scholarly journals SMALL-ANGLE SCATTERING OF NEUTRONS ON Sr2FeMoO6–δ SAMPLES WITH DIFFERENT-DEGREE SUPERSTRUCTURAL ORDERING OF Fe/Mo CATIONS

Doklady BGUIR ◽  
2020 ◽  
Vol 18 (2) ◽  
pp. 5-13
Author(s):  
L. I. Hurski ◽  
N. A. Kalanda ◽  
M. V. Yarmolich ◽  
I. A. Bobrikov ◽  
A. L. Zhaludkevich ◽  
...  
Keyword(s):  
Small Angle ◽  
Magnetic Moment ◽  
Solid Phase ◽  
Electronic Configuration ◽  
Magnetic Characteristics ◽  
Angle Scattering ◽  
Porod Law ◽  
Temperature Dependences ◽  
The Difference ◽  
Curie Temperatures

Single-phase Sr2FeMoO6-δ samples with different-degreesuperstructiral ordering Fe/Mo cations superstructural ordering (P, 76, 86 and 93 %) were obtained by the solid-phase technique. Based on the results of measuring the magnetic characteristics in the samples, we found that an increase in magnetization (26.41, 32.36 and 42.66 A·m2·kg–1), magnetic moment (1.33, 3.07 and 3.58 μB/f.u.) and Curie temperatures (422, 428 and 437 K) withparameter P (76, 86 and 93 %) can be explained by the presence of antistructural defects, as well as antiferromagnetic inclusions. This determines the redistribution of electron density, which is accompanied by the change in electronic configuration of a part of Fe/Mo cations. Based on the temperature dependences of the magnetic moment of the samples measured in ZFC and FC modes, and on small-angle polarized neutron scattering (SANS), we found that the samples are in a magnetically inhomogeneous state. An important result to mention is that we detected the difference between the slope of the SANS curves of samples with different oxygen content, which demonstrates a different microstructure of inhomogeneities. The main inhomogeneities are magnetic inclusions with the dimensions depending on the superstructural ordering of Fe/Mo cations. According to the Porod law, it was shown that the Sr2FeMoO6-δ samples with wave vector values 0.1 > q > 0.002 Å–1 contain polydisperse grains with a smooth surface. For q > 0.1 Å–1 a deviation from the Porod law is observed, confirming the presence of magnetic inhomogeneities with a diameter < 6 nm in the grains.

Phenylalanyl-tRNA Synthetase from Baker'Yeast: Structural Organization of the Enzyme and Its Complex with tRNAPhe as Determined by X-Ray Small-Angle Scattering

1979 ◽  
Vol 34 (1-2) ◽  
pp. 20-26 ◽  
Author(s):  
Ingrid Pilz ◽  
Karin Goral ◽  
Friedrich v. d. Haar
Keyword(s):  
Molecular Weight ◽  
Small Angle ◽  
Quaternary Structure ◽  
Trna Synthetase ◽  
Distribution Functions ◽  
Maximum Diameter ◽  
Radius Of Gyration ◽  
X Ray ◽  
Angle Scattering ◽  
The Difference

Abstract The quaternary structure of the phenylalanyl-tRNA synthetase and its complex with tRNAPhe was studied in dilute solutions by small angle X-ray scattering. For the free synthetase the radius of gyration was determined as 5.5 nm, the volume 523 nm3, the maximum diameter 17.5 nm and the molecular weight as 260 000 using an isopotential specific volume of 0.735. The overall shape could be best approximated by a flat cylinder with dimensions 18.2 nm X 11.5 nm X 4 nm ; the loose structure was approximated by building up the cylinder by spheres (diameter 4.2 nm).The corresponding parameters of the enzyme tRNA complex were the following: radius of gyration 5.9 nm, volume 543 nm 3, maximum diameter 21 nm and molecular weight 290 000. These parameters suggest an 1:1 complex, whereby it must be assumed that the tRNA molecule is attached in the extension of the longer axis. From the difference in the distance distribution functions of the free enzyme and the complex it is evident that we have to assume a change of conformation (contraction) of the enzyme upon the binding of the specific tRNA.

