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  • 1. Ahniyaz, Anwar
    et al.
    Seisenbaeva, Gulam A.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Kamali, Saeed
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Kessler, Vadim G.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Johansson, Christer
    Bergström, Lennart
    Preparation of iron oxide nanocrystals by surfactant-free or oleic acid-assisted thermal decomposition of a Fe(III) alkoxide2008In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 320, no 6, p. 781-787Article in journal (Refereed)
    Abstract [en]

    A new non-hydrolytic, alkoxide-based route was developed to synthesize iron oxide nanocrystals. Surfactant-free thermal decomposition of the iron 2-methoxy-ethoxide precursors results in the formation of uniform iron oxide nanocrystals with an average size of 5.6 nm. Transmission electron microscope study shows that the nanocrystals are protected against aggregation by a repulsive surface layer, probably originating from the alkoxy-alkoxide ligands. Addition of oleic acid resulted in monodisperse nanocrystals with an average size of 4 nm. Mössbauer analysis confirmed that the nanocrystals mainly consisted of maghemite. Analysis of the magnetic hysteresis loop measurements and the zero field and field cooled measurements displayed an excellent fit to established theories for single-domain superparamagnetic nanocrystals and the size of the magnetic domains correlated well to the crystallite size obtained from transmission electron microscope.

  • 2.
    Andersson, Gabriella
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Effects of strain on magnetic anisotropy in Fe and Co based heterostructures2008In: Phase Transitions, ISSN 0141-1594, E-ISSN 1029-0338, Vol. 81, no 7 & 8, p. 679-701Article in journal (Refereed)
    Abstract [en]

    The magnetic ordering in transition metals is strongly affected by any strain in the lattice, due to the close connection between strain and anisotropy. This article reviews recent developments, both experimental and theoretical, in the field of strain-induced magnetic anisotropies, with focus on films and multilayers based on Fe and Co. It is demonstrated that the reorientation of preferred magnetization directions can be controlled through both the growth direction and the strain state, which is caused by interleaving with suitable spacers, as well as by tuning the chemical composition if the magnetic material is an alloy. Both in-plane and out-of-plane easy directions can be forced upon the films and superlattices in this manner. Some methods for local structural manipulation are also reviewed.

  • 3. Andreeva, M. A.
    et al.
    Monina, N.G.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Lindgren, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Kalska, B.
    Kamali, M
    Vdovichev, S. N
    Salashchenko, N. N.
    Semenov, V. G
    Leupold, O
    Rüffer, R
    Nuclear resonant reflectivity with standing waves for the investigation of a thin 57Fe layer buried inside a superconducting Si/[Mo/Si]45/57Fe/Nb multilayer2008In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 266, no 1, p. 187-196Article in journal (Refereed)
    Abstract [en]

    A special multilayer sample Si/[Mo/Si]45/57Fe/Nb has been prepared for the depth selective investigations of the hyperfine fields in thin iron layer at low temperatures above and below the superconducting transition in the top Nb layer (Tc 8 K) by means of the nuclear resonant reflectivity with standing waves. The periodic multilayer [Mo/Si]45 below the iron layer in our sample was used as “a standing wave generator”. A weak magnetic hyperfine splitting in the 57Fe layer was detected just at low temperature. A slight variation of the nuclear resonant reflectivity time spectra measured above and below Tc was observed. At first it was supposed that this change of the spectrum shape is caused by the spatial modulation of ferromagnetic domains in the 57Fe layer caused by a proximity effect. A closer analysis, however, reveals that the spectrum variations are due to just the changes of the relative weights of the magnetic and paramagnetic phases in 57Fe layer.

  • 4. Cardenas, M.
    et al.
    Arnebrant, T.
    Rennie, Adrian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Fragneto, G.
    Thomas, R. K.
    Lindh, L.
    Human Saliva Forms a Complex Film Structure on Alumina Surfaces2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 1, p. 65-69Article in journal (Refereed)
    Abstract [en]

    Films formed from saliva on surfaces are important for the maintenance of oral health and integrity by protection against chemical and/or biological agents. The aim of the present study was to investigate adsorbed amounts, thickness, and structure of films formed from human whole saliva on alumina surfaces by means of in situ ellipsometry, neutron reflectivity, and atomic force microscopy. Alumina (Al2O3, synthetic sapphire) is a relevant and interesting substrate for saliva adsorption studies as it has an isoelectric point close to that of tooth enamel. The results showed that saliva adsorbs rapidly on alumina. The film could be modeled in two layers:  an inner and dense thin region that forms a uniform layer and an outer, more diffuse and thicker region that protrudes toward the bulk of the solution. The film morphology described a uniformly covering dense layer and a second outer layer containing polydisperse adsorbed macromolecules or aggregates.

  • 5. Fraerman, A. A.
    et al.
    Gribkov, B. A.
    Gusev, S. A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Artificial helix nanomagnets2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 103, p. 073916-Article in journal (Refereed)
  • 6.
    Granroth, Sari
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Marcellini, Moreno
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Gorgoi, Mihaela
    Schäfers, Franz
    Braun, Walter
    Eberhardt, Wolfgang
    Olovsson, Weine
    Holmström, Erik
    Mårtensson, Nils
    Investigation of interface properties of Ni/Cu multilayers by high kinetic energy photoelectron spectroscopy2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 9, article id 094104Article in journal (Refereed)
    Abstract [en]

    High kinetic-energy photoelectron spectroscopy (HIKE) or hard x-ray   photoelectron spectroscopy has been used to investigate the alloying of   Ni/Cu (100) multilayers. Relative intensities of the corelevels and   their chemical shifts derived from binding energy changes are shown to   give precise information on physicochemical properties and quality of   the buried layers. Interface roughening, including kinetic properties   such as the rate of alloying, and temperature effects on the processes   can be analyzed quantitatively. Using HIKE, we have been able to   precisely follow the deterioration of the multilayer structure at the   atomic scale and observe the diffusion of the capping layer into the   multilayer structure which in turn is found to lead to a segregation in   the ternary system. This is of great importance for future research on   multilayered systems of this kind. Our experimental data are   supplemented by first-principles theoretical calculations of the   core-level shifts for a ternary alloy to allow for modeling of the   influence of capping materials on the chemical shifts.

