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We analyze the micromagnetics of short longitudinal modulations of a high-magnetization material in cylindrical nanowires made of a soft-magnetic material of lower magnetization such as permalloy, combining magnetic microscopy, analytical modeling, and micromagnetic simulations. The mismatch of magnetization induces curling of magnetization around the axis in the modulations, in an attempt to screen the interfacial magnetic charges. The curling angle increases with modulation length, until a plateau is reached with nearly full charge screening for a specific length scale~$\Delta_\mathrm{mod}$, larger than the dipolar exchange length of any of the two materials. The curling circulation can be switched by the Oersted field arising from a charge current with typical magnitude $10^{12} A/m^{2}$ for a diameter of $\sim$100 nm, and reaching a maximum for $\Delta_\mathrm{mod}$.

High-resolution scanning transmission x-ray microscopy (STXM) can provide quantitative access to local magnetization canting angles relative to the surface. We use this cutting-edge microscopy technique to probe the weak stripe magnetic texture hosted by a 180-nm-thick ${\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$ layer. We report a full set of measurements of the weak stripe canting angle, as well as a method that uses only a single-impinging-direction x-ray beam to extract the angle. This method also allows the spatial profile to be extracted with 30 nm resolution, and the canting angle versus applied field can be measured. Combining these information, the macroscopic magnetization versus applied field loop on a complex spin texture can be reconstructed in an unprecedented way and shows undoubtedly that flux closure domains exist. These results show that the presence of flux closure domains, at the surface of such a thick film, is difficult to demonstrate by means of the STXM technique. Beyond the characterization of the weak stripe angle, this quantitative x-ray magnetic microscopy can be used to study the local textures hosted in all materials exhibiting some circular x-ray magnetic dichroism.

Using focused electron-beam-induced deposition, we fabricate a vertical, platinum-coated cobalt nanowire with a controlled three-dimensional structure. The latter is engineered to feature bends along the height: these are used as pinning sites for domain walls, which are obtained at remanence after saturation of the nanostructure in a horizontally applied magnetic field. The presence of domain walls is investigated using x-ray magnetic circular dichroism (XMCD) coupled to photoemission electron microscopy (PEEM). The vertical geometry of our sample combined with the low incidence of the x-ray beam produce an extended wire shadow which we use to recover the wire's magnetic configuration. In this transmission configuration, the whole sample volume is probed, thus circumventing the limitation of PEEM to surfaces. This article reports on the first study of magnetic nanostructures standing perpendicular to the substrate with XMCD-PEEM. The use of this technique in shadow mode enabled us to confirm the presence of a domain wall without direct imaging of the nanowire., This work was supported by Spanish Ministry of Economy and Competitivity through projects No. MAT2014-51982C2-1-R, MAT2014-51982C2-2-R and MAT2015-69725-REDT, including FEDER funds, and by the Aragon Regional Government (Construyendo Europa desde Aragón) through project E26, with FEDER funding. Javier Pablo-Navarro grant is funded by the Ayuda para Contratos Predoctorales para la Formación de Doctores, Convocatoria Res. 05/06/15 (BOE 12/06/15) of the Secretaría de Estado de Investigación, Desarrollo e Innovación in the Subprograma Estatal de Formación of the Spanish Ministry of Economy and Competitiveness (MINECO) with the participation of the European Social Fund. Michal Staňo acknowledges grant from the Laboratoire d’excellence LANEF in Grenoble (ANR10-LABX-51-01).

The main storage components of the maize endosperm are starch, proteins and lipids. Starch and proteins are heterogeneously deposited, leading to the formation of vitreous and floury regions at the periphery and at the centre of the endosperm. The vitreous/floury mass ratio is a key physical parameter of maize end-uses for the food, feed and non-food sectors, as well as for the resistance of seeds to environmental aggressions. To improve maize breeding for vitreousness, one of the main issues is to finely delineate the molecular and physicochemical mechanisms associated with the formation of endosperm texture. In this context, we use scanning transmission X-ray microscopy at the C K-edge on maize endosperm resin-embedded ultrathin sections. The combination of local near edge X-ray absorption fine structure (NEXAFS) spectroscopy and high-resolution images enable us to achieve a quantitative fine description of the spatial distribution of the main components within the endosperm.

