You need JavaScript to view this

Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita

Conference:

Abstract

Measurements were done in Vinca on the RA reactor using a crystal neutron spectrometer. Monochromatic neutrons ({lambda} = 1.314A) were scattered on a large single crystal of haematite ({alpha}-Fe{sub 2}O{sub 3}). The angular distributions of inelastically scattered neutrons were investigated. For a number of different crystal missetting angles {Delta}{theta}, the width {Gamma} of the scattered neutron beam (so-called scattering cone) was measured. This scattering cone was ascribed to the magnon scattering surface surrounding the (111) reciprocal lattice point. For several magnon velocities the {Gamma} versus missetting angle dependence was calculated and compared with the experimental points. The value of the velocity in the [111] direction was found to be equal to 25.5{+-} 1.0 km/s. Structural anisotropy of the magnon dispersion relation was discovered. The velocity was found to be higher for the directions of propagation parallel to the [111] axis in qualitative agreement with the earlier measurements (Riste and others) giving v = 38 km/s. It was not possible to reveal the existence of an energy gap Eg in the acoustic magnon energy band. It was estimated that the Eg value must be below 1 meV. Using the formalism of Wallace the magnon dispersion relations in haematite were calculated. This  More>>
Authors:
Dimitrijevic, Z.; Rzany, H.; Todorovic, J.; Wanic, A. [1] 
  1. Institute for Nuclear Physics Cracow (Poland)
Publication Date:
Apr 15, 1965
Product Type:
Conference
Report Number:
IAEA-SM-58/29
Resource Relation:
Conference: Symposium on Inelastic Scattering of Neutrons, Bombay (India), 15-19 Dec 1964; Other Information: 12 refs., 5 figs.; 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; ANGULAR DISTRIBUTION; ANISOTROPY; DISPERSION RELATIONS; ENERGY GAP; EXPERIMENTAL DATA; FERRITES; HEMATITE; INELASTIC SCATTERING; IRON IONS; MAGNONS; MONOCHROMATIC RADIATION; MONOCRYSTALS; NEUTRON BEAMS; NEUTRON DIFFRACTION; NEUTRON SPECTROMETERS; OXYGEN IONS; R-A REACTOR; SPECTRA; SPIN; VELOCITY
OSTI ID:
22141818
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M3384096419
Submitting Site:
INIS
Size:
page(s) 443-451
Announcement Date:
Oct 24, 2013

Conference:

