Publications

2004

• Geometrical barriers and lower critical field in MgB2 single crystals
  
  • Lyard L.
  • Klein Thierry
  • Marcus J.
  • Brusetti R.
  • Marcenat C.
  • Konczykowski M.
  • Mosser V.
  • Kim K.H.
  • Kang B.W.
  • Lee H.S.
  • Lee S.I.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 70, pp.180504(R). The first penetration field sHpd has been deduced from local magnetization and specific heat measurements in magnesium diboride single crystals. For Ha ic, the geometrical barriers (GB) play a dominant role in the irreversibility mechanism. In thin samples, neglecting the GB in this direction would then lead to a large overestimation of Hc1 deduced from Hp through the standard elliptical formula. The lower critical field is found to be isotropic at low temperature (0.11±0.01 T). (10.1103/PhysRevB.70.180504)
  DOI : 10.1103/PhysRevB.70.180504
• A Raman and MAS NMR study of mixed alkali Na-K and Na-Li aluminoborosilicate glasses
  
  • Ollier Nadège
  • Charpentier Thibault
  • Boizot Bruno
  • Wallez G.
  • Ghaleb D.
  Journal of Non-Crystalline Solids, Elsevier, 2004, 341 (1-3), pp.26-34. (10.1016/j.jnoncrysol.2004.05.010)
  DOI : 10.1016/j.jnoncrysol.2004.05.010
• Chip based on In-situ Synthesis Technology utilizing Polymer as a Masking Material
  
  • Kuroiwa T.
  • Vinet F.
  • Vauchier C.
  • Yasuhiro G.
  • Ishikawa N.
  • Obara D.
  • Soucemarianadin Arthur
  , 2004, pp.pas précise.
• β irradiation in borosilicate glasses: the role of the mixed alkali effect
  
  • Ollier N.
  • Boizot B.
  • Reynard Bruno
  • Ghaleb D.
  • Petite G.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 218, pp.176-182. Two series of mixed alkali borosilicate glasses have been studied (Na/K and Na/Li) in order to examine the mixed alkali effect influence on the structure evolution of β-irradiated glasses. In both glass series, paramagnetic defects concentration shows a non-linear variation with Na content. The defect nature is also affected and more particularly boron oxygen hole center versus oxygen hole center relative proportion. By Raman spectroscopy, we showed that polymerization increase and molecular oxygen production, linked to the alkali migration, were minimized for some irradiated glass compositions. Mixed alkali effect blocks structural changes under electron irradiation in Na/Li glasses while for Na/K glasses, structural evolutions are smaller than in pure alkali glasses but non-completely annihilated. (10.1016/j.nimb.2003.12.014)
  DOI : 10.1016/j.nimb.2003.12.014
• He migration in implanted UO2 sintered disks
  
  • Guilbert Severine
  • Sauvage Thierry
  • Garcia Philippe
  • Carlot Gaelle
  • Barthe Marie-France
  • Desgardin Pierre
  • Blondiaux Gilbert
  • Corbel Catherine
  • Piron Jean-Paul
  • Gras Jean-Marie
  Journal of Nuclear Materials, Elsevier, 2004, 327 (2-3), pp.88-96. The behaviour of helium implanted in sintered uranium dioxide disks has been investigated as a function of annealing temperature. UO2 disks have been implanted with 1 MeV 3He ions at a fluence of 1 × 1016 3He cm−2 using a Van der Graaff accelerator. These implantation conditions lead to a local helium concentration of 0.2 at.% at a depth of 1.9 μm in UO2. The 3He(d,α)1H Nuclear Reaction Analysis method was used to determine the helium depth profile after the various annealing stages. The experimental results measured after 1100 °C anneal were analysed using a simple model which satisfactorily reproduces the observed helium depth profile changes. The intragranular helium diffusion coefficient is estimated and the result is assessed against other data published in the open literature. (10.1016/j.jnucmat.2004.01.024)
  DOI : 10.1016/j.jnucmat.2004.01.024
• Profile measurements of helium implanted in UO2 sintered pellets by using the 3He(d,α)1H nuclear reaction analysis technique
  
