Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
Refine search result
1234567 1 - 50 of 701
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Adalsteinsson, Sigurbjörn Már
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Moro, Marcos V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Moldarev, Dmitrii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Moscow Engn Phys Inst, Dept Mat Sci, Moscow 115409S, Russia..
    Droulias, Sotiris
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Moscow Engn Phys Inst, Dept Mat Sci, Moscow 115409S, Russia..
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Sweden.;Uppsala Univ, Tandem Lab, Box 529, S-75120 Uppsala, Sweden..
    Correlating chemical composition and optical properties of photochromic rare-earth oxyhydrides using ion beam analysis2020In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 485, p. 36-40Article in journal (Refereed)
    Abstract [en]

    We relate the photochromic response of rare-earth oxyhydride thin films (YHO, NdHO, GdHO and DyHO) synthesized by reactive magnetron sputtering to chemical composition. Depth profiles of the sample composition are extracted by a multi-method ion beam analysis approach. The total areal density of the thin films is deduced from Rutherford Backscattering Spectrometry while coincidence Time-of-Flight/Energy Elastic Recoil Detection Analysis provides depth-profiles of the film constituents. High-resolution depth profiles of the concentration of light species, i.e. hydrogen and oxygen, are additionally extracted from Nuclear Reaction Analysis and Elastic Backscattering Spectrometry, respectively. The photochromic response of the films is measured by optical transmission spectroscopy before and after illumination. We report photochromic properties for YHO, NdHO, GdHO and DyHO for chemical compositions described by the formula REH2-delta O delta in the range of 0.45 < 6 < 1.5.

  • 2.
    Adlmann, Franz A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Gutfreund, P.
    Ankner, J. F.
    Browning, J. F.
    Parizzi, A.
    Vacaliuc, B.
    Halbert, C. E.
    Rich, J. P.
    Dennison, A. J. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Towards neutron scattering experiments with sub-millisecond time resolution2015In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 48, p. 220-226Article in journal (Refereed)
    Abstract [en]

    Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. It is demonstrated that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode at the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. The opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.

  • 3.
    Adlmann, Franz A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Pálsson, Gunnar Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Bilheux, J. C.
    Oak Ridge Natl Lab, Spallat Neutron Source, Oak Ridge, TN USA..
    Ankner, J. F.
    Oak Ridge Natl Lab, Spallat Neutron Source, Oak Ridge, TN USA..
    Gutfreund, P.
    Inst Laue Langevin, BP 156, F-38042 Grenoble, France..
    Kawecki, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Överlåtaren: a fast way to transfer and orthogonalize two-dimensional off-specular reflectivity data2016In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 49, p. 2091-2099Article in journal (Refereed)
    Abstract [en]

    Reflectivity measurements offer unique opportunities for the study of surfaces and interfaces, and specular reflectometry has become a standard tool in materials science to resolve structures normal to the surface of a thin film. Off-specular scattering, which probes lateral structures, is more difficult to analyse, because the Fourier space being probed is highly anisotropic and the scattering pattern is truncated by the interface. As a result, scattering patterns collected with (especially time-of-flight) neutron reflectometers are difficult to transform into reciprocal space for comparison with model calculations. A program package is presented for a generic two-dimensional transformation of reflectometry data into q space and back. The data are represented on an orthogonal grid, allowing cuts along directions relevant for theoretical modelling. This treatment includes background subtraction as well as a full characterization of the resolution function. The method is optimized for computational performance using repeatable operations and standardized instrument settings.

  • 4.
    Adlmann, Franz Alois
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Opportunities and challenges of surface scattering at next generation neutron sources2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Complex fluids and soft matter are ubiquitously found in the world and all contacts in life are made over surfaces. To describe the mechanical behavior of such substances, rheological methods are used. Flow instabilities are a big challenge in rheology since they will be reflected in the macroscopic variables probed, like e. g. the viscosity. Many such discontinuities may actually originate at the surface. Investigating the properties of liquids in contact with the surface under mechanical load is the main course of the thesis. Neutron reflectometry and GISANS are perfect tools in this context to access the solid liquid interfaces, since they can penetrate many engineering materials and show a comparably large scattering potential at deuterated samples. In this thesis shear was applied on a model solution and neutron scattering techniques were used to investigate the structure under load. The focus was set on the development of the measurement methods themselves to enable new scientific insights in the future. First, by stroboscopic measurements the flux limitations are overcome for oscillatory rheology. By reintegration in the post processing it is shown that kinetic measurements with neutrons are possible with a time resolution below one millisecond. Second, the transformation of grazing incidence data from the laboratory system into q-space is strongly non-linear resulting in a need for re-binning. In this thesis a universal tool has been developed for this purpose. Finally, there is an ongoing discussion on depth sensitive neutron scattering experiments from solid-liquid boundaries. By using emission densities we show that such experiments face severe limitations due to the low absorption cross section of the neutron.

    List of papers
    1. Depth-resolved grazing-incidence time-of-flight neutron scattering from a solid-liquid interface
    Open this publication in new window or tab >>Depth-resolved grazing-incidence time-of-flight neutron scattering from a solid-liquid interface
    Show others...
    2014 (English)In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 47, p. 130-135Article in journal (Refereed) Published
    Abstract [en]

    Small-angle scattering in grazing-incidence beam geometry has been applied on a time-of-flight neutron instrument to investigate a solid-liquid boundary. Owing to the broad wavelength distribution provided for a specific incident beam angle, the penetration depth of the neutron beam is varied over a wide range in a single measurement. The near surface structures of block copolymer micelles close to silicon substrates with distinct surface energies are resolved. It is observed that the very near surface structure strongly depends on the surface coating, whereas further away from the surface, bulk-like ordering is found.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-219976 (URN)10.1107/S1600576713028665 (DOI)000330485100018 ()
    Available from: 2014-03-12 Created: 2014-03-09 Last updated: 2018-04-11Bibliographically approved
    2. Polymer Brush Collapse under Shear Flow
    Open this publication in new window or tab >>Polymer Brush Collapse under Shear Flow
    Show others...
    2017 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 50, no 3, p. 1215-1224Article in journal (Refereed) Published
    Abstract [en]

    Shear responsive surfaces offer potential advances in a number of applications. Surface functionalization using polymer brushes is one route to such properties, particularly in the case of entangled polymers. We report on neutron reflectometry measurements of polymer brushes in entangled polymer solutions performed under controlled shear as well as coarse-grained computer simulations corresponding to these interfaces. Here we show a reversible and reproducible collapse of the brushes, increasing with the shear rate. Using two brushes of greatly different chain lengths and grafting densities, we demonstrate that the dynamics responsible for the structural change of the brush are governed by the free chains in solution rather than the brush itself, within the range of parameters examined. The phenomenon of the brush collapse could find applications in the tailoring of nanosensors and as a way to dynamically control surface friction and adhesion.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2017
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:uu:diva-320464 (URN)10.1021/acs.macromol.6b02525 (DOI)000394410200053 ()
    Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-04-11Bibliographically approved
    3. Probing the dynamics of high-viscosity entangled polymers under shear using Neutron Spin Echo spectroscopy
    Open this publication in new window or tab >>Probing the dynamics of high-viscosity entangled polymers under shear using Neutron Spin Echo spectroscopy
    Show others...
    2016 (English)In: VI European Conference On Neutron Scattering (ECNS2015), 2016, article id UNSP 012014Conference paper, Published paper (Refereed)
    Abstract [en]

    Neutron Spin Echo spectroscopy provides unique insight into molecular and submolecular dynamics as well as intra-and inter-molecular interactions in soft matter. These dynamics may change drastically under shear flow. In particular in polymer physics a stress plateau is observed, which might be explained by an entanglement-disentanglement transition. However, such a transition is difficult to identify directly by experiments. Neutron Spin Echo has been proven to provide information about entanglement length and degree by probing the local dynamics of the polymer chains. Combining shear experiments and neutron spin echo is challenging since, first the beam polarisation has to be preserved during scattering and second, Doppler scattered neutrons may cause inelastic scattering. In this paper we present a new shear device adapted for these needs. We demonstrate that a high beam polarisation can be preserved and present first data on an entangled polymer solution under shear. To complement the experiments on the dynamics we present novel SANS data revealing shear-induced conformational changes in highly entangled polymers.

    Series
    Journal of Physics Conference Series, ISSN 1742-6588 ; 746
    National Category
    Accelerator Physics and Instrumentation
    Identifiers
    urn:nbn:se:uu:diva-346197 (URN)10.1088/1742-6596/746/1/012014 (DOI)000409470900014 ()
    Conference
    6th European Conference on Neutron Scattering (ECNS), AUG 30-SEP 04, 2015, Univ Zaragoza, CSIC, Mat Sci Inst Aragon, Zaragoza, SPAIN
    Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2019-02-19Bibliographically approved
    4. Depth resolved grazing incidence neutron scattering experiments from semi-infinite interfaces: a statistical analysis of the scattering contributions
    Open this publication in new window or tab >>Depth resolved grazing incidence neutron scattering experiments from semi-infinite interfaces: a statistical analysis of the scattering contributions
    Show others...
    2018 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, article id 165901Article in journal, Letter (Refereed) Published
    Abstract [en]

    Grazing incidence neutron scattering experiments offer surface sensitivity by reflecting from an interface at momentum transfers close to total external reflection. Under these conditions the penetration depth is strongly non-linear and may change by many orders of magnitude. This fact imposes severe challenges for depth resolved experiments, since the brilliance of neutron beams is relatively low in comparison to e.g. synchrotron radiation. In this article we use probability density functions to calculate the contribution of scattering at different distances from an interface to the intensities registered on the detector. Our method has the particular advantage that the depth sensitivity is directly extracted from the scattering pattern itself. Hence for perfectly known samples exact resolution functions can be calculated and visa versa. We show that any tails in the resolution function, e.g. Gaussian shaped, hinders depth resolved experiments. More importantly we provide means for a descriptive statistical analysis of detector images with respect to the scattering contributions and show that even for perfect resolution near surface scattering is hardly accessible.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2018
    Keywords
    GISANS, neutrons, interfaces, depth profiling, resolution
    National Category
    Condensed Matter Physics
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-348219 (URN)10.1088/1361-648X/aab573 (DOI)000428466400001 ()29521272 (PubMedID)
    Funder
    Swedish Research Council, 2016-04645The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG-2011-2067
    Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-06-20Bibliographically approved
    5. Normalization of stroboscopic neutron scattering experiments
    Open this publication in new window or tab >>Normalization of stroboscopic neutron scattering experiments
    Show others...
    2018 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 434, p. 61-65Article in journal (Refereed) Published
    Abstract [en]

    Neutron scattering studies of kinetic processes are often flux limited. For processes which can be repeated many times, this can be mitigated by stroboscopic reintegration. The recorded scattering events are assigned to different time slices of the process and corresponding slices from all repetitions are summed up. The normalization of such data with respect to the incident beam spectrum can be challenging since the incident neutron flux may not necessarily be evenly distributed over all time slices. In this paper, we discuss how this can result in misleading information and we expand on a technique to amend these issues.