International audience; We introduce an observation chamber dedicated to image, at the nanoscale, the kinetics of reactions taking place at the liquid/solid interface. The assembly of this microfluidic cell is straightforward and, most importantly, its design allow the operator to precisely regulate the hydrodynamic flow and control the concentration in reagents at the observation window.

We report on apparently charged domain walls in MnAs-on-GaAs(0 0 1) layers. For head-on domains, described as two domains facing each other with opposite magnetization, the domain walls of greater than or similar to 200 nm thick films exhibit a zig-zag pattern. Depending on the width of the ferromagnetic stripes, which is a function of temperature and thus the strain in the easy axis direction, the zig-zag angle 20 increases from 90 degrees in the case of wide stripes to 180 degrees (i.e., to a straight wall) for narrow stripes. The underlying domain structure was calculated using a three-dimensional micromagnetic simulator. The calculations reveal a number of distinct domain patterns as a result of the system's attempt to reduce its energy through the formation of closure domain-like patterns in the easy plane. A diamond-like state consisting of two intersecting sub-surface domain walls is the underlying magnetic structure resulting in the observed, apparently charged domain walls. The zig-zag pattern of the domain boundary is explained by stray field minimization of the diamond state along the stripe. (C) 2006 Elsevier B.V. All rights reserved.

The present study focuses on the growth mode and interface reactivity of the prototypical Co/α-Fe2O3(0 0 0 1) ferromagnet/antiferromagnet interface. The knowledge of these properties is essential to improve our understanding of the exchange bias phenomenon. The chemical composition of the interface has been determined by means of X-ray absorption spectroscopy and the morphology of the growing Co film by scanning tunneling microscopy. Our experiments evidence a 3D growth and the presence of a spatially limited reactive interface that spreads to approximately one atomic layer on either side of the interface. This area is chemically composed by a layer of reduced hematite and a layer of oxidized cobalt. In the early stages of growth the interface composition is found to be dependent on the Co coverage and reaches quickly a steady state of fixed composition.

International audience; The manipulation of magnetic domain walls in thin films and nanostructures opens new opportunities for fundamental and applied research. But controlling reliably the position of a moving domain wall still remains challenging. So far, most of the studies aimed at understanding the physics of pinning and depinning processes in the magnetic layer in which the wall moves (active layer). In these studies, the role of other magnetic layers in the stack has been often ignored. Here, we report an indirect localization process of 180° domain walls that occurs in magnetic tunnel junctions, commonly used in spintronics. Combining Scanning Transmission X-Ray Microscopy and micromagnetic simulations, magnetic configurations in both layers are resolved. When nucleating a 180° domain wall in the active layer, a quasi wall is created in the reference layer, atop the wall. The wall and its quasi wall must then be moved or positioned together, as a unique object. As a mutual effect, a localized change of the magnetic properties in the reference layer induces a localized quasi wall in the active layer. The two types of quasi walls are shown to be responsible for an indirect localization process of the 180° domain wall in the active layer.

Mesoscopic ferromagnetic systems are not only of practical interest for high density recording and storage devices but also as models of cooperative phenomena in low dimensions. The magnetization distribution in such systems is studied in this paper by X-ray Magnetic Circular Dichroism Photo Emission Microscopy (XMCDPEEM), using thin rectangular and ring-shaped patterned Co films and by Spin-Polarized Low Energy Electron Microscopy (SPLEEM), using epitaxial Fe nanostructures. Copyright (C) 2006 John Wiley & Sons, Ltd.

Two aspects of low-dimensional magnetism are discussed: the spin-dependent quantization effects in perfect two-dimensional single crystal layers and the magnetic domain structure of submicron magnetic patterns. Both require high lateral resolution and surface sensitivity. This is provided by spin-polarized low energy electron microscopy (SPLEEM) and X-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM).

