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  • 1.
    Avdeev, M. V.
    et al.
    Joint Inst Nucl Res, Frank Lab Neutron Phys, Dubna 141980, Moscow Reg, Russia..
    Petrenko, V. I.
    Joint Inst Nucl Res, Frank Lab Neutron Phys, Dubna 141980, Moscow Reg, Russia.;Kyiv Taras Shevchenko Natl Univ, Kiev, Ukraine..
    Gapon, I. V.
    Joint Inst Nucl Res, Frank Lab Neutron Phys, Dubna 141980, Moscow Reg, Russia.;Kyiv Taras Shevchenko Natl Univ, Kiev, Ukraine..
    Bulavin, L. A.
    Kyiv Taras Shevchenko Natl Univ, Kiev, Ukraine..
    Vorobiev, Alexey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Soltwedel, O.
    Max Planck Inst Solid State Res, Outstn MLZ, Garching, Germany..
    Balasoiu, M.
    Joint Inst Nucl Res, Frank Lab Neutron Phys, Dubna 141980, Moscow Reg, Russia.;Natl Inst Phys & Nucl Engn, Bucharest, Romania..
    Vekas, L.
    Acad Romana, Ctr Fundamental & Adv Tech Res, Timisoara Branch, Timisoara, Romania..
    Zavisova, V.
    SAS, Inst Expt Phys, Kosice, Slovakia..
    Kopcansky, P.
    SAS, Inst Expt Phys, Kosice, Slovakia..
    Comparative structure analysis of magnetic fluids at interface with silicon by neutron reflectometry2015Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 352, s. 49-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption of surfactant coated magnetic nanoparticles from highly stable magnetic fluids on crystalline functionalized silicon is studied by neutron reflectometry. Two types of magnetic fluids based on nanomagnetite dispersed and stabilized in non-polar organic solvent (deuterated benzene) and strongly polar solvent (heavy water) are considered. In both cases the interface shows the formation of just one well-defined adsorption layer of nanoparticles, which is insensitive to the effect of the external magnetic field. Still, the particle concentration in the benzene-based fluid is higher in the vicinity to the silicon surface as compared to the bulk distribution. Despite the presence of an aggregate fraction in the water-based system the width of the adsorption layer is consistent with the size of separated particles, thus showing the preferable adsorption of non-aggregated particles.

  • 2.
    Chakravarty, Sujay
    et al.
    UGC DAE Consortium Sci Res, Kalpakkam Node, Kokilamedu, India..
    Shukla, Neeraj
    UGC DAE Consortium Sci Res, Kalpakkam Node, Kokilamedu, India..
    Devishvili, Anton
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Inst Laue Langevin, Grenoble, France..
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Inst Laue Langevin, Grenoble, France..
    Amarendra, G.
    Indira Gandhi Ctr Atom Res, Mat Sci Div, Kalpakkam, Tamil Nadu, India..
    Simultaneous measurement of volume and grain boundary diffusivity separately in Fe thin film with stable nanostructure using polarized neutron reflectivity2016Inngår i: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 3, nr 8, artikkel-id 085001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polarized neutron reflectivity (PNR) measurements have been used for simultaneous measurement of volume and grain boundary diffusivity separately in stable nanocrystalline Fe thin film at very low homologous temperature (0.2 T-m < T < 0.3 Tm). PNR measurements were done on Si (substrate)/Fe (150 nm)/[Fe-57 (3 nm)/Fe-nat (9 nm)](x10) thin film system with periodic Fe-57 isotope modulation. PNR from as deposited film shows strong Bragg peaks due to neutron scattering length contrast between Fe-57 and Fe-nat layers. Atomic Diffusivity was measured from decrease in the intensity of the Bragg peak due to interdiffusion of Fe-57 and Fe-nat layers after annealing the film at three different temperatures 418 K, 483 K and 548 K, respectively for different time intervals starting from 30 min to several hours. The change in the nanostructure of the film after annealing is characterized using grazing incidence x-ray diffraction. No appreciable grain growth within error bar is observed in the film after annealing indicating that the diffusion measurements were done in stable nanostructure. It is observed that the grain boundary diffusivity is two orders of magnitude higher than the volume diffusivity. However, the mechanism of atomic diffusion is similar in both grain and grain boundary.

