Publications

2004

• 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
• 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
• Transfer of magnetization by spin injection between both interfaces of a Ni nanowire
  
  • Wegrowe J. -E.
  • Dubey M.
  • Wade T.
  • Drouhin H. -J.
  • Konczykowski M.
  Journal of Applied Physics, American Institute of Physics, 2004, 96, pp.4490-4493. Magnetization switching provoked by spin-injection is studied in Ni nanowires of various size and morphology. The response of the magnetization to the spin-injection is studied as a function of the amplitude of the current, the temperature, and the symmetry of the interfaces. The amplitude of the response of the magnetization to spin-injection is a decreasing function of the temperature, does not depend on the current sign, and occurs only in the case of asymmetric interfaces. It is shown that the spin-injection does not act on small magnetic inhomogeneities inside the layer. Some consequences in terms of longitudinal spin-transfer are discussed.
• Tailoring bulk and surface grafting of poly(acrylic acid) in electron-irradiated PVDF
  
  • Clochard Marie-Claude
  • Bègue J
  • Lafon A
  • Caldemaison D
  • Bittencourt C
  • Pireaux J.-J
  • Betz N
  Polymer, Elsevier, 2004, 45, pp.8683. Endowing conventional hydrophobic poly(vinylidene fluoride) (PVDF) films with hydrophilic properties was conducted using electron beam irradiation. Grafting of acrylic acid (AA) in/onto pre-irradiated PVDF films was investigated. Reaction parameters, monomer concentration and inhibitor concentration were examined. Radiation grafted films (PVDF-g-PAA) were synthesized with various grafting yields ranging from 12 to 130 wt % in presence of Mohr's salt (25 wt %). Below 80 wt % of monomer concentration, the degree of swelling was found to increase with the grafting yield. The PAA was arranged randomly in all PVDF matrix (grafting through). Above 80 wt % of monomer concentration, the PAA was grafted only onto the surface of PVDF films leading to a highly dense layer of PAA. Grafting through or surface grafting processes were achieved by varying the water fraction in the initial monomer solution. Water molecule acts not only as a carrier for the monomer but also as a plasticizer expanding the film in the three dimensions. Evidences of grafting through and surface grafting were produced using FTIR in ATR mode, SEM coupled to X-ray detection and XPS. An accurate quantification of AA units was possible up to the micromole via a Cu 2C –EDTA complex analyzed by UV–vis spectroscopy. q (10.1016/j.polymer.2004.10.052)
  DOI : 10.1016/j.polymer.2004.10.052
• Alfred Wilm and the beginnings of Duralumin
  
  • Hardouin Duparc Olivier
  Revue de Métallurgie, EDP Sciences, 2004, n° 5, pp.353-360. The discovery of Duralumin took place in a military context. The Prussian engineer Alfred Wilm had been mandated in Neubabelsberg near Berlin to develop such an improved alloy, the name of which is as much due to the fact that it is hard as to the fact it has first been industrially produced in Düren. International cooperations as well as harsh competitions have accompanied the first researches on this alloy in the beginning of the twentieth century
• beta irradiation borosilicate glasses: the role of the mixed alkali effect
  
  • Ollier N.
  • Boizot B.
  • Reynard B.
  • Ghaleb D.
  • Petite G.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 218, pp.176. We investigate the photoemission for a set of wide band-gap crystals irradiated by femtosecond Ti-Sapphire laser pulses at intensities varying from 0.5 to 6 TW/cm(2) (below the optical breakdown threshold). The measured total electron yield increases linearly with the laser intensity in this intensity range. An intense and wide plateau of high energy electrons appears in the photoelectron spectra at excitation intensities larger than 1 TW/cm(2). The exponential cut-off of this plateau reaches 40 eV at maximal applied intensities. In order to explain such a behavior, we propose a mechanism where the heating is due to a sequence of direct interbranch one- and multi-photon transitions in the conduction band
• Study of excimer laser irradiation effects on properties of crystalline YBaCuO thin films
  
