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Univ. Paris-Saclay
15 avril 2020
La recherche de nouveaux états de la matière, allant au-delà de la description classique "à la Landau" suscite un très fort engouement en physique.
17 mars 2020
A. C. Ferreira, S. Paofai, A. Létoublon, J. Ollivier, S. Raymond, B. Hehlen, B. Rufflé, S. Cordier, C. Katan, J. Even & P. Bourges   Hybrid organolead perovskites (HOP) have started to establish themselves in the field of photovoltaics, mainly due to their great optoelectronic properties and steadily improving solar cell efficiency. Study of the lattice dynamics is key in understanding the electron-phonon interactions at play, responsible for such properties.
14 janvier 2020
N. Martin, M. Deutsch, T. C. Hansen, M. T. Fernandez-Diaz, L. N. Fomicheva, A. V. Tsvyashchenko, and I. Mirebeau In the MnGe chiral magnet, the helimagnetic order and local moment collapse in two steps, showing the succession of high spin (HS) and low spin (LS) states as pressure increases. Here, we use high-pressure neutron diffraction to study the doped compounds Mn0.86Co0.14Ge and Mn0.9Rh0.1Ge, and show that the evolution of their microscopic magnetic properties is instead continuous.
21 décembre 2019
M. Ruminy, S. Guitteny, J. Robert, L.-P. Regnault, M. Boehm, P. Steffens, H. Mutka, J. Ollivier, U. Stuhr, J. S. White, B. Roessli, L. Bovo, C. Decorse, M. K. Haas, R. J. Cava, I. Mirebeau, M. Kenzelmann, S. Petit, and T. Fennell Tb2Ti2O7 presents an ongoing conundrum in the study of rare-earth pyrochlores.
25 novembre 2019
A. S. Sukhanov, Praveen Vir, A. S. Cameron, H. C. Wu, N. Martin, S. Mühlbauer, A. Heinemann, H. D. Yang, C. Felser, and D. S. Inosov The cubic chiral helimagnets with the P213 space group represent a group of compounds in which the stable skyrmion-lattice state is experimentally observed. The key parameter that controls the energy landscape of such systems and determines the emergence of a topologically nontrivial magnetic structure is the Dzyaloshinskii-Moriya interaction (DMI).
23 octobre 2019
N. Martin, I. Mirebeau, C. Franz, G. Chaboussant, L. N. Fomicheva, and A. V. Tsvyashchenko We study the helimagnetic ground state of the MnGe cubic alloy using small-angle neutron scattering and a high-resolution method, the so-called MIEZE spectroscopy. Upon cooling below the Néel temperature TN = 170(5) K, we observe the proliferation of long-wavelength gapless spin fluctuations, concomitant with a continuous evolution of the helical correlation length.
25 septembre 2019
La physique de la matière condensée repose sur quelques concepts fondateurs, comme le paradigme de Néel (avec sa description des ordres magnétiques classiques), la théorie des liquides de Fermi (avec le concept de quasi-particule), et la théorie de Landau des transitions de phases (mettant en exergue le concept de brisure spontanée de symétrie).
25 janvier 2019
M. Deutsch, W. Peng, P. Foury-Leylekian, V. Balédent, S. Chattopadhyay, M. T. Fernandez-Diaz, T. C. Hansen, A. Forget, D. Colson, M. Greenblatt, M.-B. Lepetit, S. Petit, and I. Mirebeau The magnetic structure of TbMn2O5 and DyMn2O5 multiferroics has been studied by high-pressure neutron diffraction in a large pressure range up to 6.6 GPa.
24 septembre 2018
Fengjiao Qian, Lars J. Bannenberg, Heribert Wilhelm, Grégory Chaboussant, Lisa M. Debeer-Schmitt, Marcus P. Schmidt, Aisha Aqeel, Thomas T. M. Palstra, Ekkes Brück, Anton J. E. Lefering, Catherine Pappas, Maxim Mostovoy, Andrey O.
08 septembre 2018
Lien avec leurs propriétés photovoltaïques et maitrise de la séparation e--trou
Les cellules solaires à base de pérovskites présentent de fort rendement car elles permettent d'élargir la fraction du spectre solaire qui peut être converti en électricité. Ces performances sont directement liées à leur structure cristalline bien particulière, dont les propriétés de vibrations ont été étudiées par diffusion de neutrons.
29 août 2018
I. Mirebeau, N. Martin, M. Deutsch, L. J. Bannenberg, C. Pappas, G. Chaboussant, R. Cubitt, C. Decorse, and A. O. Leonov Reentrant spin glasses are frustrated disordered ferromagnets developing vortexlike textures under an applied magnetic field. Our study of a Ni0.81Mn0.19Ni0.81Mn0.19 single crystal by small angle neutron scattering clarifies their internal structure and shows that these textures are randomly distributed.
28 mai 2018
Béatrice Gillon, Albert Hammerschmied, Arsen Gukasov, Alain Cousson, Thomas Cauchy, Eliseo Ruiz, John A. Schlueter, Jamie L. Manson We report neutron‐diffraction investigations of the quasi‐2D MnII(dca)2(pym)(H2O) (pym = N2C4H4) compound, where high‐spin MnII ions are bridged by dicyanamide anions, [N(CN)2]– (herein abbreviated dca). Inside the layers, Mn2+ ions are connected by single or double dca bridges.
17 novembre 2017
A. K. Nayak, V. Kumar, T. Ma, P. Werner, E. Pippel, R. Sahoo, F. Damay, U. K. Rößler, C. Felser and S. S. P. Parkin,  Nature 548, 561–566. Magnetic skyrmions are topologically stable, vortex-like objects surrounded by chiral boundaries that separate a region of reversed magnetization from the surrounding magnetized material.

 

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