  • Sauvage Thierry
  • Erramli Hassan
  • Guilbert Severine
  • Vincent Laetitia
  • Barthe Marie-France
  • Desgardin Pierre
  • Blondiaux Gilbert
  • Corbel Catherine
  • Piron Jean-Paul
  • Labohm F.
  • van Veen A.
  Journal of Nuclear Materials, Elsevier, 2004, 327 (2-3), pp.159-164. (10.1016/j.jnucmat.2004.02.002)
  DOI : 10.1016/j.jnucmat.2004.02.002
• Direct Transition from Bose Glass to Normal State in the (K,Ba)BiO3 Superconductor
  
  • Klein Thierry
  • Marcenat C.
  • Blanchard S.
  • Marcus J.
  • Bourbonnais C.
  • Brusetti R.
  • J. van Der Beek C.
  • Konczykowski M.
  Physical Review Letters, American Physical Society, 2004, 92, pp.037005. The introduction of columnar defects in K; Ba BiO3 single crystals shifts both the irreversibility and thermodynamic transition lines, respectively, deduced from ac susceptibility (and/or transport) and specific heat measurements, upwards. This shift can be attributed to the defect-induced decrease of the difference ( F) between the free energies in the superconducting and the normal states, assuming that the position of the superconducting transition is given by the condition j Fj kBT= 3. This criterion also perfectly reproduces the influence of the angle between the tracks and the external field. This result suggests that no vortex liquid phase exists in this system. (10.1103/PhysRevLett.92.037005)
  DOI : 10.1103/PhysRevLett.92.037005
• Electronic structure and electron energy-loss spectroscopy of ZrO2 zirconia
  
  • K. Dash L.
  • Vast N.
  • Baranek P.
  • C. Cheynet M.
  • Reining L.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 70, pp.245116. The atomic and electronic structures of zirconia are calculated within density functional theory, and their evolution is analyzed as the crystal-field symmetry changes from tetrahedral [cubic (c-ZrO2) and tetragonal (t-ZrO2) phases] to octahedral (hypothetical rutile ZrO2), to a mixing of these symmetries (monoclinic phase, m-ZrO2). We find that the theoretical bulk modulus in c-ZrO2 is 30% larger than the experimental value, showing that the introduction of yttria in zirconia has a significant effect. Electronic structure fingerprints which characterize each phase from their electronic spectra are identified. We have carried out electron energy-loss spectroscopy experiments at low momentum transfer and compared these results to the theoretical spectra calculated within the random phase approximation. We show a dependence of the valence and 4p (N2,3 edge) plasmons on the crystal structure, the dependence of the latter being brought into the spectra by local-field effects. Last, we attribute low energy excitations observed in EELS of m-ZrO2 to defect states 2 eV above the top of the intrinsic valence band, and the EELS fundamental band gap value is reconciled with the 5.2 or 5.8 eV gaps determined by vacuum ultraviolet spectroscopy
• Superconducting pinning by magnetic domains in a ferromagnet-superconductor bilayer
  
  • Z. Cieplak M.
  • Adamus Z.
  • Konczykowski M.
  • M. Chen X.
  • Byczuk A.
  • Abal'Oshev A.
  • Sang H.
  • L. Chien C.
  Acta Physica Polonica A, Polish Academy of Sciences. Institute of Physics, 2004, 106, pp.693. The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model
• Amorphous vortex phase in Bi2Sr2CaCu2O8 after the first order liquid-solid phase transition
  