  • 7.
    Hartman, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Karlsson, Erik B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Chatzidimitriou-Dreismann, C. A.
    Neutron Compton scattering anomaly verified with Rh-resonance foil2008In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 10, p. 104248-Article in journal (Refereed)
    Abstract [en]

    Compton scattering experiments with neutrons usually employ Au- or U-foils for energy selection of the scattered neutrons. A series of experiments on various H-containing materials have shown a large deficit in the scattering intensity of protons using Au-foils and it has been claimed that the anomalies arise from a faulty analysis of the data by neglecting effects of the tails of the Au- resonance lines. In the present experiments a Rh-103 resonance foil is used. It has considerably different resonance characteristics, but the H/metal ratio derived shows nearly the same anomalous value as with Au- foils. The present result therefore supports the existence of the mentioned anomalies.

  • 8.
    Hase, Thomas
    et al.
    Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom.
    Raanaei, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Lidbaum, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Sanchez-Hanke, Cecilia
    National Synchrotron Light source, Brookhaven national laboratory, Upton, New York 11973 USA.
    Wilkins, Stuart
    Department of CMPMSD, Brookhaven national laboratory, Upton, New York 11973 USA.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Spin and orbital moment in amorphous Co68Fe24Zr8 layers2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 13, p. 134402-Article in journal (Refereed)
    Abstract [en]

    The ratio of the orbital to the spin magnetic moment was determined for both Fe and Co in amorphous Co68 Fe24 Zr8 layers using x-ray circular dichroism. The investigations were performed on both thick Co68 Fe24 Zr8 layers as well as on amorphous Co68 Fe24 Zr8 / Al70 Zr30 multilayers grown by dc sputtering. Structural characterization was performed using x-ray reflectometry, x-ray diffraction, and transmission electron microscopy. X-ray circular dichroism, x-ray magnetic scattering as well as the magneto-optic Kerr effect were used to characterize the magnetic properties of the amorphous materials. The ratio of the orbital to spin moments in the single CoFeZr-layer sample was 0.012±0.005 for Fe and 0.078±0.005 for Co. Substantial reduction in the the ratio of the orbital to spin moments was observed with decreasing CoFeZr-layer thickness.

  • 9. Hellwig, M. Ay. O
    et al.
    Becker, H. W.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Zabel, H.
    Oxidation of epitaxial Y(0001) films2008In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 254, no 10, p. 3184-3190Article in journal (Refereed)
    Abstract [en]

    We have investigated the oxidation behavior of MBE grown epitaxial Y(0 0 0 1)/Nb(1 1 0) films on sapphire (11 (2) over bar0) substrates at elevated temperatures under atmospheric conditions with a combination of experimental methods. At room temperature X-ray diffraction (XRD) reveals the formation of a 25 A thick YOxHx layer at the surface, while simultaneously oxide growth proceeds along defect lines normal to the film plane, resulting in the formation of a single crystalline cubic Y2O3 (2 2 2) phase. Furthermore, nuclear resonance analysis (NRA) reveals that hydrogen penetrates into the sample and transforms the entire Y film into the hydride YH2 phase. Additional annealing in air leads to further oxidation radially out from the already existing oxide channels. Finally material transport during oxidation results in the formation of conically shaped oxide precipitations at the surface above the oxide channels as observed by atomic force microscopy (AFM).

  • 10.
    Hjörvarsson, Björgvin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Dura, J. A.
    Udovic, P.
    Isberg, P.
    Majkrzak, C. F.
    Temperature dependence of the magnetic interlayer ordering in Fe(3)/V(14)Hx (001) superlattices2008In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 43, no 2, p. 101-111Article in journal (Refereed)
    Abstract [en]

    The magnetic interlayer ordering in Fe(3)/V (14)Hx (001) superlattices exhibits dramatic changes on changing the hydrogen concentration. From initial antiferromagnetic (AF) coupling with , the introduction of H (H/V atomic ratio of 0.06) gives rise to ferromagnetic (FM) alignment at room temperature. When cooled, the magnetic ordering exhibits a transition from FM to a canted state below 200 K. Further increase of the hydrogen content (H/V ≈1) gives rise to FM-ordering at temperatures between 30 and 300 K.

  • 11. Hjörvarsson, Björgvin
    et al.
    Marcellini, Moreno
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Ahlberg, Martina
    Wolff, Maximilian
    The effect of boundaries on ordering in finite magnetsIn: Physical Review LettersArticle in journal (Refereed)
  • 12.
    Hjörvarsson, Björgvin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Pentcheva, R.
    Modern growth problems and growth techniques2008In: Magnetic Heterostructures, Advances and Perspectives in Spinstructures and Spintransport, Berlin: Springer , 2008, p. 1-44Chapter in book (Other academic)
  • 13.
    Häggström, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Kamali, Saeed
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ahniyaz, Anwar
    Bergström, L.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Mössbauer and magnetisation studies of iron oxide  nanocrystals2008In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 183, no 1-3, p. 49-53Article in journal (Refereed)
    Abstract [en]

    Monodisperse iron oxide nanocrystals have been produced following non-hydrolytic, thermal decomposition routes. Spherically shaped particles with diameter of 4 and 12 nm and cubic shaped particles with an edge length of 9 nm have been studied. The particles have been shown to consist of mainly maghemite. A reduction of the saturation magnetic hyperfine field is observed for the 4 nm particles as compared to the corresponding bulk value. The anisotropy energy determined from the temperature variation of the magnetic hyperfine field was strongly enhanced for the 4 nm particles.

