Publications

2011

• Experimental Evidence of Fluctuation-Dissipation Theorem Violation in a Superspin Glass
  
  • Komatsu Katsuyoshi
  • L'Hote D.
  • Nakamae Sawako
  • Mosser Vincent
  • Konczykowski Marcin
  • Dubois Emmanuelle
  • Dupuis V.
  • Perzynski Régine
  Physical Review Letters, American Physical Society, 2011, 106, pp.150603. We present the experimental observation of the fluctuation-dissipation theorem (FDT) violation in an assembly of interacting magnetic nanoparticles in the low temperature superspin glass phase. The magnetic noise is measured with a two-dimension electron gas Hall probe and compared to the out of phase ac susceptibility of the same ferrofluid. For "intermediate" aging times of the order of 1 h, the ratio of the effective temperature $T_{\rm eff}$ to the bath temperature T grows from 1 to 6.5 when T is lowered from $T_g$ to 0.3 $T_g$, regardless of the noise frequency. These values are comparable to those measured in an atomic spin glass as well as those calculated for a Heisenberg spin glass. (10.1103/PhysRevLett.106.150603)
  DOI : 10.1103/PhysRevLett.106.150603
• Ab initio calculation of many-body effects on the second-harmonic generation spectra of hexagonal SiC polytypes
  
  • Hübener Hannes
  • Luppi Eleonora
  • Véniard Valérie
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2011, 83, pp.115205. We investigate the influence of crystal local fields and excitonic effects on the spectrum of the second harmonic generation of three polytypes of silicon carbide by using time-dependent density-functional theory including many-body effects, namely, quasiparticle corrections through the scissors operator, crystal local field effects, and excitonic interaction. The relation between the scalar density response and the components of the rank 3 tensor d(2) is established by calculating the response along different polarization directions. We find that local-field effects, although necessary for a rigorous description in the theory, yield only small contributions to the spectra, whereas excitonic effects have a strong influence on the second harmonic generation. We compare static values of the second harmonic coefficients to recent measurements and obtain very good agreement. (10.1103/PhysRevB.83.115205)
  DOI : 10.1103/PhysRevB.83.115205
• Transport d'ions et d'objets dans des nanopores
  
  • Tasserit Christophe
  , 2011. Il existe différentes techniques de manipulation et de détection de molécules uniques. Parmi elles, la mesure du courant ionique traversant un pore nanométrique unique est la plus ancienne. Le travail effectué dans cette thèse utilise cette technique et s'articule autour de deux objectifs. Tout d'abord, l'utilisation d'un nanopore unique obtenu par attaque de trace permet d'imiter les expériences déjà faites dans la littérature avec d'autres types de pores. Certains phénomènes, tels que la rectification par exemple, ont pu être observés, mais d'autres comme la translocation n'ont pu l'être. Ensuite, une étude du bruit de conductance électrique démontre l'existence d'un phénomène qui n'avait jusqu'alors pas été soulevé dans la littérature. En effet, ce bruit ne peut pas être imputé aux fluctuations des caractéristiques de la géométrie du pore ou de sa paroi, mais plutôt à des effets coopératifs sur la mobilité des ions dans un milieu confiné.
• Miniaturization of micrometric SiC from a detonation process of highly energetic material
  
  • Gibot P.
  • Mory J.
  • Moitrier F.
  • Vidal L.
  • Fousson E.
  • Spitzer D.
  Powder Technology, Elsevier, 2011, 208 (2), pp.324-328. (10.1016/j.powtec.2010.08.024)
  DOI : 10.1016/j.powtec.2010.08.024
• Thermo-stimulated luminescence of ion-irradiated yttria-stabilized zirconia
  