  • 3.
    Chen, K.
    et al.
    Helmholtz Zentrum Berlin Mat & Energie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Philippi-Kobs, A.
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany.
    Lauter, V.
    Oak Ridge Natl Lab, Neutron Scattering Div, Neutron Sci Directorate, Oak Ridge, TN 37831 USA.
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Dyadkina, E.
    European Synchrotron Radiat Facil, Swiss Norwegian Beamlines, F-38043 Grenoble, France.
    Yakovchuk, V. Yu.
    Siberian Fed Univ, Krasnoyarsk 660041, Russia.
    Stolyar, S.
    Siberian Fed Univ, Krasnoyarsk 660041, Russia;RAS, SB, Kirensky Inst Phys, Krasnoyarsk 660036, Russia.
    Lott, D.
    Helmholtz Zentrum Geesthacht, Inst Mat Res, Max Planck Str 1, D-21502 Geesthacht, Germany.
    Observation of a Chirality-Induced Exchange-Bias Effect2019Inngår i: Physical Review Applied, E-ISSN 2331-7019, Vol. 12, nr 2, artikkel-id 024047Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chiral magnetism that manifests in the existence of skyrmions or chiral domain walls offers an alternative way for creating anisotropies in magnetic materials that might have large potential for application in future spintronic devices. Here we show experimental evidence for an alternative type of in-plane exchange-bias effect present at room temperature that is created from a chiral 90 degrees domain wall at the interface of a ferrimagnetic-ferromagnetic Dy-Co/Ni-Fe bilayer system. The chiral interfacial domain wall forms due to the exchange coupling of Ni-Fe and Dy-Co at the interface and the presence of Dzyaloshinskii-Moriya interaction in the Dy-Co layer. As a consequence of the preferred chirality of the interfacial domain wall, the sign of the exchange-bias effect can be reversed by changing the perpendicular orientation of the Dy-Co magnetization. The chirality-created tunable exchange bias in Dy-Co/Ni-Fe is very robust against high in-plane magnetic fields (mu H-0 <= 6 T) and does not show any aging effects. Therefore, it overcomes the limitations of conventional exchange-bias systems.

  • 4.
    Iakunkov, Artem
    et al.
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Sun, Jinhua
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Rebrikova, Anastasia
    Moscow MV Lomonosov State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Korobov, Mikhail
    Moscow MV Lomonosov State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Klechikov, Alexey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Boulanger, Nicolas
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Talyzin, Alexandr V.
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Swelling of graphene oxide membranes in alcohols: effects of molecule size and air ageing2019Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, nr 18, s. 11331-11337Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from approximate to 7 angstrom (solvent free) up to approximate to 26 angstrom (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5-1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.

    Fulltekst (pdf)
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  • 5.
    Kan, Zhipeng
    et al.
    Ist Italiano Tecnol, Ctr Nano Sci & Technol PoliMi, Via Giovanni Pascoli 70-3, I-20133 Milan, Italy..
    Colella, Letizia
    Politecn Milan, Dipartimento Chim Mat & Ing Chim G Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy.;Osserv Astron Brera, INAF, Via Bianchi 46, I-23807 Merate, Italy..
    Canesi, Eleonora V.
    Ist Italiano Tecnol, Ctr Nano Sci & Technol PoliMi, Via Giovanni Pascoli 70-3, I-20133 Milan, Italy.;Politecn Milan, Dipartimento Chim Mat & Ing Chim G Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Skrypnychuk, Vasyl
    Umea Univ, Nanoengineered Mat & Organ Elect Lab, Umea, Sweden..
    Terraneo, Giancarlo
    Ist Italiano Tecnol, Ctr Nano Sci & Technol PoliMi, Via Giovanni Pascoli 70-3, I-20133 Milan, Italy.;Politecn Milan, Dipartimento Chim Mat & Ing Chim G Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Barbero, David R.
    Umea Univ, Nanoengineered Mat & Organ Elect Lab, Umea, Sweden..
    Bertarelli, Chiara
    Ist Italiano Tecnol, Ctr Nano Sci & Technol PoliMi, Via Giovanni Pascoli 70-3, I-20133 Milan, Italy.;Politecn Milan, Dipartimento Chim Mat & Ing Chim G Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    MacKenzie, Roderick C. I.
    Univ Nottingham, Fac Engn, Univ Pk, Nottingham NG7 2RD, England..
    Keivanidis, Panagiotis E.
    Cyprus Univ Technol, Dept Mech Engn & Mat Sci & Engn, 45 Kitiou Kyprianou Str, CY-3041 Limassol, Cyprus..
    Charge transport control via polymer polymorph modulation in ternary organic photovoltaic composites2016Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, nr 4, s. 1195-1201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The control on the charge transport properties of ternary organic photovoltaic P3HT : PCBM : QBT devices is enabled by modulating the distribution of P3HT polymorphs in the device photoactive layers. Negligible amounts of QBT induce striking modifications in the P3HT lamellar stacking direction, forming both densely packed and non-densely packed P3HT chains. The former reduce the charge carrier recombination rate, enabling an increased fill factor and short-circuit device photocurrent.

  • 6.
    Klechikov, Alexey
    et al.
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    Sun, Jinhua
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Talyzin, Alexandr V.
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    Swelling of Thin Graphene Oxide Films Studied by in Situ Neutron Reflectivity2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 24, s. 13106-13116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Permeation of multilayered graphene oxide (GO) membranes by polar solvents is known to correlate with their swelling properties and amount of sorbed solvent. However, quantitative estimation of sorption using standard (e.g., gravimetric) methods is technically challenging for few nanometers thick GO membranes/films exposed to solvent vapors. Neutron reflectivity (NR) was used here to evaluate the amount of solvents intercalated into the film which consists of only similar to 31.5 layers of GO. Analysis of NR data recorded from the GO film exposed to vapors of polar solvents provides information about change of film thickness due to swelling, amount of intercalated solvent, and selectivity in sorption of solvents from binary mixtures. A quantitative study of GO film sorption was performed for D2O, d-methanol, ethanol, dimethyl sulfoxide (DMSO), acetonitrile, dimethylformamide (DMF), and acetone. Using isotopic contrast, we estimated selectivity in sorption of ethanol/d-methanol mixtures by the GO film. Estimation of sorption selectivity was also performed for D2O/DMF, D2O/DMSO, and D2O/acetonitrile binary mixtures. Sorption of polar solvents was compared for the thin GO film, micrometer thick free standing GO membranes, and graphite oxide powders.

  • 7.
    Pilkington, Georgia A.
    et al.
    KTH Royal Inst Technol, Dept Chem, Surface & Corros Sci, Stockholm, Sweden.
    Harris, Kathryn
    KTH Royal Inst Technol, Dept Machine Design, Syst & Component Design, Stockholm, Sweden.
    Bergendal, Erik
    KTH Royal Inst Technol, Dept Chem, Surface & Corros Sci, Stockholm, Sweden.
    Reddy, Akepati Bhaskar
    KTH Royal Inst Technol, Dept Machine Design, Syst & Component Design, Stockholm, Sweden.
    Pálsson, Gunnar K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Antzutkin, Oleg. N.
    Lulea Univ Technol, Chem Interfaces, Lulea, Sweden.
    Glavatskih, Sergei
    KTH Royal Inst Technol, Dept Machine Design, Syst & Component Design, Stockholm, Sweden;Univ Ghent, Dept Elect Energy Syst & Automat, Ghent, Belgium.
    Rutland, Mark W.
    KTH Royal Inst Technol, Dept Chem, Surface & Corros Sci, Stockholm, Sweden;RISE Res Inst Sweden, Surfaces Proc & Formulat, Stockholm, Sweden.
    Electro-responsivity of ionic liquid boundary layers in a polar solvent revealed by neutron reflectance2018Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, nr 19, artikkel-id 193806Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using neutron reflectivity, the electro-responsive structuring of the non-halogenated ionic liquid (IL) trihexyl(tetradecyl)phosphonium-bis(mandelato)borate, [ P-6,P-6,P-6,P-14][BMB], has been studied at a gold electrode surface in a polar solvent. For a 20% w/w IL mixture, contrast matched to the gold surface, distinct Kiessig fringes were observed for all potentials studied, indicative of a boundary layer of different composition to that of the bulk IL-solvent mixture. With applied potential, the amplitudes of the fringes from the gold-boundary layer interface varied systematically. These changes are attributable to the differing ratios of cations and anions in the boundary layer, leading to a greater or diminished contrast with the gold electrode, depending on the individual ion scattering length densities. Such electro-responsive changes were also evident in the reflectivities measured for the pure IL and a less concentrated (5% w/w) IL-solvent mixture at the same applied potentials, but gave rise to less pronounced changes. These measurements, therefore, demonstrate the enhanced sensitivity achieved by contrast matching the bulk solution and that the structure of the IL boundary layers formed in mixtures is strongly influenced by the bulk concentration. Together these results represent an important step in characterising IL boundary layers in IL-solvent mixtures and provide clear evidence of electro-responsive structuring of IL ions in their solutions with applied potential.

