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  • 101.
    Björkman, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Adaptive smearing for Brillouin zone integrationManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    We suggest a simple scheme for automatically determining the witdth parameter of smearing methods of the Brillouin zone integration in electronic structure calculation. The scheme retains one free parameter that at any time can be eliminated by choosing a denser k-space mesh until the desired accuracy is obtained. Tests are carried out in the context of Methfessel-Paxton smearing. This adaptive Gaussian smearing (AGS) is easily implemented, variational with respect to partial occupancies and free from spurious occupancies that are negative or larger than one. Its convergence properties are similar to those obtained with the modified tetrahedron method for energy resolution of ≥ 0 .1 meV.

  • 102.
    Björkman, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Lizárraga, Raquel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Wills, John M.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Andersson, Per H.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Theoretical studies of the incommensurate magnetic structure of a heavy fermion system: CeRhIn52010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 9, p. 094433-Article in journal (Refereed)
    Abstract [en]

    We have investigated the electronic structure and the incommensurate magnetic configuration of the pressure-induced superconductor CeRhIn5. Noncollinear first-principles calculations were performed in the local-density approximation plus U scheme. The observed magnetic configuration is described accurately in our calculations, especially considering the minute energy scale which is relevant (microelectron volt). The band structure and Fermi surfaces were investigated and nesting was found to be responsible for the complex noncollinear magnetic state of CeRhIn5.

  • 103.
    Björneholm, Olle
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Ohrwall, Gunnar
    Tchaplyguine, Maxim
    Free clusters studied by core-level spectroscopies2009In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 601, no 1-2, p. 161-181Article, review/survey (Refereed)
    Abstract [en]

    In this review we describe the development and current status of free clusters studied using core-level spectroscopies. This topic ranges from simple model systems, such as rare gas clusters, to molecular clusters, and clusters of solids, held together by ionic, covalent and metallic bonding.

  • 104. Bleskov, I. D.
    et al.
    Smirnova, A
    Vekilov, Kh
    Korzhavyi, A
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Katsnelson, M
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Abrikosov, A
    Isaev, E. I.
    Ab initio calculations of elastic properties of Ru1-xNixAl superalloys2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 16, p. 161901-Article in journal (Refereed)
    Abstract [en]

    Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C-' and C-11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.

  • 105. Blomquist, J.
    et al.
    Walle, L. E.
    Uvdal, P.
    Borg, A.
    Sandell, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Water Dissociation on Single Crystalline Anatase TiO2(001) Studied by Photoelectron Spectroscopy2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 42, p. 16616-16621Article in journal (Refereed)
    Abstract [en]

    The adsorption of water on the anatase TiO2(001)-(4 x 1) surface is studied using synchrotron radiation-excited core level photoelectron spectroscopy. The coverage-dependent adsorption of water at low temperature is monitored and compared to the sequence obtained after heating of a water multilayer. Two adsorption phases of submonolayer coverage can be defined: Phase 1 consists only of dissociated water, observed as OH-groups. This phase is found at low coverage at low temperature (190 K) and is the only state of adsorbed water above similar to 230 K. The saturation coverage of phase 1 is consistent with dissociation on the 4-fold-coordinated Ti ridge atoms of the (4 x 1) surface reconstruction. Phase 2 is found at higher coverage, reached at lower temperature. It consists of a mixture of dissociated and molecular water with a ratio of 1:1 at 170 K. The molecular water is found to bond to the hydroxyl groups. The hydroxyl coverage of phase 2 is approximately 2 times that of phase 1. The results suggest that the OH and H2O species of phase 2 are confined to the ridges of the surface.

  • 106. Bolton, Kim
    et al.
    Saalman, Elisabeth
    Christie, Michael
    Ingerman, Åke
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    SimChemistry as an active learning tool in chemical education.2008In: Chemistry education, ISSN 1109-4028, E-ISSN 1109-4028, Vol. 9, no 3, p. 277-284Article in journal (Refereed)
    Abstract [en]

    The publicly available free computer program, SimChemistry, was used as an active learning tool in the chemical engineering curriculum at the University College of Borås, Sweden. The activity involved students writing their own simulation programs on topics in the area of molecular structure and interactions. Evaluation of the learning experience was done using interviews and by comparing learning outcomes with previous teachings of the topics. Overall, the outcome was interactively engaging group work, high quality construction of simulations, and a much better ability to explain molecular-level chemical concepts and their relations. An interesting perception that emerged during the interviews was that many of the students were unable to explicitly describe the improvement in learning that they had experienced. However, they did recognize that learning had occurred, and all firmly and positively recommended that the initiative be continued for subsequent courses.