The spin reorientation transition (SRT) of ultrathin FeCo alloy films on an Au(111) surface and the magnetic/structural phase transition of epitaxial MnAs films on a GaAs(100) surface are studied by two electron microscopic techniques with very high surface sensitivity, i.e. spin-polarized low-energy electron microscopy (SPLEEM) and x-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM), combined with low-energy electron microscopy (LEEM) and low-energy electron diffraction (LEED), respectively. A new SRT mechanism is found and the interrelation between ferromagnetism and structure is elucidated. Copyright © 2005 John Wiley & Sons, Ltd.

The growth mode of iron on Au(0 0 1) surface at room temperature has been studied by means of photoelectron spectroscopy and scanning photoemission microscopy. The analysis of Au4f core level shifts reveals the segregation of gold atoms during the growth, leading for high coverage to the floating of Au surface layer burying Fe thin film and AuFe interfacial alloy. The formation of such segregating layer is coherent with energetic criteria (low gold surface energy, negative interfacial mixing energy, size effect,…). The synergy between these effects may favour the intermixing at the interface and the gold segregation. Photoemission microscopy measurements have been carried out to characterize local morphological and compositional inhomogeneities. The growth proceeds via the segregation of small three-dimensional AuFe gold islands surrounded by a flat Fe/Au region.

The HERMES beamline (High Efficiency and Resolution beamline dedicated to X-ray Microscopy and Electron Spectroscopy), built at Synchrotron SOLEIL (Saint-Auban, France), is dedicated to soft X-ray microscopy. The beamline combines two complementary microscopy methods: XPEEM (X-ray Photo Emitted Electron Microscopy) and STXM (Scanning Transmission X-ray Microscopy) with an aim to reach spatial resolution below 20 nm and to fully exploit the local spectroscopic capabilities of the two microscopes. The availability of the two methods within the same beamline enables the users to select the appropriate approach to study their specific case in terms of sample environment, spectroscopy methods, probing depthetc. In this paper a general description of the beamline and its design are presented. The performance and specifications of the beamline will be reviewed in detail. Moreover, the article is aiming to demonstrate how the beamline performances have been specifically optimized to fulfill the specific requirements of a soft X-ray microscopy beamline in terms of flux, resolution, beam sizeetc. Special attention has been dedicated to overcome some limiting and hindering problems that are usually encountered on soft X-ray beamlines such as carbon contamination, thermal stability and spectral purity.

We report on the Fe doping and on the comparative Ni-Fe codoping with composition close to $\mathrm{NiF}{\mathrm{e}}_{2}$ of fully oxidized $\mathrm{BaTi}{\mathrm{O}}_{3}$ layers (\ensuremath{\sim}20 nm) elaborated by atomic oxygen plasma assisted molecular beam epitaxy; specifically any role of oxygen vacancies can be excluded in our films. Additionally to the classical in situ laboratory tools, the films were thoroughly characterized by synchrotron radiation x-ray diffraction and x-ray absorption spectroscopy. For purely Fe-doped layers, the native tetragonal perovskite structure evolves rapidly toward cubiclike up to 5% doping level above which the crystalline order disappears. On the contrary, low codoping levels $(\ensuremath{\sim}5%\mathrm{NiF}{\mathrm{e}}_{2})$ fairly improve the thin film crystalline structure and surface smoothness; high levels (\ensuremath{\sim}27%) lead to more crystallographically disordered films, although the tetragonal structure is preserved. Synchrotron radiation magnetic dichroic measurements reveal that metal clustering does not occur, that the Fe valence evolves from ${\mathrm{Fe}}^{2+}$ for low Fe doping levels to ${\mathrm{Fe}}^{3+}$ for high doping levels, and that the introduction of Ni favors the occurrence of the ${\mathrm{Fe}}^{2+}$ valence in the films. For the lower codoping levels it seems that ${\mathrm{Fe}}^{2+}$ substitutes ${\mathrm{Ba}}^{2+}$, whereas ${\mathrm{Ni}}^{2+}$ always substitutes ${\mathrm{Ti}}^{4+}$. Ferromagnetic long-range ordering can be excluded with great sensitivity in all samples as deduced from our x-ray magnetic absorption circular dichroic measurements. On the contrary, our linear dichroic x-ray absorption results support antiferromagnetic long-range ordering while piezoforce microscopy gives evidence of a robust ferroelectric long-range ordering showing that our films are excellent candidates for magnetic exchange coupled multiferroic applications.