  • 8. Qviller, A. J.
    et al.
    Dennison, A. J. C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Haug, H.
    You, C. C.
    Hasle, I. M.
    Ostreng, E.
    Fjellvag, H.
    Vorobiev, Alexey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Hjörvarsson, Björgvin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Marstein, E. S.
    Frommen, C.
    Hauback, B. C.
    Thermal stability of photovoltaic a-Si:H determined by neutron reflectometry2014Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, nr 23, s. 231909-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutron and X-ray reflectometry were used to determine the layer structure and hydrogen content of thin films of amorphous silicon (a-Si:H) deposited onto crystalline silicon (Si) wafers for surface passivation in solar cells. The combination of these two reflectometry techniques is well suited for non-destructive probing of the structure of a-Si:H due to being able to probe buried interfaces and having sub-nanometer resolution. Neutron reflectometry is also unique in its ability to allow determination of density gradients of light elements such as hydrogen (H). The neutron scattering contrast between Si and H is strong, making it possible to determine the H concentration in the deposited a-Si:H. In order to correlate the surface passivation properties supplied by the a-Si:H thin films, as quantified by obtainable effective minority carrier lifetime, photoconductance measurements were also performed. It is shown that the minority carrier lifetime falls sharply when H has been desorbed from a-Si:H by annealing. (C) 2014 AIP Publishing LLC.

  • 9.
    Suturin, S. M.
    et al.
    Ioffe Inst, 26 Polytech Skaya St, St Petersburg 194021, Russia.
    Korovin, A. M.
    Ioffe Inst, 26 Polytech Skaya St, St Petersburg 194021, Russia.
    Bursian, V. E.
    Ioffe Inst, 26 Polytech Skaya St, St Petersburg 194021, Russia.
    Lutsev, L. , V
    Bourobina, V
    Ioffe Inst, 26 Polytech Skaya St, St Petersburg 194021, Russia.
    Yakovlev, N. L.
    ASTAR, Inst Mat Res & Engn, Singapore 138634, Singapore.
    Montecchi, M.
    E Ferrari Univ Modena & Reggio Emilia, Engn Dept, Via Vigolese 905, I-41125 Modena, Italy.
    Pasquali, L.
    E Ferrari Univ Modena & Reggio Emilia, Engn Dept, Via Vigolese 905, I-41125 Modena, Italy;IOM CNR Inst, Area Sci Pk,Str Statale 14,Km 163-5, I-34149 Trieste, Italy;Univ Johannesburg, Dept Phys, POB 524, ZA-2006 Auckland Pk, South Africa.
    Ukleev, V
    Paul Scherrer Inst, Lab Neutron Scattering & Imaging LNS, CH-5232 Villigen, Switzerland.
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Devishvili, A.
    Lund Univ, Dept Phys Chem, Box 124, SE-22100 Lund, Sweden.
    Sokolov, N. S.
    Ioffe Inst, 26 Polytech Skaya St, St Petersburg 194021, Russia.
    Role of gallium diffusion in the formation of a magnetically dead layer at the Y3Fe5O12/Gd3Ga5O12 epitaxial interface2018Inngår i: PHYSICAL REVIEW MATERIALS, E-ISSN 2475-9953, Vol. 2, nr 10, artikkel-id 104404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have clarified the origin of a magnetically dead interface layer formed in yttrium iron garnet (YIG) films grown at above 700 degrees C onto a gadolinium gallium garnet (GGG) substrate by means of laser molecular beam epitaxy. The diffusion-assisted formation of a Ga-rich region at the YIG/GGG interface is demonstrated by means of composition depth profiling performed by x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and x-ray and neutron reflectometry. Our finding is in sharp contrast to the earlier expressed assumption that Gd acts as a migrant element in the YIG/GGG system. We further correlate the presence of a Ga-rich transition layer with considerable quenching of ferromagnetic resonance and spin wave propagation in thin YIG films. Finally, we clarify the origin of the enigmatic low-density overlayer that is often observed in neutron and x-ray reflectometry studies of the YIG/GGG epitaxial system.

  • 10.
    Tarnavich, V.
    et al.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia..
    Tartakovskaya, E.
    Natl Acad Sci Ukraine, Inst Magnetism, UA-03142 Kiev, Ukraine.;Kiev Natl Univ, Inst High Technol, Glushkovaave 4-G, UA-03022 Kiev, Ukraine..
    Chetverikov, Yu.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia..
    Golub, V.
    Natl Acad Sci Ukraine, Inst Magnetism, UA-03142 Kiev, Ukraine..
    Lott, D.
    Helmholtz ZentrumGeesthacht, D-21502 Geesthacht, Germany..
    Chernenkov, Yu.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia..
    Devishvili, Anton
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Ukleev, V.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia.;RIKEN, Ctr Emergent Matter Sci, Wako, Saitama 3510198, Japan..
    Kapaklis, Vassilios
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Oleshkevych, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Fedorov, V.
    St Petersburg Acad Univ, St Petersburg 194021, Russia..
    Bairamukov, V.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia..
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Grigoriev, S.
    Natl Res Ctr, Kurchatov Inst, Petersburg Nucl Phys Inst, Gatchina 188300, Russia.;St Petersburg State Univ, St Petersburg 198504, Russia..
    Magnetic field induced chirality in Ho/Y multilayers with gradually decreasing anisotropy2017Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, nr 1, artikkel-id 014415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal rare-earth magnetic/nonmagnetic Ho/Y superlattice structures possess a coherent spin helix propagating through many superlattice layer repetitions. An externalmagnetic field applied in the film plane induces a nonzero average chirality of the helices. It is shown that the direction of the applied in-plane field can modify the value and sign of the chirality parameter.. The dependence of. on the relative angle of applied field during the field`-cooling procedure has an oscillatory character and can be described by simple sinusoidal function with p periodicity. The experimental finding is discussed from the point of view of an interbalance between Zeeman energy, magnetocrystalline anisotropy, and induced uniaxial anisotropy.

  • 11. Theis-Broehl, Katharina
    et al.
    Gutfreund, Philipp
    Vorobiev, Alexey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Wolff, Max
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Toperverg, Boris P.
    Dura, Joseph A.
    Borchers, Julie A.
    Self assembly of magnetic nanoparticles at silicon surfaces2015Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, nr 23, s. 4695-4704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutron reflectometry was used to study the assembly of magnetite nanoparticles in a water-based ferrofluid close to a silicon surface. Under three conditions, static, under shear and with a magnetic field, the depth profile is extracted. The particles have an average diameter of 11 nm and a volume density of 5% in a D2O-H2O mixture. They are surrounded by a 4 nm thick bilayer of carboxylic acid for steric repulsion. The reflectivity data were fitted to a model using a least square routine based on the Parratt formalism. From the scattering length density depth profiles the following behavior is concluded: the fits indicate that excess carboxylic acid covers the silicon surface and almost eliminates the water in the densely packed wetting layer that forms close to the silicon surface. Under constant shear the wetting layer persists but a depletion layer forms between the wetting layer and the moving ferrofluid. Once the flow is stopped, the wetting layer becomes more pronounced with dense packing and is accompanied by a looser packed second layer. In the case of an applied magnetic field the prolate particles experience a torque and align with their long axes along the silicon surface which leads to a higher particle density.

  • 12.
    Ukleev, V.
    et al.
    BP Konstantinov Petersburg Nucl Phys Inst, Natl Res Ctr, Kurchatov Inst, Gatchina 188300, Russia.;Russian Acad Sci, St Petersburg Acad Univ Nanotechnol Res & Educ, St Petersburg 194021, Russia..
    Dyadkina, E.
    BP Konstantinov Petersburg Nucl Phys Inst, Natl Res Ctr, Kurchatov Inst, Gatchina 188300, Russia..
    Vorobiev, Alexey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Gerashchenko, O. V.
    BP Konstantinov Petersburg Nucl Phys Inst, Natl Res Ctr, Kurchatov Inst, Gatchina 188300, Russia..
    Caron, L.
    Delft Univ Technol, NL-2628 CN Delft, Netherlands.;Max Planck Inst Chem Phys Solids, D-01187 Dresden, Germany..
    Sitnikov, A. V.
    Voronezh State Tech Univ, Voronezh 394026, Russia..
    Kalinin, Yu. E.
    Voronezh State Tech Univ, Voronezh 394026, Russia..
    Grigoriev, S. V.
    BP Konstantinov Petersburg Nucl Phys Inst, Natl Res Ctr, Kurchatov Inst, Gatchina 188300, Russia.;St Petersburg State Univ, St Petersburg 198904, Russia..
    Morphology and magnetic properties of nanocomposite magnetic multilayers [(Co(4)oFe(40)B(2)O)(34)(SiO2)(66)]/[C](47)2016Inngår i: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 432, s. 499-504Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the investigation of morphology, magnetic and conductive properties of the mutilayered nanostructures [(Co40Fe40B20)(34)(SiO2)(66)]/[C](47) consisting of the contacting magnetic (Co Fe-40 (40) B (20)) (34)(SiO2)(66) nanocomposite and amorphous semiconductor carbon C layers. It is shown by Grazing-Incidence Small-Angle X-ray Scattering method that the ordering and the size of nanoparticles in the magnetic layers do not change profoundly with increasing of carbon layer thickness. Meanwhile, the electrical conductance and the magnetic properties are significantly varied: resistance of the samples changes by four orders of magnitude and superparamagnetic blocking temperature changes from 15 K to 7 K with the increment of carbon layer thickness h(c) from 0.4 nm to 1.8 nm. We assume that the formation of the homogeneous semiconductor interlayer leads to modification of the metal-insulator growth process that drives the changes in the magnetic and conductive properties.

  • 13.
    Ukleev, V.
    et al.
    BP Konstantinov Petersburg Nucl Phys Inst, Kurchatov Inst, Natl Res Ctr, Gatchina 188300, Russia.;RIKEN, Ctr Emergent Matter Sci, Wako, Saitama 3510198, Japan..
    Khassanov, A.
    Friedrich Alexander Univ Erlangen Nurnberg, Dept Mat Sci, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Snigireva, I.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Konovalov, O.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Dudnik, M.
    BP Konstantinov Petersburg Nucl Phys Inst, Kurchatov Inst, Natl Res Ctr, Gatchina 188300, Russia..
    Dubitskiy, I.
    BP Konstantinov Petersburg Nucl Phys Inst, Kurchatov Inst, Natl Res Ctr, Gatchina 188300, Russia..
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France.
    Self-assembly of a binary mixture of iron oxide nanoparticles in Langmuir film: X-ray scattering study2017Inngår i: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 202, s. 31-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In present study we exploited Langmuir technique to produce self-assembled arrays composed of monodisperse iron oxide nanoparticles 10 nm and 20 nm in diameter and of their binary mixture. A combination of in-situ X-ray reflectometry and Grazing-incident small-Angle X-ray scattering was used to obtain in-plane and out-of-plane structure of the arrays directly on the water surface. Surface pressure isotherms and X-ray reflectometry analysis showed that monodisperse 10 nm nanoparticles form a highly ordered monolayer, while 20 nm particles pack in three-dimensional clusters with a short-range (nearest-neighbor) correlations between the particles. In a binary mixture of 10 nm and 20 nm nano particles composed in proportion 3:1 the self-assembly process results in a structure where the monolayer of 10 nm particles is perturbed by the larger particles. Non-trivial mixing causes an enlargement of interparticle distance but keeps the symmetry of two-dimensional lattice of smaller nanoparticles. Estimation of the acting interactions and micromagnetic simulation suggest the optimal formation for monodisperse and binary ensembles.

  • 14.
    Ukleev, V.
    et al.
    Natl Res Ctr Kurchatov Inst, BP Konstantinov Petersburg Nucl Phys Inst, Gatchina 188300, Russia..
    Khassanov, A.
    Friedrich Alexander Univ Erlangen Nurnberg, Dept Mat Sci, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Snigireva, I.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Konovalov, O.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Vorobiev, Alexey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    X-ray scattering characterization of iron oxide nanoparticles Langmuir film on water surface and on a solid substrate2016Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 616, s. 43-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study we compare a structure of a Langmuir film assembled from magnetic iron oxide nanoparticles on water surface and a structure of the same film after its transfer to a solid substrate by the Langmuir-Schaefer method. In contrast to most of related studies, where different techniques are used to characterize the films before and after the deposition, we use the same combination of X-ray reflectometry and Grazing Incidence Small-Angle X-ray scattering. In both cases - on a liquid and on a solid substrate - the film was identified as a well-ordered monolayer of the nanoparticles laterally organized in a two-dimensional hexagonal lattice. However parameters of the lattice were found to be slightly different depending on the type of the substrate. It is also demonstrated that Langmuir-Schaefer technique is the right way for deposition of such kind of the particles on a solid substrate.