    National Category
    Condensed Matter Physics
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-348265 (URN)10.1016/j.nimb.2018.08.030 (DOI)000447577000011 ()
    Funder
    Swedish Research Council, C0511501
    Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-12-19Bibliographically approved
    6. Överlåtaren: a fast way to transfer and orthogonalize two-dimensional off-specular reflectivity data
    Open this publication in new window or tab >>Överlåtaren: a fast way to transfer and orthogonalize two-dimensional off-specular reflectivity data
    Show others...
    2016 (English)In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 49, p. 2091-2099Article in journal (Refereed) Published
    Abstract [en]

    Reflectivity measurements offer unique opportunities for the study of surfaces and interfaces, and specular reflectometry has become a standard tool in materials science to resolve structures normal to the surface of a thin film. Off-specular scattering, which probes lateral structures, is more difficult to analyse, because the Fourier space being probed is highly anisotropic and the scattering pattern is truncated by the interface. As a result, scattering patterns collected with (especially time-of-flight) neutron reflectometers are difficult to transform into reciprocal space for comparison with model calculations. A program package is presented for a generic two-dimensional transformation of reflectometry data into q space and back. The data are represented on an orthogonal grid, allowing cuts along directions relevant for theoretical modelling. This treatment includes background subtraction as well as a full characterization of the resolution function. The method is optimized for computational performance using repeatable operations and standardized instrument settings.

    Keywords
    off-specular scattering, neutron reflectometry, interfaces, surfaces
    National Category
    Atom and Molecular Physics and Optics Other Physics Topics Computational Mathematics
    Identifiers
    urn:nbn:se:uu:diva-315086 (URN)10.1107/S1600576716014382 (DOI)000391195900025 ()
    Funder
    Swedish Research Council, C0511501The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG-2011-2067
    Available from: 2017-02-09 Created: 2017-02-09 Last updated: 2018-04-11Bibliographically approved
    7. Towards neutron scattering experiments with sub-millisecond time resolution
    Open this publication in new window or tab >>Towards neutron scattering experiments with sub-millisecond time resolution
    Show others...
    2015 (English)In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 48, p. 220-226Article in journal (Refereed) Published
    Abstract [en]

    Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. It is demonstrated that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode at the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. The opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.

    Keywords
    neutron scattering, in situ rheology, block copolymers, time-resolved studies, surface kinetics, large amplitude oscillatory shear (LAOS), time-of-flight reflectometry
    National Category
    Other Physics Topics
    Identifiers
    urn:nbn:se:uu:diva-246826 (URN)10.1107/S1600576714027848 (DOI)000349210700028 ()
    Available from: 2015-03-10 Created: 2015-03-10 Last updated: 2018-04-11Bibliographically approved
    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
  • 5.
    Adlmann, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Busch, S.
    Vacaliuc, B.
    Nelson, A.
    Ankner, J.F.
    Browning, J.F.
    Parizzi, A.
    Bilheux, J. -K.
    Halbert, C.E.
    Korolkovas, Airidas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Normalization of stroboscopic neutron scattering experiments2018In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 434, p. 61-65Article in journal (Refereed)
    Abstract [en]

    Neutron scattering studies of kinetic processes are often flux limited. For processes which can be repeated many times, this can be mitigated by stroboscopic reintegration. The recorded scattering events are assigned to different time slices of the process and corresponding slices from all repetitions are summed up. The normalization of such data with respect to the incident beam spectrum can be challenging since the incident neutron flux may not necessarily be evenly distributed over all time slices. In this paper, we discuss how this can result in misleading information and we expand on a technique to amend these issues.

  • 6.
    Adlmann, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Herbel, Jörg
    ETH Zürich, Zürich, Switzerland.
    Korolkovas, Airidas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Bliersbach, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Toperverg, Boris
    Petersburg Nuclear Physics Institute, Gatchina, Russia.
    Van Herck, Walter
    Forschungszentrum Jülich GmbH, Garching, Germany.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Kitchen, Brian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Depth resolved grazing incidence neutron scattering experiments from semi-infinite interfaces: a statistical analysis of the scattering contributions2018In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, article id 165901Article in journal (Refereed)
    Abstract [en]

    Grazing incidence neutron scattering experiments offer surface sensitivity by reflecting from an interface at momentum transfers close to total external reflection. Under these conditions the penetration depth is strongly non-linear and may change by many orders of magnitude. This fact imposes severe challenges for depth resolved experiments, since the brilliance of neutron beams is relatively low in comparison to e.g. synchrotron radiation. In this article we use probability density functions to calculate the contribution of scattering at different distances from an interface to the intensities registered on the detector. Our method has the particular advantage that the depth sensitivity is directly extracted from the scattering pattern itself. Hence for perfectly known samples exact resolution functions can be calculated and visa versa. We show that any tails in the resolution function, e.g. Gaussian shaped, hinders depth resolved experiments. More importantly we provide means for a descriptive statistical analysis of detector images with respect to the scattering contributions and show that even for perfect resolution near surface scattering is hardly accessible.

  • 7.
    Ahlberg, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Critical Phenomena and Exchange Coupling in Magnetic Heterostructures2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The continuous phase transition in thin magnetic films and superlattices has been studied using the magneto-optical Kerr effect (MOKE) and polarized neutron scattering (PNR).  It has been shown that the critical behavior of amorphous thin films belonging to the 2D XY universality class can be described within the same theory as crystalline sample. This means that quenched disorder only serves as a marginal perturbation in systems with this symmetry.

    The connection between interlayer exchange coupling and the observed critical behavior in Fe/V superlattices was explored. The results prove that the origin of unusually high values of the exponent β can be traced to a position dependence of the magnetization at elevated temperatures. The magnetization of the outermost layers within the superlattice shows a more pronounced decrease at lower temperatures, compared to the inner layers, which in turn have a more abrupt decrease in the vicinity of the critical temperature. This translates to a high exponent, especially when the layers are probed by a technique where more weight is given to the layers close to the surface, e.g.MOKE.  The interlayer exchange coupling as a function of spacer thickness and temperature was also studied in its own right. The data was compared to the literature, and a dependence on the thickness of the magnetic layers was concluded.

    The phase transition in amorphous FeZr/CoZr multilayers, where the magnetization emanates from ferromagnetic proximity effects, was investigated. Even though the determined exponents of the zero-field magnetization, the susceptibility and the critical isotherm did not correspond to any universality class, scaling plots displayed an excellent data collapse.

    Samples consisting of Fe δ-layers (0.3-1.4 monolayers) embedded in Pd were studied using element-specific resonant x-ray magnetic scattering. The magnetization of the two constituents showed distinctly different temperature dependences.

    List of papers
    1. Influence of boundaries on magnetic ordering in Fe/V superlattices
    Open this publication in new window or tab >>Influence of boundaries on magnetic ordering in Fe/V superlattices
    Show others...
    2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 21, p. 214429-Article in journal (Refereed) Published
    Abstract [en]

    We study the role of surface boundaries on the magnetic properties of [Fe/V](n) superlattice structures, with n=2-10. Using the magneto-optical Kerr effect and polarized neutron reflectivity measurements, we examine the evolution of both the total and the layer-resolved magnetizations as a function of temperature. By varying n, we observe a large shift in the transition temperatures T-c and a substantial change in the total magnetization critical exponent beta. In particular, the thicker samples exhibit nonuniversal exponent values. By resolving the magnetization as a function of position within the superlattice, we show that this behavior arises from contributions of the surfaces. Furthermore, we attribute the large shift in T-c to long-ranged interactions present in the superlattice.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-136258 (URN)10.1103/PhysRevB.81.214429 (DOI)000278936900004 ()
    Available from: 2010-12-11 Created: 2010-12-11 Last updated: 2022-01-28Bibliographically approved
    2. Two-dimensional XY-like amorphous Co68Fe24Zr8/Al70Zr30 multilayers
    Open this publication in new window or tab >>Two-dimensional XY-like amorphous Co68Fe24Zr8/Al70Zr30 multilayers
    2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 22, p. 224404-Article in journal (Refereed) Published
    Abstract [en]

    We present an experimental realization of a magnetic two-dimensional XY system using amorphous materials. The classification of the dimensionality is based on the critical behavior of amorphous Co68Fe24Zr8(d)/Al70O30 (20 angstrom) multilayers, where d = 11 - 16 angstrom. Analysis of the remanent magnetization, the magnetic isotherms, the initial susceptibility, and the magnetic correlation length shows that the magnetic phase transition can be described by the 2D XY model. The samples are not paramagnetic above the critical temperature but are characterized by local magnetic order manifested in the field and temperature dependence of the magnetization. Furthermore, an average spin-spin interaction length of 8.1 angstrom was estimated using the thickness dependence of the Curie temperature.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-155916 (URN)10.1103/PhysRevB.83.224404 (DOI)000291727600006 ()
    Available from: 2011-07-05 Created: 2011-07-04 Last updated: 2017-12-11Bibliographically approved
    3. Experimental realization of amorphous two-dimensional XY magnets
    Open this publication in new window or tab >>Experimental realization of amorphous two-dimensional XY magnets
    2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 2, p. 024430-Article in journal (Refereed) Published
    Abstract [en]