  • 107. Bonhommeau, S.
    et al.
    Ottosson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Pokapanich, Wandared
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Eberhardt, W.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Aziz, E.
    Solvent Effect of Alcohols at the L-edge of Iron in Solution: X-ray Absorption and Multiplet Calculations2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 40, p. 12571-12574Article in journal (Refereed)
  • 108. Boström, Jannika E.
    et al.
    Fransson, Thord
    Henshaw, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Jakobsson, Sven
    Kullberg, Cecilia
    Åkesson, Susanne
    Autumn migratory fuelling: a response to simulated magnetic displacements in juvenile wheatears, Oenanthe oenanthe2010In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 64, no 11, p. 1725-1732Article in journal (Refereed)
    Abstract [en]

    Recent experiments exposing migratory birds to altered magnetic fields simulating geographical displacements have shown that the geomagnetic field acts as an external cue affecting migratory fuelling behaviour. This is the first study investigating fuel deposition in relation to geomagnetic cues in long-distance migrants using the western passage of the Mediterranean region. Juvenile wheatears (Oenanthe oenanthe) were exposed to a magnetically simulated autumn migration from southern Sweden to West Africa. Birds displaced parallel to the west of their natural migration route, simulating an unnatural flight over the Atlantic Ocean, increased their fuel deposition compared to birds experiencing a simulated migration along the natural route. These birds, on the other hand, showed relatively low fuel loads in agreement with earlier data on wheatears trapped during stopover. The experimental displacement to the west, corresponding to novel sites in the Atlantic Ocean, led to a simulated longer distance to the wintering area, probably explaining the observed larger fuel loads. Our data verify previous results suggesting that migratory birds use geomagnetic cues for fuelling decisions and, for the first time, show that birds, on their first migration, can use geomagnetic cues to compensate for a displacement outside their normal migratory route, by adjusting fuel deposition.

  • 109.
    Brucas, Rimantas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hanson, M.
    Apell, P.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, R.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Tunneling and charging effects in discontinuous superparamagnetic Ni81Fe19/Al2O3 multilayers2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 22, p. 224437-Article in journal (Refereed)
    Abstract [en]

    The magnetic and transport properties of films based on discontinuous layers of Ni81Fe19 (Py) embedded in Al2O3 were investigated. In films with nominal Py thicknesses 6 and 8 angstrom superparamagnetic particles with median diameters D-med = 2.8 and 3.1 nm and distribution widths sigma(D)= 1.2 and 1.3 nm were formed. Current voltage (IU) curves were measured with the current perpendicular to the film plane. The analyses show that the charge transport occurs via tunneling; with the charging energy supplied by thermal fluctuations at high temperature, T >= 100 K, and by the electric field at low temperature, T < 10 K. The separation of the two regimes allows independent estimates of the mean charging energy < EC > approximate to 40 meV for both samples; from the resistance R versus T analyzed in an effective-medium model at high temperature and from I versus U at 4 K. In order to obtain a consistent description of the transport properties, the size distributions must be included to account for the deviation from the single size behavior R similar to exp(E-C/k(B)T) at high T. The scaling parameter in the relation I proportional to (U/U-th-1)(gamma), where U-th is the threshold for conduction, is estimated to gamma approximate to 2 at 4 K. The superparamagnetic relaxation of the particles becomes blocked below a temperature T approximate to 20 K respective 30 K for 6 and 8 angstrom. The magnetic field (B) dependence of the resistance R(B) displays a single maximum of the ratio MR = [R(B)-R(2 T)]/R(2 T) in zero field at room temperature and a characteristic splitting of the peak at 4 K, attributed to the blocking. The maxima, approximate to 0.9% for 6 angstrom and 1.1% for 8 angstrom, are positioned at fields about a factor of two to three higher than the coercive fields of the samples.

  • 110.
    Bruehwiler, Paul A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Barbezat, Michel
    Necola, Adly
    Kohls, Doug J.
    Bunk, Oliver
    Schaefer, Dale W.
    Poetschke, Petra
    Comparison of quasistatic to impact mechanical properties of multiwall carbon nanotube/polycarbonate composites2010In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 25, no 6, p. 1118-1130Article in journal (Refereed)
    Abstract [en]

    We report the quasistatic tensile and impact penetration properties (falling dart test) of injection-molded polycarbonate samples, as a function of multiwall carbon nanotube (MWNT) concentration (0.0-2.5%). The MWNT were incorporated by dilution of a commercial MWNT/polycarbonate masterbatch. The stiffness and quasistatic yield strength of the composites increased approximately linearly with MWNT concentration in all measurements. The energy absorbed in fracture was, however, a negative function of the MWNT concentration, and exhibited different dependencies in quasistatic and impact tests. Small-angle x-ray scattering (SAXS) showed that the dispersion of the MWNT was similar at all concentrations. The negative effects on energy absorption are attributed to agglomerates remaining in the samples, which were observed in optical microscopy and SAXS. Overall, there was a good correspondence between static and dynamic energy absorption.

  • 111.
    Brändas, Erkki J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Levitina, Tatiana
    Filter Diagonalization: filtering and postprocessing with prolates.2009In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 180, no 9, p. 1448-1457Article in journal (Refereed)
    Abstract [en]

    A detailed account is given of a recent modification of the Filter Diagonalization technique that serves to analyze a signal spectrum within a selected energy range. Our approach employs for filtering the eigenfunctions of the Finite Fourier Transform, or prolates, which are superior to other filters due to their special properties. In particular, prolates are simultaneously band-limited and highly concentrated at a finite time-interval, producing filters with optimal accuracy. In addition both features are acquired by the convolution of a band-limited function with a prolate, that permits the latter to be interpolated via the Walter and Shen sampling formula, which essentially simplifies the supplementary computations. Rigorous filtering error estimates are obtained. Test calculations illustrate the facilities of the presented modification.