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

We report the discovery of a nearly-free electronlike resonant state for a ?-Si3N4(0001)-8×8 layer grown on Si(111), as observed by angle-resolved photoemission and scanning tunneling spectroscopy. Comparison with measurements performed on a Si(111)-7×7 surface helped us in the identification of the band. It is found that this parabolic state is degenerate with surface projected bulk bands of the Si(111) substrate.

We present a photoelectron spectroscopy study of three single crystal PtxPd1−x(1 1 1) alloy surfaces (x=0.1, 0.5, 0.9) using synchrotron radiation. The surface and chemical sensitivity of core level photoemission allows us to quantify an oscillatory depth concentration profile and the palladium segregation at the surface of each alloy. The experimental results are compared to theory based on regular solution and tight binding Ising model formalisms, a good agreement is found. In the second part of the paper the effect of CO adsorption on the alloy surfaces is investigated. The variety of adsorption site geometry and chemistry as a function of surface segregation and bulk alloy concentration is revealed in both valence band and core level spectra.

In the present work HCl–propanol treated and vacuum annealed GaAs(1 0 0) surfaces were studied by means of soft X-ray photoemission and reflectance anisotropy spectroscopies (SXPS, RAS). On the as-treated surface, As 3d and Ga 3d core level spectra (CLs) are found to be similar to the ones observed on As-capped GaAs(1 0 0) surfaces after annealing at 350 °C, which desorbs most of the overlayer. RAS measurements of the as-treated surface and after annealing up to 350 °C show spectra similar to those detected on the as-grown surfaces with c(4×4) reconstruction. Anneals in the 380–470 °C temperature range lead to the appearance of a RAS line at 3 eV which is characteristic of As dimers. This finding coincides with the presence of a surface component in the As 3d core level spectrum with a chemical shift of −0.5 eV, which we attribute to As-dimers. Further annealing at 540 °C yields in RAS spectra an intense line at 2.2 eV due to Ga dimers, while the Ga 3d CLs do not exhibit any appreciable change.

High resolution photoemission measurements performed at low temperatures on a single-grained sample of the AlPdMn icosahedral phase show that the density of states N(E) strongly depends on the nature of the surface. For an ordered quasicrystalline surface, prepared by Ar etching and ultra high vacuum annealing, a dip feature is observed in N(E) near the Fermi level, which energy dependence can be analyzed with a simple square-root power law. By contrast, N(E) varies only little with energy both for a disordered surface and a crystalline surface of the same sample. A sharp Fermi edge is then clearly observed. This shows that the metallic character of the surface of a quasicrystal is strongly reduced when the surface presents a quasicrystalline ordering.

We present experiments of photoemission and tunneling spectroscopy which indicate the presence of a dip in the density of states around the Fermi level E F in the icosahedral-Al–Pd–Mn (i-Al–Pd–Mn) phase. From high resolution photoemission experiments on a single grain of i-Al–Pd–Mn, we have got clear evidence that the surface state (quasicrystalline or disordered) strongly affects the measured density of states. For a quasicrystalline surface we observe a pseudo-gap feature at E F . The remaining density of states at E F is compatible with the γ term of specific heat. The band edge shows a square root dependence in the vicinity of E F . This is similar to the single square root anomaly found by tunneling spectroscopy around E F in the range ±300 meV. The photoemission data show a filling of this feature for the disordered surface where a Fermi edge clearly develops.

