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  • 1.
    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. 

  • 2.
    Amft, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Skorodumova, Natalia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Small gold clusters on graphene, their mobility and clustering: a DFT study2011In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 23, no 20, p. 205301-Article in journal (Refereed)
    Abstract [en]

    Motivated by the experimentally observed high mobility of gold atoms on graphene and their tendency to form nanometer-sized clusters, we present a density functional theory study of the ground state structures of small gold clusters on graphene, their mobility and clustering. Our detailed analysis of the electronic structures identifies the opportunity to form strong gold-gold bonds and the graphene-mediated interaction of the pre-adsorbed fragments as the driving forces behind gold's tendency to aggregate on graphene. While clusters containing up to three gold atoms have one unambiguous ground state structure, both gas phase isomers of a cluster with four gold atoms can be found on graphene. In the gas phase the diamond-shaped Au-4(D) cluster is the ground state structure, whereas the Y-shaped Au-4(Y) becomes the actual ground state when adsorbed on graphene. As we show, both clusters can be produced on graphene by two distinct clustering processes. We also studied in detail the stepwise formation of a gold dimer out of two pre-adsorbed adatoms, as well as the formation of Au-3. All reactions are exothermic and no further activation barriers, apart from the diffusion barriers, were found. The diffusion barriers of all studied clusters range from 4 to 36 meV only, and are substantially exceeded by the adsorption energies of -0.1 to -0.59 eV. This explains the high mobility of Au1-4 on graphene along the C-C bonds.

  • 3.
    Amft, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Catalytic activity of small MgO-supported Au clusters towards CO oxidation: A density functional study2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 81, no 19, p. 195443-Article in journal (Refereed)
    Abstract [en]

    In order to explain the experimentally found catalytic characteristics of Au1-4 /MgO (100) we have performed a comprehensive density functional study of these systems and their ability to (co)adsorb CO and O2 molecules. Starting from the carefully determined ground-state structures we have analyzed binding mechanisms, the influence of spin-orbit coupling, and charge redistributions in Au1-4 /MgO+CO (O2). Experimentally Au1,2 /MgO were found to be inactive under a mixed atmosphere. We show that O2 strongly binds to Au1 /MgO that prevents coadsorption. Although a catalytic reaction cycle towards CO oxidation, analogous to the gas phase reaction involving Au 2-, is energetically possible for Au2 /MgO, the cluster will get blocked by a strongly bound CO. On the other hand, the catalytic activity of Au3,4 /MgO could be explained by their ability to coadsorb CO and O2, hence indicating the occurrence of a Langmuir- Hinshelwood-type reaction mechanism for these clusters.

  • 4.
    ANDERSSON, JO
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    MATTSSON, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    OVERLAP LENGTH IN A CU-MN SPIN-GLASS PROBED BY AC SUSCEPTIBILITY1993In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 48, p. 13977-13980Article in journal (Refereed)
    Abstract [en]

    An important theoretical concept in the ‘’droplet” model of spin glasses is the existence of an overlap length. Experimentally this concept was verified by dc-magnetization measurements. However, recent ac-susceptibility measurements by Lefloch et al. [Europhys. Lett. 18, 647 (1992)] have been interpreted to contradict this result. In this paper, ac-susceptibility and dc-magnetization measurements on a Cu (2% Mn) spin glass are reported. The results of the ac-susceptibility measurements are consistent with dc measurements and provide evidence for the existence of an overlap length in 3d spin glasses at low temperatures.

  • 5.
    Andersson, Per H.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Fast, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Theoretical study of structural and electronic properties of VHx1998In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 58, no 9, p. 5230-5235Article in journal (Refereed)
    Abstract [en]

    We have calculated the change in the electronic structure and the distortion of the lattice in vanadium upon hydrogenation from first principles using the full-potential linear muffin-tin-orbital method and the linear augmented plane-wave method in the local-density approximation. The calculated hydrogen induced volume expansions agree with experiment and the change in the c/a ratio is also in good agreement with observations where such are available for single phase VHx. Among several changes in the electronic structure, we note a hybridization of the d band of vanadium with the hydrogen 1s band. We also observe an antiferromagnetically ordered moment at V/Vexp=1.08. The possibility of producing magnetic V by means of hydrogenation in combination with epitaxial growth is suggested.

  • 6.
    Andersson, Per H.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Effect of hydrogenation on the magnetic state in cubic Pd3Mn1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 9, p. 6765-6769Article in journal (Refereed)
    Abstract [en]

    The effect of hydrogenation on the magnetic and electronic state of cubic Pd3Mn has been calculated using a full-potential linear augmented plane-wave method in the local spin-density approximation. A complex magnetic structure is found in very good agreement with experiment. For the nonhydrogenated system we observe a noncommensurate spin spiral although we cannot identify the ground state of the spin structure as the total energy of the trigonal spin structure is almost degenerate with the total energy of the tetragonal spin structure. When hydrogenated the direction of the spiral is aligned along the (001) axis. The spin structures agree with experiment and are connected to features on the calculated Fermi surfaces.

  • 7.
    Aperis, Alex
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Maldonado, Pablo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ab initio theory of magnetic-field-induced odd-frequency two-band superconductivity in MgB22015In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 92, no 5, article id 054516Article in journal (Refereed)
  • 8. Bergqvist, Lars
    et al.
    Taroni, Andrea
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Etz, Corina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Olle, Eriksson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Atomistic spin dynamics of low-dimensional magnets2013In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 87, no 144401Article in journal (Refereed)
    Abstract [en]

    We investigate the magnetic properties of a range of low-dimensional   ferromagnets using a combination of first-principles calculations and   atomistic spin dynamics simulations. This approach allows us to evaluate   the ground state and finite temperature properties of experimentally   well characterized systems such as Co/Cu(111), Co/Cu(001), Fe/Cu(001)   and Fe/W(110), for different thicknesses of the magnetic layer. We   compare our calculated spin wave spectra with experimental data   available in the literature, and find a good quantitative agreement. We   also predict magnon spectra for systems for which no experimental data   exist at the moment, and estimate the role of temperature effects.

  • 9.
    Bielecki, Johan
    et al.
    Dept of applied physics, CHT, Göteborg.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tibebu, Dessie T.
    Dept of chemical and biological engineering, CTH, Göteborg.
    Cai, Shengzhen
    Dept of chemical and biological engineering, CTH, Göteborg.
    Eriksson, Sten-G.
    Dept of chemical and biological engineering, CTH, Göteborg.
    Börjesson, Lars
    Dept of applied physics, CHT, Göteborg.
    Knee, Christopher S.
    Dept of chemical and biological engineering, CTH, Göteborg.
    Structural and magnetic properties of isovalently substituted multiferroic BiFeO3: Insights from Raman spectroscopy2012In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 86, no 18, p. 184422-Article in journal (Refereed)
    Abstract [en]

    Raman spectra, supplemented by powder x-ray diffraction and magnetization data of isovalently A- and B-site substituted BiFeO3 in the Bi1−xLaxFeO3 (0≤x≤1), Bi1−xTbxFeO3 (0≤x≤0.2), and Bi0.9Sm0.1Fe1−xMnxO3 (0≤x≤0.3) series, are presented. A good agreement between the structural transitions observed by x-ray diffraction and the vibrational modes observed in the Raman spectra is found over the whole substitutional ranges, and in particular we find spectroscopic signatures of a PbZrO3-type structure for Bi0.8La0.2FeO3. Mode assignments in the substituted materials are made based on Raman spectra of the end-members BiFeO3 and LaFeO3. Moreover, by comparing spectra from all samples with R3c structure, the phonon assignment in BiFeO3 is revisited. A close connection between the degree of octahedral tilt and the Raman shift of the A1 oxygen aaa tilt mode is established. An explanation for the strong second-order scattering observed in Bi1−xLaxFeO3 and Bi1−xTbxFeO3 is suggested, including the assignment of the previously mysterious BiFeO3 mode at 620 cm−1. Finally, the magnetization data indicates a transition from a cycloidal modulated state towards a canted antiferromagnet with increasing A-site substitution, while Bi0.9Sm0.1Fe1−xMnxO3 with x=0 and 0.15 exhibit an anomalous closing of the hysteresis loop at low temperatures. For low A-site substitution levels (x≤0.1) the decreasing Raman intensity of the Fe derived modes correlates with the partial destruction of the spin cycloid as the substitution level increases.

  • 10.
    Bijelovic, Stojanka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Råsander, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wear-resistant magnetic thin film material based on a Ti1−xFexC1−y nanocomposite alloy2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 81, no 1, p. 014405-Article in journal (Refereed)
    Abstract [en]

    In this study we report on the film growth and characterization of thin films deposited on amorphous quartz. The experimental studies have been complemented by first-principles density-functional theory metastable Ti-Fe-C film changes. With increasing annealing time, there is a depletion of iron close to the surface of the film, while regions enriched in iron are simultaneously formed deeper into the film. Both the magnetic ordering temperature and the saturation magnetization changes significantly upon annealing. The DFT calculations show that the critical temperature and the magnetic moment both increase with increasing Fe and C-vacancy concentration. The formation of the metastable iron-rich Ti-Fe-C compound is reflected in the strong increase in the magnetic ordering temperature. Eventually, after enough annealing time nanocrystalline -Fe starts to precipitate, the amount and size of which can be controlled by the annealing procedure; after 20 min of annealing, the experimental results indicate a nanocrystalline iron-film embedded in a wear-resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single-crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material. approximately 50-nm-thick Ti-Fe-CDFT calculations. Upon annealing of as-prepared films, the composition of the10 min, nanocrystalline -Fe starts to precipitate, the amount and size of which can be controlled by the annealing procedure; after 20 min of annealing, the experimental results indicate a nanocrystalline iron-film embedded in a wear-resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single-crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material.

  • 11.
    Black-Schaffer, Annica M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Yudin, Dmitry
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Spontaneous gap generation on the surface of weakly interacting topological insulators using nonmagnetic impurities2014In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 90, no 16, p. 161413-Article in journal (Refereed)
    Abstract [en]

    Strong nonmagnetic impurities on the surface of three-dimensional topological insulators (TIs) generate localized resonance peaks close to the Dirac point. We show that this results in a strongly reduced critical Coulomb interaction strength to reach a magnetic surface state, following a Stoner-like criterion. Thus even weakly interacting TIs host a finite (local) magnetization around strong nonmagnetic impurities. The local magnetization gives rise to a global energy gap, linearly dependent on the maximum value of the magnetization but decreasing with reduced impurity concentration.

  • 12.
    Blundell, S A
    et al.
    SPSMS, UMR-E CEA/UJF-Grenoble.
    Haldar, Soumyajyoti
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kanhere, D G
    Metallic clusters on a model surface: Quantum versus geometric effects2011In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 84, no 7, p. 075430-Article in journal (Refereed)
  • 13. Brena, Barbara
    et al.
    Luo, Yi
    Nyberg, Mats
    Carniato, Stephane
    Nilson, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Alfredsson, Ylvi
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Åhlund, John
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Equivalent core-hole time-dependent density functional theory calculations of carbon 1s shake-up states of phthalocyanine2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 19, p. 195214-Article in journal (Refereed)
    Abstract [en]

    The shake-up transition energies of the carbon 1s photoelectron spectrum of metal-free phthalocyanine (H2Pc) have been calculated by means of time-dependent density functional theory, for which an equivalent core approximation is adopted. Model calculations for the C 1s shake-up states of benzene are in excellent agreement with the latest experimental results. The complex C 1s shake-up structures associated with the aromatic and pyrrole carbons in the phthalocyanine are computed, as well as their ionization potentials. They allow us to determine the origin of the anomalous intensity ratio between the pyrrole and benzene carbons in a high resolution C 1s photoelectron spectrum measured for a H2Pc film, as due to a benzene-related shake-up contribution, hidden under the pyrrole main intensity feature.

  • 14.
    Burkert, Till
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    James, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Simak, Sergei I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Calculation of uniaxial magnetic anisotropy energy of tetragonal and trigonal Fe, Co, and Ni2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 69, no 10, p. 104426-Article in journal (Refereed)
  • 15.
    Burkert, Till
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Simak, Sergei I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ruban, Andrei V.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Wills, John M.
    Magnetic anisotropy of L10 FePt and Fe1-xMnxPt2005In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 71, no 13, p. 134411-Article in journal (Refereed)
    Abstract [en]

    The uniaxial magnetic anisotropy energy (MAE) of L10 FePt and Fe1−xMnxPt, x=0−0.25, was studied from first principles using two fully relativistic computational methods, the full-potential linear muffin-tin orbitals method and the exact muffin-tin orbitals method. It was found that the large MAE of 2.8 meV/f.u. is caused by a delicate interaction between the Fe and Pt atoms, where the large spin-orbit coupling of the Pt site and the hybridization between Fe 3d and Pt 5d states is crucial. The effect of random order on the MAE was modeled by mutual alloying of the sublattices within the coherent potential approximation (CPA), and a strong dependence of the MAE on the degree of chemical long-range order was found. The alloying of FePt with Mn was investigated with the virtual crystal approximation and the CPA as well as supercell calculations. The MAE increases up to 33% within the concentration range studied here, an effect that is attributed to band filling. Furthermore, the dependence of the MAE on the structural properties was studied.