Three-dimensional reconstruction of liquid phases in disordered mesopores usingin situsmall-angle scattering

2013 ◽  
Vol 46 (2) ◽  
pp. 493-504 ◽  
Author(s):  
Cedric J. Gommes
Keyword(s):  
Mesoporous Materials ◽  
Small Angle ◽  
Solid Phase ◽  
Gaussian Random Field ◽  
Three Dimensional ◽  
Small Angle Scattering ◽  
Scattering Data ◽  
Wetting Transition ◽  
X Rays ◽  
Angle Scattering

Small-angle scattering of X-rays (SAXS) or neutrons is one of the few experimental methods currently available for thein situanalysis of phenomena in mesoporous materials at the mesoscopic scale. In the case of disordered mesoporous materials, however, the main difficulty of the method lies in the data analysis. A stochastic model is presented, which enables one to reconstruct the three-dimensional nanostructure of liquids confined in disordered mesopores starting from small-angle scattering data. This so-called plurigaussian model is a multi-phase generalization of clipped Gaussian random field models. Its potential is illustrated through the synchrotron SAXS analysis of a gel permeated with a critical nitrobenzene/hexane solution that is progressively cooled below its consolute temperature. The reconstruction brings to light a wetting transition whereby the nanostructure of the pore-filling liquids passes from wetting layers that uniformly cover the solid phase of the gel to plugs that locally occlude the pores. Using the plurigaussian model, the dewetting phenomenon is analyzed quantitatively at the nanometre scale in terms of changing specific interface areas, contact angle and specific length of the triple line.

scholarly journals Tемпературная зависимость магнитных свойств и магнитополевого поведения тонкопленочных трехслойных Co/Gd/Co систем

2021 ◽  
Vol 63 (10) ◽  
pp. 1542
Author(s):  
А.М. Харламова ◽  
А.В. Макаров ◽  
А.В. Свалов ◽  
Е.Е. Шалыгина
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Coercive Force ◽  
Magnetic Moment ◽  
Hysteresis Loops ◽  
Magnetic Characteristics ◽  
Temperature Changes ◽  
Ion Plasma ◽  
Temperature Dependences ◽  
Oriented Parallel

The results of studies of the temperature dependences of the magnetic properties and magnetic field behavior of thin-film three-layer Co/Gd/Co system, obtained by ion-plasma magnetron sputtering, are present. The thickness of the cobalt layers is 5.0 nm, and the thickness of the Gd layers, tGd, varies from 3.0 to 10.0 nm. The bulk magnetic characteristics of the samples are measured on a vibrating magnetometer at the external magnetic field oriented parallel to the plane of the samples. The influence of the temperature and Gd thickness on the shape of the hysteresis loops, the values of the magnetic moment m and coercive force are discovered. In particular, with the temperature changes from 100 to 300 K, the decrease of the coercive force is observed. At a temperature above 150 K, magnetic moment increases. With increasing thickness of gadolinium, the value of m decreases.

Electron and phonon scattering II. Thermoelectricity in rubidium, caesium and alloys at very low temperatures

1963 ◽  
Vol 274 (1357) ◽  
pp. 154-162 ◽  
Keyword(s):  
Fermi Surface ◽  
Electron Scattering ◽  
Small Angle ◽  
Low Temperatures ◽  
Phonon Scattering ◽  
Large Angle ◽  
Phonon Drag ◽  
Diffusion Term ◽  
Angle Scattering ◽  
The Difference

Following earlier measurements on pure potassium and alloys, we have now made a corresponding study at very low temperatures of thermoelectricity in rubidium, caesium, and their alloys with each other and with potassium. The results have proved in accord with our interpretation of the earlier work, and we discuss the trends observed in both the ‘electron diffusion’ and ‘phonon-drag’ contributions to the absolute thermoelectric power. Both contributions as observed in these metals are consistent with a larger distortion in the Fermi surface of caesium than in those of potassium or rubidium. It appears that the changes in the thermoelectric diffusion term can be attributed consistently to the difference arising from large-angle and small angle scattering. It is supposed that in turn these types of electron scattering arise from the presence of homovalent and heterovalentim purity centres.