  • 112. Buitelaar, M. R.
    et al.
    Fransson, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Cantone, A. L.
    Smith, C. G.
    Anderson, D.
    Jones, G. A. C.
    Ardavan, A.
    Khlobystov, A. N.
    Watt, A. A. R.
    Porfyrakis, K.
    Briggs, G. A. D.
    Pauli spin blockade in carbon nanotube double quantum dots2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 24, p. 245439-Article in journal (Refereed)
    Abstract [en]

    We report Pauli spin blockade in a carbon nanotube double quantum dot defined by tunnel barriers at the contacts and a structural defect in the nanotube. We observe a pronounced current suppression for negative source-drain bias voltages, which is investigated for both symmetric and asymmetric coupling of the quantum dots to the leads. The measured differential conductance agrees well with a theoretical model of a double quantum dot system in the spin-blockade regime, which allows us to estimate the occupation probabilities of the relevant singlet and triplet states. This work shows that effective spin-to-charge conversion in nanotube quantum dots is feasible and opens the possibility of single-spin readout in a material that is not limited by hyperfine interaction with nuclear spins.

  • 113.
    Bultmark, F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Dewhurst, K.
    Singh, D. J.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Tests of the efficiency of an augmented distorted planewave basis in electronic structure calculations2008In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 23, p. 235241-Article in journal (Refereed)
    Abstract [en]

    An augmented distorted planewave plus local orbital basis set has been developed and implemented in a simple fashion in order to test its efficiency for electronic structure calculations. It is based on the idea of using distorted planewaves (Gygi 1993 Phys. Rev. B 48 11692) as basis functions in the interstitial region instead of ordinary planewaves, as in the usual linearized augmented planewave and augmented planewave plus local orbitals methods. This is shown to lead to a significantly more rapid convergence for open structures as well as a modestly improved convergence for close packed structures.

  • 114.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Distorted Space and Multipoles in Electronic Structure Calculations2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns methods for electronic structure calculations and some applications of the methods.

    The augmented planewave (APW) basis set and it’s relatives LAPW (linearised APW) and APW+lo (local orbitals) have been widely used for electronic structure calculations. Here a modification of the APW basis set based on a transformation of the basis functions from a curvilinear coordinate system. Applications to a few test systems show that the modified basis set may speed up electronic structure calculations of sparse systems.

    The local density approximation (LDA) is used in density functional theory. Although it is the simplest possible approximation possible for the unknown exchange-correlation energy functional, it has proven to give quite accurate results for a wide range of systems. LDA fails in systems where the non-local effects are important. By including non-local effects by adding an orbital dependent term to the energy functional, through for example the LDA+U method, the calculated properties of many materials are closer to experimental observations. In the thesis the most general formulation of the LDA+U method is presented and a new way of interpreting the results of a calculations by formulating the orbital dependent part of the energy functional in terms of multipole momentum tensors. Applications to some early actinide systems leads to a reformulations of Hund’s rules for polarisations associated with the spin and orbital magnetic moment and a suggestion for similar rules, Katt’s rules, valid in the strong spin orbit coupling regime.

    List of papers
    1. Tests of the efficiency of an augmented distorted planewave basis in electronic structure calculations
    Open this publication in new window or tab >>Tests of the efficiency of an augmented distorted planewave basis in electronic structure calculations
    2008 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 23, p. 235241-Article in journal (Refereed) Published
    Abstract [en]

    An augmented distorted planewave plus local orbital basis set has been developed and implemented in a simple fashion in order to test its efficiency for electronic structure calculations. It is based on the idea of using distorted planewaves (Gygi 1993 Phys. Rev. B 48 11692) as basis functions in the interstitial region instead of ordinary planewaves, as in the usual linearized augmented planewave and augmented planewave plus local orbitals methods. This is shown to lead to a significantly more rapid convergence for open structures as well as a modestly improved convergence for close packed structures.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98058 (URN)10.1088/0953-8984/20/23/235241 (DOI)000256172800043 ()
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2017-12-13Bibliographically approved
    2. Multipole decomposition of LDA+U energy and its application to actinides compounds
    Open this publication in new window or tab >>Multipole decomposition of LDA+U energy and its application to actinides compounds
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 3, p. 035121-Article in journal (Refereed) Published
    Abstract [en]