  • 16.
    Chimata, Raghuveer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Isaeva, Leyla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kádas, Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mentink, Johan H.
    Radboud University Nijmegen, Institute of Molecules and Materials.
    Katsnelson, Mikhail I.
    Radboud University Nijmegen, Institute of Molecules and Materials.
    Rasing, Theo
    Radboud University Nijmegen, Institute of Molecules and Materials.
    Kirilyuk, Andrei
    Radboud University Nijmegen, Institute of Molecules and Materials.
    Kimel, Alexey
    Radboud University Nijmegen, Institute of Molecules and Materials.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    All-thermal switching of amorphous Gd-Fe alloys: analysis of structural properties and magnetization dynamicsIn: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795Article in journal (Refereed)
  • 17.
    Cricchio, Francesco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grånäs, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Low spin moment due to hidden multipole order from spin-orbital ordering in LaFeAsO2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 81, no 14, p. 140403-Article in journal (Refereed)
    Abstract [en]

    An antiferromagnetic (AF) low-moment solution, 0.35 μB / Fe, is found in the case of LaOFeAs for an intermediately strong Coulomb interaction U of 2.75 eV. This solution is stabilized over a large moment solution due to the gain in exchange energy in the formation of large multipoles of the spin magnetization density. The multipoles are of rank four and can be understood as a type of spin-orbital ordering. Parallels can be drawn to the stabilization of the AF order in, e.g., CaCuO2.

  • 18.
    DJURBERG, C
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    GRANBERG, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    MATTSON, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    OVERLAP LENGTH IN SPIN-GLASSES IMPOSED BY MAGNETIC-FIELD PERTURBATIONS1994In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 50, p. 15775-15778Article in journal (Refereed)
  • 19.
    Festin, Örjan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Rönnung, Fredrik
    Winkler, Dag
    Vortex fluctuations in high-Tc films close to the resistive transition2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 2, article id 024511Article in journal (Refereed)
    Abstract [en]

    Flux noise and ac susceptibility measurements have been performed on epitaxial YBa2Cu3O7 films to investigate dynamical properties of vortex fluctuations close to the resistive transition. The validity of the fluctuation-dissipation theorem is verified by the proportionality between flux noise and ac susceptibility results. The zero-field flux-noise spectrum [Sϕ(f)] can be characterized as follows. Below a temperature dependent frequency f0(T), the flux noise spectrum is frequency independent. For frequencies f>f0(T), the flux noise spectrum follows f−x, with x≈1.5–1.75. The characteristic frequency f0 exhibits a dramatic decrease close to the resistive transition; f0 decreases by 3–4 orders of magnitude in a temperature interval of ΔT≈1K. Moreover, the flux noise spectrum scales as fSϕ=g(f∕f0(T)), where g(∙) is a scaling function. The influence of a weak perturbing magnetic field (Hdc) on the characteristics of the flux noise spectrum has been investigated. While the general characteristics of the flux noise spectrum remain, except for a change in frequency dependence at f>f0, the characteristic frequency f0 exhibits a dramatic increase with increasing applied field; f0 increases by 3–4 orders of magnitude on increasing the field from zero to a few oersteds. Moreover, it is found that f0 is proportional to Hydc, with y≈1.15. The results are interpreted in terms of thermally generated vortex-antivortex fluctuations in combination with fluctuations of field-generated vortices.

  • 20.
    Fransson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandalov, Igor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Effects of nonorthogonality in the time-dependent current through tunnel junctions2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 64, no 15, p. 153403-Article in journal (Refereed)
    Abstract [en]

    A theoretical technique which allows one to include contributions from nonorthogonality of the electron states in the leads connected to a tunneling junction is derived. The theory is applied to a single-barrier tunneling structure and a simple expression for the time-dependent tunneling current is derived showing explicit dependence of the overlap. The overlap proves to be necessary for a better quantitative description of the tunneling current, and our theory reproduces experimental results substantially better compared to standard approaches.

  • 21.
    GRANBERG, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    MATTSSON, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    STUBI, R
    BASS, J
    LESLIEPELECKY, DL
    COWEN, JA
    DYNAMICS OF COUPLED 2-DIMENSIONAL CU(MN) SPIN-GLASS FILMS1991In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 44, p. 4410-4414Article in journal (Refereed)
    Abstract [en]

    Time-dependent susceptibility measurements have been performed on multilayered two-dimensional (2D) 40-angstrom-wide Cu0.865Mn0.135 spin-glass films, separated by Cu interlayers of width 10 < w(il) < 1200 angstrom. It is found that samples with w(il) < 30 angstrom display 3D dynamic behavior. For 30 < w(il) < 600 angstrom a gradual decoupling of the spin-glass layers occurs, and for w(il) greater-than-or-equal-to 600 angstrom typical 2D behavior is observed. The effect of a finite interlayer coupling on the dynamic susceptibility is a distinct crossover from 2D dynamic behavior at short observation times to 3D dynamic behavior at long times. A clear influence on the spin-glass dynamics is still observable for interlayer thicknesses of order 500 angstrom; i.e., multilayered spin-glass films are extremely sensitive probes of the effective range of Ruderman-Kittel-Kasuya-Yosida interaction mediated via metallic interlayers. The results also yield information on the relation between time scale and length scale in relaxation experiments, a fundamental concept of domain theories of the spin-glass phase.

  • 22.
    GRANBERG, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SANDLUND, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    OBSERVATION OF A TIME-DEPENDENT SPATIAL CORRELATION LENGTH IN A METALLIC SPIN-GLASS1988In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 38, p. 7097-7100Article in journal (Refereed)
  • 23.
    GRANBERG, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    TIME DECAY OF THE SATURATED REMANENT MAGNETIZATION IN A METALLIC SPIN-GLASS - REPLY1988In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 37Article in journal (Refereed)
  • 24.
    GRANBERG, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    CHEN, HS
    Bell.
    TIME DECAY OF THE SATURATED REMANENT MAGNETIZATION IN A METALLIC SPIN-GLASS1987In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 35, p. 2075-2078Article in journal (Refereed)
  • 25.
    Grechnev, Alexei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Irkhin, Valentin Yu.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Katsnelson, Mikhail I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Thermodynamics of a two-dimensional Heisenberg ferromagnet with dipolar interaction2005In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 71, no 2, p. 024427-Article in journal (Refereed)
    Abstract [en]

    Thermodynamics of quantum and classical two-dimensional (2D) Heisenberg models with long-range dipole-dipole interaction has been investigated using various forms of self-consistent spin-wave theory (SSWT). It has been found that SSWT gives a much lower transition temperature T-c than the free-magnon (spin-wave) theory. For the classical spin, the T-c from SSWT lies within 9% of the Monte Carlo value, making SSWT the best approximation among those considered. It is proven that the random phase approximation vertex corrections to SSWT are rather small. The results depend strongly on the value of the spin, emphasizing the importance of using the quantum and not the classical 2D Heisenberg model even for large spins such as S=7/2.

  • 26.
    GUNNARSSON, K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ANDERSSON, JO
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KATORI, HA
    ITO, A
    MAGNETIC-BEHAVIOR OF A REENTRANT ISING SPIN-GLASS1992In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 46, p. 8227-8231Article in journal (Refereed)
    Abstract [en]

    The ac susceptibility of the reentrant Ising spin glass Fe0.62Mn0.38TiO3 has been investigated in a superconducting-quantum-interference-device magnetometer. The data show a transition from a paramagnetic to an antiferromagnetic state at T(N) = 32.8 K. At lower temperatures, the in-phase component of the susceptibility, chi’(omega), becomes frequency dependent and, simultaneously, a finite out-of-phase component of the susceptibility, chi”(omega)), appears. This behavior is interpreted to arise from a transition to a mixed spin-glass and antiferromagnetic state at T(g) = 25. 8 K. A dynamic scaling analysis of chi”(omega) yields critical exponents quite different from those found for the pure Ising spin glass Fe0.5Mn0.5TiO3. However, some apparent deviations from optimal scaling behavior are observed. Magnetic relaxation experiments on this reentrant spin glass reveal the existence of an aging phenomenon similar to that observed in ordinary spin glasses. It is also found that the behavior of the magnetic relaxation can be interpreted within the context of spin-glass domain theories.

  • 27.
    GUNNARSSON, K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ARUGA, H
    ITO, A
    STATIC SCALING IN A SHORT-RANGE ISING SPIN-GLASS1991In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 43, p. 8199-8203Article in journal (Refereed)
    Abstract [en]

    The nonlinear ac susceptibility chi’-nl of the short-range Ising spin glass Fe0.5Mn0.5TiO3 has been measured using a superconducting-quantum-interference-device magnetometer. The spin-glass temperature, T(g), and the critical exponent gamma were estimated from the temperature dependence of the quadratic field term of chi’nl, yielding T(g) = 20.70 and gamma = 4.0. Static-scaling analyses, using different scaling equations, gave similar results. Using gamma and results from previous dynamic-scaling analyses, a number of critical exponents have been obtained through different scaling relations, e.g., delta = 8.4 and nu = 1.7. The results support the existence of a finite-temperature phase transition in a three-dimensional Ising spin glass.

