You need JavaScript to view this

Diffuse Scattering from Alloys and Disordered Systems: Experimental Techniques and Potentialities; Diffusion dans les Alliages et les Systemes Desordonnes; Methodes Experimentales et Possibilites d'Application; Diffuznoe rasseyanie na splavakh i razuporyadochennykh sistemakh. ehksperimental'nye metody i potentsial'nye vozmozhnosti; Dispersion Difusa en Aleaciones y Sistemas Desordenados; Tecnicas Experimentales y Posibilidades

Conference:

Abstract

The purpose of this paper is to review, both with regard to principles and practice, the types of information that may be obtained by studying the elastic diffuse scattering of neutrons. Attention will be concentrated on systems where there is a random arrangement of defects each of which may be assumed to be unaffected by the presence of its fellows, either because of dilution or because of an intrinsic lack of dependence on environment. In these circumstances the pattern of scattered intensity is proportional to the square of the modulus of a Fourier transform over the disturbance in scattering amplitude associated with a defect. Thus, information on the spatial distribution of defect scattering amplitude can be obtained by carrying out the relevant neutron scattering measurements and performing a Fourier inversion. In practice, because of the large number of processes contributing to the diffuse scattering background, measurements have so far been possible only in a limited number of fields. In particular considerable progress has been made in connection with magnetic defects in ferromagnets where the magnetic cross-section may be controlled by changing the direction of magnetization relative to the neutron scattering vector. In this way the scattering of interest can be  More>>
Authors:
Low, G. G. [1] 
  1. Atomic Energy Research Establishment, Harwell, Berks (United Kingdom)
Publication Date:
Apr 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-58/63
Resource Relation:
Conference: Symposium on Inelastic Scattering of Neutrons, Bombay (India), 15-19 Dec 1964; Other Information: 18 refs., 1 fig.; Related Information: In: Inelastic Scattering of Neutrons. Vol. I. Proceedings of the Symposium on Inelastic Scattering of Neutrons| 476 p.
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COVALENCE; CROSS SECTIONS; CRYSTAL DEFECTS; DIFFUSE SCATTERING; DISTURBANCES; EXPERIMENTAL DATA; FOURIER TRANSFORMATION; MAGNETIZATION; MONOCRYSTALS; NEUTRON DIFFRACTION; PARAMAGNETISM; SALTS; SCATTERING AMPLITUDES; SPATIAL DISTRIBUTION; SPIN; WAVELENGTHS
OSTI ID:
22141816
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M3382096417
Submitting Site:
INIS
Size:
page(s) 413-429
Announcement Date:
Oct 24, 2013

Conference:

