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Now showing items 1 - 3 of 3

  • Pressure-Induced Disordering in SnO2 Nanoparticles

    Girao, Helainne T.   Cornier, Thibaut   Daniele, Stephane   Debord, Regis   Caravaca, Maria A.   Casali, Ricardo A.   Melinon, Patrice   Machon, Denis  

    The high-pressure behavior of SnO2 nanoparticles (similar to 2.8 nm) was studied up to approximately 20 GPa using Raman spectroscopy in a diamond anvil cell and ab initio simulations. Above similar to 7 GPa, the disordering, initially located at the surface, was found to propagate to the core of nanoparticles, ultimately leading to amorphous-like spectra. This observation can be interpreted as a disordering of the oxygen sublattice sensitively probed by Raman spectroscopy in contrast to powder X-ray diffraction techniques. The low -frequency mode can'be related to the nanopartide vibration as an elastic isotropic sphere motion. The pressure-induced shift of this mode allows for the constraining of the mechanical properties data reported in the literature.
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  • Observation of various magnetic-field-induced states in B20 cubic MnGe

    Viennois, Romain   Reibel, Corine   Ravot, Didier   Debord, Regis   Pailhes, Stephane  

    We report on the magnetic properties of the B20 polycrystalline MnGe compound synthesized under high-temperature and high-pressure conditions. From isothermal ac susceptibility experiments, we found the presence of several different magnetic-field-induced phases presenting similarities with those in the isostructural compounds MnSi and FeGe but with much broader existence range in the (B, T) domain. From anomalies found in the ac magnetic susceptibility, we found not only the presence of an A phase similar to the one observed in MnSi but also a second phase we call B, whose magnetic signature is very similar to that of the A phase. Our discovery indicates that MnGe is a promising compound in order to further explore the existence conditions of the phases containing skyrmions. Copyright (C) EPLA, 2015
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  • Thermoelectric La-doped SrTiO3 epitaxial layers with single-crystal quality:from nano to micrometers

    Apreutesei, Mihai   Debord, Regis   Bouras, Mohamed   Regreny, Philippe   Botella, Claude   Benamrouche, Aziz   Carretero-Genevrier, Adrian   Gazquez, Jaume   Grenet, Genevieve   Pailhes, Stephane   Saint-Girons, Guillaume   Bachelet, Romain  

    High-quality thermoelectric La0.2Sr0.8TiO3 (LSTO) films, with thicknesses ranging from 20nm to 0.7 mu m, have been epitaxially grown on SrTiO3(001) substrates by enhanced solid-source oxide molecular-beam epitaxy. All films are atomically flat (with rms roughness<0.2nm), with low mosaicity (<0.1 degrees), and present very low electrical resistivity (<5 x 10(-4) Omega cm at room temperature), one order of magnitude lower than standard commercial Nb-doped SrTiO3 single-crystalline substrate. The conservation of transport properties within this thickness range has been confirmed by thermoelectric measurements where Seebeck coefficients of approximately -60 mu V/K have been recorded for all films. These LSTO films can be integrated on Si for non-volatile memory structures or opto-microelectronic devices, functioning as transparent conductors or thermoelectric elements.
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