    A general reformulation of the exchange energy of 5f shell is applied   in the analysis of the magnetic structure of various actinides compounds in the framework of LDA + U method. The calculations are   performed in a convenient scheme with essentially only one free   parameter, the screening length. The results are analyzed in terms of  different polarization channels due to different multipoles. Generally   it is found that the spin-orbital polarization is dominating. This can   be viewed as a strong enhancement of the spin-orbit coupling in these   systems. This leads to a drastic decrease in spin polarization in   accordance with experiments. The calculations are able to correctly   differentiate magnetic and nonmagnetic Pu system. Finally, in all   magnetic systems an unusual multipolar order is observed, whose   polarization energy is often larger in magnitude than the one of spin polarization.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98059 (URN)10.1103/PhysRevB.80.035121 (DOI)000268617800055 ()
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2017-12-13Bibliographically approved
    3. Exchange energy dominated by large orbital spin-currents in δ-Pu
    Open this publication in new window or tab >>Exchange energy dominated by large orbital spin-currents in δ-Pu
    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 10, p. 100404-Article in journal (Refereed) Published
    Abstract [en]

    The electronic structure of the anomalous delta phase of Pu is analyzed by a general and exact reformulation of the exchange energy of the f shell. It is found that the dominating contribution to the exchange energy is a polarization of orbital spin-currents that preserves the time-reversal symmetry; hence a nonmagnetic solution in accordance with experiments. The analysis brings a unifying picture of the role of exchange in the 5f shell with its relatively strong spin-orbit coupling. The results are in good accordance with recent measurements of the branching ratio for the d to f transition in the actinides.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98060 (URN)10.1103/PhysRevB.78.100404 (DOI)000259690400008 ()
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2017-12-13Bibliographically approved
    4. Itinerant Magnetic Multipole Moments of Rank Five as the Hidden Order in URu2Si2
    Open this publication in new window or tab >>Itinerant Magnetic Multipole Moments of Rank Five as the Hidden Order in URu2Si2
    2009 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 10, p. 107202-Article in journal (Refereed) Published
    Abstract [en]

    A broken symmetry ground state without any magnetic moments has been   calculated by means of the local-density approximation to density   functional theory plus a local exchange term, the so-called LDA+U   approach, for URu2Si2. The solution is analyzed in terms of a multipole   tensor expansion of the itinerant density matrix and is found to be a   nontrivial magnetic multipole. Analysis and further calculations show   that this type of multipole enters naturally in time reversal breaking   in the presence of large effective spin-orbit coupling and coexists   with magnetic moments for most magnetic actinides.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98061 (URN)10.1103/PhysRevLett.103.107202 (DOI)000269639800053 ()
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2017-12-13Bibliographically approved
    5. Analysis of dynamical exchange and correlation in terms of coupled multipoles
    Open this publication in new window or tab >>Analysis of dynamical exchange and correlation in terms of coupled multipoles
    (English)Manuscript (Other academic)
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98062 (URN)
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2012-08-01Bibliographically approved
    6. Sr2CrOsO6: End point of a spin-polarized metal-insulator transition by 5d band filling
    Open this publication in new window or tab >>Sr2CrOsO6: End point of a spin-polarized metal-insulator transition by 5d band filling
    Show others...
    2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 2, p. 020404-Article in journal (Refereed) Published
    Abstract [en]

    In the search for new spintronic materials with high spin polarization at room temperature, we have synthesized an osmium-based double perovskite with a Curie temperature of 725 K. Our combined experimental results confirm the existence of a sizable induced magnetic moment at the Os site, supported by band-structure calculations, in agreement with a proposed kinetic-energy-driven mechanism of ferrimagnetism in these compounds. The intriguing property of Sr2 CrOs O6 is that it is at the end point of a metal-insulator transition due to 5d band filling and at the same time ferrimagnetism and high-spin polarization are preserved.

    Keywords
    strontium compounds, chromium compounds, ferrimagnetic materials, spin polarised transport, metal-insulator transition, magnetic moments
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-98063 (URN)10.1103/PhysRevB.75.020404 (DOI)000243895100008 ()
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2017-12-13Bibliographically approved
  • 115.
    Bultmark, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Cricchio, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Multipole decomposition of LDA+U energy and its application to actinides compounds2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 3, p. 035121-Article in journal (Refereed)
    Abstract [en]

    A general reformulation of the exchange energy of 5f shell is applied   in the analysis of the magnetic structure of various actinides compounds in the framework of LDA + U method. The calculations are   performed in a convenient scheme with essentially only one free   parameter, the screening length. The results are analyzed in terms of  different polarization channels due to different multipoles. Generally   it is found that the spin-orbital polarization is dominating. This can   be viewed as a strong enhancement of the spin-orbit coupling in these   systems. This leads to a drastic decrease in spin polarization in   accordance with experiments. The calculations are able to correctly   differentiate magnetic and nonmagnetic Pu system. Finally, in all   magnetic systems an unusual multipolar order is observed, whose   polarization energy is often larger in magnitude than the one of spin polarization.

