase).Comment: 5 pages, 2 figure
Magnetic and Superconducting Phase Diagram of Nb/Gd/Nb trilayers
We report on a study of the structural, magnetic and superconducting
properties of Nb(25nm)/Gd()/Nb(25nm) hybrid structures of a
superconductor/ ferromagnet (S/F) type. The structural characterization of the
samples, including careful determination of the layer thickness, was performed
using neutron and X-ray scattering with the aid of depth sensitive
mass-spectrometry. The magnetization of the samples was determined by SQUID
magnetometry and polarized neutron reflectometry and the presence of magnetic
ordering for all samples down to the thinnest Gd(0.8nm) layer was shown. The
analysis of the neutron spin asymmetry allowed us to prove the absence of
magnetically dead layers in junctions with Gd interlayer thickness larger than
one monolayer. The measured dependence of the superconducting transition
temperature has a damped oscillatory behavior with well defined
positions of the minimum at =3nm and the following maximum at =4nm;
the behavior, which is in qualitative agreement with the prior work (J.S. Jiang
et al, PRB 54, 6119). The analysis of the dependence based on Usadel
equations showed that the observed minimum at =3nm can be described by the
so called "" to "" phase transition of highly transparent S/F
interfaces with the superconducting correlation length nm in
Gd. This penetration length is several times higher than for strong
ferromagnets like Fe, Co or Ni, simplifying thus preparation of S/F structures
with which are of topical interest in superconducting
spintronics
On the feasibility to study inverse proximity effect in a single S/F bilayer by Polarized Neutron Reflectometry
Here we report on a feasibility study aiming to explore the potential of
Polarized Neutron Reflectometry (PNR) for detecting the inverse proximity
effect in a single superconducting/ferromagnetic bilayer. Experiments,
conducted on the V(40nm)/Fe(1nm) S/F bilayer, have shown that experimental spin
asymmetry measured at T = 0.5TC is shifted towards higher Q values compared to
the curve measured at T = 1.5TC. Such a shift can be described by the
appearance in superconducting vanadium of magnetic sub-layer with thickness of
7 nm and magnetization of +0.8 kG.Comment: Changes in the 2nd version: small mistypes are corrected. Manuscript
submitted to JETP let. 4 pages, 2 figure
Possibilities of performance of nonstandard operative interventions in patients, suffering early gastric cancer
Objective. To study a possibility of performance of nonstandard organ-preserving operations in patients, suffering early gastric cancer, using application of the sentinel lymph nodes visualization procedures and the lymph node dissection procedure.
Materials and methods. There were performed operative interventions in 35 patients, suffering early gastric cancer (Stages T1 and T2). For identification of sentinel lymph nodes a procedure of luminescence, using green indocyan, was applied.
Results. In all the patients early gastric cancer was diagnosed (T1,T2). Possibility for performance of organ-preserving operations in early gastric cancer was shown. Miniinvasive interventions in a patient with severe concurrent diseases have appeared sufficiently effective and radical. The patients’ quality of life after laparoscopic pylorus-preserving and organ-preserving operations was significantly better, than quality of life in patients, to whom gastric resection with extended D2 lymph node dissection was done.
Conclusion. There was established, that intraoperative lymphography constitutes he informative method, which helps to estimate the disease Stage in gastric cancer and to apply the adequate scheme of combined and complex treatment. More sensitive is a procedure of luminescence, using green indocyan. Determination of the affection degree of «sentinel lymph nodes» in gastric cancer may serve as an argument for change of the selection tactics while changing the tactics for the operative intervention volume choice
Magnetic proximity effect in [Nb/Gd] superlattices seen by neutron scattering
We have used spin-polarized neutron reflectometry to investigate the
magnetization profile of superlattices composed of ferromagnetic Gd and
superconducting Nb layers. We have observed a partial suppression of
ferromagnetic (F) order of Gd layers in [Gd()/Nb(25nm)]
superlattices below the superconducting (S) transition of the Nb layers. The
amplitude of the suppression decreases with increasing . By analyzing the
neutron spin asymmetry we conclude that the observed effect has an
electromagnetic origin - the proximity-coupled S layers screen out the external
magnetic field and thus suppress the F response of the Gd layers inside the
structure. Our investigation demonstrates the considerable influence of
electromagnetic effects on the magnetic properties of S/F systems
Evidence for nonmonotonic magnetic field penetration in a type-I superconductor
Polarized neutron reflectometry (PNR) provides evidence that nonlocal
electrodynamics governs the magnetic field penetration in an extreme low-k
superconductor. The sample is an indium film with a large elastic mean free
path (11 mkm) deposited on a silicon oxide wafer. It is shown that PNR can
resolve the difference between the reflected neutron spin asymmetries predicted
by the local and nonlocal theories of superconductivity. The experimental data
support the nonlocal theory, which predicts a nonmonotonic decay of the
magnetic field.Comment: 5 pages, 4 figures, LaTex, corrected typos and figure
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