  • Menghini M.
  • Fasano Y.
  • de La Cruz F.
  • Banerjee S.S.
  • Myasoedov Y.
  • Zeldov E.
  • J. van Der Beek C.
  • Konczykowski M.
  • Tamegai T.
  Journal of Low Temperature Physics, Springer Verlag (Germany), 2004, 135, pp.139. It is widely accepted that the first-order vortex liquid-solid phase transition is associated with a crystalline solid phase and the second order transition with an amorphous one. The combination of a technique that determines the order of the transition with the visualization of the vortex structure has allowed the detection, for the first time, of a first-order liquid-solid transition without structural symmetry change. The results show that the quasi-long range order of the solid phase is not a necessary condition for the first-order phase transition to occur. This opens an important question on the microscopic origin of the liquid-solid phase transition in vortex matter
• Persistence of the intrinsic transition in the vortex matter of disordered BSCCO:2212 crystals
  
  • Konczykowski M.
  • J. van Der Beek C.
  • Zeldov E.
  • Ming Li.
  • H. Kes P.
  Physica C: Superconductivity and its Applications, Elsevier, 2004, 408, pp.547. The first order melting transition (FOT) in vortex matter of clean Bi2Sr2CaCu2O8 crystals, is identified by a discontinuity in the reversible magnetization, which extends to the low temperature (irreversible) regime in the form of a jump in the energy barrier vs. current, U(J), variation. Heavy ion irradiation disorders the vortex lattice, enhances flux pinning, and is believed to suppress the FOT. However, in underdoped samples, detailed measurements of magnetic relaxation by the Hall-array technique reveal the existence of a discontinuous jump in the U(J) curve precisely at the location of FOT of pristine crystals
• Photoconductivity and photoemission studies of diamond irradiated by ultrashort VUV pulses
  
  • Gaudin Jérôme
  • Geoffroy Ghita
  • Guizard Stéphane
  • Petite Guillaume
  • Klimentov Serguei M.
  • Garnov Serguei V.
  • Pivovarov Pavel A.
  • Carre Bertrand
  • Belsky Andrei
  • Martin Patrick
  Applied Physics B - Laser and Optics, Springer Verlag, 2004, 78, pp.1001.
• SPATIALLY PERIODIC STRUCTURES, UNDER FEMTOSECOND PULSED EXCITATION OF CRYSTALS
  
  • Petite Guillaume
  • Martynovitch Evgueni F.
  • Dresvianski Vladimir P.
  • Starchenko Anton A.
  Applied Physics Letters, American Institute of Physics, 2004, 84, pp.4550. Measuring the luminescence intensity of specially prepared irradiation defects induced in crystals, we observe that the longitudinal structure of quasi-interferences induced by two orthogonally polarized femtosecond pulses propagating together with different velocities is insensitive to the spatial broadening due to velocity dispersion in the crystals. On the contrary, it does depend on the pulse duration when it is changed by varying the spectral width of the radiation. It thus allows a direct measurement of the coherence time of such pulses. Stability of the axial selectivity is a good sign, taking away a number of serious limitations concerning possible applications.
• Neural correlates of implicit object identification.
  
  • Pins D.
  • Meyer M. E.
  • Foucher J.
  • Humphreys G.
  • Boucart M.
  Neuropsychologia, Elsevier, 2004, 42 (9), pp.1247-59. The present study sought to assess neural correlates of implicit identification of objects by means of fMRI, using tasks that require matching of the physical properties of objects. Behavioural data suggests that there is automatic access to object identity when observers attend to a physical property of the form of an object (e.g. the object's orientation) and no evidence for semantic processing when subjects attend to colour. We evaluated whether, in addition to neural areas associated with decisions to specific perceptual properties, areas associated with access to semantic information were activated when tasks demanded processing of the global configuration of pictures. We used two perceptual matching tasks based on the global orientation or on the colour of line drawings. Our results confirmed behavioural data. Activations in the inferior occipital cortex, fusiform and inferior temporal gyri in both tasks (orientation and colour) account for perceptual and structural processing involved in each task. In contrast, activations in the posterior and medial parts of the fusiform gyrus, shown to be involved in explicit semantic judgements, were more pronounced in the orientation-matching task, suggesting that semantic information from the pictures is processed in an implicit way even when not required by the task. Thus, this study suggests that cortical regions usually involved in explicit semantic processing are also activated when implicit processing of objects occurs. (10.1016/j.neuropsychologia.2004.01.005)
  DOI : 10.1016/j.neuropsychologia.2004.01.005
• Potentialities of GaN-based microcavities in strong coupling regime at room temperature.
  