    The temperature dependence of the magnetization of thin amorphous Fe(89)Zr(11)/Al(78)Zr(22) layerswas investigated. Dimensionality analysis of the ferromagnetic transition of 15 A thick layers yielded critical exponents characteristic of the 2D XY (planar rotor) model. Above the ordering temperature significant polarizability with an applied field is observed, due to the existence of large-scale magnetic correlations, of which the extent and origin have been determined.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-156953 (URN)10.1103/PhysRevB.84.024430 (DOI)000292873700002 ()
    Available from: 2011-08-20 Created: 2011-08-11 Last updated: 2017-12-08Bibliographically approved
    4. Temperature dependence of magnetic properties in weakly exchange coupled Fe/V superlattices
    Open this publication in new window or tab >>Temperature dependence of magnetic properties in weakly exchange coupled Fe/V superlattices
    2013 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 341, p. 142-147Article in journal (Refereed) Published
    Abstract [en]

    We use Fe(3)/V(x)Fe(3)/V(x) superlattices, x = 16-27 monolayers (ML) to explore the interlayer exchange coupling (IEC) as a function of both spacer layer thickness and temperature. Fe/V is a common model system for studies addressing the IEC, but the behavior in the weakly exchange coupled regime, complemented with the temperature dependence of the magnetic properties, have remained unexplored. We observe clear regions with ferro- and antiferromagnetic coupling, which is manifested in oscillations in the saturation field, the remanence and the critical temperature. The oscillation in the interlayer coupling (J') has a period of 5.8(1) ML. This is approximate to 0.8 ML smaller than observed for Fe(7)/V(x) superlattices which illustrates the influence of the magnetic layer thickness on the interlayer coupling. The temperature dependence of the remanent magnetization was proven to be significantly affected by the strength of the ferromagnetic coupling, leading to high values of the effective critical exponent beta(eff).

    Keywords
    Magnetic superlattice, Magnetic phase transition, Exchange interaction
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-168308 (URN)10.1016/j.jmmm.2013.04.058 (DOI)000320583800026 ()
    Available from: 2012-02-16 Created: 2012-02-08 Last updated: 2022-01-28Bibliographically approved
    5. Effect of ferromagnetic proximity on critical behavior
    Open this publication in new window or tab >>Effect of ferromagnetic proximity on critical behavior
    2012 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 85, no 22, p. 224425-1-224425-6Article in journal (Refereed) Published
    Abstract [en]

    We have investigated the magnetic phase transition in amorphous Fe93Zr7(x angstrom)/Co95Zr5(1 angstrom) multilayers, where x = 25, 50, and 75. The extremely thin CoZr layer induces magnetic order at temperatures well above the inherent ordering temperature of Fe93Zr7. The changes in the critical exponent beta, associated with the temperature dependence of the magnetization, imply a crossover from two-to three-dimensional behavior as the FeZr thickness is reduced, consistent with a substantial magnetic induction in the FeZr layers. In addition we determined the exponents delta and gamma, of the critical isotherm and the susceptibility, respectively, and their values confirm the nonuniversal character of the phase transition. Scaling of the results yields an excellent data collapse and is found to hold in the crossover regime where the universality hypothesis is not applicable. 

    National Category
    Condensed Matter Physics
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-168796 (URN)10.1103/PhysRevB.85.224425 (DOI)000305532200002 ()
    Funder
    Swedish Research CouncilKnut and Alice Wallenberg Foundation
    Available from: 2012-02-16 Created: 2012-02-15 Last updated: 2017-12-07Bibliographically approved
    6. Element specific magnetization in Fe/Pd quantum well structures
    Open this publication in new window or tab >>Element specific magnetization in Fe/Pd quantum well structures
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-168443 (URN)
    Available from: 2012-02-16 Created: 2012-02-10 Last updated: 2012-08-01
    Download full text (pdf)
    fulltext
  • 8.
    Ahlberg, Martina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Two-dimensional XY-like amorphous Co68Fe24Zr8/Al70Zr30 multilayers2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 22, p. 224404-Article in journal (Refereed)
    Abstract [en]

    We present an experimental realization of a magnetic two-dimensional XY system using amorphous materials. The classification of the dimensionality is based on the critical behavior of amorphous Co68Fe24Zr8(d)/Al70O30 (20 angstrom) multilayers, where d = 11 - 16 angstrom. Analysis of the remanent magnetization, the magnetic isotherms, the initial susceptibility, and the magnetic correlation length shows that the magnetic phase transition can be described by the 2D XY model. The samples are not paramagnetic above the critical temperature but are characterized by local magnetic order manifested in the field and temperature dependence of the magnetization. Furthermore, an average spin-spin interaction length of 8.1 angstrom was estimated using the thickness dependence of the Curie temperature.

    Download full text (pdf)
    fulltext
  • 9.
    Ahlberg, Martina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Korelis, Panagiotis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Effect of ferromagnetic proximity on critical behavior2012In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 85, no 22, p. 224425-1-224425-6Article in journal (Refereed)
    Abstract [en]

    We have investigated the magnetic phase transition in amorphous Fe93Zr7(x angstrom)/Co95Zr5(1 angstrom) multilayers, where x = 25, 50, and 75. The extremely thin CoZr layer induces magnetic order at temperatures well above the inherent ordering temperature of Fe93Zr7. The changes in the critical exponent beta, associated with the temperature dependence of the magnetization, imply a crossover from two-to three-dimensional behavior as the FeZr thickness is reduced, consistent with a substantial magnetic induction in the FeZr layers. In addition we determined the exponents delta and gamma, of the critical isotherm and the susceptibility, respectively, and their values confirm the nonuniversal character of the phase transition. Scaling of the results yields an excellent data collapse and is found to hold in the crossover regime where the universality hypothesis is not applicable. 

    Download full text (pdf)
    fulltext
  • 10.
    Ahlberg, Martina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Papaioannou,, Evangelos Th
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Temperature dependence of magnetic properties in weakly exchange coupled Fe/V superlattices2013In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 341, p. 142-147Article in journal (Refereed)
    Abstract [en]

    We use Fe(3)/V(x)Fe(3)/V(x) superlattices, x = 16-27 monolayers (ML) to explore the interlayer exchange coupling (IEC) as a function of both spacer layer thickness and temperature. Fe/V is a common model system for studies addressing the IEC, but the behavior in the weakly exchange coupled regime, complemented with the temperature dependence of the magnetic properties, have remained unexplored. We observe clear regions with ferro- and antiferromagnetic coupling, which is manifested in oscillations in the saturation field, the remanence and the critical temperature. The oscillation in the interlayer coupling (J') has a period of 5.8(1) ML. This is approximate to 0.8 ML smaller than observed for Fe(7)/V(x) superlattices which illustrates the influence of the magnetic layer thickness on the interlayer coupling. The temperature dependence of the remanent magnetization was proven to be significantly affected by the strength of the ferromagnetic coupling, leading to high values of the effective critical exponent beta(eff).

  • 11.
    Ahlberg, Martina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Zamani, Atieh
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Östman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Fashandi, Hossein
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Jönsson, Petra E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Reversed interface effects in amorphous FeZr/AlZr multilayers2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 18, p. 184403-Article in journal (Refereed)
    Abstract [en]

    We report an anomalous enhancement of the critical temperature (T-c) when the thickness (d) of the magnetic layer is decreased from 60 to 20 angstrom in amorphous FeZr/AlZr multilayers. Further reduction of the thickness causes a decrease of T-c, as expected by finite-size scaling, while the magnetic moment decreases monotonically for all values of d. The increase of the critical temperature is attributed to a reversed interface effect where local changes in the nearest-neighbor distance and coordination number gives a higher effective magnetic coupling at the interfaces compared to the interior of the layer. We have successfully described the results within a model where such interface effects are combined with finite-size scaling.

  • 12. Ainalem, M. L.
    et al.
    Campbell, R. A.
    Khalid, S.
    Gillams, R .J.
    Rennie, Adrian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Nylander, T.
    On the Ability of PAMAM Dendrimers and Dendrimer/DNA Aggregates To Penetrate POPC Model Biomembranes2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 21, p. 7229-7244Article in journal (Refereed)
    Abstract [en]

    Poly(amido amine) (PAMAM) dendrimers have previously been shown, as cationic condensing agents of DNA, to have high potential for nonviral gene delivery. This study addresses two key issues for gene delivery: the interaction of the biomembrane with (i) the condensing agent (the cationic PAMAM dendrimer) and (ii) the corresponding dendrimer/DNA aggregate. Using in situ null ellipsometry and neutron reflection, parallel experiments were carried out involving dendrimers or generations 2 (G2), 4 (G4), and 6 (G6). The study demonstrates that free dendrimers of all three generations were able to traverse supported palmitoyloleoylphosphatidylcholine (POPC) bilayers deposited on silica surfaces. The model biomembranes were elevated front the solid surfaces upon dendrimer penetration, which offers a promising new way to generate more realistic model biomembranes where the contact with the supporting surface is reduced and where aqueous cavities are present beneath the bilayer. The largest dendrimer (GO) induced partial bilayer destruction directly upon penetration, whereas the smaller dendrimers (G2 and G4) leave the bilayer intact, so we propose that lower generation dendrimers have greater potential as transfection mediators. In addition to the experimental observations, coarse-grained simulations on the interaction between generation 3 (03) dendrimers and POPC bilayers were performed in the absence and presence of a bilayer-supporting negatively charged surface that emulates the support. The simulations demonstrate that G3 is transported across free-standing POPC bilayers by direct penetration and not by endocytosis. The penetrability was, however, reduced in the presence of a surface, indicating that the membrane transport observed experimentally was not driven solely by the surface. The experimental reflection techniques were also applied to dendrimer/DNA aggregates of charge ratio = 0.5, and while G2/DNA and G4/DNA aggregates interact with POPC bilayers. G6/DNA displays no such interaction. These results indicate that, in contrast to free dendrimer molecules, dendrimer/DNA aggregates of low charge ratios are not able to traverse a membrane by direct penetration.

  • 13.
    Akansel, Serkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Venugopal, Vijayaharan
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gupta, Rahul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    George, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Neagu, Alexandra
    Tai, Cheuk-Wai
    Gubbins, Mark
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films2018In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 30, article id 305001Article in journal (Refereed)
    Abstract [en]

    Fe65Co35 thin films have been deposited on SiO2 substrates using sputtering technique with different choices of seed layer; Ru, Ni82.5Fe17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni82.5Fe17.5 and Rh. Adding these seed layers, the coercivity of the Fe65Co35 films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10-3 and 4.5X10-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10-3 and 4.0X10-3 for annealed samples.