We used time-resolved pump-probe core level photoemission spectroscopy to study the transient regime of the charge distribution at ${\mathrm{SiO}}_{2}/\mathrm{S}\mathrm{i}$ interfaces after photoexcitation with an UV free electron laser. We found that electrons generated in the Si substrate can accumulate at the surface of the oxide layer, strongly affecting the electric field at the interface. For n-type silicon, this effect can lead to an enhancement of the curvature of the bands, rather than to the expected flattening due to surface photovoltage. The characteristic decay time of this vacuum transient charging at the surface of the oxide layer depends markedly on its thickness; our results indicate that for about 12-\AA{} oxide thickness, it is comparable to the typical excess carrier recombination time in silicon space charge layers.

The structure of cobalt thin films on an Au(111) surface has been studied using x-ray absorption spectroscopy at the cobalt K edge. The polarization dependence of x-ray absorption near-edge spectra and extended x-ray absorption fine structure (EXAFS) spectra evidences a hexagonal stacking for films thicker than 4 ML. For all the thicknesses, the analysis of the first-nearest-neighbor shell shows that this hexagonal structure is very close to that of the Co hcp bulk one: the cobalt does not grow in a coherent epitaxy on the Au(111) surface. This incoherent epitaxy leads to a wide radial distribution of the Co-Au bonds at the interface: this effect and the contribution of Au atoms to the EXAFS signal are discussed. The weak strains inside the Co magnetic thin films allow us to neglect the contribution of the magnetoelastic anisotropy to the perpendicular-magnetic anisotropy existing in this system.

The formation of the Pt/Co(10 1 0) interface has been investigated by AES, XPS, UPS and LEED. We evidence, at room temperature, a quasi-layer-by-layer growth mode with the presence of a slight interdiffusion process at the interface. Through a rather simple kinematical approach of the LEED patterns, we discuss both the in-plane and out-of-plane parameters of the layers. At room temperature, when increasing thicknesses, the long-range order is progressively lost and the epilayer undergoes a structural transition (1×1)→C(2×2)→(1×1). The formation of metastable alloys stabilized in the near surface region has been investigated by AES, XPS, UPS, EELS and LEED for both growth at 600 K and anneals. The growth at 600 K leads to a perfect rotational epitaxy and ends up with a Pt 2 Co alloy layer on top of which pure Pt layers grow. Annealing of room temperature deposited layers improves the structural quality of the layer and in some cases leads to reconstructions enhancing the layer density. In this case interdiffusion needs a 2.5 ML (monolayer) critical thickness. The composition of the alloyed layer is driven by the temperature and not by the annealing time, evidencing the metastable nature of the surface alloys.

Upon deposition of one lead monolayer on the clean, In-terminated InAs(100)4×2/c(8×2) surface, we have obtained a new 1×2/1×4 superstructure and have studied its electronic properties by synchrotron radiation photoelectron spectroscopy (valence bands and In 4d plus Pb 5d core levels). The markedly increased emission in the vicinity of the Fermi level for this reconstruction, as compared to the bare surface, and its narrow localization in k space are the signature of the formation of a strong two-dimensional electron gas in the sub-surface region.

Upon deposition and annealing of one Pb monolayer on the clean, In-terminatedInAs(100)-4 x 2/c(8 x 2) surface we have obtained a sharp1 x 2/1 x 4 superstructure. We have investigated its electronic structure by angle-resolved photoemission using synchrotron radiation. From valence-band spectra measured at normal emission as well as along the¯Γ-¯J and¯Γ-¯J′ directions of the surface Brillouin zone, two surface induced states were identified and mapped out.

The room temperature deposition of Sb on to Cu (111) gives rise to two different Sb states as seen from the Sb 4d shallow core level: an adstate similar to the [Formula: see text] structure formed after annealing at 400°C, and an overlayer of unreacted Sb . The unreacted Sb overlayer is rapidly dissolved into a subsurface position in the crystal during annealing, where it forms a quasistable structure which is dissolved very slowly.

The growth and structure of cobalt on a platinum (111) single crystal is studied using X-ray absorption spectroscopy at the cobalt K-edge. A polarisation dependent analysis of the EXAFS spectra shows first neighbours distances in Co Pt (111) films identical to those in bulk cobalt for thicknesses between 2 and 10 monolayers. The full shell spectra polarisation dependence indicates the hexagonal stacking of the thicker film. Influences of annealing and recovering by platinum on the structure of the cobalt films are also described.