  • 14.
    Ivanov, Sergey A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tellgren, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Rundlöf, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Structural, magnetic and Mössbauer spectroscopic investigations of the magnetoelectric relaxor Pb(Fe0.6W0.2Nb0.2)O32007In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 9, no 5, p. 440-450Article in journal (Refereed)
    Abstract [en]

    The complex perovskite lead iron tungsten niobium oxide, Pb(Fe0.6W0.2Nb0.2)O3 (PFWN) which belongs to the class of disordered magnetoelectrics, has been studied by X-ray and neutron powder diffraction, magnetic and Mössbauer spectroscopic measurements. Structural, dielectric and magnetic properties of PFWN are presented and reviewed. Magnetic measurements indicate that the most important interactions are of antiferromagnetic nature yielding TN = 300 K, however, with indications of a reentrant spin glass behaviour below 20 K. The parameters of Mössbauer spectra also support the existence of the magnetic order and are consistent with the presence of high-spin Fe3+ cations located in the octahedral B-site. Rietveld refinements of diffraction data at different temperatures between 10 and 700 K have been carried out. The long-range structure of PFWN is cubic (space group Pm−3m) over the whole temperature interval. The Fe, W and Nb cations were found to be disordered over the perovskite B-sites. The Pb cations show a position disorder along the 111 direction shifting from their high-symmetry position. At the temperatures below TN, an antiferromagnetic arrangement of the magnetic moments of Fe3+ cations in the B-site is proposed in accordance with the antiferromagnetic properties of PFWN. The factors governing the observed nuclear and magnetic structures of PFWN are discussed and compared with those of pure Pb(Fe0.67W0.33)O3, Pb(Fe0.5Nb0.5)O3 and other quaternary Pb-based perovskites containing iron.

  • 15.
    Jönsson, Petra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Takenaka, K
    Niitaka, S
    Sasagawa, T
    Sugai, S
    Takagi, H
    Correlation-driven heavy-fermion formation in LiV2O4.2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, no 16, p. 167402.1-167402.4Article in journal (Refereed)
    Abstract [en]

    Optical reflectivity measurements were performed on a single crystal of the d-electron heavy-fermion (HF) metal LiV2O4. Our results evidence the highly incoherent charge dynamics above T*≈20  K and the redistribution of the spectral weight of the optical conductivity over broad energy scales (∼5  eV) as the quantum coherence of the charge carriers is recovered. This reveals that LiV2O4 is close to a correlation-driven insulating state and indicates that, in sharp contrast to f-electron HF Kondo-lattice systems, strong electronic correlation effects dominate the heavy quasiparticle formation in LiV2O4

    .

  • 16. Kalvius, G. M.
    et al.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Krimmel, A.
    Wagner, F. E.
    Wäppling, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Tsurkan, V.
    Loidl, A.
    Krug von Nidda, H-A
    Spin-Lattice Instability in the Chromium Sulfur Spinel Fe0.5Cu0.5Cr2S42008In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 25, p. 252204-Article in journal (Refereed)
    Abstract [en]

    Zero field mu SR spectroscopy was applied to a polycrystalline sample of the ferrimagnetic sulfur spinel Fe0.5Cu0.5Cr2S4 between 5 and 315 K. The temperature dependence of the interstitial magnetic field B-mu as well as the transverse and longitudinal relaxation rates were deduced. At around 100 K, the temperature dependence of the interstitial field exhibits a strong deviation from the expected Brillouin-like behavior together with a maximum of the transverse relaxation rate. These features are characteristic for a spin reorientation transition. This instability of the ferrimagnetic spin-lattice has not been reported previously. Fe-57 Mossbauer data from the same sample show no irregularity in the temperature dependence of the Fe hyperfine field which could indicate that the spin reorientation involves primarily the Cr sublattice. Above and below the spin reorientation regime, disorder in the spin-lattice is sizable, but not excessive. At low temperatures, the spins are essentially static, spin dynamics sets in above the reorientation range. The mu SR data are also complemented by new susceptibility and magnetization data taken on similar material.

  • 17.
    Karlsson, E. B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Siegbahn, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Introduction to Kai Siegbahn's memorial issue2009In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 601, no 1-2, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Kai Siegbahn is mainly known to the afterworld for his development of spectroscopies which have provided a detailed understanding of the electronic structure of atoms, molecules and condensed matter. These spectroscopies are based on the discoveries made by him and his collaborators in the beginning of the 1960s which led to a Nobel prize in physics for Kai in 1981. The collection of papers in the present volume illustrate the present status of the many flourishing aspects of electron spectroscopy which have developed as a result of his initial ideas and their background in nuclear physics experimentation. (C) 2009 Elsevier B.V. All rights reserved.