Simple inversion formula for the small-angle X-ray scattering intensity from polydisperse systems of spheres

2012 ◽  
Vol 45 (3) ◽  
pp. 406-416 ◽  
Author(s):  
Robert Botet ◽  
Bernard Cabane
Keyword(s):  
Size Distribution ◽  
Small Angle ◽  
Inversion Formula ◽  
Colloidal Dispersions ◽  
Inversion Method ◽  
X Ray Scattering ◽  
Angle Scattering ◽  
Porod Law ◽  
Simple Inversion ◽  
Scattering Signal

A practical inversion method to calculate the size distribution of colloidal homogeneous particles from small-angle scattering experiments is presented. It is based on the analysis of the deviations of the scattering signal from the Porod law. The resulting inversion formula provides a reliable way to assess complex size distributions such as power-law, multimodal or very broad distributions. It is particularly suitable for colloidal dispersions that have a substantial fraction of very small particles. These cases correspond to large deviations from the Porod law over a broad range of scattering vector values,q. Shannon's theorem gives a way to obtain the maximum amount of information concerning the size distribution, without requiring an arbitrary extrapolation of the data beyond the availableqrange. It is demonstrated that this protocol yields a calculated distribution of particle sizes that is stable.

Multiphase approximation for small-angle scattering

2009 ◽  
Vol 43 (1) ◽  
pp. 8-11 ◽  
Author(s):  
Dragomir Tatchev
Keyword(s):  
Small Angle ◽  
Small Angle Scattering ◽  
Multiphase System ◽  
Contrast Variation ◽  
Two Phase ◽  
Angle Scattering ◽  
Multiphase Systems ◽  
Phase Systems ◽  
The Difference ◽  
Two Phases

The two-phase approximation in small-angle scattering is well known and is still the dominant approach to data analysis. The intensity scattered at small angles is proportional to the second power of the difference between the scattering densities of the two phases. Nevertheless, scattering contrast variation techniques are widely used, and they are obviously suitable for multiphase systems or systems with gradually varying scattering density, since if no parasitic scattering contributions are present the scattering contrast variation would only change a proportionality coefficient. It is shown here that the scattered intensity at small angles of a multiphase system can be represented as a sum of the scattering of two-phase systems and terms describing interference between all pairs of phases. Extracting two-phase scattering patterns from multiphase samples by contrast variation is possible. These two-phase patterns can be treated with the usual small-angle scattering formalism. The case of gradually varying scattering density is also discussed.

Illustration of the anisotropic Porod law

2002 ◽  
Vol 35 (3) ◽  
pp. 304-313 ◽  
Author(s):  
S. Ciccariello ◽  
J.-M. Schneider ◽  
B. Schönfeld ◽  
G. Kostorz
Keyword(s):  
Small Angle ◽  
Small Angle Scattering ◽  
Two Dimensional ◽  
Simple Derivation ◽  
Ellipsoidal Particles ◽  
Asymptotic Term ◽  
Angle Scattering ◽  
Porod Law

A simple derivation of the leading asymptotic term of small-angle scattering intensities relevant to anisotropic particulate samples is reported. The result is illustrated for the case of ellipsoidal particles. It is discussed under what circumstances the anisotropic Porod law can be applied to scattering intensities collected by a two-dimensional detector.

