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15 janvier 2016

Structure refinement using precession electron diffraction tomography and dynamical diffraction

The method for accurate structure refinements from three-dimensional precession electron diffraction data using dynamical diffraction theory has been applied to different samples. The data were measured on different instruments and with variable precession angles. A large series of tests revealed that the method provides structure models with an average error in atomic positions typically between 0.01 and 0.02 Å compared to the reference structures. The method allows a reliable determination of site occupancies and absolute structure.
See also Closing the gap between electron and X-ray crystallography, a scientific commentary on this article.
Corresponding author : Philippe Boullay

L. Palatinus, C. A. Corrêa, G. Steciuk, D. Jacob, P. Roussel, P. Boullay, M. Klementová, M. Gemmi, J. Kopecek, M. C. Domeneghetti, F. Cámara and V. Petrícek.

Acta Cryst. B71 (2015) 740-751. DOI : 10.1107/S2052520615017023

Hétérostructures et Oxydes à Propriétés Electroniques (HOPE)

7 janvier 2016

Advances in Magnetoelectric Materials and Their Application

The present contribution is an updated supplement to the review “Magneto- electricity” published in Chapter 3 of Volume 19 of the series Handbook of Magnetic Materials (Fuentes-Cobas et al., 2011). The combined research area of magnetoelectric/multiferroic materials continues to show, as general tendency, an exponential growth. The basic science of magnetoelectricity is as charming as challenging. Particularly for single-phase magnetoelectric multiferroics, quantum theory has already provided answers to important questions, but several (old and new) open issues demand attention, targetted here. Magnetoelectricity has just started to show its potentialities, magnetoelectric composites for instance as materials mostly used in the real world to develop practical applications. In this aim, textured polycrystalline ME tensor modeling are described. In the bse article (Fuentes-Cobas et al., 2011), Magnetoelectricity was represented as a young and gorgeous princess (awakening from a one-century sleep), with plenty of mysteries and promises. In 2015, our princess has grown from her teens and she is preparing herself to work as a Queen. She already visualizes her contributions in the utilization of relatively simple systems and now she feels attracted by challenges from highly complex objects. Who knows, maybe she finds her way to participate actively in the cure of some cancers

L.E. Fuentes-Cobas, J.A. Matutes-Aquino, M.E. Botello-Zubiate, A. Gonzalez-Vazquez, M.E. Fuentes-Montero and D. Chateigner

"Handbook of Magnetic Materials", Vol. 24 Edité par K.H.J. Buschow chez Elsevier, chapitre 3,pages 237-322 dédié aux matériaux magnéto-électriques :

Matériaux Fonctionnels et de Structure (MFS)

23 novembre 2015

Interplay between 3d-3d and 3d-4f interactions at the origin of the magnetic ordering in the Ba2LnFeO5 oxides

The perovskite derivatives of formulation Ba2LnFeO5 (Ln = Sm, Eu, Gd, Dy, Ho, Er, Yb, as well as Y) exhibit a peculiar structure in which isolated FeO4 tetrahedra are linked by LnO6 octahedra. As a result, the strong super-exchange (SE) Fe-O-Fe coupling usually observed in LnFeO3 perovskites is absent, and one is left in a situation where only a weaker super-super exchange (SSE) Fe-O-O-Fe mechanism competes with SE Fe-O-Ln. This Ba2LnFeO5 series offers a rare opportunity to investigate experimentally a situation where the 3d-3d and 3d-4f interactions co-operate on an equal footing to trigger a unique long-range magnetic ordering in insulating oxides.

A. K Kundu, V. Hardy, V. Caignaert, B. Raveau

J. Phys.:Condens. Matter 27, 486001 (2015)

Collaboration PSOM & NMF2

Physique et Structures d’Oxydes Magnétiques (PSOM)

Nouveaux Matériaux : Fondements, Fonctionnalités (NMF2)

3 novembre 2015

A new active Li–Mn–O compound for high energy density Li-ion batteries

In this work, we report on a new electrochemically active compound with the ‘Li4Mn2O5’ composition, prepared by direct mechanochemical synthesis at room temperature. This rock-salt type nanostructured material shows a discharge capacity of 355 mAh/g, which is the highest one among the known lithium manganese oxide electrode materials ever reported. According to the magnetic measurements, this exceptional capacity results from the electrochemical activity of the Mn3+/Mn4+ and O2-/O- redox couples, and, importantly, of the Mn4+/Mn5+ couple also.
M. Freire, N. V. Kosova, C. Jordy, D. Chateigner, O. I. Lebedev, A. Maignan and V. Pralong*
Nature Materials Letters Vol 14, December 2015 DOI : 10.1038/NMAT4479

Nouveaux Matériaux : Fondements, Fonctionnalités (NMF2)

Actualités Toutes les actualités

2 mai 2016

Prix de Thèse de l’Association Française de Cristallographie (AFC) 2016 – Mention Chimie

Décerné à Morgane POUPON pour ces travaux intitulés :

Synthèse d’oxydes à base d’éléments à paire libre (SeIV et TeIV) dans le but d’obtenir des structures cristallines non-centrosymétriques originales

Ce travail a porté sur l’établissement d’un protocole de synthèse par voie hydrothermale (chauffage classique et micro-ondes) en vue d’obtenir de nouveaux matériaux présentant des propriétés de couplage magnétoélectrique ou multiferroïques dans les systèmes Ca-Te-O et (Ni/Co)-(Te/Se)-O. De nouveaux polymorphes de CaTeO3 et les phases Co3Te2O6(OH)2(H2O)0,5, Ni3Se2O6(OH)2, CoSeO3(H2O)x et NiSeO3(H2O) ont ainsi pu être synthétisés et caractérisés (structures et propriétés).

Thèse co-encadrée par Nicolas Barrier et Olivier Pérez soutenue le 09 Novembre 2015.

Hétérostructures et Oxydes à Propriétés Electroniques (HOPE)

29 avril 2016

La journée de remise des Grands Prix, des Prix binationaux et des titres de Membre distingué 2015, de la SCF aura lieu à Caen le jeudi 26 Mai prochain.

L’entrée est libre et gratuite.