Citation Formats

Low, G. G. Diffuse Scattering from Alloys and Disordered Systems: Experimental Techniques and Potentialities; Diffusion dans les Alliages et les Systemes Desordonnes; Methodes Experimentales et Possibilites d'Application; Diffuznoe rasseyanie na splavakh i razuporyadochennykh sistemakh. ehksperimental'nye metody i potentsial'nye vozmozhnosti; Dispersion Difusa en Aleaciones y Sistemas Desordenados; Tecnicas Experimentales y Posibilidades. IAEA: N. p., 1965. Web.
Low, G. G. Diffuse Scattering from Alloys and Disordered Systems: Experimental Techniques and Potentialities; Diffusion dans les Alliages et les Systemes Desordonnes; Methodes Experimentales et Possibilites d'Application; Diffuznoe rasseyanie na splavakh i razuporyadochennykh sistemakh. ehksperimental'nye metody i potentsial'nye vozmozhnosti; Dispersion Difusa en Aleaciones y Sistemas Desordenados; Tecnicas Experimentales y Posibilidades. IAEA.
Low, G. G. 1965. "Diffuse Scattering from Alloys and Disordered Systems: Experimental Techniques and Potentialities; Diffusion dans les Alliages et les Systemes Desordonnes; Methodes Experimentales et Possibilites d'Application; Diffuznoe rasseyanie na splavakh i razuporyadochennykh sistemakh. ehksperimental'nye metody i potentsial'nye vozmozhnosti; Dispersion Difusa en Aleaciones y Sistemas Desordenados; Tecnicas Experimentales y Posibilidades." IAEA.
@misc{etde_22141816,
title = {Diffuse Scattering from Alloys and Disordered Systems: Experimental Techniques and Potentialities; Diffusion dans les Alliages et les Systemes Desordonnes; Methodes Experimentales et Possibilites d'Application; Diffuznoe rasseyanie na splavakh i razuporyadochennykh sistemakh. ehksperimental'nye metody i potentsial'nye vozmozhnosti; Dispersion Difusa en Aleaciones y Sistemas Desordenados; Tecnicas Experimentales y Posibilidades}
author = {Low, G. G.}
abstractNote = {The purpose of this paper is to review, both with regard to principles and practice, the types of information that may be obtained by studying the elastic diffuse scattering of neutrons. Attention will be concentrated on systems where there is a random arrangement of defects each of which may be assumed to be unaffected by the presence of its fellows, either because of dilution or because of an intrinsic lack of dependence on environment. In these circumstances the pattern of scattered intensity is proportional to the square of the modulus of a Fourier transform over the disturbance in scattering amplitude associated with a defect. Thus, information on the spatial distribution of defect scattering amplitude can be obtained by carrying out the relevant neutron scattering measurements and performing a Fourier inversion. In practice, because of the large number of processes contributing to the diffuse scattering background, measurements have so far been possible only in a limited number of fields. In particular considerable progress has been made in connection with magnetic defects in ferromagnets where the magnetic cross-section may be controlled by changing the direction of magnetization relative to the neutron scattering vector. In this way the scattering of interest can be isolated from the non-magnetic effects as a difference between two intensity measurements. A process contributing to the diffuse scattering background which is partly magnetic in character and therefore not eliminated by the above technique is multiple Bragg scattering in a magnetic polycrystal. This may be avoided by the use of a single -crystal specimen or by employing long wavelength neutrons such that no Bragg processes are possible. An instrument based on the latter principle has been developed at Harwell and used in connection with a wide range of measurements on dilute ferromagnetic alloys. These observations are discussed along with a number of other likely future developments in the field. Included among the latter are measurements of the diffuse magnetic scattering from paramagnetic salts. Observations of such scattering are of great interest since they contain direct information on the amount of spin transferred as a result of covalency, from a magnetic ion on to the ligands which surround it. (author) [French] Le memoire a pour objet d'examiner, du point de vue des principes et de la pratique, les divers renseignements que l'on peut obtenir en etudiant la diffusion elastique des neutrons. L'auteur traite surtout des systemes comportant une disposition stochastique des defauts, au sujet desquels on peut supposer qu'aucun n'est affecte par la presence des autres, soit en raison de la dilution, soit en raison d'une independance intrinseque 1 l'egard de l'environnement. Dans ces conditions, l'intensite diffusee est proportionnelle au carre du module d'une transformee de Fourier sur la perturbation de l'amplitude de diffusion associee a un defaut. On peut ainsi obtenir des renseignements sur la distribution spatiale de cette amplitude de diffusion en procedant aux mesures appropriees de diffusion des neutrons et en operant une inversion de Fourier. En pratique, vu le grand nombre de phenomenes qui contribuent au bruit de fond de diffusion, on n'a pu jusqu'a present faire des mesures que pour un petit nombre de champs. On a notamment realise des progres considerables en ce qui concerne les defauts magnetiques dans les ferro-aimants ou l'on peut faire varier la section efficace magnetique en modifiant la direction de magnetisation par rapport au vecteur de diffusion des neutrons. Cto parvient ainsi a separer la diffusion consideree des effets non magnetiques sous la forme d'une difference entre les deux mesures d'intensite. Un phenomene qui contribue au bruit de fond de diffusion et qui possede un caractere partiellement magnetique et par consequent n'est pas elimine par la technique