  • Ollier N.
  • Natali F.
  • Byrne D.
  • Disseix Pierre
  • Vasson A.
  • Leymarie Joël
  • Semond F.
  • Massies J.
  Superlattices and Microstructures, Elsevier, 2004, 34 (4-6), pp.599-606. In a recent publication [N. Antoine-Vincent, F. Natali, D. Byrne, A. Vasson, P. Disseix, J. Leymarie, M. Leroux, F. Semond, J. Massies, Phys. Rev. B 68 (2003) 153313], we have highlighted for the first time the exciton–photon strong coupling in a GaN-based microcavity and obtained a Rabi splitting of 31 meV persistent at 77 K. Our aim is now to study the feasibility of GaN-based microcavities for which the strong coupling regime would be maintained at room temperature. A complex heterostructure containing GaN/AlGaN quantum wells (QWs) is investigated by photoreflectivity and reflectivity at 5 K. The QW thickness is 3 nm and the Al composition and thickness of the barriers are respectively 0.11 and 10 nm. From the modeling of the experimental spectra, the values of the oscillator strength, the energy and the broadening parameter of the QW fundamental transition are determined; the broadening is found to be relatively weak (15 meV). Simulations of microcavities containing QWs have then been performed including this set of parameters: a theoretical Rabi splitting of 34 meV is obtained at 5 K. Considering an additional broadening induced by the increase of the temperature (23 meV), the strong coupling regime could be maintained theoretically at room temperature in such a structure. This is due to the low value of the inhomogeneous broadening related to the QW transition which is lower than in bulk GaN. The influence of the QW number and the nature of the Bragg mirror on the Rabi splitting is then discussed in realistic structures. (10.1016/j.spmi.2004.09.017)
  DOI : 10.1016/j.spmi.2004.09.017
• Vortex Phase Diagram in Bi2Sr2CaCu2O8+$\delta$ with Damage Tracks Created by 30 MeV Fullerene Irradiation
  
  • Ishikawa N.
  • van der Beek C. J.
  • Dunlop A.
  • Jaskierowicz G.
  • Li Ming
  • Kes P. H.
  • Della-Negra S.
  Journal of the Physical Society of Japan, Physical Society of Japan 日本物理学会, 2004, 73, pp.2813-2821. Using 30 MeV C60 fullerene irradiation, we have produced latent tracks of diameter 20 nm and length 200 nm, near the surface of single crystalline Bi2Sr2CaCu2O8+δ. A preliminary transmission electron microscopy study shows evidence for a very high density of deposited energy, and the ejection of material from the track core in very thin specimens. The latent tracks reveal themselves to be exceptionally strong pinning centers for vortices in the superconducting mixed state. Both the critical current density and magnetic irreversibility line are significantly enhanced. The irradiated crystals present salient features of the (B,T) phase diagram of vortex matter both of pristine crystals, such as the first order vortex phase transition, and the exponential Bose-glass line characteristic of heavy ion-irradiated crystals. We show that the latter is manifestly independent of the pinning potential (10.1143/JPSJ.73.2813)
  DOI : 10.1143/JPSJ.73.2813
• b-irradiation in borosilicate glasses : the role of the mixed alkali effect
  
  • Ollier Nadège
  • Boizot Bruno
  • Reynard Bruno
  • Ghaleb Dominique
  • Petite Guillaume
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 218, pp.176-182.
• Porous vortex matter
  