  • Costantini Jean-Marc
  • Beuneu Francois
  • Fasoli Mauro
  • Galli Anna
  • Vedda Anna
  • Martini Marco
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2011, 23, pp.115901. Yttria-stabilized zirconia (ZrO2:Y3+) single crystals (with 9.5 mol% Y2O3) were irradiated with ions (from 1 MeV He to 2.6 GeV U). Electron paramagnetic resonance (EPR) data show that two kinds of colour centres (F+-type and T centres) are produced. Thermo-stimulated luminescence (TSL) data exhibit a quite strong peak at ∼500–550 K in the glow curves of all irradiated samples regardless of the ion species and energy. Moreover, the 3D-TSL measurements reveal that this peak is correlated with a light emission at a wavelength of ∼620 nm (i.e. photon energy ∼ 2 eV). The TSL peak maximum temperatures are consistent with characteristic temperatures of about 500 K of annealing stages of colour centres. However, the trap-depth energies (ranging between 0.7 and 1.4 eV) deduced from the initial rise of partially cleaned TSL peaks, or from a rough approximation using Urbach's formula, are rather larger than the activation energies for defect recovery, ranging between 0.3 and 0.7 eV, as deduced from the EPR data. The processes involved in TSL are discussed in relation to available photoluminescence and defect energy-level data.
• Point defects induced in yttria-stabilized zirconia by electron and swift heavy ion irradiations
  
  • Costantini Jean-Marc
  • Beuneu Francois
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2011, 23, pp.115902. We present an extensive study of point-defect creation in yttria-stabilized zirconia (ZrO2:Y) exposed to 2.5 MeV electrons and various heavy ions (from C to U) covering an energy range from 100 MeV to several GeV. A synthesis of results from UV–visible optical absorption spectroscopy and electron paramagnetic resonance spectroscopy is provided with special emphasis on the respective roles of elastic collisions and electronic excitations. The colour centre production and recovery are the main focus in this survey. It is concluded that F+-type centres (involving singly ionized oxygen vacancies) are produced by elastic-collision processes. The large threshold displacement energy and defect volume hint that these colour centres might actually be small paramagnetic oxygen vacancy clusters, most probably divacancies (i.e. F+2 centres). Such a picture is consistent with the (100) axial symmetry, inhomogeneous broadening of the optical absorption band, lack of hyperfine splitting, and weak spin–lattice coupling found for this defect.
• Design of effective kernels for spectroscopy and molecular transport: Time-dependent current–density-functional theory
  
  • Gatti Matteo
  The Journal of Chemical Physics, American Institute of Physics, 2011, 134, pp.084102. Time-dependent current–density-functional theory (TDCDFT) provides an, in principle, exact scheme to calculate efficiently response functions for a very broad range of applications. However, the lack of approximations valid for a range of parameters met in experimental conditions has so far delayed its extensive use in inhomogeneous systems. On the other side, in many-body perturbation theory accurate approximations are available, but at a price of a higher computational cost. In the present work, the possibility of combining the advantages of both approaches is exploited. In this way, an exact equation for the exchange-correlation kernel of TDCDFT is obtained, which opens the way for a systematic improvement of the approximations adopted in practical applications. Finally, an approximate kernel for an efficient calculation of spectra of solids and molecular conductances is suggested and its validity is discussed. (10.1063/1.3558738)
  DOI : 10.1063/1.3558738
• EPR study of Ti3+ ions formed under beta irradiation in silicate glasses.
  
  • Lombard Pierre
  • Ollier Nadège
  • Boizot Bruno
  Journal of Non-Crystalline Solids, Elsevier, 2011, 357 (7), pp.1685-1689. Reduction processes of Ti4+ ions in various silicate glasses have been studied by EPR spectroscopy at 20 K. Different parameters like the [Na]/[Ti] ratio, the integrated dose and Ti3+ ions ageing processes were analyzed in this work. Simulation of the Ti3+ ion EPR spectra in different Ti-doped silicate glasses has shown three different Ti3+ environment attributed to one [VI]Ti3+ and two [V]Ti3+ environment (square pyramid and trigonal bi-pyramid). The [VI]Ti3+ ion environment is observed only for [Na]/[Ti] ratios higher or equal to 68 although the two others are observed for all values of the [Na]/[Ti] ratio considered. In terms of relative proportions, the Ti3+ ions in a square pyramid of oxygen are the dominant species. (10.1016/j.jnoncrysol.2010.12.015)
  DOI : 10.1016/j.jnoncrysol.2010.12.015
• Evolution of Yb3+ environment and luminescence properties under ionizing irradiation in aluminoborosilicate glasses
  