  • 14.
    Alhanash, Mirna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Atomic scale modelling of Lithium (2,5-dilitium-oxy)-terephthalate organic electrode materials2020Student paper other, 10 credits / 15 HE creditsStudent thesis
  • 15.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science. Uppsala Univ, Dept Engn Sci, Appl Mat Sci, Electron Microscopy & Nanoengn, Box 534, S-75121 Uppsala, Sweden..
    Negi, Devendra Singh
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden.;Max Planck Inst Solid State Res, Stuttgart Ctr Electron Microscopy, Heisenbergstr 1, D-70569 Stuttgart, Germany..
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science. Uppsala Univ, Dept Engn Sci, Appl Mat Sci, Electron Microscopy & Nanoengn, Box 534, S-75121 Uppsala, Sweden..
    Atomic resolution energy-loss magnetic chiral dichroism measurements enabled by patterned apertures2020In: Physical Review Research, E-ISSN 2643-1564, Vol. 2, no 2, article id 023330Article in journal (Refereed)
    Abstract [en]

    Electron energy-loss magnetic chiral dichroism (EMCD) has the potential to measure magnetic properties of the materials at atomic resolution but the complex distribution of magnetic signals in the zone axis and the overlapping diffraction discs at higher beam convergence angles make the EMCD signal acquisition challenging. Recently, the use of ventilator apertures to acquire the EMCD signals with atomic resolution was proposed. Here we give the experimental demonstration of several types of ventilator apertures and obtain a clear EMCD signal at beam semiconvergence angles of 5 mrad. To simplify the experimental procedures, we propose a modified ventilator aperture which not only simplifies the complex scattering conditions but reduces the influence of lens aberrations on the EMCD signal as compared to the originally proposed ventilator apertures. In addition, this modified aperture can be used to analyze magnetic crystals with various symmetries and we demonstrate this feature by acquiring EMCD signals on different zone axis orientations of an Fe crystal. With the same aperture we obtain EMCD signals with convergence angles corresponding to atomic resolution electron probes. After the theoretical demonstration of the EMCD signal on a zone axis orientation at high beam convergence angles, this work thus overcomes the experimental and methodological hurdles and enables atomic resolution EMCD on the zone axis by using apertures.

    Download full text (pdf)
    FULLTEXT01
  • 16.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science. Mirpur Univ Sci & Technol MUST, Dept Elect Engn, Mirpur 10250, Ajk, Pakistan.;Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden. .
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, article id 2180Article in journal (Refereed)
    Abstract [en]

    When magnetic properties are analysed in a transmission electron microscope using the technique of electron magnetic circular dichroism (EMCD), one of the critical parameters is the sample orientation. Since small orientation changes can have a strong impact on the measurement of the EMCD signal and such measurements need two separate measurements of conjugate EELS spectra, it is experimentally non-trivial to measure the EMCD signal as a function of sample orientation. Here, we have developed a methodology to simultaneously map the quantitative EMCD signals and the local orientation of the crystal. We analyse, both experimentally and by simulations, how the measured magnetic signals evolve with a change in the crystal tilt. Based on this analysis, we establish an accurate relationship between the crystal orientations and the EMCD signals. Our results demonstrate that a small variation in crystal tilt can significantly alter the strength of the EMCD signal. From an optimisation of the crystal orientation, we obtain quantitative EMCD measurements.

    Download full text (pdf)
    fulltext
  • 17.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xie, Ling
    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 Astronomy, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS2019In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 196, p. 192-196Article in journal (Refereed)
    Abstract [en]

    The weak signal strength in electron magnetic circular dichroism (EMCD) measurements remains one of the main challenges in the quantification of EMCD related EELS spectra. As a consequence, small variations in peak intensity caused by changes of background intervals, choice of method for extraction of signal intensity and equally differences in sample quality can cause strong changes in the EMCD signal. When aiming for high resolution quantitative EMCD, an additional difficulty consists in the fact that the two angular resolved EELS spectra needed to obtain the EMCD signal are taken at two different instances and it cannot be guaranteed that the acquisition conditions for these two spectra are identical.  Here, we present an experimental setup where we use a double hole aperture in the transmission electron microscope to obtain the EMCD signal in a single acquisition. This geometry allows for the parallel acquisition of the two electron energy loss spectra (EELS) under exactly the same conditions. We also compare the double aperture acquisition mode with the qE acquisition mode which has been previously used for parallel acquisition of EMCD. We show that the double aperture mode not only offers better signal to noise ratio as compared to qE mode but also allows for much higher acquisition times to significantly improve the signal quality which is crucial for quantitative analysis of the magnetic moments.

    Download full text (pdf)
    DA EMCD
  • 18.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Warnatz, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Xie, Ling
    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 Astronomy, Materials Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Towards Quantitative Nanomagnetism in Transmission Electron Microscope by the Use of Patterned Apertures2019In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no S2, p. 654-655Article in journal (Other academic)
    Download full text (pdf)
    fulltext
  • 19.
    Allen, Roland E.
    et al.
    Texas A&M Univ, Dept Phys & Astron, College Stn, TX 77843 USA..
    Lidström, Suzy
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Royal Swedish Acad Sci, Phys Scripta, SE-10405 Stockholm, Sweden..
    21st Century frontiers-a series of articles on current challenges and future opportunities Preface2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 92, no 1, article id 010302Article in journal (Refereed)
  • 20.
    Allen, Roland E.
    et al.
    Texas A&M Univ, Dept Phys & Astron, College Stn, TX 77843 USA..
    Lidström, Suzy
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Royal Swedish Acad Sci, Phys Scripta, SE-10405 Stockholm, Sweden..
    Life, the Universe, and everything: 42 fundamental questions2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 92, no 1, article id 012501Article in journal (Refereed)
    Abstract [en]

    In The Hitchhiker's Guide to the Galaxy, by Douglas Adams, the Answer to the Ultimate Question of Life, the Universe, and Everything is found to be 42 - but the meaning of this is left open to interpretation. We take it to mean that there are 42 fundamental questions which must be answered on the road to full enlightenment, and we attempt a first draft (or personal selection) of these ultimate questions, on topics ranging from the cosmological constant and origin of the Universe to the origin of life and consciousness.

    Download full text (pdf)
    fulltext
  • 21. Allen, Roland E.
    et al.
    Lidström, Suzy
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Your Higgs number-how fundamental physics is connected to technology and societal revolutions2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 2, article id 028002Article in journal (Other academic)
    Abstract [en]

    Fundamental physics, as exemplified by the recently discovered Higgs boson, often appears to be completely disconnected from practical applications and ordinary human life. But this is not really the case, because science, technology, and human affairs are profoundly integrated in ways that are not immediately obvious. We illustrate this by defining a 'Higgs number' through overlapping activities. Following three different paths, which end respectively in applications of the World Wide Web, digital photography, and all modern electronic devices, we find that most people have a Higgs number of no greater than 3.

  • 22.
    Al-Mukadam, R.
    et al.
    Tech Univ Clausthal, Inst Nonmetall Mat, Zehntnerstr 2a, D-38678 Clausthal Zellerfeld, Germany..
    Götz, Inga
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stolpe, M.
    Heraeus AMLOY Technol GmbH, Heraeusstr 12-14, D-63450 Hanau, Germany..
    Deubener, J.
    Tech Univ Clausthal, Inst Nonmetall Mat, Zehntnerstr 2a, D-38678 Clausthal Zellerfeld, Germany..
    Viscosity of metallic glass-forming liquids based on Zr by fast-scanning calorimetry2021In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 221, article id 117370Article in journal (Refereed)
    Abstract [en]

    Fast-scanning calorimetry was applied to retrieve the viscosity of supercooled liquids of the Zr-based bulk metallic glasses (BMGs) Vitreloy 105 and AMZ4 for temperatures from standard glass transition down to similar to 0.78T(g)/T. Characteristic temperatures of the glass transition were translated into viscosity values by means of composition-independent shift factors based on the equivalency between structural relaxation and viscous flow. The extended MYEGA model with a fragile term dominant at high-temperatures and a strong term dominant at low-temperatures describes the entire viscous range. The analysis revealed that Vitreloy 105 and AMZ4 are strong liquids for log(10) eta >= 4.9-5.5. In turn, the fragile-to-strong crossover is centred on 0.69T(g)/T for Vitreloy 105 and on 0.66T(g)/T for AMZ4. The extent of the fragile-to-strong transition was found to be larger for Vitreloy 105 than for AMZ4, while their values agreed well with the inverse relation between transition factor and kinetic fragility of the strong regime established for BMG-forming liquids. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 23.
    Alouhmy, M.
    et al.
    Hassan II Univ Casablanca, LPMMAT, FSAC, BP 5366 Maarif,Route dEl Jadida,Km 8, Casablanca, Morocco..
    Moubah, Reda
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Hassan II Univ Casablanca, LPMMAT, FSAC, BP 5366 Maarif,Route dEl Jadida,Km 8, Casablanca, Morocco..
    Alouhmy, G.
    Hassan II Univ Casablanca, LPMMAT, FSAC, BP 5366 Maarif,Route dEl Jadida,Km 8, Casablanca, Morocco..
    Abid, M.
    Hassan II Univ Casablanca, LPMMAT, FSAC, BP 5366 Maarif,Route dEl Jadida,Km 8, Casablanca, Morocco..
    Lassri, H.
    Hassan II Univ Casablanca, LPMMAT, FSAC, BP 5366 Maarif,Route dEl Jadida,Km 8, Casablanca, Morocco..
    Effects of hydrogen implantation on the magnetocaloric properties of amorphous FeZr films2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 186, article id 110063Article in journal (Refereed)
    Abstract [en]

    We report on the effects of H-implantation on the magnetic and magnetocaloric properties of amorphous FeZr films. Arrott plots reveal a second order ferromagnetic to paramagnetic phase transition for the as-grown and H-implanted films, with an increase in T-C from 160 to 200 K upon implantation. The maximum change in magnetic entropy (-Delta S-M) increases from 0.66 to 0.77J/kgK for a field change mu 0 Delta H = 1.5T, as well as the relative cooling power (RCP) values were improved from 84.5 to 108.6J/kg. This improvement was attributed to the increase in magnetization and chemical inhomogeneity induced by the implantation process. The increase in the chemical inhomogeneity was supported by the determination of the local exponent n extracted from the slope of Ln(-Delta S-M) as a function of Ln(mu 0H), which is line with the simulated depth profile of hydrogen atoms through the FeZr film.