International audience; Graphene quantum dots, nanoribbons, and nanographene are great promising in various applications owing to the quantum confinement and edge effects. Here we evidence the presence of epitaxial nanographene on SiC. Morphology and electronic structure of the graphene layers have been analyzed by SPELEEM. Using Scanning Tunneling Microscopy, we show that the increase of relative number of clusters carbon enabled the observation of nanographene, the diameter of which was around 20 nm. This nanographene shows a honeycomb structure at atomic level. The local chemical and electronic properties of the sample have been determined by photoelectron spectroscopy using synchrotron radiation.

The transport of boronophenylalanine (BPA) and its metabolic fate have been studied in a human uveal melanoma cell line isolated from a primary enucleated tumor. The boronated compound was rapidly incorporated into the cells reaching a peak of incorporation in two hours. This was followed by a trough between 10 and 24 hours and by an increase thereafter. The analogy with the amino acids phenylalanine (Phe) and tyrosine (Tyr) was studied in competition experiments incubating cultures of cell line MK-T, isolated in this laboratory, with [(3)H]-Phe and [(125)I]-Tyr, in the presence or absence of various concentrations of BPA, between 0 and 5 min. The presence of BPA severely reduced the uptake of both amino acids. The kinetics of the transport of [(3)H]-Phe and [(3)H]-Tyr in the presence of BPA, measured after 10 sec of incubation, showed that the boronated compound exerted a competitive inhibition on both transport systems. The intracellular metabolism of BPA was followed by measuring boron concentration (measured with Ionization Coupled Mass Spectrometry) in subcellular fractions and after membrane extraction by the detergent Triton X-100. The results showed that BPA remained in the supernatant and was not metabolized into macromolecules. These results and the relative absence of melanine in these cells, as observed by electron microscopy, suggest that BPA may be actively transported into melanoma cells but not metabolized. The results may have a relevance in studies on Boron Neutron Capture Therapy.

The effect of oxygen adsorption on the local structure and electronic properties of monolayer graphene grown on SiC(0001) has been studied by means of Low Energy Electron Microscopy (LEEM), microprobe Low Energy Electron Diffraction (\muLEED) and microprobe Angle Resolved Photoemission (\muARPES). We show that the buffer layer of epitaxial graphene on SiC(0001) is partially decoupled after oxidation. The monitoring of the oxidation process demonstrates that the oxygen saturates the Si dangling bonds, breaks some Si-C bonds at the interface and intercalates the graphene layer. Accurate control over the oxidation parameters enables us to tune the charge density modulation in the layer., 12 pages, 4 figures

International audience; The current process of growing graphene by thermal decomposition of 3C-SiC(100) on silicon is technologically attractive. Here, we study epitaxial graphene on single domain 3C-SiC films on off-axis Si(100). The structural and electronic properties of such graphene layers are explored by atomic force microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. Using low energy electron diffraction, we show that graphene exhibits single planar domains. Near-edge x-ray absorption fine structure is used to characterize the sample, which confirms that the graphene layers present sp(2) hybridization and are homogeneously parallel to the substrate surface

We report on experimental evidence for the formation of a two dimensional Si/Au(110) surface alloy. In this study, we have used a combination of scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy and ab initio calculations based on density functional theory. A highly ordered and stable Si-Au surface alloy is observed subsequent to growth of a sub-monolayer of silicon on an Au(110) substrate kept above the eutectic temperature.

We have analysed by use of synchrotron radiation induced angle resolved photoemission spectroscopy (PES), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) the growth of ultrathin Co layers deposited at room temperature on Pt(111) surfaces. The LEED patterns indicate an incoherent epitaxy and AES data can be explained by a near layer by layer growth mode. Decomposition of the Pt 4f7/2 photoemission line shows characteristic core level shifts for the different environments of Pt atoms, giving insight concerning a relatively sharp interface structure. On the other hand, the Pt/Co interface in the Pt/Co/Pt(111) sandwich is less sharp, giving rise to two Pt surface sites. Annealing of the Co/Pt(111) system at 400 degrees C gives a surface alloy structure with the same symmetry and orientation as the Pt substrate.