  • 18.
    Karlsson, Erik B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Coherent proton and deuteron states in neutron scattering2008In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 77, no 6, p. 065301-Article in journal (Refereed)
    Abstract [en]

    Neutron Compton scattering has been used for a long time as a method to obtain information about proton momentum distributions in organic molecules, metal hydrides, etc. However, in a number of recent papers it has been shown that scattering on protons (and to some extent also on deuterons) shows intensities that are much smaller than expected when compared to those of the other constituents of the measured systems. This has raised the question if the Compton scattering process is fully understood (do, for instance, electron excitations take up part of the recoil energy and momentum?) and casts doubts on the reliability of the method for its original purpose. The present paper presents a detailed explanation for the intensity deficits in a number of studied systems without involving any participation of a third body in the scattering process. It is a development of an earlier proposed model, in which the intensity loss is caused by destructive interference in the waves representing the scattered neutron and the recoiling particle. These interferences appear when the scattering particles are indistinguishable (and therefore in a quantum superposition state) when seen by the neutron. It requires that the neutron coherence length (which is determined by the energy selection) is comparable to the internuclear distances. It is shown that the latter condition is at least partially fulfilled for two, three or four particles in the experiments and that it is likely that the necessary coherence remains over the very short duration (femtosecond (fs)) of the scattering process. Quantitative agreement is obtained for several proton and deuteron containing systems, including the observed dependence of the intensity deficit on scattering angle, which is explained in terms of the actual recoil energy as related to the proton- or deuteron-binding energy in the different systems. The question of available final states for the scattering system is discussed.

  • 19.
    Karlsson, Erik B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Den komplicerade fotonen2008In: Fysik-aktuellt, ISSN 0283-9148, Vol. 3, p. 20-Article in journal (Refereed)
  • 20.
    Landström, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Lu, Jun
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Heszler, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Size-Distribution and Emission Spectroscopy of W Nanoparticles Generated byLaser-Assisted CVD for Different WF6/H2/Ar Mixtures2003In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, no 42, p. 11615-11621Article in journal (Refereed)
    Abstract [en]

    Tungsten nanoparticles were produced by ArF excimer laser-assisted chemical vapor deposition fromWF6/H2/Ar gas mixtures. Subsequent pulses excited the gas-phase particles, allowing optical emissionspectroscopy to monitor the intensity of the emitted radiation and temperature of the laser-heated particles.A systematic study on size-distributions of the deposited particles, determined by electron microscopy, inconnection with emission spectroscopy and rate of deposition measurements is presented, with respect todifferent partial pressures of the reactants. The rates of deposition of W nanoparticle films were determinedby X-ray fluorescence spectroscopy. In addition, the intensity of the scattered 193 nm laser line was alsomonitored as the partial pressure of H2 was varied.

  • 21.
    Lidbaum, Hans
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Raanaei, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Papaioannou, Evangelos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers2010In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 312, no 4, p. 580-586Article in journal (Refereed)
    Abstract [en]

    The structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers grown by using magnetron Sputtering were investigated with X-ray reflectivity, transmission electron microscopy and magnetooptical Kerr effect. The Co68Fe24Zr8 form amorphous islands when the nominal thickness of the Co68Fe24Zr8 layers is 10 angstrom, exhibiting an isotropic superparamagnetic behavior. Continuous layers with mostly a nano-crystalline structure are instead formed when the nominal thickness of the Co68Fe24Zr8 layers is increased to 20 angstrom. The continuous layers exhibit random, in-plane, magnetic anisotropy resulting from the growth Process. However, induced uniaxial anisotropy is obtained when growing the sample in the presence of an applied magnetic field, regardless of the combination of amorphous and nano-crystalline material.

  • 22.
    Lidbaum, Hans
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Liebig, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Björgvin, Hjörvarsson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Oppeneer, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Quantitative magnetic information from reciprocal space maps in transmission electron microscopy2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 3, p. 037201-Article in journal (Refereed)
    Abstract [en]

    One of the most challenging issues in the characterization of magnetic materials is to obtain a quantitative analysis on the nanometer scale. Here we describe how electron magnetic circular dichroism (EMCD) measurements using the transmission electron microscope can be used for that purpose, utilizing reciprocal space maps. Applying the EMCD sum rules, an orbital to spin moment ratio of mL/mS=0.08±0.01 is obtained for Fe, which is consistent with the commonly accepted value. Hence, we establish EMCD as a quantitative element-specific technique for magnetic studies, using a widely available instrument with superior spatial resolution.

  • 23.
    Lundquist, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Wessman, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Melittin–Lipid interaction: A comparative study using liposomes, micelles and bilayer disks2008In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1778, no 10, p. 2210-2216Article in journal (Refereed)
    Abstract [en]

    Comparison of melittin interaction with liposomes, bilayer disks and micelles showed that melittin binding to lipid aggregates is largely dictated by the amount of highly curved areas in the aggregates. The PEG-stabilised bilayer disks were characterised by a combination of small angle neutron scattering, cryo-transmission electron microscopy and dynamic light scattering. Importantly, the theoretically foreseen partial segregation of the lipid components, important for maintaining the structure of the bilayer disk, was confirmed. Steady state fluorescence spectroscopy indicated that melittin mainly resides at the rim of the bilayer disks. Results of the present study help increase the understanding of the mechanisms behind, and the physico-chemical factors affecting, melittin–lipid interaction. We suggest that bilayer disks, due to their stable structure, constitute interesting vehicles for transport of peptides that have high propensity to associate with lipid surfaces of high curvature.

  • 24.
    Marcellini, Moreno
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Magnetic Ordering in Layered Magnets2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The preparation of layered magnets needs the knowledge of growth techniques which are focused on the growth of Fe/V(001) superlattices. Such films have been structurally investigated by X-rays reflectivity and diffraction.