  • 24.
    Alouhmy, M.
    et al.
    Hassan II Univ Casablanca, Fac Sci Ain Chock, LPMAT, BP 5366, Casablanca, Morocco..
    Moubah, Reda
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Hassan II Univ Casablanca, Fac Sci Ain Chock, LPMAT, BP 5366, Casablanca, Morocco.
    Charkaoui, A.
    Hassan II Univ Casablanca, Fac Sci Ain Chock, LPMAT, BP 5366, Casablanca, Morocco..
    Sajieddine, M.
    Sultan Moulay Slimane Univ, LPM, FST, BP 23000, Beni Mellal, Morocco.;Natl Sch Appl Sci, BP 25000, Khouribga, Morocco..
    Abid, M.
    Hassan II Univ Casablanca, Fac Sci Ain Chock, LPMAT, BP 5366, Casablanca, Morocco..
    Lassri, H.
    Hassan II Univ Casablanca, Fac Sci Ain Chock, LPMAT, BP 5366, Casablanca, Morocco..
    Effects of carbon implantation on the low temperature magnetism behavior in amorphous Fe93Zr7 films2022In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 279, article id 115661Article in journal (Refereed)
    Abstract [en]

    We present a detailed investigation on the effects of C-implantation on low temperature magnetic behavior in Fe93Zr7 amorphous films using spin wave theory, law of approach to saturation, and Alben and Becker's theory. Significant increase in Curie temperature with a decrease in coercivity were observed upon C-implantation. Bloch's law was used to analyze the temperature dependence of magnetization, and several important param-eters were extracted such as the stiffness constant of the spin wave, and the exchange constant. The local random anisotropy constant decreases from 0.35 to 0.19 MJ/m(3) with increasing carbon concentration from 0 to 11%. The ferromagnetic correlation length for which the anisotropy directions are assumed to be arbitrarily oriented in-creases significantly with increasing carbon content. By the use of the theory of Alben and Becker, we also extracted the local anisotropy from coercivity, and reasonable agreement was found with random magnetic anisotropy approach.

  • 25.
    Alouhmy, M.
    et al.
    FSAC Hassan II Univ Casablanca, LPMMAT, BP 5366 Maarif,Route Jadida,Km 8, Casablanca, Morocco.
    Moubah, Reda
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. FSAC Hassan II Univ Casablanca, LPMMAT, BP 5366 Maarif, Route Jadida, Km 8, Casablanca, Morocco.
    Yamkane, Z.
    FSAC Hassan II Univ Casablanca, LPMMAT, BP 5366 Maarif,Route Jadida,Km 8, Casablanca, Morocco.
    Abid, M.
    FSAC Hassan II Univ Casablanca, LPMMAT, BP 5366 Maarif,Route Jadida,Km 8, Casablanca, Morocco.
    Lassri, H.
    FSAC Hassan II Univ Casablanca, LPMMAT, BP 5366 Maarif,Route Jadida,Km 8, Casablanca, Morocco.
    Random magnetic anisotropy approach in amorphous Fe88.4Zr11.6 films: Effects of hydrogen implantation2021In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 566, article id 120876Article in journal (Refereed)
    Abstract [en]

    The effects of hydrogen implantation on the magnetic properties in amorphous Fe88.4Zr11.6Hx films with different hydrogen contents (0≤ x≤16) were investigated. The Curie temperature increases with increasing hydrogen content while the coercivity presents an important decrease upon H implantation. Based on the analysis of the approach to saturation in magnetization, the local random anisotropy constant KL was extracted. The local random anisotropy constant decreases from 1.468 MJ/m3 to 0.667 MJ/m3 when the concentration of H increases from 0 to 16%. The ferromagnetic correlation length was found to significantly increase with increasing hydrogen content. The local anisotropy was also extracted from the coercivity based on the Alben and Becker theory, which fits reasonably with that obtained using random magnetic anisotropy approach.

  • 26.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Larsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Förstaårsstudenters och lärares förhållningssätt till laborationer i fysik2014Conference paper (Refereed)
    Abstract [sv]

    Laborationer används som ett närmast självklart inslag på naturvetenskapliga utbildningar. Mål och syften med laborationer kan skifta mellan olika kurser och är inte alltid uppenbara för studenterna (Hart et al., 2000; Russell & Weaver, 2008). Ofta förväntas de lära sig hantering av utrustning, tolkning av data och rapportskrivning, samtidigt som de ska få bättre förståelse för teorin genom att se

    Johan Larsson undersökte 2012 hur hans studenter på tekniskt-naturvetenskapligt basår (högskoleförberedande) värderade olika undervisningsformer. Laborationer fick då sämst betyg. För att undersöka möjliga orsaker till detta tog vi initiativ till en fenomenografisk studie (Marton, 1981) av attityder till fysiklaborationer. Skriftliga enkätsvar samlades in från 38 förstaårsstudenter på kandidatprogrammet i fysik vid Uppsala universitet. Den öppna enkätfrågan inspirerades av en amerikansk studie

    besvarades även av 18 anonyma lärare på Institutionen för fysik och astronomi. Både lärare och studenter har skrivit långa svar som vi kategoriserat fenomenografiskt, det vill säga vi har kartlagt förekomsten av attityder.

    Det finns tydliga nivåer av progression; från ett distanserat, ointresserat förhållningssätt till en nivå där man har en uppfattning om framtida behov. Studien visar inte på några större skillnader mellan lärarnas och studenternas syn. Laborationer förväntas koppla teori till praktik samt ge tillfälle att träna på instrumenthantering och vetenskapligt arbetssätt. Några nämner också att laborationer ökar deras förståelse och lärande, ger social träning och förbereder dem för ett kommande arbetsliv.

    Vår avsikt är att använda resultaten för att öka laborationernas upplevda värde, genom att uppmärksamma kollegor på de förekommande förhållningssätten och tillsammans förbereda oss för att bemöta dem. Frågor som vi vill diskutera är t.ex.: Vill vi att studenterna ska tycka så här?

    Hur speglar våra laborationsinstruktioner det vi vill att studenterna ska lära sig? Hur kommunicerar vi mål och syften med varje laboration på bästa sätt?

    Hart C., Mulhall, P., Berry, A., Loughran, J., & Gunstone, R. (2000). What is the purpose of this experiment? Or can students learn something from doing experiments? Journal of Research in Science Teaching, 37(7), 655-675. Marton, F. (1981). Phenomenography Describing conceptions of the world around us. Instructional Science, 10, 177-200.

    Russell, C. B., & Weaver, G. C. (2008). Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning, 2(2), 1-14.

  • 27.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Larsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Förstaårsstudenters och lärares syn på laborationer i fysik2013Conference paper (Refereed)
    Abstract [sv]

    Bakgrund

    Då institutionen för fysik och astronomi under 2013 identifierat laborationerna som ett problemområde har vi gjort en fenomenografisk studie som undersökte studenters och lärares syn på laborationer.

     

    Datainsamling och analys

    Vi har samlat in skriftliga enkätsvar från 18 lärare och 38 förstaårsstudenter på kandidatprogrammet i fysik.

    Den öppna enkätfrågan var : - Varför har vissa kurser laborationer?

    Svaren visar på många olika uppfattningar och vi har kategoriserat dessa fenomenografiskt.

     

    Resultat

    Vi ser tydliga nivåer av progression i svaren; från ett distanserat och ointresserat förhållningssätt, till en uppfattning om lärande och framtida yrkesliv.

    Studien visar att lärare och studenterna har mycket lika syn på laborationer.

    Uppfattningar som fördes fram var att kurser har laborationer för att :

     

    l   det är obligatoriskt

    l   koppla teori till praktik

    l   öva instrumenthantering

    l   träna vetenskapligt arbetssätt

    l   öka förståelsen och lärandet

    l   ge social träning

    l   utgöra förberedelse för arbetsliv

     

     

    Referenser

    Marton, F. (1981) Phenomenography – Describing conceptions of the world around us. Instructional Science, 10, 177-200.

    Russell, C. B. and Weaver, G. C. (2008) Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning 2(2).

                 

  • 28.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Rätt klack - och rätt sula2013In: Skor är huvudsaken: Sjutton kvinnliga forskares funderingar om skor / [ed] Eriksson Lindvall, Carin; Rydbeck, Kerstin; Rügheimer, Louise, Uppsala universitet, 2013, p. 32-34Chapter in book (Other (popular science, discussion, etc.))
  • 29.
    Andersson, Gabriella
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Aktiverande problemlösningsövningar i grupp.2010In: Att undervisa med vetenskaplig förankring – i praktiken!: Universitetspedagogisk utvecklingskonferens 8 oktober 2009 / [ed] Britt-Inger Johansson, Uppsala: Universitetstryckeriet , 2010, p. 103-113Chapter in book (Other academic)
  • 30.
    Andersson, Mikael S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pappas, Spyridon D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Östman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stein, A.
    Brookhaven Natl Lab, Ctr Funct Nanomat, POB 5000, Upton, NY 11973 USA..
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermally induced magnetic relaxation in square artificial spin ice2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 37097Article in journal (Refereed)
    Abstract [en]

    The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice - we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.