  • Banerjee S.S.
  • Zeldov E.
  • Soibel A.
  • Myasoedov Y.
  • Rappaport M.
  • Menghini M.
  • Fasano Y.
  • de La Cruz F.
  • J. van Der Beek C.
  • Konczykowski M.
  • Tamegai T.
  Physica C: Superconductivity and its Applications, Elsevier, 2004, 408, pp.495. Structure, dynamics, and thermodynamic properties of vortex matter in the presence of a low density of columnar defects (CDs) were studied in BSCCO crystals. Magnetic decorations show that when vortices outnumber CDs a heterogeneous vortex matter is formed consisting of two populations of vortices: vortices residing on CDs form a matrix of pinned vortices, whereas the interstitial vortices form ordered crystallites within the 'pores' of the matrix. Differential magneto-optical studies reveal that at elevated fields this porous phase melts in two stages, a first-order melting of the crystallites at a temperature considerably higher than the pristine melting, and a continuous melting of the matrix at still higher temperature. At low fields the two transitions occur simultaneously, giving rise to a sharp kink in the observed melting line
• Applications of Time-Dependent Density Functional Theory
  
  • Botti Silvana
  Physica Scripta, IOP Publishing, 2004, T109, pp.54. The progress of experimental techniques makes more and more precise measurements available. Their interpretation requires improved theoretical tools. The time-dependent density functional theory (TDDFT) allows to study electronic excitations involved in spectroscopic experiments, possibly conserving a computational effort comparable to that of ground-state density functional theory. I will present some applications of TDDFT to the calculation of absorption and electron energy loss spectra in extended and finite systems, discussing the advantages and the limits of different approximation schemes. (10.1238/Physica.Topical.109a00054)
  DOI : 10.1238/Physica.Topical.109a00054
• Long- and short-range magnetic order charge transfer, and superconductivity in Yba2Cu3 -xCOxO7
  
  • Maury F.
  • Mirebeau I.
  • A. Hodges J.
  • Bourges P.
  • Sidis Yvan
  • Forget A.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 69, pp.094506. We have performed powder-neutron-diffraction measurements in YBa2Cu3–xCoxO7 for a large range of Co concentrations (x = 0.04–0.72) and determined the magnetic phase diagram. As previously observed, superconductivity disappears for x0.42 and antiferromagnetic long-range order emerges above this value. The antiferromagnetic order shows noticeable differences compared to that in unsubstituted YBa2Cu3O6 + and surprisingly survives to a much higher hole doping. In contrast to recent results in YBa2Cu3–xCoxO7 single crystals, there is no evidence of any long-range antiferromagnetic order in the superconducting phase. The Co valence evolves from 4+ to 3+ with increasing Co concentration. We studied the short-range chemical and magnetic correlations between the Co ions in superconducting (x0.36) and antiferromagnetic (x0.42) samples. The Co ions predominantly occupy the Cu1 sites and their moments remain mostly disordered, forming random antiferromagnetic next nearest neighbor pairs, which compete with the long-range order. This can explain the low value for the ordered Cu1 site moment
• Raman investigation of structural changes induced by e-beam irradiation in Ge doped silica MCVD glasses
  
  • S. Jacqueline A.
  • Poumellec B.
  • C. Chervin J.
  • Garcia-Blanco S.
  • Esnouf S.
  Materials Science and Engineering: B, Elsevier, 2004, 107, pp.46. Microstructural changes of germanium (Ge)-doped silica glasses irradiated with electron beam (e-beam) have been investigated by Raman spectroscopy. Two mechanisms correlated to the specific volume changes induced by e-beam irradiation were observed by surface topography measurement. As we have previously demonstrated, they depend on the Ge content and the irradiation dose. The compaction of the structure (which decreases with the Ge concentration) is attributed to an increase of the three and four-membered ring species which is maximal at the surface and decreases with depth. By means of Monte-Carlo simulations, we have correlated the energy deposition with the compaction process. Some specific Raman components are attributed to the expansion of the structure observed for high Ge content and high irradiation dose. In this case, an increase of the anti-symmetric stretching modes of the bridging oxygen in the Si---O---Ge and Si---O---Si groups are observed at the surface
• Local crystallization induced in Fe-based amorphous alloys by swift heavy projectiles
  