  • Abal'Oshev A.
  • Abal'Osheva I.
  • J. Lewandowski S.
  • J. van Der Beek C.
  • Konczykowski M.
  • Rizza G.
  • Barbanera S.
  Acta Physica Polonica A, Polish Academy of Sciences. Institute of Physics, 2004, 106, pp.681. The influence of UV laser irradiation on the physical properties of epitaxial YBa2CU3O7-delta thin (< 1 mum) films fabricated by laser ablation was studied. The samples were irradiated by pulsed excimer laser beam at different incident energy densities E-ir less than or equal to 130 mJ/cm(2), i.e. 2-3 times below the ablation threshold of YBaCuO. The analysis of the sample cross-section using transmission electron microscope shows that such irradiation forms a disordered layer on the top of the crystalline film. Sample surface amorphization was observed also by atomic force microscope. Due to strong UV irradiation absorption in YBaCuO this surface layer acts like a protective cover for the sample interior. Only a small reduction of superconducting critical temperature T-c was observed. Both transport measurements in normal state and magneto-optical studies in superconducting state indicate that between the disordered layer and the bottom non-modified part of the film there exists a wide transitional region with reduced carrier concentration
• Heating of Conduction Band Electrons by Intense Femtosecond Laser Pulses
  
  • Belsky Andrei
  • Martin Patrick
  • Bachau Henri
  • Vassiliev A.N.
  • Yatsenko Boris
  • Guizard Stéphane
  • Geoffroy Ghita
  • Petite Guillaume
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2004, 67, pp.301-306.
• 111. Observation of high energy photoelectrons from solids at moderate laser intensity
  
  • Belsky Andrei
  • Bachau Henri
  • Gaudin Jérôme
  • Geoffroy Ghita
  • Guizard Stéphane
  • Martin Patrick
  • Petite Guillaume
  • Philippov A.
  • Vassil'Ev Andrei N.
  • Yatsenko Boris
  Applied Physics B - Laser and Optics, Springer Verlag, 2004, 78, pp.989-994.
• A structural approach by MAS NMR spectroscopy of mechanisms occurring under β-irradiation in mixed alkali aluminoborosilicate glasses
  
  • Ollier Nadège
  • Charpentier Thibault
  • Boizot Bruno
  • Petite Guillaume
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2004, 16, pp.7625-7635. Two series of mixed Na/K and Na/Li aluminoborosilicate glasses have been irradiated with electrons of 1.8 MeV at doses close to 109 Gy. Si, B and Al glass former environment changes under irradiation have been probed by MAS NMR spectroscopy. It was shown that the mixed alkali effect acts on the middle range compositions by operating with a selective blockage in irradiated glasses, depending on the alkali nature and concerning either modifier or charge compensator alkalis.
• Optical absorption and electron energy loss spectra of carbon and boron nitride nanotubes: a first-principles approach
  
  • G. Marinopoulos A.
  • Wirtz L.
  • Marini A.
  • Olevano Valério
  • Rubio A.
  • Reining L.
  Applied physics. A, Materials science & processing, Springer Verlag, 2004, 78, pp.1157. We present results for the optical absorption spectra of small-diameter single-walled carbon and boron nitride nanotubes obtained by ab initio calculations in the framework of time-dependent density-functional theory. We compare the results with those obtained for the corresponding layered structures, i.e. the graphene and hexagonal boron nitride sheets. In particular, we focus on the role of depolarization effects, anisotropies, and interactions in the excited states. We show that the random phase approximation reproduces well the main features of the spectra when crystal local field effects are correctly included, and discuss to what extent the calculations can be further simplified by extrapolating results obtained for the layered systems to results expected for the tubes. The present results are relevant for the interpretation of data obtained by recent experimental tools for nanotube characterization, such as optical and fluorescence spectroscopies, as well as polarized resonant Raman scattering spectroscopy. We also address electron energy loss spectra in the small-q momentum-transfer limit. In this case, the interlayer and intertube interactions play an enhanced role with respect to optical spectroscopy
• Ab initio and semiempirical dielectric response of superlattices
  
  • Botti Silvana
  • Vast Nathalie
  • Reining Lucia
  • Olevano Valério
  • Claudio Andreani Lucio
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 70, pp.045301. We present a study of the dielectric response of (GaAs)p∕(AlAs)p (001) superlattices in a wide range of barrier and well widths. We applied density functional theory and a semiempirical method to obtain the superlattice band structures. These were then used as a starting point to evaluate the optical spectra and macroscopic dielectric constants using time-dependent density functional theory. In this context, we investigated the role of crystal local field effects in determining the anisotropy of the dielectric constants. Furthermore, we calculated absorption spectra including the strong continuum excitonic effect through the use of an appropriate model exchange-correlation kernel. We analyzed in detail the complementarity of the ab initio and semiempirical approaches and we compared the successes and limitations of the different approximation schemes. (10.1103/PhysRevB.70.045301)
  DOI : 10.1103/PhysRevB.70.045301
• Flux lenses in the crossing lattices regime of layered superconductors
  