    Download full text (pdf)
    fulltext
  • 31.
    Andreasson, Jakob
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Iwan, Bianca Stella
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Andrejczuk, A.
    Abreu, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Bergh, M.
    Caleman, Carl
    Nelson, A. J.
    Bajt, S.
    Chalupsky, J.
    Chapman, H. N.
    Faeustlin, R. R.
    Hajkova, V.
    Heimann, P. A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Juha, L.
    Klinger, D.
    Krzywinski, J.
    Nagler, B.
    Pålsson, Gunnar Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Singer, W.
    Seibert, Marvin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Sobicrajski, R.
    Tolcikis, S.
    Tschentscher, T.
    Vinko, S. M.
    Lee, R. W.
    Hajdu, Janos
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Timneanu, Nicusor
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser2011In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 83, no 1, p. 016403-Article in journal (Refereed)
    Abstract [en]

    Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 1017 W/cm2 were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 1016 W/cm2. This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

  • 32.
    Andreeva, M. A.
    et al.
    Moscow MV Lomonosov State Univ, Fac Phys, Moscow 119991, Russia..
    Baulin, R. A.
    Moscow MV Lomonosov State Univ, Fac Phys, Moscow 119991, Russia..
    Slinko, O. V.
    Moscow MV Lomonosov State Univ, Fac Phys, Moscow 119991, Russia..
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Asadchikov, V. E.
    RAS, Shubnikov Inst Crystallog, Moscow 119333, Russia..
    Karimov, D. N.
    RAS, Shubnikov Inst Crystallog, Moscow 119333, Russia..
    Roshchin, B. S.
    RAS, Shubnikov Inst Crystallog, Moscow 119333, Russia..
    Ponomarev, D. A.
    MN Mikheev Inst Met Phys UB RAS, Ekaterinburg 620990, Russia..
    Romashev, L. N.
    MN Mikheev Inst Met Phys UB RAS, Ekaterinburg 620990, Russia..
    Chumakov, A. I.
    ESRF European Synchrotron, F-38043 Grenoble 9, France.;Kurchatov Inst, Natl Res Ctr, Moscow 123182, Russia..
    Bessas, D.
    ESRF European Synchrotron, F-38043 Grenoble 9, France..
    Ruffer, R.
    ESRF European Synchrotron, F-38043 Grenoble 9, France..
    Polarization selection in Mössbauer reflectivity for magnetic multilayer investigation2019In: VII Euro-Asian Symposium on Trends In Magnetism / [ed] Ustinov, V; Mushnikov, N, IOP Publishing , 2019, article id 012016Conference paper (Refereed)
    Abstract [en]

    Mossbauer reflectivity experiment with polarization selection are reported. The use of the LiF polarization analyzer allows us to get the pi ->sigma' peak on the reflectivity curve at the critical angle and Mossbauer pi ->sigma' reflectivity spectra of reasonable quality at the critical angle and also at the Bragg angles of superlattice. The impressive difference of the reflectivity spectra measured near the critical angle with and without polarizations analysis is observed for [Fe-57(10)/V-10](20) multilayer characterizing by the ferromagnetic interlayer coupling. The combined fit of the whole set of spectra measured at different angles reveals the existence of antiferromagnetic Fe oxide phases in the top three bilayers. The experiment demonstrates benefits of the Mossbauer reflectivity with polarization analysis in ultrathin surface layer investigations.

    Download full text (pdf)
    fulltext
  • 33.
    Ansari, Shaquib Rahman
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Suárez-López, Yael del Carmen
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Thersleff, Thomas
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Katsaros, Ioannis
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Material Science.
    Åhlén, Michelle
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Nanotechnology and Functional Materials.
    Karlgren, Maria
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Rinaldi-Ramos, Carlos
    Teleki, Alexandra
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Science for Life Laboratory, SciLifeLab.
    A pharmaceutical quality by design approach to develop high-performance nanoparticles for magnetic hyperthermiaManuscript (preprint) (Other academic)
  • 34.
    Anyfantis, Dimitrios I.
    et al.
    Univ Patras, Sch Nat Sci, Dept Mat Sci, Patras 26504, Greece..
    Ballani, Camillo
    Martin Luther Univ Halle Wittenberg, Inst Phys, Von Danckelmann Pl 3, D-06120 Halle, Germany..
    Kanistras, Nikos
    Univ Patras, Sch Nat Sci, Dept Mat Sci, Patras 26504, Greece..
    Barnasas, Alexandros
    Univ Patras, Sch Nat Sci, Dept Mat Sci, Patras 26504, Greece..
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Schmidt, Georg
    Martin Luther Univ Halle Wittenberg, Inst Phys, Von Danckelmann Pl 3, D-06120 Halle, Germany.;Martin Luther Univ Halle Wittenberg, Interdisziplinares Zentrum Mat Wissensch, Nanotechnikum Weinberg, Heinrich Damerow Str 4, D-06120 Halle, Germany..
    Papaioannou, Evangelos Th
    Martin Luther Univ Halle Wittenberg, Inst Phys, Von Danckelmann Pl 3, D-06120 Halle, Germany..
    Poulopoulos, Panagiotis
    Univ Patras, Sch Nat Sci, Dept Mat Sci, Patras 26504, Greece..
    Growth, Magnetic Anisotropies and Exchange Bias of Thin Ni0.95Fe0.05/NiFeO Multilayers2022In: Coatings, ISSN 2079-6412, Vol. 12, no 5, article id 627Article in journal (Refereed)
    Abstract [en]

    Ni0.95Fe0.05/NiFeO multilayers were fabricated by radio frequency magnetron sputtering and natural oxidation. Doping of Ni by only 5 at. % Fe results in enhanced layering quality as X-ray reflectivity reveals. Due to magnetostatic anisotropy, the multilayers were found to be in-plane magnetized. The influence of mild thermal annealing (T = 525 K) on the magnetic properties of NiFe/NiFeO multilayers is also investigated. Annealing results in the enhancement of perpendicular magnetic anisotropy, mainly due to an increase in the uniaxial volume anisotropy term. Temperature-dependent hysteresis measurements between 4-400 K revealed considerable enhancement of coercivity and appearance of exchange bias effect.

    Download full text (pdf)
    FULLTEXT01
  • 35.
    Anyfantis, Dimitrios, I
    et al.
    Univ Patras, Dept Mat Sci, Patras 26504, Greece.
    Sarigiannidou, Eirini
    Univ Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France.
    Rapenne, Laetitia
    Univ Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France.
    Stamatelatos, Alkeos
    Univ Patras, Dept Mat Sci, Patras 26504, Greece.
    Ntemogiannis, Dimitrios
    Univ Patras, Dept Mat Sci, Patras 26504, Greece.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Poulopoulos, Panagiotis
    Univ Patras, Dept Mat Sci, Patras 26504, Greece.
    Unexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO Multilayers After Mild Thermal Annealing2019In: IEEE Magnetics Letters, ISSN 1949-307X, E-ISSN 1949-3088, Vol. 10, article id 6104105Article in journal (Refereed)
    Abstract [en]

    We report on the significant enhancement of perpendicular magnetic anisotropy of Ni/NiO multilayers after mild annealing up to 90 min at 250 degrees C. Transmission electron microscopy shows that after annealing, a partial crystallization of the initially amorphous NiO layers occurs. This turns out to be the source of the anisotropy enhancement. Magnetic measurements reveal that even multilayers with Ni layers as thick as 7 nm, which in the as-deposited state showed in-plane anisotropy with square hysteresis loops, show reduced in-plane remanence after thermal treatment. Hysteresis loops recorded with the field in the normal-to-film-plane direction provide evidence for perpendicular magnetic anisotropy with up and down magnetic domains at remanence. A plot of effective uniaxial magnetic anisotropy constant times individual Ni layer thickness as a function of individual Ni layer thickness shows a large change in the slope of the data attributed to a drastic change of volume anisotropy. Surface anisotropy showed a small decrease because of some layer roughening introduced by annealing.

  • 36.
    Arnalds, Unnar B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Magnetic Order in Artificial Structures2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The topic of this thesis is the investigation of the magnetic properties of artificially created magnetic structures. Applying different characterization techniques, ranging from direct imaging methods to reciprocal space techniques, the properties of lithographically patterned arrays of magnetic thin film and multilayer elements are investigated by exploring their magnetic state, extending from the atomic scale up to collective ordering phenomena of nano-magnetic elements.

    Laterally patterned amorphous multilayer arrays of combined circular and ellipsoidal islands were investigated. The arrays contain a variety of length scales, ranging from their nanometer scale multilayer structure to their lateral periodicity in the micrometer range. The attributes of these arrays are explored using different techniques, applicable for addressing the magnetization at different length scales, including magneto-optical techniques, micromagnetic simulations and x-ray resonant magnetic scattering.

    Arrays of dipole interacting elongated magnetic elements composed of Pd(Fe) thin films were investigated. Pd(Fe) films have a low Curie temperature which can be tuned by the thickness of the Fe layer embedded in Pd. By this, the interaction and the shape anisotropy energies can be brought down to energy scales comparable to room temperature enabling the possibility of investigating the effect of thermal excitations on such arrays. The temperature dependent magnetization of an artificial square spin ice array was investigated by magneto-optical measurements demonstrating the possibility of observing an order-disorder transition in an artificial square spin ice system. The role of dipolar interactions and the possibility of achieving thermal ground state ordering was then further investigated by magnetically sensitive photoemission electron microscopy imaging of ring arrangements of elongated Pd(Fe) elements. The results reveal a high probability of achieving a thermal ground state ordering of the magnetization of the islands.

    List of papers
    1. Magnetic structure and diffracted magneto-optics of patterned amorphous multilayers
    Open this publication in new window or tab >>Magnetic structure and diffracted magneto-optics of patterned amorphous multilayers
    Show others...
    2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 14, p. 144434-1-144434-8, article id 144434Article in journal (Refereed) Published
    Abstract [en]

    We present magneto-optical Kerr effect measurements of patterned arrays of Co68Fe24Zr8 / Al2O3 amorphous multilayers. The multilayers were patterned in two dimensions into two different arrangements of circular and ellipsoidal islands. Magnetization loops were recorded in a longitudinal geometry using both the specularly reflected beam as well as diffracted beams scattered off the patterned films. The magnetization of the patterned structures is significantly different from the magnetization of a continuous multilayer owing to the lateral confinement of the pattern and the introduction of additional dipolar coupling between the layers at the edges of the islands. By investigating the magnetic response at the different diffraction orders from the two different configurations of islands we are able to observe the magnetization at different length scales and determine the magnetic response of the circular and ellipsoidal islands individually.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-133717 (URN)10.1103/PhysRevB.82.144434 (DOI)000283423000004 ()
    Funder
    Swedish Research CouncilKnut and Alice Wallenberg Foundation
    Available from: 2010-11-18 Created: 2010-11-15 Last updated: 2017-12-12Bibliographically approved
    2. X-ray resonant magnetic scattering from patterned multilayers
    Open this publication in new window or tab >>X-ray resonant magnetic scattering from patterned multilayers
    Show others...
    2012 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 6, p. 064426-Article in journal (Refereed) Published
    Abstract [en]

    We report on x-ray resonant magnetic scattering from laterally patterned arrays of amorphous Co68Fe24Zr8/Al2O3 multilayers. The arrays are composed of circular and ellipsoidal elements which display distinct individual magnetic responses enabling the investigation of the dependence of the observed magnetization on the scattering condition. We focus our attention to special points in reciprocal space, relating to the lateral and perpendicular structure of the samples, thereby revealing the magnetic structure of the multilayered arrays. This allows a comparison of the observed magnetization under different scattering conditions to magneto-optical measurements. The scattering data are supported by micromagnetic simulations which further enhance our understanding of the intricate charge and magnetic scattering from three dimensional patterns.