  • Rizza G.
  • Dunlop A.
  • Jaskierowicz G.
  • Kopcewicz M.
  Nuclear Instruments and Methods in Physics Research, North-Holland ; Elsevier [1981-1984], 2004, 226, pp.609-621. We report the effect of the high density of electronic excitation deposited along the path of swift heavy ions in various amorphous alloys. The samples were irradiated at low temperature with GeV Pb ions up to fluences of 1 × 1011 to 2.3 × 1013 cm−2. The formation of nanocrystalline phases was observed by transmission electron microscopy in the FINEMET-like Fe73.5Nb4.5Cr5Cu1B16 alloy and in the NANOPERM ternary Fe90Zr7B3 glassy systems but not in the Fe80.5Nb7B12.5 alloy. The crystallization phenomenon was interpreted in terms of the relaxation of the high level of energy deposited in electronic excitations along the path of Pb ions in the target, which induce radial pressure waves in the vicinity of the projectile trajectories. These mechanical stresses destabilize the amorphous structure and induce nanocrystallization
• Long range contribution to the exchange-correlation kernel of time-dependent density functional theory
  
  • Botti Silvana
  • Sottile F.
  • Vast N.
  • Olevano Valério
  • Reining L.
  • Weissker H-Ch.
  • Rubio A.
  • Onida G.
  • del Sole R.
  • Godby R.W.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 69, pp.155112. We discuss the effects of a static long-range contribution -α/q2 to the exchange-correlation kernel fxc(q) of time-dependent density functional theory. We show that the optical absorption spectrum of solids exhibiting a strong continuum excitonic effect is considerably improved with respect to calculations where the adiabatic local-density approximation is used. We discuss the limitations of this simple approach, and in particular that the same improvement cannot be found for the whole spectral range including the valence plasmons and bound excitons. On the other hand, we also show that within the range of validity of the method, the parameter α depends linearly on the inverse of the dielectric constant, and we demonstrate that this fact can be used to predict continuum excitonic effects in semiconductors. Results are shown for the real and imaginary part of the dielectric function of Si, GaAs, AlAs, diamond, MgO, SiC and Ge, and for the loss function of Si. (10.1103/PhysRevB.69.155112)
  DOI : 10.1103/PhysRevB.69.155112
• Ferromagnetic and twin domains in LCMO manganites
  
  • Jung G.
  • Markovich V.
  • Mogilyanski D.
  • van Der Beek C.
  • Mukovskii Y.M.
  Journal of Magnetism and Magnetic Materials, Elsevier, 2004, 290-291 (Part 2), pp.902-905. Ferromagnetic and twin domains in lightly Ca-doped La1-xCaxMnO3 single crystals have been visualized and investigated by means of the magneto-optical technique. Both types of domains became visible below the Curie temperature. The dominant structures seen in applied magnetic field are associated with magneto-crystalline anisotropy and twin domains. In a marked difference to the twin domains which appear only in applied magnetic field, ferromagnetic domains show up in zero applied field and are characterized by oppositely oriented spontaneous magnetization in adjacent domains. Ferromagnetic domains take form of almost periodic, corrugated strip-like structures. The corrugation of the ferromagnetic domain pattern is enforced by the underlying twin domains
• Guest displacement in silicon clathrates
  
  • Tournus Florent
  • Masenelli Bruno
  • Mélinon Patrice
  • Connétable Damien
  • Blase Xavier
  • Flank Anne-Marie
  • Lagarde Pierre
  • Cros Christian
  • Pouchard Michel
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 69 (3), pp.035208 (6 p.). We study both theoretically and experimentally the structure of the doped silicon clathrate II NaxSi34. We find that contrary to published works, the sodium atoms do not retain the Td symmetry inside the Si28 cages and move about 1 Å away from the center of the cage. This displacement, in conjunction with that of a sodium atom in an adjacent Si28 cage, leads to a “dimerization” of sodium atoms. As a consequence, Rietveld refinements of x-ray diffraction spectra and transport, vibrational, and electronic properties must be revisited. (10.1103/PhysRevB.69.035208)
  DOI : 10.1103/PhysRevB.69.035208