La therapie par capture de neutrons (TCN) ouvre une voie nouvelle pour le traitement de tumeurs considerees aujourd'hui incurables. Le premier objectif est la fixation selective de bore au sein de la tumeur. La technique de neutronographie rapportee permet d'obtenir l'image de'la distribution et le profil de concentration de l'element dans les tissus, ainsi qu'a l'echelle cellulaire

We have observed peculiar magnetization textures in Ni${}_{80}$Pd${}_{20}$ nanostrips using three different imaging techniques: magnetic force microscopy, photoemission electron microscopy under polarized x-ray absorption, and scanning electron microscopy with polarization analysis. The appearance of diamondlike domains with strong lateral charges and of weak-stripe structures reveals the presence of both a transverse and a perpendicular anisotropy in these nanostructures. The anisotropy is seen to reinforce as temperature decreases, as testified by observations performed at 150 K. A thermal stress model with relaxation is proposed to account for these observations. Elastic calculations coupled to micromagnetic simulations support qualitatively this model.

International audience; Graphene ranks highly as a promising material for future nanoelectronic devices because of its exceptional electron-transport properties. It appears as a material of choice for high-frequency applications. We report the growth and structure of epitaxial graphene layers on 3C-SiC(100)/Si(100) wafers using low-energy electron microscopy. Selective-area low-energy electron diffraction highlights the presence of two graphene domains, rotated by ±15◦ with respect to the SiC lattice. Micro-Raman spectroscopy demonstrates the characteristic signature of few layer graphene on the SiC. X-ray photoemission spectroscopy evidences a sharp interface between graphene and 3C-SiC(100). It appears that epitaxial graphene layers obtained on 3C-SiC(100)/Si(100) have properties similar to those obtained using classical 6H or 4H-SiC substrates with the advantage of being compatible with the current Si processing technology

Magnetic frustration effects in artificial kagome arrays of nanomagnets are investigated using x-ray photoemission electron microscopy and Monte Carlo simulations. Spin configurations of demagnetized networks reveal unambiguous signatures of long range, dipolar interaction between the nanomagnets. As soon as the system enters the spin ice manifold, the kagome dipolar spin ice model captures the observed physics, while the short range kagome spin ice model fails., Comment: 4 pages, 4 figures, 1 table

Development of a technological basis for the fabrication of diffraction optical elements has been underway at Synchrotron SOLEIL since April 2009. These diffraction focusing elements are: zone plates and condenser lenses for soft x‐rays (80–2500 eV), focusing zone plates for hard x‐rays (4–24 keV), and diffraction elements working under complete external reflection conditions with elliptical diffraction zones and a topology appropriate to operate at a glancing incidence to fulfill the conditions of total external reflection (energy range 100–1500 eV). This work discusses fabrication of circular germanium‐based zone plates and results of numerical calculations of the behavior of zone plates with real topologies under real experimental conditions. The software used for these calculations allows us to take into account the undercut of zones that occurs after plasmachemical etching as well as variations in the zone heights. Such variations could be used to correct or improve zone plate efficiency after electroplating or plasmachemical etching and can be performed by a focused ion beam etching [1] (direct or with active gas assistance). Data preparation and ion beam control for these corrections can be carried out by Nanomaker software (Interface Ltd).

International audience; Structural and electronic properties of epitaxial graphene on 3C-SiC(111) pseudosubstrate epilayers on silicon was investigated in detail by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), scanning transmission electron microscopy (STEM), and synchrotron angle-resolved photoemission spectroscopy (ARPES). The graphitization process has been observed by distinct features in the atomically resolved STM images and abrupt interface with the number of stacked-graphene layer has been revealed in STEM image. Two different types of carbon atom networks, honeycomb and one sublattice, were atomically resolved by STM. Electronic properties and band structures of the epitaxial graphene are examined with angle-resolved photoemission spectroscopy, showing linear band dispersion K point of the Brillouin zone, with Dirac point about 500 meV below the Fermi level (E-F). These findings are of relevance for various potential applications based on graphene-SiC/Si(111) structures.