Citation Formats

Dimitrijevic, Z., Rzany, H., Todorovic, J., and Wanic, A. Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita. IAEA: N. p., 1965. Web.
Dimitrijevic, Z., Rzany, H., Todorovic, J., & Wanic, A. Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita. IAEA.
Dimitrijevic, Z., Rzany, H., Todorovic, J., and Wanic, A. 1965. "Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita." IAEA.
@misc{etde_22141818,
title = {Neutron Investigation of Magnon Spectrum in Haematite; Etude du Spectre de Magnons dans l'Hematite, au Moyen des Neutrons; Nejtronnoe issledovanie spektra magnona v gematite; Estudio, por Metodos Neutronicos, del Espectro de Magnones en la Hematita}
author = {Dimitrijevic, Z., Rzany, H., Todorovic, J., and Wanic, A.}
abstractNote = {Measurements were done in Vinca on the RA reactor using a crystal neutron spectrometer. Monochromatic neutrons ({lambda} = 1.314A) were scattered on a large single crystal of haematite ({alpha}-Fe{sub 2}O{sub 3}). The angular distributions of inelastically scattered neutrons were investigated. For a number of different crystal missetting angles {Delta}{theta}, the width {Gamma} of the scattered neutron beam (so-called scattering cone) was measured. This scattering cone was ascribed to the magnon scattering surface surrounding the (111) reciprocal lattice point. For several magnon velocities the {Gamma} versus missetting angle dependence was calculated and compared with the experimental points. The value of the velocity in the [111] direction was found to be equal to 25.5{+-} 1.0 km/s. Structural anisotropy of the magnon dispersion relation was discovered. The velocity was found to be higher for the directions of propagation parallel to the [111] axis in qualitative agreement with the earlier measurements (Riste and others) giving v = 38 km/s. It was not possible to reveal the existence of an energy gap Eg in the acoustic magnon energy band. It was estimated that the Eg value must be below 1 meV. Using the formalism of Wallace the magnon dispersion relations in haematite were calculated. This was done under the assumption that there exist two non-vanishing exchange integrals J{sub 1} and J{sub 2}. J{sub 1} and J{sub 2} denote the superexchange energy coupling between the spins of neighbouring iron ions bonded via an oxygen ion. The Fe-O-Fe angles of the bonds taken into consideration are correspondingly 132 and 126 Degree-Sign . Satisfactory agreement between the theory and existing experimental data is obtained when SJ{sub 1} = SJ{sub 2} = 5.1 meV. Apart from the acoustic magnon branch, the calculations revealed the existence of an optic branch but this was not accessible to investigation by the neutron diffraction technique. (author) [French] Les mesures ont ete faites a Vinea, dans le reacteur RA, au moyen d'un spectrometre a cristal. Des neutrons monochromatiques ({lambda} = 1.314A) ont ete diffuses par un grand monocristal d'hematite ({alpha}-Fe{sub 2}O{sub 3}). Les auteurs ont etudie la distribution angulaire des neutrons diffuses inelastiquement. Pour plusieurs angles de decalage {Delta}{theta} du cristal, ils ont mesure la largeur {Gamma} du faisceau de neutrons diffuses (appele cone de diffusion). Ils ont attribue ce cone a la surface de diffusion des magnons qui entoure le point du reseau reciproque (1,1,1). Pour plusieurs vitesses de magnons, ils ont mesure {Gamma}, en fonction de l'angle de decalage, et l*ont comparee aux points experimentaux. Ils ont constate que dans la direction [111], la vitesse avait une valeur egale a 25,5{+-}1,0 km/s. Ils ont decouvert une anisotropie structurelle de la relation de dispersion des magnons. Ils ont note que la vitesse etait plus elevee pour les directions de propagation paralleles a l'axe [111], ce qui concorde qualitativement avec les mesures anterieures (faites par Riste et d'autres) qui ont donne v = 38 km/s. Il n'a pas ete possible de mettre en evidence l'existence d'une discontinuite Eg dans la bande acoustique de l'energie des magnons. Selon les evaluations, Eg doit avoir une valeur inferieure a 1 meV. En utilisant le formalisme de Wallace, les auteurs ont calcule les relations de dispersion des magnons dans l'hematite. A cet effet, ils ont admis l'existence de deux integrales d'echange J{sub 1} et J{sub 2} qui ne disparaissent pas. J{sub 1} et J{sub 2} expriment le couplage a superechange d'energie entre les spins d'ions Fe voisins lies par l'intermediaire d'un ion oxygene. Les angles Fe-O-Fe des liaisons considerees sont respectivement de 132 et 126 Degree-Sign . Les resultats theoriques et les donnees experimentales