    The magnetic investigations have been carried out by magneto-optic Kerr effect (MOKE), Superconducting Quantum Interference Device (SQUID) magnetometry and polarized neutron reflectivity (PNR). This latter technique has been used in cooperation with the Institute Laue Langvin (Grenoble, France) and Ruhr Universität (Bochum, Germany).

    The cross-over in universality class is shown in a series of layered magnets where a δ-doping layer of Fe has been embedded between two layers of Pd showing that the magnetization depends on the effective magnetic thickness of the polarized Pd. A model for the cross-over has been developed in terms of magnetic excitations.

    The interlayer exchange coupling (IEC) mediated by a non-magnetic spacer has been reviewed focusing the attention on the recent theoretical and experimental works based on Fe/V(001) superlattices.

    The IEC can be tailored at will by reversibly alloying of the spacer with H: this has been proved in Fe/V(001) double layers showing that in the two dimensional limit, the universality class is not affected by the coupling.

    The magnetic order-disorder transitions in Fe/V(001) superlattices do not seem to belong to any universality class. A phenomenological model which accounts for the effective coupling at the boundaries has been developed.

    The influence of the inherent ordering temperatures of single magnetic layers has been investigated in Fe/V(001) superlattices proving that the weakest ferromagnetic layer affects the overall magnetic ordering.

    A new kind of layered magnet has been developed to increase the effect of the boundaries. PNR measurements show that the universality class depends on which length-scale is investigated.

    List of papers
    1. Dimensionality crossover in the induced magnetization of Pd layers
    Open this publication in new window or tab >>Dimensionality crossover in the induced magnetization of Pd layers
    Show others...
    2007 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 19, no 24, p. 246213-Article in journal (Refereed) Published
    Abstract [en]

    The magnetic ordering of a series of samples consisting of ultrathin Fe layersembedded in Pd was investigated using the magneto-optical Kerr effect. Thesamples consisted of a single Fe layer with nominal thickness 0.2 dFe 1.6monolayers sandwiched between two 20 monolayer Pd layers. A dimensionalitycrossover from two dimensions to three dimensions occurs as dFe is increasedfrom 0.4 to 1.0 monolayers. First-principles calculations were performed inorder to determine the magnetic profile, and we used a spin-wave quantum wellmodel for obtaining a qualitative description of the dimensionality crossover.The results clearly prove the existence of a dimensionality crossover in theinduced magnetization, opening new routes for addressing the influence ofextension on order.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95880 (URN)10.1088/0953-8984/19/24/246213 (DOI)000247074700028 ()
    Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2017-12-14Bibliographically approved
    2. Oscillatory exchange coupling in the two-dimensional limit
    Open this publication in new window or tab >>Oscillatory exchange coupling in the two-dimensional limit
    2005 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 17, p. L477-483Article in journal (Refereed) Published
    Abstract [en]

    The dimensionality aspects of the order–disorder transition in single and double magnetic layers is addressed. A single Fe film of three monolayers, embedded in V(001) layers, was determined to be two-dimensional and XY-like. Two Fe layers, separated by 14.4 monolayers of V(001), were determined to belong to the same universality class as the single Fe film. The interlayer exchange coupling was altered in situ by introducing hydrogen in the V layers. An oscillation of the ordering temperature was observed, consistent with an oscillatory interlayer exchange coupling. The two-dimensional nature of the bilayer was confirmed by the ratio of the interlayer and intralayer couplings (). The results therefore support the existence of an oscillatory exchange coupling in the quasi-two-dimensional limit.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95878 (URN)10.1088/0953-8984/17/44/L03 (DOI)
    Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2017-12-14Bibliographically approved
    3. The influence of interlayer exchange coupling on the magnetic ordering in Fe/V superlattices
    Open this publication in new window or tab >>The influence of interlayer exchange coupling on the magnetic ordering in Fe/V superlattices
    Show others...
    2009 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 321, no 9, p. 1214-1220Article in journal (Refereed) Published
    Abstract [en]

    The relation between the interlayer exchange coupling and magnetic order is addressed, using Fe/V(0 0 1) superlattices as a model system. Large decrease in the ordering temperature (Tc) is observed with decreasing interlayer exchange coupling. The effective exponents of the magnetization were determined to be larger than 0.5 for all the samples, which is strongly deviating from the classical values of both two- and three-dimensional systems. This effect can partially be ascribed to the presence of boundaries, invoked by the finite number of magnetic layers.

    Keywords
    Magnetic superlattices, Magnetic phase transitions, Critical exponents
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96975 (URN)10.1016/j.jmmm.2008.11.010 (DOI)000264170500022 ()
    Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2017-12-14Bibliographically approved
    4. The influence of the distribution of the inherent ordering temperature on the ordering in layered magnets
    Open this publication in new window or tab >>The influence of the distribution of the inherent ordering temperature on the ordering in layered magnets
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 14, p. 144426-Article in journal (Refereed) Published
    Abstract [en]

    We study the influence of gradients in the inherent ordering temperature of coupled layered magnets on the overall magnetic ordering. The gradients were accomplished by growing Fe(001) layers with thicknesses ranging from two to three monolayers, all separated by   seven monolayers of V(001). Two types of gradient superstructures were grown: one with the highest and one with the lowest inherent ordering temperature in the center of the samples. The superstructure with the thinnest outermost Fe layers exhibits lower ordering temperature,  demonstrating the importance of the sequence of the layers. Both these   structures order at temperatures significantly lower than a superlattice with a constant thickness of the Fe layers (three monolayers). The results highlight the intricate collective aspects of  the magnetic ordering in layered magnets, which are not captured by current models in magnetism research.