  • 28.
    Hellsvik, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Skubic, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Simulation of a spin-wave instability from atomistic spin dynamics2009In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 79, no 18, p. 184426-Article in journal (Refereed)
    Abstract [en]

    We study the spin dynamics of a Heisenberg model at finite temperature in the presence of an external fieldor a uniaxial anisotropy. For the case of the uniaxial anisotropy, our simulations show that the macromomentpicture breaks down. An effect which we refer to as a spin-wave instability results in a nondissipative Bloch-Bloembergen-type relaxation of the macromoment where the size of the macromoment changes and can evenbe made to disappear. This relaxation mechanism is studied in detail by means of atomistic spin dynamics simulations.

  • 29.
    Hugosson, Håkan W.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Theoretical studies of substitutional impurities in molybdenum carbide1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 22, p. 15123-15130Article in journal (Refereed)
    Abstract [en]

    First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.

  • 30. Hultman, L.
    et al.
    Bareno, J.
    Flink, A.
    Söderberg, H.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Petrova, V.
    Odén, M.
    Green, J.E.
    Petrov, I.
    Interface structure in superhard TiN-SiN nanolaminates and nanocomposites: Films growth experiments and ab initio calculations2007In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 75, p. 155437-Article in journal (Refereed)
  • 31.
    Kapaklis, Vassilios
    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.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Vlachos, A.
    Galanakis, I.
    Poulopoulos, P.
    Özdogan, K.
    Angelakeris, M.
    Wilhelm, F.
    Rogalev, A.
    Violation of Hund’s third rule in structurally disordered ferromagnets2011In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 84, no 2, p. 024411-Article in journal (Refereed)
    Abstract [en]

    Violation of Hund’s third rule caused by structural disorder is observed for the induced magnetic moment of Zr, using X-ray magnetic circular dischroism. The induced spin and orbital magnetic moments are anti-parallel in the crystalline state, but parallel in an amorphous state of the investi- gated Co- and Fe-based materials. First principles calculations are used to provide physical insight into the dependency of the spin-orbit coupling on the interatomic distance and coordination number.

  • 32.
    Keshavarz, Samara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kvashnin, Yaroslav O.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rodrigues, Debora C. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Fed Univ Para, Fac Fis, BR-66075110 Belem, Para, Brazil..
    Pereiro, Manuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Di Marco, Igor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Autieri, Carmine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Solovyev, I. V.
    atl Inst Mat Sci, 1-1 Namiki, Tsukuba, Ibaraki 3050044, Japan.; Ural Fed Univ, Dept Theoret Phys & Appl Math, Mira St 19, Ekaterinburg 620002, Russia..
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Exchange interactions of CaMnO3 in the bulk and at the surface2017In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 95, article id 115120Article in journal (Refereed)
    Abstract [en]

    We present electronic and magnetic properties of CaMnO3 (CMO) as obtained from ab initio calculations. We identify the preferable magnetic order by means of density functional theory plus Hubbard U calculations and extract the effective exchange parameters (Jij ' s) using the magnetic force theorem. We find that the effects of geometrical relaxation at the surface as well as the change of crystal field are very strong and are able to influence the lower-energymagnetic configuration. In particular, our analysis reveals that the exchange interaction between the Mn atoms belonging to the surface and the subsurface layers is very sensitive to the structural changes. An earlier study [A. Filippetti and W. E. Pickett, Phys. Rev. Lett. 83, 4184 (1999)] suggested that this coupling is ferromagnetic and gives rise to the spin-flip (SF) process on the surface of CMO. In our work, we confirm their finding for an unrelaxed geometry, but once the structural relaxations are taken into account, this exchange coupling changes its sign. Thus, we suggest that the surface of CMO should have the same G-type antiferromagnetic order as in the bulk. Finally, we show that the suggested SF can be induced in the system by introducing an excess of electrons.

  • 33. Kollár, J.
    et al.
    Vitos, Levente
    Osorio-Guillén, J. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Calculation of surface stress for fcc transition metals2003In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 68, no 24, p. 245417-Article in journal (Refereed)
    Abstract [en]

    Using the density functional theory, formulated within the framework of the exact muffin-tin orbitals method, we have calculated the surface stress for the (111) free surfaces of the fcc 4d and 5d transition metals. Good agreement is obtained with the available ab initio data for Pd, Ir, and Au, while for Pt we predict a surface stress, which is about 33% lower compared to former theoretical results. The present surface stress values for the 4d and 5d fcc metals show the typical trend characteristic for the cohesive or surface energies of d series.