    National Category
    Atom and Molecular Physics and Optics
    Research subject
    Physics of Matter
    Identifiers
    urn:nbn:se:uu:diva-172373 (URN)10.1103/PhysRevB.86.064426 (DOI)000307719400003 ()
    Available from: 2012-04-09 Created: 2012-04-09 Last updated: 2017-12-07Bibliographically approved
    3. Melting artificial spin ice
    Open this publication in new window or tab >>Melting artificial spin ice
    Show others...
    2012 (English)In: New Journal of Physics, E-ISSN 1367-2630, Vol. 14, p. 035009-Article in journal (Refereed) Published
    Abstract [en]

    Artificial spin ice arrays of micromagnetic islands are a means of engineering additional energy scales and frustration into magnetic materials. Here we demonstrate a magnetic phase transition in an artificial square spin ice and use the symmetry of the lattice to verify the presence of excitations far below the ordering temperature. We do this by measuring the temperature dependent magnetisation in different principal directions and comparing with simulations of idealised statistical mechanical models. Our results confirm a dynamical pre-melting of the artificial spin ice structure at a temperature well below the intrinsic ordering temperature of the island material. We thus create a spin ice array that has real thermal dynamics of the artificial spins over an extended temperature range.

    Keywords
    artificial spin ice, ising model, magnetization dynamics
    National Category
    Other Physics Topics
    Research subject
    Physics of Matter
    Identifiers
    urn:nbn:se:uu:diva-168982 (URN)10.1088/1367-2630/14/3/035009 (DOI)000302342000002 ()
    Funder
    Swedish Research Council
    Available from: 2012-02-21 Created: 2012-02-21 Last updated: 2024-01-17Bibliographically approved
    4. Thermalized ground state of artificial kagome spin ice building blocks
    Open this publication in new window or tab >>Thermalized ground state of artificial kagome spin ice building blocks
    Show others...
    2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 11, p. 112404-Article in journal, Letter (Other academic) Published
    Abstract [en]

    We present a direct magnetic imaging study on the thermal macrospin ordering of artificial kagome spin ice building blocks. Using photoemission electron microscopy, employing x-ray magnetic circular dichroism, we are able to resolve the single domain magnetic nature of the macrospins and determine the states of the combined building block structures. The nano-patterning and material selection allows thermally activated magnetization reversal for the macrospins to occur. The ordering of the macrospins is dominated by the ground state, consistent with a thermal ground state ordering. This work paves the way for the realization of extended artificial spin ice structures exhibiting experimentally accessible thermal behavior

    National Category
    Condensed Matter Physics
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-172374 (URN)10.1063/1.4751844 (DOI)000309329300045 ()
    Available from: 2012-04-09 Created: 2012-04-09 Last updated: 2017-12-07Bibliographically approved
    5. Element specific magnetization in Fe/Pd quantum well structures
    Open this publication in new window or tab >>Element specific magnetization in Fe/Pd quantum well structures
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-168443 (URN)
    Available from: 2012-02-16 Created: 2012-02-10 Last updated: 2012-08-01
    Download full text (pdf)
    fulltext
  • 37.
    Arnalds, Unnar B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ahlberg, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brewer, Matthew S.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Papaioannou, Evangelos Th.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Karimipour, Masoud
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Korelis, Panagiotis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stein, Aaron
    Olafsson, Sveinn
    Hase, Thomas P. A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermal transitions in nano-patterned XY-magnets2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 4, p. 042409-Article in journal (Refereed)
    Abstract [en]

    We have fabricated ultra-thin disc shaped islands wherein shape anisotropy confines the moment to the island plane, creating XY-like superspins. At low temperatures, the superspins are blocked, and, as the temperature is increased, they undergo a transition into a superparamagnetic state. The onset of this dynamic superspin state scales with the diameter of the islands, and it persists up to a temperature governed by the intrinsic ordering temperature of the island material defining a range in temperature in which dynamic behavior of the magnetic islands can be obtained.

  • 38.
    Arnalds, Unnar B.
    et al.
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Chico, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Bärenbold, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Verschuuren, Marc A.
    Philips Res Labs, Eindhoven, Netherlands..
    Wolff, Ulrike
    IFW Dresden, Inst Metall Mat, D-01171 Dresden, Germany..
    Neu, Volker
    IFW Dresden, Inst Metall Mat, D-01171 Dresden, Germany..
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    A new look on the two-dimensional Ising model: thermal artificial spins2016In: New Journal of Physics, E-ISSN 1367-2630, Vol. 18, article id 023008Article in journal (Refereed)
    Abstract [en]

    We present a direct experimental investigation of the thermal ordering in an artificial analogue of an asymmetric two-dimensional Ising system composed of a rectangular array of nano-fabricated magnetostatically interacting islands. During fabrication and below a critical thickness of the magnetic material the islands are thermally fluctuating and thus the system is able to explore its phase space. Above the critical thickness the islands freeze-in resulting in an arrested thermalized state for the array. Determining the magnetic state we demonstrate a genuine artificial two-dimensional Ising system which can be analyzed in the context of nearest neighbor interactions.

    Download full text (pdf)
    fulltext
  • 39.
    Arnalds, Unnar B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Papaioannou, Evangelos Th.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hase, Thomas P. A.
    Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom.
    Raanaei, Hossein
    Department of Physics, Persian Gulf University, Bushehr 75168, Iran.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Charlton, Timothy R.
    ISIS, Harwell Science and Innovation Campus, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxon OX11 0QX, United Kingdom.
    Langridge, Sean
    ISIS, Harwell Science and Innovation Campus, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxon OX11 0QX, United Kingdom.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Magnetic structure and diffracted magneto-optics of patterned amorphous multilayers2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 14, p. 144434-1-144434-8, article id 144434Article in journal (Refereed)
    Abstract [en]

    We present magneto-optical Kerr effect measurements of patterned arrays of Co68Fe24Zr8 / Al2O3 amorphous multilayers. The multilayers were patterned in two dimensions into two different arrangements of circular and ellipsoidal islands. Magnetization loops were recorded in a longitudinal geometry using both the specularly reflected beam as well as diffracted beams scattered off the patterned films. The magnetization of the patterned structures is significantly different from the magnetization of a continuous multilayer owing to the lateral confinement of the pattern and the introduction of additional dipolar coupling between the layers at the edges of the islands. By investigating the magnetic response at the different diffraction orders from the two different configurations of islands we are able to observe the magnetization at different length scales and determine the magnetic response of the circular and ellipsoidal islands individually.

    Download full text (pdf)
    fulltext
  • 40.
    Arnalds, Unnar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Farhan, Alan
    Paul Scherrer Institut.
    Chopdekar, Rajesh
    Paul Scherrer Institut.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Balan, Ana
    Paul Scherrer Institut.
    Papaioannou, Evangelos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahlberg, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nolting, Frithjof
    Paul Scherrer Institut.
    Heyderman, Laura
    Paul Scherrer Institut.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermalized ground state of artificial kagome spin ice building blocks2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 11, p. 112404-Article in journal (Other academic)
    Abstract [en]

    We present a direct magnetic imaging study on the thermal macrospin ordering of artificial kagome spin ice building blocks. Using photoemission electron microscopy, employing x-ray magnetic circular dichroism, we are able to resolve the single domain magnetic nature of the macrospins and determine the states of the combined building block structures. The nano-patterning and material selection allows thermally activated magnetization reversal for the macrospins to occur. The ordering of the macrospins is dominated by the ground state, consistent with a thermal ground state ordering. This work paves the way for the realization of extended artificial spin ice structures exhibiting experimentally accessible thermal behavior

  • 41.
    Arnalds, Unnar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hase, Thomas
    University of Warwick.
    Papaioannou, Evangelos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Raanaei, Hossein
    Persian Gulf University.
    Abrudan, Radu
    Ruhr-Universitat Bochum.
    Charlton, Timothy
    ISIS, Rutherford Appleton Laboratory.
    Langridge, Sean
    ISIS, Rutherford Appleton Laboratory.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    X-ray resonant magnetic scattering from patterned multilayers2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 6, p. 064426-Article in journal (Refereed)
    Abstract [en]

    We report on x-ray resonant magnetic scattering from laterally patterned arrays of amorphous Co68Fe24Zr8/Al2O3 multilayers. The arrays are composed of circular and ellipsoidal elements which display distinct individual magnetic responses enabling the investigation of the dependence of the observed magnetization on the scattering condition. We focus our attention to special points in reciprocal space, relating to the lateral and perpendicular structure of the samples, thereby revealing the magnetic structure of the multilayered arrays. This allows a comparison of the observed magnetization under different scattering conditions to magneto-optical measurements. The scattering data are supported by micromagnetic simulations which further enhance our understanding of the intricate charge and magnetic scattering from three dimensional patterns.

