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
• 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
• 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
• 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
• 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
• 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
• Colour center production in yttria-stabilizing zirconia by swift charge particle irradiations.
  
  • Costantini Jean-Marc
  • Beuneu François
  • Gourier Didier
  • Trautmann Christina
  • Calas Georges
  • Toulemonde Marcel
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2004, 16, pp.3971. We have studied the colour centre production by swift electron and heavy ion irradiations of yttria-stabilized zirconia (YSZ), i.e. ZrO2:Y with 9.5 mol% Y2O3. For this purpose, we performed irradiations of \langle 100\rangle - or \langle 110\rangle -oriented YSZ single crystals with 2.5 MeV electrons, 145 MeV 13C, 180 MeV 32S, 200 MeV 58Ni, 230 MeV 79Br, 120 MeV 127I, 200 MeV 127I, 200 MeV 197Au, and 2.6 GeV 238U ions. X-band electron paramagnetic resonance (EPR) and UV–visible optical absorption measurements were used to monitor the point defect formation. The EPR line saturations were measured between 6 and 150 K, in order to obtain the spin–lattice relaxation time (T1). Electron and ion beams produce the same two colour centres: (i) the first one is identified as an F+-type centre (singly ionized oxygen vacancy) with an axial \langle 100\rangle symmetry, a small g-factor anisotropy (g_{\bot }=1.972 and g_{\parallel }=1.996 ) and long T1 values, (ii) the second one is similar to the well known T-centre (Zr3+ in a trigonal oxygen environment) with an axial \langle 111\rangle symmetry and a large g-factor anisotropy (g_{\bot }=1.855 and g_{\parallel }=1.986 ), which is also produced by photon irradiations. A broad optical absorption band centred at a wavelength near 500 nm is observed with an absorption coefficient proportional to the volume density of the F+-type centre deduced from the room temperature EPR spectra. Since no change of this band occurs between 10 and 300 K, it indicates that the electron–phonon coupling of this colour centre must be strong, in agreement with an F+-type centre. Owing to the axial \langle 100\rangle symmetry and lack of hyperfine structure of the EPR lines of this defect, it is suggested that the first coordination shell must contain one native oxygen vacancy. The plots of the volume density of this centre versus fluence are on the whole rescaled as functions of the number of displacements per atom induced by elastic collisions. (10.1088/0953-8984/16/23/014)
  DOI : 10.1088/0953-8984/16/23/014
• Ab initio study of the optical absorption and wave-vector-dependent dielectric response of graphite
  
  • G. Marinopoulos A.
  • Reining L.
  • Rubio A.
  • Olevano Valério
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 6924, pp.5419. We performed ab initio calculations of the optical absorption spectrum and the wave-vector-dependent dielectric and energy-loss functions of graphite in the framework of the random-phase approximation. In the absorption spectrum, the most prominent peaks were analyzed in terms of interband transitions from specific regions of the Brillouin zone. The inclusion of the crystal local-field effects (LFE) in the response had an important influence on the absorption spectrum for light polarization parallel to the c axis. The calculated electron energy-loss spectra, even without LFE, were in very good agreement with existing momentum-dependent energy-loss experiments concerning the peak positions of the two valence-electron plasmons. Important aspects of the line shape and anisotropy of the energy-loss function at large momentum transfer q were also well described: the splitting of the total (pi+sigma) plasmon and the appearance of peaks originating from interband transitions. Finally, the role of the interlayer interaction was studied, in particular with regard to its effect on the absorption spectrum for light polarization parallel to c, and to the position of the higher-frequency pi+sigma plasmon
• 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
• 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
• Origin of linear extended defects in single crystalline Bi2Sr2CaCu2O8
  
  • Li M.
  • H. Kes P.
  • F. W. R. Rycroft S.
  • J. van Der Beek C.
  • Konczykowski M.
  Physica C: Superconductivity and its Applications, Elsevier, 2004, 408, pp.25. Magneto-optical imaging and direction-dependent resistivity measurements are cross-correlated to provide evidence that the extended line defects in Bi2Sr2CaCu2O8 single crystals are needle-like Bi2Sr2Ca2Cu3O10 intergrowths that form along the crystal growth direction
• Vortex-lattice melting front in thin superconductors with pinning
  
  • V. Indenbom M.
  • H. Brandt E.
  • J. van Der Beek C.
  • Konczykowski M.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2004, 7014, pp.4525. Magneto-optical observations of a second flux front, which occurs at the second peak in the magnetization of Bi2Sr2CaCu2Ox single crystals related to the known first-order "vortex-lattice melting," are reconsidered. We show that, in thin samples, electrodynamics necessarily leads to an extended region in which the magnetic induction adopts a nearly constant value close to that at which the phase transition occurs at thermal equilibrium. In this region a dynamical phase mixture of vortex "solid" and "liquid" should exist. Interestingly, the observed second flux front does not mark the "melting" front, as it was naively interpreted earlier, but indicates the disappearance of the last "solid droplets".
• 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
• 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
• 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
• 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.
• 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.
• 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.