  • 15.
    Ukleev, V.
    et al.
    Natl Res Ctr, Kurchatov Inst, BP Konstantinov Petersburg Nucl Phys Inst, Gatchina 188300, Russia.;RIKEN Ctr Emergent Matter Sci CEMS, Wako, Saitama 3510198, Japan..
    Snigireva, I.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Vorobiev, Alexei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France.
    Polarized neutron reflectometry study from iron oxide nanoparticles monolayer2017Inngår i: SURFACES AND INTERFACES, ISSN 2468-0230, Vol. 9, s. 143-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the polarized neutron reflectometry investigation of monolayer of magnetic iron oxide nanoparticles assembled by the Langmuir-Schaefer method. After deposition onto a solid substrate the polarized neutron reflectometry measurements in the external magnetic field were carried out. Thickness, density, roughness and in-depth resolved magnetization profile of the resulted layer were obtained from accurate fitting routine.

  • 16.
    Vorobiev, Alexei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Dennison, Andrew
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Chernyshov, Dmitry
    Skrypnychuk, Vasyl
    Barbero, David
    Talyzin, Alexandr V.
    Graphene oxide hydration and solvation: an in situ neutron reflectivity study2014Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, nr 20, s. 12151-12156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphene oxide membranes were recently suggested for applications in separation of ethanol from water using a vapor permeation method. Using isotope contrast, neutron reflectivity was applied to evaluate the amounts of solvents intercalated into a membrane from pure and binary vapors and to evaluate the selectivity of the membrane permeation. Particularly, the effect of D2O, ethanol and D2O-ethanol vapours on graphene oxide (GO) thin films (similar to 25 nm) was studied. The interlayer spacing of GO and the amount of intercalated solvents were evaluated simultaneously as a function of vapour exposure duration. The significant difference in neutron scattering length density between D2O and ethanol allows distinguishing insertion of each component of the binary mixture into the GO structure. The amount of intercalated solvent at saturation corresponds to 1.4 molecules per formula unit for pure D2O (similar to 1.4 monolayers) and 0.45 molecules per formula unit (one monolayer) for pure ethanol. This amount is in addition to H2O absorbed at ambient humidity. Exposure of the GO film to ethanol-D2O vapours results in intercalation of GO with both solvents even for high ethanol concentration. A mixed D2O-ethanol layer inserted into the GO structure is water enriched compared to the composition of vapours due to slower ethanol diffusion into GO interlayers.

  • 17.
    Vorobiev, Alexey
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. European Synchrotron Radiat Facil, F-38043 Grenoble 9, France..
    Khassanov, A.
    European Synchrotron Radiat Facil, F-38043 Grenoble 9, France.;Univ Erlangen Nurnberg, Organ Mat & Devices, D-91058 Erlangen, Germany..
    Ukleev, V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik. Petersburg Nucl Phys Inst, St Petersburg 188300, Russia..
    Snigireva, I.
    European Synchrotron Radiat Facil, F-38043 Grenoble 9, France..
    Konovalov, O.
    European Synchrotron Radiat Facil, F-38043 Grenoble 9, France..
    Substantial Difference in Ordering of 10, 15, and 20 nm Iron Oxide Nanoparticles on a Water Surface: In Situ Characterization by the Grazing Incidence X-ray Scattering2015Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 42, s. 11639-11648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, for the first time, a unique combination of in situ grazing incidence small-angle X-ray scattering and X-ray reflectivity, accompanied by the pressure area isotherm analysis, Brewster angle microscopy, and ex situ scanning electron microscopy, was applied for investigation of two-dimensional superlattices of magnetic nanoparticles as they form on a water surface in a Langmuir trough. Iron oxide particles of different sizes stabilized with a single layer of oleic acid were used. It is demonstrated that monodisperse 10 nm particles on a water surface reproducibly form identical highly ordered monolayers in a wide range of experimental conditions, while monodisperse 20 nm particles always form compact three-dimensional clusters and never the monolayers. Monodisperse particles of an intermediate size, 15 um in diameter, build a metastable monolayer, which shows a tendency for spontaneous transformation to bi-, tri-, and multilayer islands. The importance to use both grazing incidence small-angle X-ray scattering and X-ray reflectivity together with the complementary techniques, to avoid misinterpretation of separate experimental data sets, is underlined.

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