    Keywords
    antiferromagnetic materials, ferromagnetic materials, iron, magnetic multilayers, monolayers, vanadium
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96976 (URN)10.1103/PhysRevB.79.144426 (DOI)000265943200088 ()
    Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2017-12-14Bibliographically approved
    5. The effect of boundaries on ordering in finite magnets
    Open this publication in new window or tab >>The effect of boundaries on ordering in finite magnets
    (English)In: Physical Review LettersArticle in journal (Refereed) In press
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-96977 (URN)
    Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2015-03-10Bibliographically approved
  • 25.
    Marcellini, Moreno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Pärnaste, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Wolff, Maximilian
    The influence of the distribution of the inherent ordering temperature on the ordering in layered magnets2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 14, p. 144426-Article in journal (Refereed)
    Abstract [en]

    We study the influence of gradients in the inherent ordering temperature of coupled layered magnets on the overall magnetic ordering. The gradients were accomplished by growing Fe(001) layers with thicknesses ranging from two to three monolayers, all separated by   seven monolayers of V(001). Two types of gradient superstructures were grown: one with the highest and one with the lowest inherent ordering temperature in the center of the samples. The superstructure with the thinnest outermost Fe layers exhibits lower ordering temperature,  demonstrating the importance of the sequence of the layers. Both these   structures order at temperatures significantly lower than a superlattice with a constant thickness of the Fe layers (three monolayers). The results highlight the intricate collective aspects of  the magnetic ordering in layered magnets, which are not captured by current models in magnetism research.

  • 26. Nowak, G.
    et al.
    Zabel, H.
    Westerholt, I.
    Garfullin, M.
    Marcellini, Moreno
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Liebig, A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Superconducting spin valves based on epitaxial Fe/V superlattices2008In: Physical review B. Condensed matter and materials physics, ISSN 1550-235X, Vol. 78, no 13, p. 134520-Article in journal (Refereed)
    Abstract [en]

    In superconducting spin valves of the type S/F1/N/F2 or F1/S/F2 with a superconducting layer S, two ferromagnetic layers F1 and F2, and a normal metallic layer N, the superconducting transition temperature T-S depends on the relative magnetization direction of the ferromagnetic layers F1 and F2. The difference of the transition temperature Delta T-S=T-s(AP)-T-s(P) with the magnetization direction of F1 and F2 either antiparallel or parallel is called the superconducting spin valve effect. We have prepared both types of spin valves by growing Fe/V thin-film heterostructures with epitaxial quality on MgO(001) substrates. In the S/F1/N/F2-type spin valves the ferromagnetic layers were the first two Fe layers of a [Fe/V] superlattice coupled antiferromagnetically via the interlayer exchange interaction. Here we observed a superconducting spin valve shift of up to Delta T-S approximate to 200 mK when aligning the sublattice magnetization in an external magnetic field. In the F1/S/F2-type spin valves the ferromagnetic layer F1 was either a [Fe/V] or a [FexV1-x/V] superlattice, the F2 layer was a Fe-, a Co-, or a FexV1-x film. Using weakly ferromagnetic FexV1-x alloy layers as F1 and F2 we find a spin valve effect of up to Delta T-S approximate to 20 mK, which is more than a factor of 2 larger than reported in the literature before for spin valves with comparable transition temperatures. Our results indicate that a high interface transparency and a large superconducting correlation length are prerequisites for the observation of a sizable superconducting spin valve effect.

  • 27. Nylander, Tommy
    et al.
    Campell, Richard
    Vandoolaeghe, Pauline
    Cárdenas, Marité
    Linse, Per
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Neutron Reflectometry to Investigate the Delivery of Lipids and DNA to Interfaces2008In: Biointerphases, ISSN 1559-4106, Vol. 3, no 2, p. FB64-FB82Article, review/survey (Refereed)
    Abstract [en]

    The application of scattering methods in the study of biological and biomedical problems is a field of research that is currently experiencing fast growth. In particular, neutron reflectometry (NR) is a technique that is becoming progressively more widespread, as indicated by the current commissioning of several new reflectometers worldwide. NR is valuable for the characterization of biomolecules at interfaces due to its capability to provide quantitative structural and compositional information on relevant molecular length scales. Recent years have seen an increasing number of applications of NR to problems related to drug and gene delivery. We start our review by summarizing the experimental methodology of the technique with reference to the description of biological liquid interfaces. Various methods for the interpretation of data are then discussed, including a new approach based on the lattice mean-field theory to help characterize stimulus-responsive surfaces relevant to drug delivery function. Recent progress in the subject area is reviewed in terms of NR studies relevant to the delivery of lipids and DNA to surfaces. Lastly, we discuss two case studies to exemplify practical features of NR that are exploited in combination with complementary techniques. The first case concerns the interactions of lipid-based cubic phase nanoparticles with model membranes (a drug delivery application), and the second case concerns DNA compaction at surfaces and in the bulk solution (a gene delivery application).

