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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)

4 décembre 2015

Hydrothermal Synthesis and Dehydration of CaTeO3(H2O) : An Original Route to Generate New CaTeO3 Polymorphs

Hydrothermal synthesis of hydrated oxotellurate, CaTeO3(H2O), combined with dehydration reaction, is an original route to generate new CaTeO3 polymorphs. CaTeO3(H2O) presents a layered and non-centrosymmetric structure. The topotactic dehydration reaction above 120°C leads to a new non-centrosymmetric metastable d-CaTeO3 polymorph, which conserves a layered structure. These phases were further characterized using powder X-ray diffraction, DFT calculations, infrared spectroscopy, time-resolved second harmonic generation, and thermal analysis.

Corresponding author:Nicolas Barrier

Morgane Poupon, Nicolas Barrier, Sebastien Petit, Simon Clevers, and Valerie Dupray

Inorg. Chem., 2015, 54 (12), pp 5660–5670. DOI : 10.1021/acs.inorgchem.5b00037

Hétérostructures et Oxydes à Propriétés Electroniques (HOPE)

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

18 novembre 2015

Action Nationale de Formation : Chimie du solide CAEN

Une action de formation nationale du CNRS sur la Chimie du Solide est organisée par le laboratoire CRISMAT au Musée des Beaux Arts de Caen du 23 au 25 Novembre 2015.

Pour plus d’infos, cliquer sur ce lien

6 novembre 2015

Comment s’évanouissent les vortex dans un supraconducteur

Dans un supraconducteur (SC), une onde quantique permet le transport d’électrons sans aucune dissipation, et le matériau expulse les champs magnétiques : totalement pour un supraconducteur de premièreespèce (SCI) ou partiellement pour un supraconducteur de deuxième espèce (SCII)....

Lire la suite page 11,

8 octobre 2015

Rigid Phosphonic Acids as Building Blocks for Crystalline Hybrid Materials

Un livre concernant la synthèse de matériaux hybrides vient d’être édité chez Wiley

Le chapitre 9

Rigid Phosphonic Acids as Building Blocks for Crystalline Hybrid Materials 

a été rédigé par J-M RUEFF, G.B. HIX et P-A JAFFRES

Nouveaux Matériaux : Fondements, Fonctionnalités (NMF2)

Le mot du directeur