susmentionnee, est la diffusion multiple de Bragg dans un polycristal magnetique. On parvient a l'eviter en utilisant un echantillon monocristal ou en employant des neutrons ayant une longueur d'onde suffisante pour qu'aucun phenomene de Bragg ne puisse se produire. Un appareil fonde sur ce dernier principe a ete mis au point a Harwell et utilise pour une gamme etendue de mesures portant sur des alliages ferromagnetiques dilues. L'auteur discute ces travaux ainsi que plusieurs autres qui pourraient etre entrepris dans ce domaine. Parmi ces derniers figurent des mesures de la diffusion magnetique par les sels paramagnetiques. L'observation de cette diffusion revet un grand interet car elle fournit des renseignements directs sur la fraction de spin transferee, par suite de la covalence, d'un ion magnetique aux coordinats qui l'entourent. (author) [Spanish] La finalidad de la memoria es analizar, desde el punto de vista de la teoria y de la practica, las informaciones que pueden obtenerse estudiando la dispersion elastica difusa de neutrones. Se presta particular atencion a los sistemas con distribucion aleatoria de defectos, cada uno de los cuales puede considerarse aislado de los demas, bien por efecto de la dilucion o bien por ser intrinsecamente independiente del medio. En estas condiciones, la intensidad dispersa es proporcional al cuadrado del modulo de una transformada de Fourier respecto de la perturbacion de la amplitud de dispersion asociada al defecto. De este modo pueden obtenerse datos sobre la distribucion espacial de la amplitud de dispersion por defectos realizando las mediciones pertinentes por dispersion neutronica y efectuando una inversion de Fourier. En la practica, dada la gran cantidad de procesos que contribuyen a la actividad de fondo debida a la dispersion difusa, solo se han podido realizar determinados tipos de mediciones. En particular, se han logrado progresos considerables en lo que respecta a los defectos magneticos de las sustancias ferromagneticas en las que la seccion eficaz magnetica puede controlarse cambiando la direccion de magnetizacion con respecto al vector de dispersion neutronica. De este modo, la dispersion de interes puede distinguirse de los efectos no magneticos como diferencia entre dos intensidades medidas. Un proceso que contribuye al fondo de dispersion difusa, en parte de caracter magnetico y que, por tanto, la mencionada tecnica no elimina, es la dispersion miiltiple de Bragg en un poli- cristal magnetico. Puede prevenirse utilizando una muestra monocristalina o empleando neutrones de gran longitud de onda, de forma que impidan los procesos de Bragg. En Harwell se ha construido un instrumento basado en este principio, que se utiliza para una amplia serie de mediciones en aleaciones ferromagneticas diluidas. Se examinan estos experimentos y otras novedades que cabe anticipar en la materia, entre ellas la medicion de la dispersion magnetica difusa en sales paramagneticas. El estudio de esta dispersion reviste enorme interes, pues proporciona informacion dilecta sobre la cantidad de spin transmitida por un ion magnetico a los ligandos que le rodean como resultado de la covalencia. (author) [Russian] Zadachej nastojashhej raboty javljaetsja rassmotrenie kak v principe, tak i s prakticheskoj tochki zrenija teh vidov dannyh, kotorye mozhno poluchit' v rezul'tate izuchenija neuprugogo diffuznogo rassejanija nejtronov. Vnimanie skoncentrirovano na teh sistemah, v kotoryh imeetsja razuporjadochen- noe raspolozhenie defektov, kazhdyj iz kotoryh mozhno uslovno schitat' ne podverzhennym vlijaniju drugih imejushhihsja defektov libo v rezul'tate razbavlenija, libo v rezul'tate otsutstvija zavisimosti ot okruzhenija. Pri jetih uslovijah intensivnost' rassejanija proporcional'na kvadratu modulja razlozhenija Fur'e po vozmushheniju v amplitude rassejanija, vyzvannomu defektom. Takim obrazom, dannye ob amplitude prostranstvennogo raspredelenija rassejanija defektov mogut byt' polucheny v rezul'tate vypolnenija sootvetstvujushhih izmerenij rassejanija nejtronov i proizvedenija preobrazovanija Fur'e. Na praktike, v svjazi s tem, chto bol'shoe kolichestvo processov igraet rol' v sozdanii fona diffuznogo rassejanija, izmerenija udalos' poka proizvesti v ogranichennom chisle oblastej. V chastnosti, znachitel'nye uspehi dostignuty v oblasti magnitnyh defektov v ferromagnitnyh telah, v kotoryh magnitnye sechenija mogut kontrolirovat'sja putem izmenenija napravlenija namagnichivanija v otnoshenii vektora rassejanija nejtronov. Takim obrazom, interesujushhee rassejanie mozhet byt' otdeleno ot nemagnitnyh jeffektov putem opredelenija raznicy mezhdu rezul'tatami dvuh izmerenij intensivnosti. Processom, igrajushhim rol' v sozdanii fona diffuznogo rasseja- njja, kotoryj javljaetsja otchasti magnitnym po svoemu harakteru i ne mozhet byt' pojetomu iskljuchen s pomoshh'ju vysheukazannogo metoda, javljaetsja brjeggovskoe rassejanie na magnitnom polikristalle. Jetot process mozhno ustranit' putem ispol'zovanija monokristallicheskih obrazcov ili takih dlinnovolnovyh nejtronov, pri kotoryh nevozmozhen brjeggovskij process. Pribor, osnovannyj na jetom principe, byl razrabotan v Harujelle i ispol'zovalsja dlja shirokogo kruga izmerenij, svjazannyh s razbavlennymi ferromagnitnymi splavami. Jeti voprosy rassmatrivajutsja vmeste s nekotorymi drugimi voprosami, kasajushhimisja vozmozhnyh budushhih razrabotok v jetoj oblasti. V chislo jetih poslednih vhodjat izmerenija diffuznogo magnitnogo rassejanija na paramagnitnyh soljah. Nabljudenie takogo rassejanija predstavljaet bol'shoj interes, poskol'ku pozvoljaet poluchit' neposredstvennye dannye o velichine spina, peredannoj v rezul'tate kovalentnosti ot magnitnogo iona k okruzhajushhim ego ligandam. (author)}
place = {IAEA}
year = {1965}
month = {Apr}
}