  • 42. Asano, Kohta
    et al.
    Westerwaal, Ruud J.
    Anastasopol, Anca
    Mooij, Lennard P. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Boelsma, Christiaan
    Ngene, Peter
    Schreuders, Herman
    Eijt, Stephan W. H.
    Dam, Bernard
    Destabilization of Mg Hydride by Self-Organized Nanoclusters in the Immiscible Mg-Ti System2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 22, p. 12157-12164Article in journal (Refereed)
    Abstract [en]

    Mg is an attractive hydrogen storage material not only because of its high gravimetric and volumetric hydrogen capacities but also because of it low material costs. However, the hydride of MgH2 is too stable to release hydrogen under moderate conditions. We demonstrate that the formation of nanometer-sized clusters of Mg reduces the stability of MgH2 by the interface energy effect in the immiscible Mg-Ti system. Ti-rich MgxTi1-x (x < 0.5) thin films deposited by magnetron sputtering have a hexagonal close packed (HCP) structure, which forms a face-centered cubic (FCC) hydride phase upon hydrogenation. Positron Doppler broadening depth profiling demonstrates that after hydrogenation, nanometer-sized MgH2 clusters are formed which are coherently embedded in an FCC TiH2 matrix. The P (pressure)-T (optical transmission) isotherms measured by hydrogenography show that these MgH2 clusters are destabilized. This indicates that the formation of nanometer-sized Mg allows for the development of a lightweight and cheap hydrogen storage material with a lower desorption temperature.

  • 43. Aslibeiki, B.
    et al.
    Kameli, P.
    Ehsani, M. H.
    Salamati, H.
    Muscas, Giuseppe
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Agostinelli, E.
    Foglietti, V.
    Casciardi, S.
    Peddis, D.
    Solvothermal synthesis of MnFe2O4 nanoparticles: The role of polymer coating on morphology and magnetic properties2016In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 399, p. 236-244Article in journal (Refereed)
  • 44.
    Aslibeiki, Bagher
    et al.
    Department of Physics, University of Tabriz, Tabriz 51666-16471, Iran .
    Kameli, Parviz
    Department of Physics, Isfahan University of Technology, Isfahan, 84156-83111, Iran .
    Salamati, Hadi
    Department of Physics, Isfahan University of Technology, Isfahan, 84156-83111, Iran .
    Concas, Giorgio
    Dipartimento di Fisica, Università di Cagliari, S.P. Monserrato-Sestu km 0,700, 09042 Monserrato (CA), Italy.
    Salvador Fernandez, Maria
    Dipartimento di Scienze, Università degli Studi Roma Tre, via della vasca navale, 84 - 00146 Roma, Italy; Department of Physics, University of Oviedo, Campus de Viesques, 33204 Gijón, Spain.
    Talone, Alessandro
    Dipartimento di Scienze, Università degli Studi Roma Tre, via della vasca navale, 84 - 00146 Roma, Italy; Istituto di Struttura della Materia-CNR, 00015 Monterotondo Scalo (RM), Italy .
    Muscas, Giuseppe
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Peddis, Davide
    Istituto di Struttura della Materia-CNR, 00015 Monterotondo Scalo (RM), Italy; Department of Chemistry and Industrial Chemistry (DCIC), University of Genova, Genova, Italy .
    Co-doped MnFe2O4 nanoparticles: magnetic anisotropy and interparticle interactions2019In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 10, p. 856-865Article in journal (Refereed)
    Abstract [en]

    The effect of cobalt doping on the magnetic properties of Mn1−xCoxFe2O4 nanoparticles was investigated. All samples consist of ensembles of nanoparticles with a spherical shape and average diameter of about 10 nm, showing small structural changes due to the substitution. Besides having the same morpho-structural properties, the effect of the chemical composition, i.e., the amount of Co doping, produces marked differences on the magnetic properties, especially on the magnetic anisotropy, with evident large changes in the coercive field. Moreover, Co substitution has a profound effect on the interparticle interactions, too. A dipolar-based interaction regime is detected for all samples; in addition, the intensity of the interactions shows a possible relation with the single particle anisotropy. Finally, the sample with the strongest interaction regime shows a superspin glass state confirmed by memory effect dynamics.

    Download full text (pdf)
    fulltext
  • 45.
    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 University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    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 reflectometry2015In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 352, p. 49-53Article in journal (Refereed)
    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.

  • 46.
    Aydin, Alhun
    et al.
    Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA..
    Sisman, Altug
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Black-Schaffer, Annica M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dutta, Paramita
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Phys Res Lab, Theoret Phys Div, Ahmadabad 380009, Gujarat, India.;Birla Inst Technol & Sci Pilani, Dept Phys, Pilani 333031, Rajasthan, India..
    Thermodefect voltage in graphene nanoribbon junctions2022In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 34, no 19, article id 195304Article in journal (Refereed)
    Abstract [en]

    Thermoelectric junctions are often made of components of different materials characterized by distinct transport properties. Single material junctions, with the same type of charge carriers, have also been considered to investigate various classical and quantum effects on the thermoelectric properties of nanostructured materials. We here introduce the concept of defect-induced thermoelectric voltage, namely, thermodefect voltage, in graphene nanoribbon (GNR) junctions under a temperature gradient. Our thermodefect junction is formed by two GNRs with identical properties except the existence of defects in one of the nanoribbons. At room temperature the thermodefect voltage is highly sensitive to the types of defects, their locations, as well as the width and edge configurations of the GNRs. We computationally demonstrate that the thermodefect voltage can be as high as 1.7 mV K-1 for 555-777 defects in semiconducting armchair GNRs. We further investigate the Seebeck coefficient, electrical conductance, and electronic thermal conductance, and also the power factor of the individual junction components to explain the thermodefect effect. Taken together, our study presents a new pathway to enhance the thermoelectric properties of nanomaterials.

    Download full text (pdf)
    fulltext
  • 47.
    Azimi Mousolou, Vahid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Isfahan, Fac Math & Stat, Dept Appl Math & Comp Sci, Esfahan 8174673441, Iran..
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delin, Anna
    Alballova Univ Ctr, Sch Engn Sci, KTH Royal Inst Technol, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, Swedish Sci Res Ctr SeRC, SE-10044 Stockholm, Sweden..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Thonig, Danny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Quantum Matter Theory.
    Entanglement duality in spin-spin interactions2022In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 106, no 3, article id 032407Article in journal (Refereed)
    Abstract [en]

    We examine entanglement of thermal states for spin-1/2 dimers in external magnetic fields. Entanglement transition in the temperature-magnetic-field plane demonstrates a duality in spin-spin interactions. This identifies a pair of dual categories of symmetric and antisymmetric dimers with each category classified into toric entanglement classes. The entanglement transition line is preserved from each toric entanglement class to its dual toric class. The toric classification is an indication of the topological signature of the entanglement, which bring about topological stability that could be relevant for quantum information processing.

    Download full text (pdf)
    FULLTEXT01
  • 48.
    Azimi Mousolou, Vahid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Isfahan, Fac Math & Stat, Dept Appl Math & Comp Sci, Esfahan 8174673441, Iran.
    Liu, Yuefei
    AlbaNova Univ Ctr, KTH Royal Inst Technol, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden..
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delin, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. AlbaNova Univ Ctr, KTH Royal Inst Technol, Sch Engn Sci, Dept Appl Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, Swedish E Sci Res Ctr, SE-10044 Stockholm, Sweden..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Thonig, Danny
    Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Quantum Matter Theory.
    Magnon-magnon entanglement and its quantification via a microwave cavity2021In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 104, no 22, article id 224302Article in journal (Refereed)
    Abstract [en]

    Quantum magnonics is an emerging research field, with great potential for applications in magnon based hybrid systems and quantum information processing. Quantum correlation, such as entanglement, is a central resource in many quantum information protocols that naturally comes about in any study toward quantum technologies. This applies also to quantum magnonics. Here, we investigate antiferromagnetic coupling of two ferromagnetic sublattices that can have two different magnon modes. We show how this may lead to experimentally measurable bipartite continuous-variable magnon-magnon entanglement. The entanglement can be fully characterized via a single squeezing parameter or, equivalently, entanglement parameter. The clear relation between the entanglement parameter and the Einstein, Podolsky, and Rosen (EPR) function of the ground state opens up for experimental quantification magnon-magnon continuous-variable entanglement and EPR nonlocality. We propose a practical experimental realization to measure the EPR function of the ground state, in a setting that relies on magnon-photon interaction in a microwave cavity.

    Download full text (pdf)
    FULLTEXT01
  • 49. Azofeifa, D. E.
    et al.
    Clark, N.
    Vargas, W. E.
    Solis, H.
    Palsson, G. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjorvarsson, B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Temperature-and hydrogen-induced changes in the optical properties of Pd capped V thin films2012In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 86, no 6, p. 065702-Article in journal (Refereed)
    Abstract [en]

    Optical properties of V thin films deposited on MgO substrates have been obtained from spectrophotometric measurements. The V films were coated with a thin Pd layer to protect them from oxidation and to favor absorption of atomic hydrogen. Electrical resistance was recorded while hydrogen pressure was increased slowly up to 750mbar keeping the temperature constant. Simultaneously, visible and near-infrared transmittance spectra of this Pd/V/MgO system were measured. The spectra were numerically inverted to obtain the spectral behavior of the Pd and V dielectric functions at 22 and 140 degrees C. Hydrogen concentrations were first determined from the combined effect of hydrogen content on the electrical resistance and on the optical direct transmission of the system. Then, determination of these concentrations was improved using retrieved values of the absorption coefficients of the hydrides and taking into account the structural change of V and the volumetric expansion of Pd. Good agreement is established when considering qualitative correlations between spectral features of the optimized PdHy and VHx dielectric functions and band structure calculations and densities of states for these two transition metal hydrides.

  • 50. Azofeifa, D. E.
    et al.
    Clark, N.
    Vargas, W. E.
    Solis, H.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hydrogen induced changes in the optical properties of Pd capped V thin films2013In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 580, no Suppl. 1, p. S114-S118Article in journal (Refereed)
    Abstract [en]

    Optical properties of 50 nm thick single crystal vanadium films deposited on double side polished MgO substrates have been obtained from spectrophotometric measurements. The films were coated with a polycrystalline Pd layer (5 nm thick) to protect them from oxidation and to favor absorption of atomic hydrogen. Electrical resistance was recorded while hydrogen pressure was increased slowly up to 750 mbar keeping temperature constant. Simultaneously, under normal incidence of non-polarized radiation [350-950 nm], transmittance spectra of this Pd/V/MgO system were measured. These were numerically inverted to obtain the spectral behavior of the Pd, V. PdHy, and VHx dielectric functions at 22 and 140 degrees C, and at 750 mbar. Hydrogen concentration in V film was first determined from a resisto-optical method. Finally, we demonstrate the possibility to determine the concentration in the Pd and the V layers independently, solely using the changes in the optical transmission. 

1234567 1 - 50 of 701
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf