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PubMed | University of Bordeaux 1, ParisTech National School of Bridges and Roads, IMPMC, French National Center for Scientific Research and 2 more.
Type: Journal Article | Journal: The Review of scientific instruments | Year: 2016

PSICHE (Pressure, Structure and Imaging by Contrast at High Energy) is the high-energy beam line of the SOLEIL synchrotron. The beam line is designed to study samples at extreme pressures, using diffraction, and to perform imaging and tomography for materials science and other diverse applications. This paper presents the tomograph and the use of the beam line for imaging, with emphasis on developments made with respect to existing instruments. Of particular note are the high load capacity rotation stage with free central aperture for installing large or complex samples and sample environments, x-ray mirror and filter optics for pink beam imaging, and multiple options for combining imaging and diffraction measurement. We describe how x-ray imaging techniques have been integrated into high-pressure experiments. The design and the specifications of the beam line are described, and several case studies drawn from the first user experiments are presented.

Matzen S.,CEA Saclay Nuclear Research Center | Moussy J.-B.,CEA Saclay Nuclear Research Center | Mattana R.,Thales Alenia | Bouzehouane K.,Thales Alenia | And 9 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We report on the epitaxial growth and physical properties of spinel MnFe 2O 4(111) thin films with thicknesses down to 2 nm. The thin films, grown on α-Al 2O 3(0001) single crystals or Pt(111) buffer layers by oxygen-assisted molecular beam epitaxy, exhibit high structural order with sharp interfaces and low roughness. The electrical and magnetic properties are carefully investigated and it is shown that MnFe 2O 4(111) ultrathin films keep an insulating and ferrimagnetic behavior at room temperature. Special attention is given to the iron/manganese valence state and the cationic ordering. X-ray absorption spectroscopy and magnetic circular dichroism measurements reveal that thin films contain mainly Fe3 + and Mn2 + cations, distributed predominantly in a normal spinel structure. This study proves the high potential of MnFe 2O 4 to be used as a magnetic tunnel barrier for spin filtering applications at room temperature. © 2011 American Physical Society.

Matzen S.,CEA Saclay Nuclear Research Center | Matzen S.,CNRS Fundamental Electronics Institute | Moussy J.-B.,CEA Saclay Nuclear Research Center | Wei P.,Massachusetts Institute of Technology | And 5 more authors.
Applied Physics Letters | Year: 2014

NiFe2O4(111) ultrathin films (3-5nm) have been grown by oxygen-assisted molecular beam epitaxy and integrated as effective spin-filter barriers. Structural and magnetic characterizations have been performed in order to investigate the presence of defects that could limit the spin filtering efficiency. These analyses have revealed the full strain relaxation of the layers with a cationic order in agreement with the inverse spinel structure but also the presence of antiphase boundaries. A spin-polarization up to +25% has been directly measured by the Meservey-Tedrow technique in Pt(111)/NiFe2O4(111)/γ-Al 2O3(111)/Al tunnel junctions. The unexpected positive sign and relatively small value of the spin-polarization are discussed, in comparison with predictions and previous indirect tunnelling magnetoresistance measurements. © 2014 AIP Publishing LLC.

Amadou N.,Ecole Polytechnique - Palaiseau | Brambrink E.,Ecole Polytechnique - Palaiseau | Benuzzi-Mounaix A.,Ecole Polytechnique - Palaiseau | Huser G.,French Atomic Energy Commission | And 12 more authors.
High Energy Density Physics | Year: 2013

The study of iron under quasi-isentropic compression using high energy lasers, might allow to understand its thermodynamical properties, in particular its melting line in conditions of pressure and temperature relevant to Earth-like planetary cores (330-1500 GPa, 5000-8000 K). However, the iron alpha-epsilon solid-solid phase transition at 13 GPa favors shock formation during the quasi-isentropic compression process which can depart from the appropriate thermodynamical path. Understanding this shock formation mechanism is a key issue for being able to reproduce Earth-like planetary core conditions in the laboratory by ramp compression. In this article, we will present recent results of direct laser-driven quasi-isentropic compression experiments on iron samples obtained on the LULI 2000 and LIL laser facilities. © 2013 Elsevier B.V.

Didier A.,CNRS Magmas and Volcanoes Laboratory | Didier A.,University of Lausanne | Bosse V.,CNRS Magmas and Volcanoes Laboratory | Bouloton J.,CNRS Magmas and Volcanoes Laboratory | And 5 more authors.
Contributions to Mineralogy and Petrology | Year: 2015

In this study, we use NanoSIMS element and isotope ratio mapping and LA-ICP-MS trace element measurements to elucidate the origins of monazites from a restitic xenolith enclosed in a 13.5 ± 0.3 Ma andesitic lava (Slovakia). The xenolith/lava interaction is mainly characterized by the growth of a plagioclase-bearing corona around the xenolith and magmatic garnet overgrowths on primary metamorphic garnets within the xenolith. NanoSIMS images (89Y, 139La, 208Pb, 232Th and 238U) and trace element analyses indicate that variations of HREE, Y and Eu contents in the monazite are correlated with the resorption and the following overgrowth of garnet and plagioclase in the xenolith. Three domains are distinguished in the monazite grains: the inherited Variscan core at ca. 310 Ma (M1 domain) characterized by low Y and HREE contents and a weak negative Eu anomaly; the inner rim (M2 domain) crystallized during the growth of the plagioclase magmatic corona (large negative Eu anomaly) and the resorption of metamorphic garnet (high HREE and Y contents); and the external rim (M3 domain) crystallized during the growth of the plagioclase corona (large negative Eu anomaly) and during the crystallization of magmatic garnet (low Y, HREE contents) at ~13 Ma, i.e. the age of the andesitic lava. The age and chemical zonation of the monazites attest to the preservation of primary monazite in the xenolith despite the interaction with the andesite lava. NanoSIMS imaging provides high-quality sub-µm scale images of the monazite that reveals chemical domains that were not distinguishable on WDS X-ray maps, especially for depleted elements such as U and Pb. Owing to its small size, the M2 domain could not be accurately dated by the LA-ICP-MS method. However, NanoSIMS isotopic maps reveal that the M2 domain has similar 208Pb/232Th isotope ratios to the M3 domain and thus similar ages. These results support the hypothesis that melt-assisted partial dissolution–precipitation in monazite efficiently records chemical and mineralogical changes during xenolith/lava interaction. © 2015, Springer-Verlag Berlin Heidelberg.

Malvoisin B.,Ecole Normale Superieure de Paris | Malvoisin B.,Joseph Fourier University | Chopin C.,Ecole Normale Superieure de Paris | Brunet F.,Ecole Normale Superieure de Paris | And 2 more authors.
Journal of Petrology | Year: 2012

In the Alpine blueschist- to eclogite-facies meta-ophiolitic units of northern Corsica, the contact between a serpentinite body and an immediately overlying siliceous marble is remarkable for the occurrence of wollastonite and, on the marble side, a dark halo around the serpentinite. The refolded, continuous contact is a rodingite-type reaction zone with a centimetre-thick nephritic selvage of diopside + andradite/grossular ± perovskite on the serpentinite side, followed towards the marble by a 1-5 cm thick zone of massive wollastonite (± grossular), followed by a 5-20 cm thick dark zone (the halo) consisting of wollastonite + quartz + graphitic material (± grossular ± diopside), with no carbonate. The transition to the overlying wollastonite-free, calcite + quartz-bearing layers is sharp. Considering the stability of calcite + quartz everywhere else in the regional metamorphic series, this low-temperature occurrence of wollastonite (c. 400-450°C) requires unusual conditions. A clue to its origin is the abundance of graphitic matter with the wollastonite within a few decimetres of the serpentinite body. We interpret this observation as evidence for local reduction of Ca-carbonate to form elemental carbon and wollastonite according to the reactionA similar carbonate + mica reduction reaction is responsible for the disappearance of phengite and the appearance of grossular + carbon within a narrow zone in the marble above the wollastonite-quartz zone. Textural and solubility considerations suggest that the development of the zonal sequence is an essentially diffusive process. Thermochemical modelling of mineral stability in the successive reaction zones suggests a positive oxygen-fugacity gradient from the serpentinite to the marble (-6 < ΔFMQ < -1), mediated through a CH. 4- and H. 2-bearing aqueous intergranular fluid. In line with the field evidence, it is calculated that a serpentinite body equilibrated at ΔFMQ -4 after oceanic serpentinization can still impose, through Fe. 2+-bearing serpentine oxidation, highly reducing conditions while entrained at depth in a subduction wedge and channel. This may contribute to the presence of H. 2 ± CH. 4 in the fluid and cause the destabilization of calcite in favour of graphite. In addition to the consequences for wollastonite and elemental carbon formation at low temperature, this finding has direct implications for redox conditions in subduction zones. © The Author 2011. Published by Oxford University Press. All rights reserved.