Small angle scattering in the Porod region from hydrated paper sheets at varying humidities

Holzforschung ◽  
2004 ◽  
Vol 58 (5) ◽  
pp. 473-479 ◽  
Author(s):  
Christopher J. Garvey ◽  
Ian H. Parker ◽  
Robert B. Knott ◽  
George P. Simon
Keyword(s):  
Small Angle ◽  
Scattering Length ◽  
Phase System ◽  
Phase Approximation ◽  
Contrast Variation ◽  
Two Phase ◽  
Scattering Angle ◽  
Angle Scattering ◽  
Porod Law ◽  
Two Phases

Abstract The microscopic changes in the structure of paper at different equilibrium moisture contents were examined using the novel technique of contrast variation small angle neutron scattering (SANS). Contrast variation, by appropriate selection of the H2O:D2O ratio, was used to simplify the scattering from hydrated paper to a two-phase approximation. The two phases were paper polymers (cellulose, lignin and hemicelluloses) and a phase consisting of water and voids. The two-phase approximation is justified by consideration of the chemistry and density of each of the polymer species belonging to paper, and by matching the scattering length density of the sorbed moisture to air. The neutron intensity at the higher scattering angles examined was successfully fitted using the Porod law, which is applicable to scattering from a two-phase system at the high scattering angle limit. This limit is related to the specific surface area between the two phases. The limiting scattered intensity of neutrons was found to increase with increasing moisture content for a range of paper materials. It is concluded that the sorption of water increased the limiting intensity because water disrupted polymer-polymer bonding. The Porod law also predicts the slope of the intensity/scattering angle curve at the high scattering angle limit.

scholarly journals Первопринципные расчеты магнитной анизотропии пленок Fe и Co, разделенных прослойкой немагнитных металлов

2021 ◽  
Vol 63 (11) ◽  
pp. 1787
Author(s):  
М.В. Мамонова ◽  
М.Ю. Макеев ◽  
Д.С. Калинин ◽  
А.А. Зенова
Keyword(s):  
Magnetic Anisotropy ◽  
Magnetic Moment ◽  
Software Package ◽  
Numerical Calculations ◽  
Magnetic Characteristics ◽  
Perpendicular Anisotropy ◽  
Monolayer Films ◽  
Surface Plane ◽  
Total Energies ◽  
The Difference

This paper presents the results of numerical calculations of the magnetic characteristics of Co and Fe monolayer films on Cu and Pt surfaces using the VASP software package. The values ​​of the difference between the total energies of the antiferromagnetic and ferromagnetic configurations are calculated depending on the convergence parameters and the thickness of the nonmagnetic material. The values ​​of the magnetic anisotropy and magnetic moment of atoms in the structures of Co / Cu / Co, Fe / Pt / Fe, Co / Pt / Co, Pt / Co / Cu / Co / Pt are determined depending on the orientation of the surface face. For the (110) and (111) faces, the phenomenon of reorientation in the Co / Cu / Co structure is confirmed, when the anisotropy of the cobalt films parallel to the surface plane is replaced by the perpendicular anisotropy due to the introduction of an ultrathin platinum film into the structure.

Small Angle Electron Scattering From Vacuum Condensed Metallic Films

1968 ◽  
Vol 26 ◽  
pp. 380-381
Author(s):  
J. Silcox ◽  
R. H. Wade
Keyword(s):  
Electron Scattering ◽  
Small Angle ◽  
Ring Structure ◽  
Two Dimensional ◽  
Metallic Films ◽  
Micro Structure ◽  
Angle Scattering ◽  
The Fourier Transform ◽  
Source Of Information ◽  
Kinematical Theory

Recent work has drawn attention to the possibilities that small angle electron scattering offers as a source of information about the micro-structure of vacuum condensed films. In particular, this serves as a good detector of discontinuities within the films. A review of a kinematical theory describing the small angle scattering from a thin film composed of discrete particles packed close together will be presented. Such a model could be represented by a set of cylinders packed side by side in a two dimensional fluid-like array, the axis of the cylinders being normal to the film and the length of the cylinders becoming the thickness of the film. The Fourier transform of such an array can be regarded as a ring structure around the central beam in the plane of the film with the usual thickness transform in a direction normal to the film. The intensity profile across the ring structure is related to the radial distribution function of the spacing between cylinders.

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