  • Cole D.
  • Crisan A.
  • J. Bending S.
  • Tamegai T.
  • van Der Beek K.
  • Konczykowski M.
  Physica C: Superconductivity and its Applications, Elsevier, 2004, 404, pp.99. We report here measurements of flux lensing behaviour which have been performed on Bi2Sr2CaCu2O8+delta single crystals placed on top of linear Hall probe arrays. In the crossing lattices regime we observe significant flux focussing as the in-plane field is swept up with a small constant density of pancake vortices. We also observe a sharp discontinous lock-in feature in local magnetic induction when the net field is close to the a-b plane
• Detailed analysis of the segregation driving forces for Ni(Ag) and Ag(Ni) in the sigma = 11{113} and sigma = 11{332} grain boundaries
  
  • Lezzar B.
  • Khalfallah O.
  • Larere A.
  • Paidar V.
  • Hardouin Duparc Olivier
  Acta Materialia, Elsevier, 2004, 52, pp.2809. The behaviour with respect to segregation is studied for two qualitatively different symmetrical tilt grain boundaries (GBs): a low energy boundary with mirror-symmetric structure on the {1 1 3} plane and the high energy {3 3 2} GB with a "zigzag" structural pattern. These two structures have been confirmed by high resolution transmission electronic microscopy observations in nickel. Intergranular segregation is studied in the limit of infinitely diluted solution for Ni(Ag) and Ag(Ni) systems modelled with Finnis–Sinclair like potentials. The atomic sites are characterized by a geometrical parameter defined by their exact Voronoy volumes and the pressure locally exerted. The segregation energies and driving forces are compared with these parameters in order to characterize a segregation "susceptibility" of intergranular atomic sites. The size effect calculated by the method of virtual impurity represents the main segregation driving force for the considered systems
• Transport properties and magnetic domain structure in low-doped LaCaMnO manganite single crystals
  
  • Jung G.
  • Markovich V.
  • Yuzhelevski Y.
  • Indenbom M.
  • J. van Der Beek C.
  • Mogilyanski D.
  • M. Mukovskii Y.
  Journal of Magnetism and Magnetic Materials, Elsevier, 2004, 272, pp.1800. The low temperature resistivity up-turn in lightly Ca doped LaCaMnO single crystals has been attributed to the domination of the tunneling mechanism in low temperature transport. The intrinsic tunnel barriers have been associated with spontaneous ferromagnetic domains walls. The magneto-optical technique has been employed to observe the relevant domain structure. A regular network of spontaneous ferromagnetic domains undergoes significant changes resulting in apparent rotation of the domain walls in the temperature range coinciding with the resistivity up-turn
• Dynamics of Femtosecond Laser Interactions with Dielectrics
  
  • Mao S.S.
  • Quéré Fabien
  • Guizard Stéphane
  • Mao X. L.
  • Russo R. E.
  • Petite Guillaume
  • Martin Philippe
  Applied physics. A, Materials science & processing, Springer Verlag, 2004, 79 (7), pp.1695. Femtosecond laser pulses appear as an emerging and promising tool for processing wide band-gap dielectric materials for a variety of applications. This article aims to provide an overview of recent progress in understanding the fundamental physics of femtosecond laser interactions with dielectrics that may have the potential for innovative materials applications. The focus of the overview is the dynamics of femtosecond laser-excited carriers and the propagation of femtosecond laser pulses inside dielectric materials.
• Exactly solvable models : a solution to different problems of laser matter interaction
  
  • Petite Guillaume
  • Shvartsburg Alexander
  , 2004, pp.11-20. With the increasing use of ultrashort laser pulses and nanoscale-materials, one is regularly confronted to situations in which the properties of the media supporting propagation are not varying slowly with time (or space). Hence, the usual WKB-type approximations fail, and one has to resort to numerical treatments of the problems, with a considerable loss in our insight into the physics of laser-matter interaction. We will present a new approach which allows a fully analytical solution of such problems, based on a transformation of the propagation equations into a new space where phase accumulation is linear with either time or space, which greatly simplifies their treatment. Though this method is restricted to some special models of the time or space varying dielectric constant, those are however general enough to encompass practically all experimental situations. It allows to introduce the concept of "non-stationarity induced" (or "inhomogeneity induced") dispersion. We will analyse the problem of reflection and propagation in two types of media whose dielectric constant vary rapidly at either the laser period or the laser wavelength scale. Extension of such techniques to the case of arbitrarily high non linearities will be considered too.
• Superconductivity from doping Boron icosahedra.
  