  • Ollier Nadège
  • Doualan Jean-Louis
  • Pukhkaya V.
  • Charpentier T.
  • Moncorge R.
  • Sen S.
  Journal of Non-Crystalline Solids, Elsevier, 2011, 357, pp.1037-1043. Yb-doped aluminoborosilicate glasses were irradiated with 2.3 MeV electron and gamma rays at different doses ranging between 10(4) and 2.6 x 10(9) Gy and the local structure around the Yb3+ ions has been studied using a combination of NMR. EPR and photoluminescence spectroscopic techniques. The spectroscopic results indicate the presence of two distinct Yb3+ sites in these glasses and their relative fractions depend on both the Yb concentration and the irradiation dose. These two sites can be attributed to Yb3+ ions with and without Yb next-nearest neighbors. The evolution of the shape of the F-7(5/2) -> F-7(7/2) infrared emission band under irradiation is explained by a preferential reduction of the Yb3+ ions with Yb next-nearest neighbors at high integrated doses (>10(8) Gy). This interpretation is supported by a strong decrease of the visible cooperative luminescence under irradiation due to the reduction into the Yb pairs. In other terms, it shows an interesting effect of ionizing irradiation on the Yb clusters. A low intensity emission band appears in irradiated samples at 390 nm that can be attributed to Yb2+. Finally, the decrease of the Yb3+ fluorescence lifetime observed under irradiation appears to be primarily due to electronic interaction of these ions with Non-Bridging Oxygen Hole Centre defects created by the ionizing radiation. (C) 2010 Elsevier B.V. All rights reserved. (10.1016/j.jnoncrysol.2010.11.041)
  DOI : 10.1016/j.jnoncrysol.2010.11.041
• Stabilité de verres de terre - rares en condition de lixiviation, irradiation et radiolyse : caractérisation par RMN et TEM
  
  • Pellerin N.
  • Allix M.
  • Corbel C.
  • Jégou C.
  • Massiot D.
  , 2011.
• Double excitations in correlated systems: A many–body approach
  
  • Sangalli Davide
  • Romaniello Pina
  • Onida Giovanni
  • Marini Andrea
  The Journal of Chemical Physics, American Institute of Physics, 2011, 134, pp.034115. A coherent approach to the description of double excitations in correlated materials is presented: We derive stringent mathematical conditions on the algebraical structure of the Bethe–Salpeter and time-dependent density functional theory kernels that avoid the occurrence of spurious and nonphysical excitations. We discuss how these conditions need to be respected at any level of approximation, including the commonly used local density and static screening approximations. We propose a correlated kernel for the Bethe–Salpeter equation, and we illustrate several aspects of our approach with numerical calculations for model molecular systems. (10.1063/1.3518705)
  DOI : 10.1063/1.3518705
• Density-based mixing parameter for hybrid functionals
  
  • Marques Miguel A. L.
  • Vidal Julien
  • Oliveira Micael J. T.
  • Reining Lucia
  • Botti Silvana
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2011, 83, pp.035119. A very popular ab initio scheme to calculate electronic properties in solids is the use of hybrid functionals in density functional theory (DFT) that mixes a portion of the Fock exchange with DFT functionals. In spite of its success, a major problem still remains, related to the use of one single mixing parameter for all materials. Guided by physical arguments that connect the mixing parameter to the dielectric properties of the solid, and ultimately to its band gap, we propose a method to calculate this parameter from the electronic density alone. This approach is able to cut significantly the error of traditional hybrid functionals for large and small gap materials, while retaining a good description of the structural properties. Moreover, its implementation is simple and leads to a negligible increase of the computational time. (10.1103/PhysRevB.83.035119)
  DOI : 10.1103/PhysRevB.83.035119
• Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation
  
  • Bigongiari A
  • Raynaud M
  • Riconda C
  • Héron Anne
  • Macchi A
  Physics of Plasmas, American Institute of Physics, 2011. The efficiency of laser overdense plasma coupling via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed over a wide range of laser pulse intensity from 10 15 to 10 20 W cm À2 lm 2 with electron density ranging from 25 to 100n c to describe the laser interaction with a grating target where a surface plasma wave excitation condition is fulfilled. The numerical studies confirm an efficient coupling with an enhancement of the laser absorption up to 75%. The simulations also show the presence of a localized, quasi-static magnetic field at the plasma surface. Two interaction regimes are identified for low (Ik 2 < 10 17 W cm À2 lm 2) and high (Ik 2 > 10 17 W cm À2 lm 2) laser pulse intensities. At " relativistic " laser intensity, steady magnetic fields as high as $580 MG lm/k 0 at 7 Â 10 19 W cm À2 lm 2 are obtained in the simulations. (10.1063/1.3646520)
  DOI : 10.1063/1.3646520
• In-Situ Raman Observation of the First Step of Uranium Dioxide Weathering Exposed to Water Radiolysis
  
  • Guimbretiere G.
  • Canizares A.
  • Simon Patrick
  • Tobon-Correa Y.A.
  • Ammar M.-R.
  • Corbel Catherine
  • Barthe Marie-France
  Spectroscopy Letters : An International Journal for Rapid Communication, Taylor & Francis, 2011 (44), pp.570-573. (10.1080/00387010.2011.610857)
  DOI : 10.1080/00387010.2011.610857
• Dynamical response function in sodium and aluminum from time-dependent density-functional theory
  
  • Cazzaniga Marco
  • Weissker H.-C.
  • Huotari Simo
  • Pylkkänen Tuomas
  • Salvestrini Paolo
  • Monaco Giulio
  • Onida Giovanni
  • Reining Lucia
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2011, 84, pp.075109. We present a detailed study of the dynamical electronic response in bulk sodium and aluminum within time-dependent density-functional theory (TDDFT). The poor results of the random-phase approximation (RPA) and the time-dependent local-density approximation (TDLDA) in sodium are greatly improved by the approximate inclusion of the finite lifetimes of electrons and holes via a modified independent-particle polarizability, which brings the calculated spectra into good agreement with experiment. For aluminum the changes are less visible, but at some values of momentum-transfer lifetime effects are necessary to obtain qualitatively correct spectra. The double-peak structure in aluminum, induced by band-structure effects, is partially washed out by the inclusion of the finite lifetimes. The latter do not, however, create a double peak by themselves as they do in the case of the homogeneous electron gas. Studying the performance of different time-dependent and nonlocal TDDFT kernels, we conclude that the Gross-Kohn, Corradini et al., and the Hubbard local-field factors improve the spectra compared to the RPA results. However, the results agree less well with experiment than those obtained using TDLDA with added lifetime effects. These results apply to both the loss spectra and the plasmon dispersion. (10.1103/PhysRevB.84.075109)
  DOI : 10.1103/PhysRevB.84.075109
• Steady magnetic-field generation via surface-plasma-wave excitation
  
  • Bigongiari A
  • Raynaud M
  • Riconda C
  Physical Review E, American Physical Society (APS), 2011, 84 (1), pp.015402(R). The possibility of inducing a magnetic field via surface plasma-wave excitation is investigated with a simple nonrelativistic hydrodynamic model. A static magnetic field is predicted at the plasma surface, scaling with the square of the surface-wave field amplitude, and the influence of the electron plasma density is studied. In the case of resonant surface-wave excitation by laser this result can be applied to low intensities such that the electron quiver velocity in the field of the surface wave is less than its thermal velocity. (10.1103/PhysRevE.84.015402)
  DOI : 10.1103/PhysRevE.84.015402
• Ion-induced elongation of gold nanoparticles in silica by irradiation with Ag and Cu swift heavy ions: track radius and energy loss threshold
  
  • Dawi E. A.
  • Vredenberg A. M.
  • Rizza G.
  • Toulemonde Marcel
  Nanotechnology, Institute of Physics, 2011, 22, pp.215607. Systematic investigations of the energy loss threshold above which the irradiation-induced elongation of spherical Au nanoparticles occurs are reported. Silica films containing Au nanoparticles with average diameters of 15-80 nm embedded within a single plane were irradiated with 12-54 MeV Ag and 10-45 MeV Cu ions at 300 K and at normal incidence. We demonstrate that the efficiency of the ion-induced nanoparticle elongation increases linearly with the electronic energy transferred per ion track length unit from the energetic ions to the silica film. Ion beam shaping occurs above a threshold value of the specific electronic energy transfer. Three relevant regions are identified with respect to the original size of the Au nanoparticles. For 15 and 30 nm diameter particles, elongation occurs for electronic stopping power larger than 3.5 keV nm−1. For Au nanoparticles with 40-50 nm diameter an electronic stopping power above 5.5 keV nm−1 is required for elongation to be observed. Elongation of Au nanoparticles with 80 nm diameter is observed for electronic stopping between ∼7-8 keV nm−1. For all combinations of ions and energies, the ion track temperature profiles are calculated within the framework of the thermal spike model. The correlation between experimental results and simulated data indicates a thermal origin of the increase in the elongation rate with increasing the track diameter. (Some figures in this article are in colour only in the electronic version)
• Ion Tracks in Polymers
  