  • 116.
    Caleman, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Huldt, Gösta
    Ortiz, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Maia, Filipe R. N. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Marklund, Erik G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Parak, Fritz G.
    van der Spool, David
    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.
    Nanocrystal imaging using intense and ultrashort X-ray pulsesManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Structural studies of biological macromolecules are severely limited by radiation damage. Traditional crystallography curbs the effects of damage by spreading damage over many copies of the molecule of interest in the crystal. X-ray lasers offer an additional opportunity for limiting damage by out-running damage processes with ultrashort and very intense X-ray pulses. Such pulses may allow the imaging of single molecules, clusters or nanoparticles, but coherent flash imaging will also open up new avenues for structural studies on nano- and micro-crystalline substances. This paper addresses the potentials and limitations of nanocrystallography with extremely intense coherent X-ray pulses. We use urea nanocrystals as a model for generic biological substances, and simulate the primary and secondary ionization dynamics in the crystalline sample. The results establish conditions for diffraction experiments as a function of X-ray fluence, pulse duration, and the size of nanocrystals.

  • 117.
    Caleman, Carl
    et al.
    Physik Department E17, Technische Universität München.
    Ortiz, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Marklund, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Gabrysch, Markus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Parak, F. G.
    Hajdu, Janos
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Timneanu, Nicusor
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Radiation damage in biological material: electronic properties and electron impact ionization in urea2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 85, no 1, p. 18005-Article in journal (Refereed)
    Abstract [en]

    Radiation damage is an unavoidable process when performing structural investigations of biological macromolecules with X-rays. In crystallography this process can be limited through damage distribution in a crystal, while for single molecular imaging it can be outrun by employing short intense pulses. Secondary electron generation is crucial during damage formation and we present a study of urea, as model for biomaterial. From first principles we calculate the band structure and energy loss function, and subsequently the inelastic electron cross-section in urea. Using Molecular Dynamics simulations, we quantify the damage and study the magnitude and spatial extent of the electron cloud coming from an incident electron, as well as the dependence with initial energy.

  • 118. Carbone, C.
    et al.
    Veronese, M.
    Moras, P.
    Gardonio, S.
    Grazioli, C.
    Zhou, P. H.
    Rader, O.
    Varykhalov, A.
    Krull, C.
    Balashov, T.
    Mugarza, A.
    Gambardella, P.
    Lebegue, S.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Katsnelson, M. I.
    Lichtenstein, A. I.
    Correlated Electrons Step by Step: Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 11, p. 117601-Article in journal (Refereed)
    Abstract [en]

    High-resolution photoemission spectroscopy and ab initio calculations have been employed to analyze the onset and progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by the free-electron environment, and Coulomb interaction among d electrons gives rise to complex electronic configurations. The multiplet structure of a single Fe atom evolves and gradually dissolves into a quasiparticle peak near the Fermi level with increasing host electron density. The effective multiorbital impurity problem within the exact diagonalization scheme describes the whole range of hybridizations.

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

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

  • 120.
    Carva, K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Legut, D
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Influence of laser-excited electron distributions on the X-ray magnetic circular dichroism spectra: Implications for femtosecond demagnetization in Ni2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 86, no 5, p. 57002-Article in journal (Refereed)
    Abstract [en]

    In pump-probe experiments an intensive laser pulse creates non-equilibrium excited-electron distributions in the first few hundred femtoseconds after the pulse. The influence of nonequilibrium electron distributions caused by a pump laser on the apparent X-ray magnetic circular dichroism (XMCD) signal of Ni is investigated theoretically here for the first time, considering electron distributions immediately after the pulse as well as thermalized ones, that are not in equilibrium with the lattice or spin systems. The XMCD signal is shown not to be simply proportional to the spin momentum in these situations. The computed spectra are compared to recent pump-probe XMCD experiments on Ni. We find that the majority of experimentally observed features considered to be a proof of ultrafast spin momentum transfer to the lattice can alternatively be attributed to non-equilibrium electron distributions. Furthermore, we find the XMCD sum rules for the atomic spin and orbital magnetic moment to remain valid, even for the laser-induced non-equilibrium electron distributions. Copyright (C) EPLA, 2009

  • 121.
    Carva, K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Turek, I
    Landauer theory of ballistic torkances in noncollinear spin valves2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 10, p. 104432-Article in journal (Refereed)
    Abstract [en]

    We present a theory of voltage-induced spin-transfer torques in ballistic noncollinear spin valves. The torkance on one ferromagnetic layer is expressed in terms of scattering coefficients of the whole spin valve, in analogy to the Landauer conductance formula. The theory is applied to Co/Cu/Ni(001)-based systems where long-range oscillations of the Ni torkance as a function of Ni thickness are predicted. The oscillations represent a novel quantum size effect due to the noncollinear magnetic structure. The oscillatory behavior of the torkance contrasts a thickness-independent trend of the conductance.