Bureau H.,IMPMC | Foy E.,CEA Saclay Nuclear Research Center | Raepsaet C.,CEA Saclay Nuclear Research Center | Somogyi A.,Synchrotron Soleil | And 3 more authors.
Geochimica et Cosmochimica Acta | Year: 2010

The geochemical partitioning of bromine between hydrous haplogranitic melts, initially enriched with respect to Br and aqueous fluids, has been continuously monitored in situ during decompression. Experiments were carried out in diamond anvil cells from 890°C to room temperature and from 1.7GPa to room pressure, typically from high P, T conditions corresponding to total miscibility (presence of a supercritical fluid). Br contents were measured in aqueous fluids, hydrous melts and supercritical fluids. Partition coefficients of bromine were characterized at pressure and temperature between fluids, hydrous melts and/or glasses, as appropriate: DBr fluid/melt=(Br)fluid/(Br) melt, ranges from 2.18 to 9.2±0.5 for conditions within the ranges 0.66-1.7GPa, 590-890°C; and DBr fluid/glass=(Br)fluid/(Br) glass ranges from 60 to 375 at room conditions. The results suggest that because high pressure melts and fluids are capable of accepting high concentrations of bromine, this element may be efficiently removed from the slab to the mantle source of arc magmas. We show that Br may be highly concentrated in subduction zone magmas and strongly enriched in subduction-related volcanic gases, because its mobility is strongly correlated with that of water during magma degassing. Furthermore, our experimental results suggest that a non negligible part of Br present in the subducted slab may remain in the down-going slab, being transported toward the transition zone. This indicates that the Br cycle in subduction zones is in fact divided in two related but independent parts: (1) a shallower one where recycled Br may leave the slab with a water and silica-bearing " fluid" leading to enriched arc magmas that return Br to the atmosphere. (2) A deeper cycle where Br may be recycled back to the mantle maybe to the transition zone, where it may be present in high pressure water-rich metasomatic fluids. © 2010 Elsevier Ltd.

Aghavnian T.,CEA Saclay Nuclear Research Center | Aghavnian T.,Synchrotron Soleil | Moussy J.-B.,CEA Saclay Nuclear Research Center | Stanescu D.,CEA Saclay Nuclear Research Center | And 7 more authors.
Journal of Electron Spectroscopy and Related Phenomena | Year: 2015

The properties of CoFe2O4/BaTiO3 artificial multiferroic multilayers strongly depend on the crystalline structure, the stoichiometry and the cation distribution between octahedral (Oh) and tetrahedral (Td) sites (inversion factor). In the present study, we have investigated epitaxial CoFe2O4 layers grown on BaTiO3, with different Co/Fe ratios. We determined the cation distribution in our samples by X-ray magnetic circular dichroism (XMCD), a well accepted method to do so, and by X-ray photoelectron spectroscopy (XPS), using a fitting method based on physical considerations. We observed that our XPS approach converged on results consistent with XMCD measurements made on the same samples. Thus, within a careful decomposition based on individual chemical environments it is shown that XPS is fully able to determine the actual inversion factor. © 2015 Elsevier B.V. All rights reserved.

Betto D.,Trinity College Dublin | Thiyagarajah N.,Trinity College Dublin | Lau Y.-C.,Trinity College Dublin | Piamonteze C.,Paul Scherrer Institute | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

The site-specific magnetic properties of thin films of the Heusler compound Mn2RuxGa, 0.6

Drouin S.,University of Tours | Boussafir M.,University of Tours | Robert J.-L.,IMPMC | Alberic P.,University of Tours | Durand A.,University of Tours
Organic Geochemistry | Year: 2010

In order to investigate the role of clay minerals in organic matter preservation, the fixation of pure organic compounds on two synthetic low charge and high charge saponites was investigated in laboratory experiments simulating marine water conditions. The clays were exposed to four carboxylic acids: pentadecanoic, docosanoic, 5β-cholanic acid and ursolic, dissolved in treated natural sea water. Characterization of the resulting organo-clay association indicates that, under marine water column conditions, the organic fixation is only a sorption process, no intercalation being observed. The surface coverage, similar for the two clays (ca. 0.04 mg organic carbon m-2), demonstrates that the sorption is controlled by the surface properties of clays rather than their cation exchange capacity. The weaker sorption of docosanoic acid underlines the major role of the molecular properties, but the lack of selectivity among the three others does not corroborate the influence of molecular size on the sorption process. The general failure of a chemolysis treatment performed on the organo-clay associations demonstrates the high stability of these complexes. Results suggest that the bonding mechanisms are dominated by ligand exchange and not by hydrophobic effects, cation bridges or cation exchange. The minor extractable organic fraction consists of acid molecules connected to clay surfaces by van der Waals interactions. The high stability of the bonds formed in this environment, close to that observed in previous studies of marine sediments, could explain in part organic matter preservation during transfer across marine water columns, especially metabolisable material. © 2009 Elsevier Ltd. All rights reserved.

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