Very large average velocities, up to 600 m/s, have been found for domain-wall motion driven by 3-ns-long pulses of electric current in zero magnetic field in the NiFe layer of 200-nm-wide NiFe/Cu/Co nanowires. For longer pulses, the domain-wall motion is strongly hindered by pinning potentials. Dipolar interactions between the NiFe and Co layers caused by anisotropy inhomogeneities have been identified as the most important among the different potential sources of DW pinning. The domain-wall velocities increase with current density, but a substantial drop is observed at current densities above $4\ifmmode\times\else\texttimes\fi{}{10}^{11}\text{ }\text{A}/{\text{m}}^{2}$.

We report a detailed structural characterization of Co films grown on $\ensuremath{\alpha}{\text{-Fe}}_{2}{\text{O}}_{3}(0001)$ for thicknesses up to 25 nm. Epitaxial and single-crystalline 20 nm thick $\ensuremath{\alpha}{\text{-Fe}}_{2}{\text{O}}_{3}(0001)$ layers deposited on $\ensuremath{\alpha}{\text{-Al}}_{2}{\text{O}}_{3}(0001)$ and Pt(111) single crystals were used as substrate. The $\text{Co}/\ensuremath{\alpha}{\text{-Fe}}_{2}{\text{O}}_{3}(0001)$ interface is a prototypical magnetic exchange coupled system for which the magnetocrystalline parameters are crucial to address. We evidence medium range order requiring a multiscale approach to reach a reliable description of the crystalline structure. Surface extended x-ray absorption fine structure (EXAFS) and surface x-ray diffraction (SXRD) have been combined to describe the structure in an extended thickness range. Additional grazing incidence small angle x-ray scattering (GISAXS) measurements show that the growth is three dimensional up to $\ensuremath{\sim}3\phantom{\rule{0.3em}{0ex}}\text{nm}$ and follows a nucleation---growth---coalescence scheme. For all thicknesses cobalt is found to grow with a lattice parameter close to its bulk lattice parameter. In the early stages of growth a disordered 2--3 monolayer thick interface exhibiting oxidized cobalt and metallic iron is evidenced. Long range order sets in for thickness above 4 nm showing the coexistence of fcc, twinned fcc, and hcp stacking within direct and in-surface-plane $30\ifmmode^\circ\else\textdegree\fi{}$ rotated epitaxial relationships.

International audience; We have investigated the micromagnetic structure of magnetic domains in Fe/CoO/Fe trilayer systems and the magnetization coupling between the iron layers. We observe very small magnetic domains separated by nanometer-sized domain walls in the top Fe layer for a narrow CoO thickness range. Such domains have lateral dimensions as low as 30 nm and present topologies which are very similar to those observed in the top layer of Fe/NiO/Fe trilayers. Both magnetic domain structure and Fe interlayer coupling dramatically change with the CoO thickness. The role of magnetocrystalline anisotropy and magnetic frustrations on the observed phenomenology is discussed.

In this article, a comprehensive study of head-to-head domain wall spin structures in Ni80Fe20 and Co nanostructures is presented. Quantitative domain wall type phase diagrams for NiFe and Co are obtained and compared with available theoretical predictions and micromagnetic simulations. Differences to the experiment are explained taking into account thermal excitations. Thermally induced domain wall type transformations are observed from which a vortex core nucleation barrier height is obtained. The stray field of a domain wall is mapped directly with sub-10nm resolution using off-axis electron holography, and the field intensity is found to decrease as 1/r with distance. The magnetic dipolar coupling of domain walls in NiFe and Co elements is studied using X-ray magnetic circular dicroism photoemission electron microscopy. We observe that the spin structures of interacting domain walls change from vortex to transverse walls, when the distance between the walls is reduced. Using the measured stray field values, the energy barrier height distribution for the nucleation of a vortex core is obtained.