  • 34.
    KUSHAUER, J
    et al.
    Univ Duisburg.
    KLEEMANN, W
    Univ Duisburg.
    MATTSSON, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    CROSSOVER FROM LOGARITHMICALLY RELAXING TO PIEZOMAGNETICALLY FROZEN MAGNETIC REMANENCE IN LOW-FIELD-COOLED FE0.47ZN0.53F21994In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 49, p. 6346-6349Article in journal (Refereed)
    Abstract [en]

    Weak-field-induced magnetization M and temporal relaxation of its remanence mu are investigated in Fe0.47Zn0.53F2 by using Faraday rotation and superconducting quantum interference device (SQUID) magnetometry. Stretched logarithmic decay as predicted by Nattermann and Vilfan is confirmed at T = 2.8 K for freezing fields 3 less-than-or-equal-to B less-than-or-equal-to 4.9 T. At very low fields, 0.001 less-than-or-equal-to B less-than-or-equal-to 1.5 T, virtually constant remanence, mu approximately 44 A/m, is observed. It is due to immobile domains, which form via piezomagnetic coupling to built-in random stress fields.

  • 35.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Carlsson, Jan-Otto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lunell, Sten
    Nearest-Neighbour Influence on Hydrocarbon Adsorption on Diamond (111): Studied by Ab Initio Calculations1995In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, p. 10003-Article in journal (Refereed)
  • 36.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lunell, Sten
    Carlsson, Jan-Otto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Adsorption of hydrocarbons on a Diamond (111) Surface: An Ab Initio Quantum Mechanical Study1993In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, no 4, p. 2666-Article in journal (Refereed)
  • 37. Lee, Y. S.
    et al.
    Arima, T.
    Onoda, S.
    Okimoto, Y.
    Tokunaga, Y.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Yu, X. Z.
    He, J. P.
    Kameko, Y.
    Matsui, Y.
    Nagaosa, N.
    Tokura, Y.
    Correlation of electronic structure and ordered charge and orbital patterns for single-layer manganites in a wide hole doping range (0 ≤ x ≤ 1)2007In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 75, no 14, p. 144407-Article in journal (Refereed)
  • 38. Lohstroh, Wiebke
    et al.
    Westerwaal, R. J.
    van Mechelen, J. L. M.
    Chacon, Cyril
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
    Johansson, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
    Dam, B.
    Griessen, Ronald
    Structural and optical properties of Mg2NiHx switchable mirrors upon hydrogen loading2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, p. 165411-Article in journal (Refereed)
    Abstract [en]

    The structural, thermodynamic and optical properties of Mg2Ni thin films covered with Pd are investigatedupon exposure to hydrogen. Similar to bulk, thin films of metallic Mg2Ni take up 4 hydrogen per formula unitand semiconducting transparent Mg2NiH4−d is formed. The dielectric function e˜ of Mg2Ni and fully loadedMg2NiH4−d is determined from reflection and transmission measurements using a Drude-Lorentz parametrization.Besides the two “normal” optical states of a switchable mirror—metallic reflecting and semiconductingtransparent—Mg2NiHx exhibit a third “black” state at intermediate hydrogen concentrations with low reflectionand essentially zero transmission. This state originates from a subtle interplay of the optical properties of theconstituent materials and a self-organized double layering of the film during loading. Mg2NiH4−d preferentiallynucleates at the film/substrate interface and not—as intuitively expected—close to the catalytic Pd cappinglayer. Using e˜Mg2Ni and e˜Mg2NiH4and this loading sequence, the optical response at all hydrogen concentrationscan be described quantitatively. The uncommon hydrogen loading sequence is confirmed by x-ray diffractionand hydrogen profiling using the resonant nuclear reaction 1Hs15N,agd12C. Pressure-composition isothermssuggest that