  • 122.
    Carva, Karel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Turek, Ilja
    Spin-mixing conductances: The influence of disorder2008In: Physica status solidi A, Applications and materials science, ISSN 1862-6300, Vol. 205, no 8, p. 1805-1808Article in journal (Refereed)
    Abstract [en]

    Spin transfer torque exerted on a magnetic layer can be viewed as a linear response to the spin accumulation inside an adjacent non-magnetic layer, information about their response coefficient is provided by the complex spin-mixing conductance C-mix. Substitutional disorder is known to affect the spin-dependent charge conductances and often reduces strongly the magnetoresistance. Here, we examine its impact on C-mix of several selected realistic systems. Recently predicted oscillations of C-mix as a function of ferromagnetic layer thickness in Ni based junctions might be suppressed by interface interdiffusion, but presented ab initio calculations disprove this possibility. Halfmetallic character of the Heusler compound Co(2)Mnsi is destroyed by often encountered antisite disorder; however the impact of this disorder to the predicted C-mix is rather weak. Diluted magnetic semiconductor (Ga,Mn)As is an intrinsically disordered system the analysis of calculations shows that the variation of C-mix with substitutional Mn content can be understood in terms of the associated change of the number of carriers, whereas the variation with lattice defects is more complex.

  • 123. Cavar, E.
    et al.
    Westerström, R.
    Mikkelsen, A.
    Lundgren, E.
    Vinogradov, A. S.
    Ng, May Ling
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Preobrajenski, A. B.
    Zakharov, A. A.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    A single h-BN layer on Pt(111)2008In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 602, no 9, p. 1722-1726Article in journal (Refereed)
    Abstract [en]

    The structure and formation of an ultrathin hexagonal boron nitride (h-BN) film on Pt(111) has been studied by a combination of scanning tunneling microscopy, low energy electron diffraction, low energy electron microscopy, X-ray absorption and high resolution core level spectroscopy. The study shows that a single boron nitride layer is formed on Pt(111), resulting in a coincidence structure. High resolution scanning tunneling microscopy (STM) images of the h-BN ultrathin film display only one of the atomic species in the unit cell. Probing the boron and nitrogen related local density of states by near edge X-ray absorption fine structure measurements we conclude that the nitrogen sublattice is visible in STM images. The growth of the single hexagonal boron nitride layer by vapourized borazine in the pressure range of 1 x 10(-6)-1 x 10(-8) at 800 degrees C is further studied by low energy electron microscopy, and reveals that the number of nucleation sites and the perfection of the growth is strongly pressure dependent. A model for the single, hexagonal, boron nitride layer on Pt(111) is proposed.

  • 124. Chantis, Athanasios N.
    et al.
    Smith, L
    Fransson, J
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Balatsky, A. V.
    Scanning tunneling microscopy detection of spin polarized resonant surface bands: The example of Fe(001)2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 16, p. 165423-Article in journal (Refereed)
    Abstract [en]

    We study theoretically the effect of a spin polarized resonant surface band on the conductance of scanning tunneling spectroscope with a spin polarized tip (SP-STM). Using the example of the Fe(001) surface, we show that a minority-spin surface state can induce a bias dependence of the tunneling differential conductance which depends strongly on the orientation of the magnetization in the SP-STM tip relative to the magnetization axis in the surface. We propose the use of this effect to determine the spin character of the surface band.

  • 125. Coleman, V. A.
    et al.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Grennberg, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, U.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Quinlan, R.
    Holloway, B. C.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Defect Formation In Graphene Nanosheets By Acid Treatment: An X-Ray Absorption Spectroscopy And Density Functional Theory Study2008In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 41, no 6, p. 062001-4Article in journal (Refereed)
    Abstract [en]

    In-plane defects have been introduced into graphene nanosheets by treatment with hydrochloric acid. Acid treatment induces bond cleavage in the C–C network via electrophilic attack. These resultant vacancy sites will then undergo further reactions with the surrounding ambient to produce C–O and C–H bonds. A σ* resonance at 287 eV in the carbon K-edge x-ray absorption spectra is observed with acid treatment and is assigned to C–O states. Theoretical modelling of a di-vacancy in a graphene bilayer reproduces all essential features of this resonance and in addition predicts a metallic conductivity of states around this vacancy. The possibility of engineering the properties of graphene via the routes explored here is an important step towards establishing strategies for building devices based on this material.

  • 126. Collier-Reed, Brandon
    et al.
    Case, Jennifer
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    The experience of interacting with technological artefacts2009In: European Journal of Engineering Education, ISSN 0304-3797, E-ISSN 1469-5898, Vol. 34, no 4, p. 295-303Article in journal (Refereed)
  • 127.
    Cricchio, Francesco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Itinerant Magnetic Multipole Moments of Rank Five as the Hidden Order in URu2Si22009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 10, p. 107202-Article in journal (Refereed)
    Abstract [en]

    A broken symmetry ground state without any magnetic moments has been   calculated by means of the local-density approximation to density   functional theory plus a local exchange term, the so-called LDA+U   approach, for URu2Si2. The solution is analyzed in terms of a multipole   tensor expansion of the itinerant density matrix and is found to be a   nontrivial magnetic multipole. Analysis and further calculations show   that this type of multipole enters naturally in time reversal breaking   in the presence of large effective spin-orbit coupling and coexists   with magnetic moments for most magnetic actinides.