  • 28. Ohgai, T.
    et al.
    Enculescu, I.
    Zet, C.
    Westerberg, Lars
    Uppsala University, The Svedberg Laboratory.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Spohr, Reimar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Neumann, R.
    Magneto-sensitive nickel nanowires fabricated by electrodeposition into multi- and single-ion track templates2006In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 36, no 10, p. 1157-1162Article in journal (Refereed)
    Abstract [en]

    Polycarbonate templates of ( 30 +/- 1) mu m thickness containing cylindrical etched-track nanochannels of ( 500 +/- 50) nm diameter were used for electrodeposition of Ni nanowires. Using 10(4) channels per cm(2), the most favourable deposition potential of -1.0 V was determined in a potentiostatic mode by varying the deposition potential with respect to an Ag/AgCl reference electrode over a range between -0.1 V and -1.5 V. The deposition efficiency at -1.0 V was estimated around 10%. The resulting single wires had a resistance around 200 W and showed an anisotropic magnetoresistance (AMR) effect of 1%, applicable to directionally sensitive magnetic field sensors.

  • 29.
    Pálsson, Gunnar K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Rennie, Adrian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Examination of the reliability of X-ray techniques for determining hydrogen-induced volume changes2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 10, p. 104118-Article in journal (Refereed)
    Abstract [en]

    The Bragg peaks in x-ray diffraction experiments are generally taken to be a reliable measure of the average lattice distance in crystals. We show that this assumption can be misleading when determining hydrogen-induced volume changes. Experiments based on simultaneous determination of the position of the Bragg peak and the sample volume of an Fe/V(001) superlattice while expanding the lattice by in situ hydrogen loading serve as an illustration of this counter-intuitive effect.

  • 30.
    Pálsson, Gunnar K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Wang, Yun Tao
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Azofeifa, Daniel
    Centro de investigatción en Ciencia e ingegnería de materiales and escuela de física, universidad de costa rica, san jose, costa rica.
    Raanaei, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Influence of Titanium and Vanadium on the Hydrogen transport through amorphous alumina films2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 494, no 1-2, p. 239-244Article in journal (Refereed)
    Abstract [en]

    The influence of titanium and vanadium on the hydrogen transport rate through thin amorphous alumina films is addressed. Only small changes in the transport rate are observed when the Al2O3 are covered with titanium or vanadium. This is in stark contrast to results with a Pd overlayer, which enhances the transport by an order of magnitude. Similarly, when titanium is embedded into the alumina the transport rate is faster than for the covered case but still slower than the undoped reference. Embedding vanadium in the alumina does not yield an increase in uptake rate compared to the vanadium covered oxide layers. These results add to the understanding of the hydrogen uptake of oxidized metals, especially the alanates, where the addition of titanium has been found to significantly enhance the rate of hydrogen uptake. The current findings eliminate two possible routes for the catalysis of alanates by Ti, namely dissociation and effective diffusion short-cuts formed by Ti. Finally, no photocatalytic enhancement was noticed on the titanium covered samples.

  • 31.
    Qazi, S. Junaid S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cockcroft, K
    Vickers, Martin
    Use of wide-angle X-ray diffraction to measure shape and size of dispersed colloidal particles2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 338, no 1, p. 105-110Article in journal (Refereed)
    Abstract [en]

    Laboratory X-ray diffraction is used to investigate the size and shape of dispersed plate-like and spherical colloidal particles. Analysis of the wide-angle diffraction data provides information about the size and shape of crystals from the width of the Bragg peaks according to the Debye-Scherrer formula. The measurements, data analysis, and evaluation are discussed. It is shown that X-ray diffraction with conventional laboratory equipment on dispersed particles is feasible as a tool to determine both particle size and shape. Data for two samples - gold colloids and nickel (II) hydroxide particles are presented. The advantages and limitations of the method are discussed. X-ray diffraction measurements that are made in combination with dynamic light scattering can be used to estimate the thickness of stabilizing layers of polymers. (C) 2009 Elsevier Inc. All rights reserved.

  • 32.
    Raanaei, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Tailoring Properties of Materials at the Nanoscale2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The knowledge of growth and characterizing techniques is essential for the preparation of high quality thin films and multilayers. Here, structural properties have been investigated by X-ray reflectivity, X-ray diffraction, and transmission electron microscopy while the composition was determined by Rutherford backscattering spectrometry. For the magnetic studies, magneto-optical Kerr effect and X-ray magnetic circular dichroism have been used.

    The structural properties of the metal/insulator multilayer system, Fe/MgO, have been investigated. The coherency of the layers was influenced by the difference of the atomic distance in the Fe and MgO layers, resulting in long range strain fields. As a consequence, the coherency between the layers is not maintained.

    The atomic steps can not exist in amorphous materials, due to the absence of well defined atomic distances. Furthermore, the magnetic properties of amorphous materials allow a tuning of magnetic properties such as magnetic anisotropy and ordering temperature. The possibility to imprint arbitrary magnetic anisotropy in nanolaminated magnetic amorphous Co68Fe24Zr8 was demonstrated. The ratio of the orbital to spin moments for both Fe and Co was determined, for both thick and thin layers embedded in amorphous Al70Zr30 layers. When growing Co68Fe24Zr8 /Al2O3 the layers exhibit large changes in layer quality with thickness of the layers, ultimately affecting the magnetic properties of the stack.

    The use of protective layers is of large importance when performing ex-situ measurements. Most of the materials used were capped by Al2O3, effectively hindering both the reaction with oxygen and water. The penetration of hydrogen through different thicknesses of alumina was investigated. The experiments confirmed high degree of passivation as well as the possibility to selectively diffuse hydrogen through these layers. The use of element specific diffusion barriers allows the tailoring of magnetic properties of magnetic thin films and multilayers.