actuelles concordent de facon satisfaisante lorsque SJ{sub 1} = SJ{sub 2} = 5,1 meV. Outre la branche acoustique des magnons, les calculs ont revele l'existence d'une branche optique qui, toutefois, ne se prete pas aux recherches par la methode de la diffusion des neutrons. (author) [Spanish] Los autoresrealizaron sus mediciones en el reactor RA de Vinca con ayuda de un espectrometro neutronicode cristal. Los neutrones monocromaticos ({lambda} = 1.314A) se dispersaron en un monocristal de hematita (Fe{sub 2}O{sub 3}{alpha}) de gran tamano. Se estudiaron las distribuciones angulares de los neutrones inelast Lea mente dispersos, midiendo para un cierto numero de angulos distintos de desplazamiento del cristal, {Delta}{theta}, la anchura {Gamma} del haz de neutrones dispersos (el llamado cono de dispersion), que fue adscrito a la superficie de dispersion magnOnica que envolvia al punto(l,l,l)delared reciproca. Se calcularon y compararon con los puntos obtenidos experimentalmente los valores de {Gamma} en funcion de la variacion del angulo de desplazamiento para diversas velocidades de los magnones. Se comprobo que el valor de la velocidad en la direccion [111] era igual a 25,5 {+-} 1,0 km/s, descubriendose asi la anisotropia estructural de la relacion de dispersion magnonica. Se encontro que la velocidad era superior para las direcciones de propagacion paralelas al eje [111], lo que esta cualitativamente de acuerdo con anteriores mediciones (Riste y otros) que daban una velocidad v = 38 km/s. No fue posible poner de manifiesto la existencia de una laguna energetica Eg en la banda de las energias magnonicas acusticas. Se calculo que el valor de Eg tiene que ser inferior a 1 meV. Utilizando las formulas propuestas por Wallace se calcularon las relaciones de dispersion de los magnones en la hematita. Este calculo se efectuo en el supuesto de que existan dos integrales de intercambio que no desaparecen: J{sub 1} y J{sub 2}, que indican el acoplamiento energetico de superintercambio entre los spins de los iones hierro proximos, enlazados por un ion oxigeno, los angulos de los enlaces Fe-O-Fe tenidos en cuenta son de 132 Degree-Sign y 126 Degree-Sign , respectivamente. Un acuerdo satisfactorio entre la teoria y los datos experimentales disponibles se tiene cuando SJ{sub 1} = SJ{sub 2} = 5,1 meV. Ademas de la rama magnonica acustica, los calculos han revelado la existencia de una rama optica, pero el estudio de esta no pudo llevarse a cabo por el metodo de difraccion neutronica. (author) [Russian] byli provedeny v Vincha na reaktore RA s ispol'zovaniem kristallicheskogo nejtronnogo spektrometra. Rassejanie monohromaticheskih nejtronov ({lambda} = 1.314A) proizvodilos' na krupnom monokristalle gematita ({alpha}-Fe{sub 2}O{sub 3}). Issledovalis' uglovye raspredelenija neuprugo rassejannyh nejtronov. Dlja rjada razlichnyh nepravil'nyh uglov kristalla AO byla izmerena shirina G puchka rassejannyh nejtronov (tak nazyvaemogo konusa rassejanija). Jetot konus rassejanija byl pripisan javleniju poverhnostnogo rassejanija magnona vokrug tochki obratnoj reshetki [1,1,1] . Dlja rjada skorostej magnona byla rasschitana i sravnena s jeksperimental'nymi tochkami zavisimost' G ot nepravil'nogo ugla. Ustanovleno, chto velichina skorosti v napravlenii [111] ravna 25,5 11,0 km/sek. Byla obnaruzhena strukturnaja anizotropija dispersionnogo sootnoshenija magnona. Bylo najdeno, chto skorost' javljaetsja bolee vysokoj v napravlenijah rasprostranenija parallel'nyh osi [111] i chto kachestvenno ona horosho soglasuetsja s bolee rannimi izmerenijami (Riste i dr.) dajushhimi v = 38km/sek. Obnaruzhit' v akusticheskoj oblasti jenergii magnona sushhestvovanie razryva jenergeticheskoj krivoj Eg ne udalos'. Bylo rasschitano, chto velichina E dolzhna byt' nizhe 1 Mjev. Pri pomoshhi formalizma Uollase byli rasschitany dispersionnye sootnoshenija magnona v gematite. Pri jetom ishodili ije predpolozhenija, chto sushhestvujut dva ne stremjashhihsja k nulju integrala obmena J{sub 1} i J{sub 2}. J{sub 1} i J{sub 2} oznachajut svjaz' sverhobmennoj jenergii mezhdu spinami sosednih ionov zheleza, svjazannyh ionom kisloroda. Ugly svjazi Fe -O -Fe, prinjatye v raschet, sostavljajut sootvetstvenno 132 Degree-Sign i 126 Degree-Sign . Polucheno udovletvoritel'noe soglasie mezhdu teoriej i sushhestvujushhimi jeksperimental'nymi dannymi, kogda SJ{sub 1}= SJ{sub 2} = -5,1 Mjev. Pomimo akusticheskoj vetvi magnona, raschety pokazali nalichie opticheskoj vetvi, no s pomoshh'ju metoda nejtronnoj difrakcii issledovat' jeto ne predstavilos' vozmozhnym. (author)}
place = {IAEA}
year = {1965}
month = {Apr}
}