  • Calandra Matteo
  • Vast Nathalie
  • Mauri Francesco
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 69, pp.224505. We propose an alternative route to achieve the superconducting state in boron-rich solids, the hole doping of B12 icosahedra. For this purpose we consider a prototype metallic phase of B13C2. We show that in this compound the boron icosahedral units are mainly responsible for the large phonon frequencies logarithmic average, 65.8 meV, and the moderate electron-phonon coupling lambda= 0.81. We suggest that this high Tc could be a general feature of hole-doped boron icosahedral solids. Moreover our calculated moderate value of lambda excludes the formation of bipolarons localized on the icosahedral length scale as suggested by previous authors. (10.1103/PhysRevB.69.224505)
  DOI : 10.1103/PhysRevB.69.224505
• beta irradiation borosilicate glasses: the role of the mixed alkali effect
  
  • Lyard L.
  • Klein T.
  • Marcus J.
  • Brusetti R.
  • Marcenat C.
  • Konczykowski M.
  • Mosser V.
  • H. Kim K.
  • W. Kang B.
  • S. Lee H.
  • I. Lee S.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 218, pp.176. The first penetration field (H-p) has been deduced from local magnetization and specific heat measurements in magnesium diboride single crystals. For H-a(parallel toc), 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 H-c1 deduced from H-p through the standard elliptical formula. The lower critical field is found to be isotropic at low temperature (similar to0.11+/-0.01 T).
• Swift heavy ion induced graft polymerization in track etched membranes' submicroscopic pores
  
  • Mazzei R.
  • García Bermúdez G.
  • Betz N.
  • Cabanillas E.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 226, pp.575. Cl or Pb irradiated foils of poly(vinylidene fluoride) (PVDF) were chemically etched to produce nuclear track membranes (NTM) with submicroscopic pores. The NTM were grafted with styrene using the remaining active sites produced by the heavy ion beams. Experimental curves of grafting yield were measured by weight difference as a function of ion fluence and etching time. As the etching time was increased from 0 to 30 min a decrease of the grafting yield was observed. Grafted foils were also analysed by Fourier transform infrared spectroscopy (FTIR). Both measurements suggest that the styrene was grafted on the pore wall of the NTM using the active sites left by the ion beam
• Spin-dependent thermopower in Co/Cu multilayer nanowires
  
  • Gravier L.
  • Fabian A.
  • Rudolf A.
  • Cachin A.
  • E. Wegrowe J.
  • P. Ansermet J.
  Journal of Magnetism and Magnetic Materials, Elsevier, 2004, 271, pp.153. The magnetic field dependence of the thermoelectrical power of a series of Co/Cu multilayered nanowires grown by electrodeposition in a polymer matrix is almost that predicted by the Mott formula in the temperature range of 15300 K. Application of the two-current model to thermopower yields (S-up arrow - S-down arrow)/(S-up arrow + S-down arrow) the relative difference between the thermopower of each spin channel
• Optical anisotropy induced by cesium adsorption on the As-rich c(2X8) reconstruction of GaAs(001)
  
  • Hogan C.
  • Paget D.
  • E. Tereshchenko O.
  • Reining L.
  • Onida G.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 6912, pp.5332. Upon adsorption of Cs, the As-rich c(2 X 8)/(2 X 4) reconstruction of GaAs(001) is found to exhibit an intense negative signal between 3 eV and 5 eV in the reflectance anisotropy spectrum. This signal has a universal character in that similar features also appear on the Ga-rich surface. The mechanism of this signal is interpreted using ab initio calculations of Cs adsorption at As and Ga sites of the As-rich surface. The calculations succeed in explaining the universality of the signal. In the vicinity of the E-0' bulk critical point at 4.5 eV, the signal arises from perturbation of bulk states terminating at the surface. At lower energies, the signal arises from the creation of new surface resonances induced by the Cs adatom
• Spin-dependent magnetoresistance in multiwall carbon nanotubes
  
  • Hoffer X.
  • Klinke C.
  • M. Bonard J.
  • Gravier L.
  • E. Wegrowe J.
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2004, 67, pp.103. The spin-dependent transport in multiwall carbon nanotubes, obtained by chemical vapour deposition in porous alumina membranes, has been investigated. The zero-bias anomaly is shown to follow the typical power law GT(-alpha) (eV/kT). In the nanotubes contacted with Ni pads, the magnetoresistance due to the spin-polarised current (SD-MR) is destroyed. In the case of those contacted with Co pads, however, the SD-MR is observed. These measurements show that both the observation of a typical scaling law of the conductance (for nanotubes tip to 1.5 mum) and a short spin diffusion length (less than 0.15 mum with nickel contacts and 0.7 mum with cobalt contacts) coexist through the nanotube. This observation may be interpreted in terms of a reminiscence of the Luttinger-liquid behaviour with spin-charge separation