    List of papers
    1. Structural coherence and layer perfection in Fe/MgO multilayers
    Open this publication in new window or tab >>Structural coherence and layer perfection in Fe/MgO multilayers
    Show others...
    2008 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 5, p. 055212-Article in journal (Refereed) Published
    Abstract [en]

    A series of Fe/MgO multilayers was grown on single-crystal MgO(001) substrates at different temperatures using magnetron sputtering. The structural quality of the samples was investigated by x-ray reflectometry, x-ray diffraction and transmission electron microscopy. The results show a strong dependence of the structural quality on the growth temperature. Although good epitaxial layers are obtained at 165 ◦C, the sample does not exhibit any superlattice diffraction peaks. This effect is shown to be related to a continuous variation of the distance between the Fe layers as well as between the MgO layers.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-13627 (URN)10.1088/0953-8984/20/5/055212 (DOI)000252923400015 ()
    Available from: 2008-01-24 Created: 2008-01-24 Last updated: 2019-04-24Bibliographically approved
    2. Imprinting layer specific magnetic anisotropies in amorphous multilayers
    Open this publication in new window or tab >>Imprinting layer specific magnetic anisotropies in amorphous multilayers
    Show others...
    2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 2, p. 023918-Article in journal (Refereed) Published
    Abstract [en]

    We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.

    Place, publisher, year, edition, pages
    AIP, 2009
    Keywords
    Amourphous multilayers
    National Category
    Physical Sciences Engineering and Technology
    Research subject
    Physics of Matter
    Identifiers
    urn:nbn:se:uu:diva-107510 (URN)10.1063/1.3169523 (DOI)000268613000101 ()
    Available from: 2009-08-13 Created: 2009-08-13 Last updated: 2019-04-24Bibliographically approved
    3. Spin and orbital moment in amorphous Co68Fe24Zr8 layers
    Open this publication in new window or tab >>Spin and orbital moment in amorphous Co68Fe24Zr8 layers
    Show others...
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 13, p. 134402-Article in journal (Refereed) Published
    Abstract [en]

    The ratio of the orbital to the spin magnetic moment was determined for both Fe and Co in amorphous Co68 Fe24 Zr8 layers using x-ray circular dichroism. The investigations were performed on both thick Co68 Fe24 Zr8 layers as well as on amorphous Co68 Fe24 Zr8 / Al70 Zr30 multilayers grown by dc sputtering. Structural characterization was performed using x-ray reflectometry, x-ray diffraction, and transmission electron microscopy. X-ray circular dichroism, x-ray magnetic scattering as well as the magneto-optic Kerr effect were used to characterize the magnetic properties of the amorphous materials. The ratio of the orbital to spin moments in the single CoFeZr-layer sample was 0.012±0.005 for Fe and 0.078±0.005 for Co. Substantial reduction in the the ratio of the orbital to spin moments was observed with decreasing CoFeZr-layer thickness.

    National Category
    Condensed Matter Physics Engineering and Technology
    Research subject
    Physics of Matter
    Identifiers
    urn:nbn:se:uu:diva-107511 (URN)10.1103/PhysRevB.80.134402 (DOI)000271351300052 ()
    Available from: 2009-08-17 Created: 2009-08-13 Last updated: 2019-04-24Bibliographically approved
    4. Structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers
    Open this publication in new window or tab >>Structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers
    Show others...
    2010 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 312, no 4, p. 580-586Article in journal (Refereed) Published
    Abstract [en]

    The structural and magnetic properties of Co68Fe24Zr8/Al2O3 multilayers grown by using magnetron Sputtering were investigated with X-ray reflectivity, transmission electron microscopy and magnetooptical Kerr effect. The Co68Fe24Zr8 form amorphous islands when the nominal thickness of the Co68Fe24Zr8 layers is 10 angstrom, exhibiting an isotropic superparamagnetic behavior. Continuous layers with mostly a nano-crystalline structure are instead formed when the nominal thickness of the Co68Fe24Zr8 layers is increased to 20 angstrom. The continuous layers exhibit random, in-plane, magnetic anisotropy resulting from the growth Process. However, induced uniaxial anisotropy is obtained when growing the sample in the presence of an applied magnetic field, regardless of the combination of amorphous and nano-crystalline material.

    Keywords
    Characterization, Crystallites, Physical vapor deposition processes, Metals, Oxides, Magnetic materials
    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-107512 (URN)10.1016/j.jcrysgro.2009.11.025 (DOI)000274761900017 ()
    Available from: 2009-08-17 Created: 2009-08-13 Last updated: 2019-04-24Bibliographically approved
    5. The influence of amorphous Al2O3 coating on the hydrogen uptake properties of materials
    Open this publication in new window or tab >>The influence of amorphous Al2O3 coating on the hydrogen uptake properties of materials
    2008 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 464, no 1-2, p. L13-L16Article in journal (Refereed) Published
    Abstract [en]

    An experimental exploration of the transport rate of hydrogen through amorphous Al2O3 layers is presented. Significant changes in the transport rate were observed when changing the thickness of the oxide from 1 to 3 nm. By coating the oxide with a catalytically active Pd layer, a fast dissociation of hydrogen is allowed, enabling a separation between the limitation imposed by dissociation and the transport through the oxide.

    Keywords
    Thin films, Hydrogen absorbing materials
    National Category
    Other Engineering and Technologies not elsewhere specified
    Identifiers
    urn:nbn:se:uu:diva-101143 (URN)10.1016/j.jallcom.2007.10.045 (DOI)000259715300004 ()
    Available from: 2009-04-20 Created: 2009-04-20 Last updated: 2017-12-13
    6. Influence of Titanium and Vanadium on the Hydrogen transport through amorphous alumina films
    Open this publication in new window or tab >>Influence of Titanium and Vanadium on the Hydrogen transport through amorphous alumina films