  • Pivin J.C.
  • Clochard Marie-Claude
  , 2011, pp.223-231. Electronic excitations produced by ions in polymers results in the formation of free radicals making them highly sensitive to chemical agents. Besides the widely developed application to the etching of membranes with controlled pore sizes and densities, the grafting of molecules selected for their chemical properties inside the tracks of swift heavy ions offers interesting potentialities such as the fabrication of intelligent membranes, detectors and captors. Carbon, silicon or metal clusters which are formed in the heavily damaged core of tracks, especially within partially inorganic polymers, are also of high interest for their optical or magnetic properties.
• “Click” Conjugation of Peptide on the Surface of Polymeric Nanoparticles for Targeting Tumor Angiogenesis
  
  • Deshayes Stéphanie
  • Maurizot Victor
  • Clochard Marie-Claude
  • Baudin Cécile
  • Berthelot Thomas
  • Esnouf Stéphane
  • Lairez Didier
  • Moenner Michel
  • Déléris Gérard
  Pharmaceutical Research, American Association of Pharmaceutical Scientists, 2011, pp.1631. Purpose Angiogenesis plays a critical role in tumor growth. This phenomena is regulated by numerous mediators such as vascular endothelial growth factor (VEGF). CBO-P11, a cyclo-peptide, has proven to specifically bind to receptors of VEGF and may be used as targeting ligand for tumor angiogenesis. We herein report the design of novel nanoparticles conjugated to CBO-P11 in order to specifically target tumor site. Methods The conjugation of CBO-P11 on the surface of poly (vinylidene fluoride) (PVDF) nanoparticles was investigated using the copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition known as " click " reaction. CBO-P11 was modified with a near-infrared cyanine dye bearing an alkyne function, allowing both " click " coupling on azido-modified nanoparticles and fluores-cence labelling. Each step of this nanodevice construction was judiciously performed in aqueous solution and successfully characterized. The cytotoxicity of nanoparticles was evaluated in human brain endothelial cell line and their affinity for VEGF receptors was determined via fluorescence-based uptake assays on porcine aortic endothelial cell line. Results Nanoparticles were found to be spherical, dense, monodisperse and stable. No cytotoxicity was observed after four days of incubation, demonstrating the biocompatibility of nanoparticles. Fluorescence highlighted the specific interaction of these functionalized nanoparticles for VEGF receptors, suggesting that the targeting peptide bioactivity was retained. Conclusions These results demonstrate the potential of these functionalized nanoparticles for targeting tumor angiogenesis and their possible use as multifunctional plateform for cancer treament if coupled with therapeutic agents. KEY WORDS angiogenesis. " click " chemistry. cyclo-peptide. nanoparticles. PVDF. tumor targeting ABBREVIATIONS AA acrylic acid ACN acetonitrile DCM dichloromethane DIEA diisopropylethylamine DLS dynamic light scattering DMEM Dulbecco's modified eagle medium EDC ethyl-3(3dimethylaminopropyl)carbodiimide EDTA ethylenediaminetetraacetic acid EGM-2 endothelial growth medium ESI electrospray ionization FBS fetal bovine serum Electronic supplementary material The online version of this article (doi:10.1007/s11095-011-0398-5) contains supplementary material, which is available to authorized users. (10.1007/s11095-011-0398-5)
  DOI : 10.1007/s11095-011-0398-5
• Synthesis and magnetic reversal of bi-conical Ni nanostructures Synthesis and magnetic reversal of bi-conical Ni nanostructures
  