  • 128.
    Cricchio, Francesco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Bultmark, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Exchange energy dominated by large orbital spin-currents in δ-Pu2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 10, p. 100404-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of the anomalous delta phase of Pu is analyzed by a general and exact reformulation of the exchange energy of the f shell. It is found that the dominating contribution to the exchange energy is a polarization of orbital spin-currents that preserves the time-reversal symmetry; hence a nonmagnetic solution in accordance with experiments. The analysis brings a unifying picture of the role of exchange in the 5f shell with its relatively strong spin-orbit coupling. The results are in good accordance with recent measurements of the branching ratio for the d to f transition in the actinides.

  • 129. Ctistis, G.
    et al.
    Papaioannou, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Patoka, P.
    Gutek, J.
    Fumagalli, P.
    Giersig, M.
    Optical and Magnetic Properties of Hexagonal Arrays of Subwavelength Holes in Optically Thin Cobalt Films2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    In this study, we present our experimental results on the optical, magnetic, as well as magneto-optic properties of hexagonal arrays of subwavelength holes in optically thin cobalt films. Different meshes were used with hole diameters ranging between 220 and 330 nm while the interhole distance has been kept constant at 470 nm. The hole pattern modifies completely the magnetic behavior of the cobalt films; it gives rise to an increase of the coercive field of the in-plane magnetization with increasing hole diameter and to the appearance of out-of-plane magnetization components. Magneto-optic measurements show a spectacular magneto-optic response at wavelengths where surface plasmon-polaritons are supported by the structure as deduced in optical measurements. The experiments demonstrate the ability to artificially control the magnetic and thus the magneto-optic properties in hole array structures.

  • 130.
    Céolin, D
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Piancastelli, Maria Novela
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Stolte, W C
    Lindle, D W
    Partial ion yield spectroscopy around the Cl 2p and C 1s ionization thresholds in CF3Cl2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 24, p. 244301-Article in journal (Refereed)
    Abstract [en]

    We present a partial ion yield experiment on freon 13, CF3Cl, excited in the vicinity of the C 1s and Cl 2p ionization thresholds. We have collected a large amount of cationic fragments and a few anionic fragments at both edges. We have observed a strong intensity dependence of Rydberg transitions with ion fragment size for the CFnCl+ and CFn+/F+ (n=0-3) series at both the Cl 2p and C 1s ionization edges. Selectivity in the fragmentation processes involving the C-Cl and C-F bonds are highlighted by the intensities of the C 1s to lowest unoccupied molecular orbital (LUMO) and LUMO+1 transitions measured on the CFnCl+ and CFn+ yields. Equally, by comparison with their cation counterpart, we discuss possible bond-length dependence for the anion formation at the carbon 1s edge.

  • 131.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Centre for Gender Research.
    Att lära sig bli fysiker: en könad process2008In: Paper presented at the Nätverk och Utveckling 2008 Lärande i en ny tid - samtal om undervisning i högre utbildning Conference, Kalmar, Sweden, 7-9 May., 2008Conference paper (Refereed)
  • 132.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Centre for Gender Research.
    Feminist and anti-oppressive strategies in: the physics laboratory?2009In: Workshop presented at the Challenging education: Feminist and anti-oppressive strategies in teaching and learning, the first Nordic conference on feminist pedagogies, Vaksalaskolan, Uppsala, 14-16 June., 2009Conference paper (Other academic)
  • 133.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Centre for Gender Research.
    Genusmedveten laborationsundervisning i fysik2008In: Genus och naturvetenskaplig undervisning Workshop, Uppsala University, October, 2008Conference paper (Other academic)
  • 134.
    Danielsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Centre for Gender Research.
    Belanger-Champange, C.
    The physics student laboratory2008In: Workshop presented at the Crossing Perspectives on Gender and Physics Conference, Uppsala University, September, 2008Conference paper (Other academic)
  • 135.
    Danielsson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Centre for Gender Research.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Learning in physics by doing laboratory work: towards a new conceptual framework2009In: Gender and Education, ISSN 0954-0253, E-ISSN 1360-0516, Vol. 21, no 2, p. 129-144Article in journal (Refereed)
    Abstract [en]

    Drawing on a study that explores university students' experiences of doing laboratory work in physics, this article outlines a proposed conceptual framework for extending the exploration of the gendered experience of learning. In this framework situated cognition and post-structural gender theory are merged together. By drawing on data that aim at exploring the gendered experience of learning in physics in the laboratory setting, a case is made for the proposed conceptual framework to facilitate an analysis of gender as an active process that relates the dynamics of this process to the emerging physicist identities of the students. In other words, this framework allows for an analysis of the gendered learning experiences in a context such as physics education that goes well beyond the usual 'women-friendly' teaching approaches.

  • 136.
    Danielsson, Anna T
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Doing Physics - Doing Gender: An Exploration of Physics Students' Identity Constitution in the Context of Laboratory Work2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In Sweden today women are greatly under-represented within university physics and the discipline of physics is also symbolically associated with men and masculinity. This motivates in-depth investigations of issues of physics, learning and gender.