  • Biziere Nicolas
  • Lassalle Ballier R
  • Clochard M.C.
  • Viret M
  • L Wade Travis
  • Balanzat E
  • Wegrowe Jean Eric
  Journal of Applied Physics, American Institute of Physics, 2011, pp.063906. Microstructure study of pinning sites of highly (0001) textured Sm(Co,Cu)5 thin films grown on Ru underlayer J. Appl. Phys. 111, 07B730 (2012) Spin-torque diode spectrum of ferromagnetically coupled (FeB/CoFe)/Ru/(CoFe/FeB) synthetic free layer J. Appl. Phys. 111, 07C917 (2012) Textured Nd2Fe14B flakes with enhanced coercivity J. Appl. Phys. 111, 07A735 (2012) Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords Appl. Phys. Lett. 100, 103112 (2012) Additional information on J. Appl. Phys. Journal Homepage: http://jap.aip.org/ Journal Information: Template synthesis in polyethylene terephthalate (PET) membranes has been used to grow hour glass shaped nickel nanowires with a constriction in the range of tens of nanometers at the center. Anisotropic magnetoresistance measurements have been performed on a single nanowire to follow magnetization reversal of the structure. The results are explained via 3D micromagnetic simulations showing the appearance of a complex vortex state close to the constriction whose propagation depends on the angle between the cone axis and the applied field. (10.1063/1.3638072)
  DOI : 10.1063/1.3638072
• Rayleigh-like instability in the ion-shaping of Au-Ag alloy nanoparticles embedded within a silica matrix
  
  • Rizza G.
  • Attouchi F.
  • Coulon Pierre-Eugène
  • Perruchas S.
  • Gacoin T.
  • Monnet Isabelle
  • Largeau L.
  Nanotechnology, Institute of Physics, 2011, 22, pp.175305. We have studied how spherical 23 ± 3 nm Au45Ag55 nanoparticles embedded within a silica matrix transform into prolate nanorods and nanowires by irradiating them with swift heavy ions. Samples were irradiated at room temperature and normal incidence with 74 MeV Kr and 36 MeV S ions for fluences up to 1.0 × 1015 cm−2. We demonstrate the existence of two regimes: (i) below a critical fluence, ∼2.0 × 1014 cm−2, the transformation of the spherical nanoparticle into a nanorod is an individual process, i.e. each nanoparticle transforms into a single nanorod; (ii) for larger fluences the transformation from nanorod to nanowire becomes a collective process, i.e. the break up and dissolution of unstable nanorods contribute to the growth of long nanowires. The passage from the first to the second regime can be interpreted in terms of a Rayleigh-like instability under irradiation. The latter becomes active when the diameter of the nanowire approaches its saturation width under irradiation. Furthermore, we show that the composition of the alloy is only slightly modified during the ion-shaping process. Finally, the energy and the fluence thresholds for deformation and the deformation strain-rate are estimated.
• Magnetic microstructures of metal grains in equilibrated ordinary chondrites and implications for paleomagnetism of meteorites
  
  • Uehara Minoru
  • Gattacceca Jérôme
  • Leroux Hugues
  • Jacob Damien
  • van Der Beek Cornelis Jacominus
  Earth and Planetary Science Letters, Elsevier, 2011, 306 (3-4), pp.241 - 252. Meteorites are a primary source of information about past magnetic field in the solar system. Yet, the small-scale magnetic properties of FeNi metals, which are the magnetic carriers of most meteorites, are poorly known. We study here the magnetic microstructures of FeNi metals in two equilibrated chondrites. Two types of tetrataenite-bearing microstructures are revealed: (1) Zoned taenite particles that consist of a “cloudy zone” (20–250 nm large tetrataenite precipitates embedded in Ni-poor matrix) and a 1–10 μm thick tetrataenite rim. (2) Zoneless plessite particles that consist of large tetrataenite grains (> 1 μm) embedded in a kamacite matrix. Magneto-optical imaging of saturation remanence shows that, the submicron-sized tetrataenite islands in cloudy zone carry a much stronger remanence than the μm-sized tetrataenite crystals in the tetrataenite rims and plessite. Micron-scale mapping of coercivity of remanence (Bcr) shows that the center part of the cloudy zone has finer tetrataenite grains (20 nm) and higher Bcr values (~ 1 T) than the outer part (250 nm and 400 mT, respectively). These results suggest that the micron-sized tetrataenite is in a multi domain state, whereas the submicron-sized tetrataenite in the cloudy zone are in a single domain-like state and may be regarded as a potentially good paleomagnetic recorder in meteorites. The stability of the remanent magnetization in ordinary chondrites is a function of the amount of the cloudy zones of the zoned taenite grains rather than the bulk amount of tetrataenite. The Fe–Ni phase diagram indicates that precursor of tetrataenite is paramagnetic when the metamorphic temperature was above 350–400 °C. Therefore, the remanent magnetization of tetrataenite cannot be an evidence of early magnetic activity on the parent body (e.g., dynamo activity) during the first 10 to 50 Myr after the peak of metamorphism, assuming 900 °C peak temperature and 50–100 °C/Myr cooling rate. Our TEM observations show that tetrataenite has a homogeneous crystallographic orientation in an individual zoned taenite grain. In low or null field, tetrataenite may acquire a spontaneous magnetization whose direction is controlled by this crystallographic orientation, which varies from grain to grain. The small-scale heterogeneity of remanence observed in equilibrated chondrites may imply that no significant magnetic field (e.g., dynamo field) was present during cooling below 350–400 °C. (10.1016/j.epsl.2011.04.008)
  DOI : 10.1016/j.epsl.2011.04.008
• Role of Thermodynamics in the Shape Transformation of Embedded Metal Nanoparticles Induced by Swift Heavy-Ion Irradiation
  
  • Ridgway M.C.
  • Giulian R.
  • Sprouster D.J.
  • Kluth P.
  • Araujo L.L.
  • Llewellyn D.J.
  • Byrne A.P.
  • Kremer F.
  • Fichtner P.F.P.
  • Rizza G.
  • Amekura H.
  • Toulemonde Marcel
  Physical Review Letters, American Physical Society, 2011, 106, pp.095505. Swift heavy-ion irradiation of elemental metal nanoparticles (NPs) embedded in amorphous SiO2 induces a spherical to rodlike shape transformation with the direction of NP elongation aligned to that of the incident ion. Large, once-spherical NPs become progressively more rodlike while small NPs below a critical diameter do not elongate but dissolve in the matrix. We examine this shape transformation for ten metals under a common irradiation condition to achieve mechanistic insight into the transformation process. Subtle differences are apparent including the saturation of the elongated NP width at a minimum sustainable, metal-specific value. Elongated NPs of lesser width are unstable and subject to vaporization. Furthermore, we demonstrate the elongation process is governed by the formation of a molten ion-track in amorphous SiO2 such that upon saturation the elongated NP width never exceeds the molten ion-track diameter. (10.1103/PhysRevLett.106.095505)
  DOI : 10.1103/PhysRevLett.106.095505
• Thermo-stimulated luminescence of x-ray- and alpha-irradiated yttria-stabilized zirconia
  
  • Costantini Jean-Marc
  • Beuneu Francois
  • Fasoli Mauro
  • Galli Anna
  • Martini Marco
  • Vedda Anna
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2011, 23, pp.455901. Yttria-stabilized zirconia single crystals (with 9.5 mol% Y2O3) were irradiated with x-rays and particles. Thermally stimulated luminescence (TSL) data show a main broad peak centred at 500-550 K in the glow curves of all irradiated samples. The TSL peak maximum temperature is consistent with the characteristic recovery temperature (450 K) of colour centres (T centres) deduced from isochronal annealing curves measured by electron paramagnetic resonance (EPR) spectroscopy. However, the trap-depth energies (ranging between 0.8 and 1.2 eV) deduced from the initial rise of partially cleaned TSL peaks (and from a rough approximation using Urbach's formula) are much larger than the activation energies for defect recovery of 0.3 eV deduced from the EPR data. A second TSL peak centred at 350-450 K found in freshly irradiated samples is seen to decay substantially in aged samples. The processes involved in TSL are discussed in relation to the defect annealing processes, and available defect-level energy and TSL data
• Radiative heat transfer from a black body to dielectric nanoparticles
  
  • Chalopin Yann
  • Dammak Hichem
  • Laroche Marine
  • Hayoun Marc
  • Greffet Jean-Jacques
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2011, 84, pp.224301. Heating of dielectric nanoparticles by black-body radiation is investigated by using molecular-dynamics simulation. The thermal interaction with the radiation is modeled by coupling the ions with a random electric field and including a radiation reaction force. This approach shows that the heat is absorbed by the polariton mode. Its subsequent redistribution among other vibration modes strongly depends on the particle size and on temperature.We observe energy trapping in a finite subset of vibrational modes (10.1103/PhysRevB.84.224301)
  DOI : 10.1103/PhysRevB.84.224301