    This thesis explores how physics students' simultaneously constitute the practice of physics as enacted in student and research laboratories and their physicist identities in relation to this practice. In particular, it focuses on how these constitutions can be understood as gendered. Previously, physics education research has often limited 'gender perspective' to focusing on comparisons between man and woman students, whereas this study conceptualises gender as an aspect of social identity constitution. A point of departure for the thesis is the theoretical framework which combines situated learning theory and post-structural gender theory. This framework allows for a simultaneous analysis of how students 'do physics' and 'do gender', thereby making a theoretical contribution to physics education research.

    In the empirical study twenty-two undergraduate and graduate physics students were interviewed about their physics studies, with a particular focus on laboratory work.

    The analytical outcomes of the study illustrate a wide variety of possible identity constitutions and possible ways of constituting the physicist community of practice. For example, the students expressed conflicting interpretations of what are suitable practices in the student laboratory in terms of the value of practical versus analytical skills. The boundaries of the physicist community of practice are constituted in relation to, for example, other disciplines, interdisciplinary practices and a traditional femininity practice. Thus, the thesis demonstrates the complexity in physics students gendered negotiations of what it can mean to be a physicist.

    The ambition of the thesis is further to promote discussions about gender and physics, by engaging readers in critical reflections about the practice of physics, and, thus, to inform the teaching practice of physics.

  • 137.
    de Almeida, J. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Kim, D. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ortiz, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    On the dynamical stability and metallic behavior of YH3 under pressure2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 25, p. 251913-Article in journal (Refereed)
    Abstract [en]

    Wereport on the behavior of structural and electronic properties ofyttrium trihydride under pressure using first principles calculations. We showthat YH3 undergoes a structural transformation and its high pressurephase is dynamically stable under pressure since the peak atthe imaginary frequencies of the phonon density of states, whichaccount for the structural instability disappears at high pressure. Additionally,our GW calculations indicate a metallization of the high pressurecubic phase of YH3.

  • 138. Delczeg, L
    et al.
    Delczeg-Czirjak, K
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Assessing common density functional approximations for the ab initio description of monovacancies in metals2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 20, p. 205121-Article in journal (Refereed)
    Abstract [en]

    Using the exact muffin-tin orbitals method, we investigate the accuracy of five common density functional approximations for the theoretical description of the formation energy of monovacancies in three close-packed metals. Besides the local density approximation (LDA), we consider two generalized gradient approximation developed by Perdew and co-workers (PBE and PBEsol) and two gradient-level functionals obtained within the subsystem functional approach (AM05 and LAG). As test cases, we select aluminum, nickel, and copper, all of them adopting the face centered cubic crystallographic structure. Our results show that, compared to the recommended experimental values, LDA is be the most reliable approximation for the vacancy formation energies in these metals. However, taking into account also the performances of the functionals for the equation of state changes the final verdict in favor of the generalized gradient approximations.

  • 139. Delczeg-Czirjak, E. K.
    et al.
    Delczeg, L.
    Punkkinen, M. P. J.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ab initio study of structural and magnetic properties of Si-doped Fe2P2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 8, p. 085103-Article in journal (Refereed)
    Abstract [en]

    Ab initio electronic-structure methods are used to study the properties of Fe2P1-xSix in ferromagnetic and paramagnetic states. The site preference and lattice relaxation are calculated with the projector augmented wave method as implemented in the Vienna ab initio simulation package. The paramagnetic state is modeled by the disordered local magnetic moment scheme, and the chemical and magnetic disorder is treated using the coherent potential approximation in combination with the exact muffin-tin orbital formalism. The calculated lattice parameters, atomic positions, and magnetic properties are in good agreement with the experimental and other theoretical results. In contrast to the observation, for the ferromagnetic state the body centered ortho-rhombic structure (bco, space group I (mm2) under bar) is predicted to have lower energy than the hexagonal structure (hex, space group P (6) over bar 2m). The zero-point spin fluctuation energy difference is found to be large enough to stabilize the hex phase. For the paramagnetic state, the hex structure is calculated to be the stable phase and the computed total energy versus composition indicates a hex to bco crystallographic phase transition with increasing Si content. The phonon vibrational free energy, estimated from the theoretical equation of state, turns out to stabilize the hexagonal phase, whereas the electronic and magnetic entropies favor the low symmetry orthorhombic structure.

  • 140. Delczeg-Czirjak, E. K.
    et al.
    Delczeg, L
    Ropo, M
    Kokko, K
    Punkkinen, M. P. J.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Ab initio study of the elastic anomalies in Pd-Ag alloys2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 8, p. 085107-Article in journal (Refereed)
    Abstract [en]

    Ab initio total-energy calculations, based on the exact muffin-tin orbital method, are used to determine the elastic properties of Pd1-xAgx random alloys in the face-centered-cubic crystallographic phase. The compositional disorder is treated within the coherent-potential approximation. The single crystal and polycrystalline elastic constants and the Debye temperature are calculated for the whole range of concentration, 0 <= x <= 1. It is shown that the variation in the elastic parameters of Pd-Ag alloys with chemical composition strongly deviates from a simple linear or parabolic trend. The complex electronic origin of these anomalies is demonstrated.

  • 141.
    Di Marco, Igor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.