  • 39.
    LUNDGREN, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    SVEDLINDH, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    RELAXATION BEHAVIOR OF FRACTAL-CLUSTER SPIN-GLASSES1986In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 34, p. 8164-8167Article in journal (Refereed)
  • 40. M. A. Hossain, B. Bohnenbuck, Y. D. Chuang, M. W. Haverkort, I. S. Elfimov, A.Tanaka, A. G. Cruz Gonzalez, Z. Hu, H.-J. Lin, C. T. Chen, R. Mathieu, Y. Tokura, Y. Yoshida, L. H. Tjeng, Z. Hussain, B. Keimer, G. A. Sawatzky and A. Damascelli
    Mott versus Slater-type metal-insulator transition in Mn-substituted Sr3Ru2O72012In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 86, p. 041102(R)-Article in journal (Refereed)
  • 41.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Guo, J H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Electronic structure investigation of CoO by means of soft x-ray scattering2002In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 65, no 20, p. 205106-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of CoO is studied by resonant inelastic soft x-ray scattering spectroscopy using photon energies across the Co 2p absorption edges. The different energy-loss structures in the Raman scattering spectra are identified as due to d-d and charge-transfer excitations. For excitation energies close to the L3 resonance, the spectral features are dominated by quartet-quartet and quartet-doublet transitions of the 3d7 configuration. At excitation energies corresponding to the satellites in the Co 2p x-ray-absorption spectrum of CoO, the emission features are instead dominated by charge-transfer transitions to the 3d8-1 final state. The spectra are interpreted and discussed with the support of simulations within the single-impurity Anderson model with full multiplet effects which are found to yield consistent spectral functions to the experimental data.

  • 42.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Butorin, Sergei M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Guo, JH
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Agui, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ogasawara, H
    Kotani, A
    Takahashi, T
    Kunii, S
    Electronic-structure investigation of CeB6 by means of soft-x-ray scattering2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 63, no 7, p. 075101-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft-x-ray scattering using photon energies across the Ce 3d and 4dabsorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral contributions from inelastic Raman scattering and normal fluorescence. Pronounced energy-loss structures are observed below the elastic peak at both the 3d and 4dthresholds. The origin and character of the inelastic scattering structures are discussed in terms of charge-transfer excitations in connection to the dipole allowed transitions with 4f character. Calculations within the single-impurity Anderson model with full multiplet effects are found to yield consistent spectral functions to the experimental data.

  • 43.
    Magnuson, Martin
    et al.
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hultman, Lars
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Electronic structure and chemical bonding of nanocrystalline-TiC/amorphous-C nanocomposites2009In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 80, no 23, p. 235108-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of nanocrystalline (nc-) TiC/amorphous C nanocomposites has been investigated bysoft x-ray absorption and emission spectroscopy. The measured spectra at the Ti 2p and C 1s thresholds of thenanocomposites are compared to those of Ti metal and amorphous C. The corresponding intensities of theelectronic states for the valence and conduction bands in the nanocomposites are shown to strongly depend onthe TiC carbide grain size. An increased charge transfer between the Ti 3d-eg states and the C 2p states hasbeen identified as the grain size decreases, causing an increased ionicity of the TiC nanocrystallites. It issuggested that the charge transfer occurs at the interface between the nanocrystalline-TiC and the amorphous-Cmatrix and represents an interface bonding which may be essential for the understanding of the properties ofnc-TiC/amorphous C and similar nanocomposites.

  • 44.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Mattesini, Maurizio
    Höglund, Carina
    Abrikosov, Igor
    Birch, Jens
    Hultman, Lars
    Electronic structure investigation of the cubic inverse perovskite Sc3AlN2008In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 78, no 23, p. 235102-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of the recently discovered inverse perovskite Sc3AlN, incomparison to those of ScN and Sc metal, have been investigated by bulk-sensitive soft-x-ray emissionspectroscopy. The measured Sc L, N K, Al L1, and Al L2,3 emission spectra are compared with calculatedspectra using first-principles density-functional theory including dipole transition-matrix elements. The mainSc 3d–N 2p and Sc 3d–Al 3p chemical bond regions are identified at −4 and −1.4 eV below the Fermi level,respectively. A strongly modified spectral shape of 3s states in the Al L2,3 emission from Sc3AlN in comparisonto that for pure Al metal is found, which reflects the Sc 3d–Al 3p hybridization observed in the Al L1emission. The differences between the electronic structures of Sc3AlN, ScN, and Sc metal are discussed inrelation to the change in the conductivity and elastic properties.

  • 45.
    Magnuson, Martin
    et al.
    Department of Physics, Chemistry and Biology, IFM, Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Mattesini, Maurizio
    Departamento de Física de la Tierra, Astronomía y Astrofísica I, Universidad Complutense de Madrid, Madrid, Spain.
    Höglund, Carina
    Department of Physics, Chemistry and Biology, IFM, Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Birch, Jens
    Department of Physics, Chemistry and Biology, IFM, Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Hultman, Lars
    Department of Physics, Chemistry and Biology, IFM, Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 81, p. 085125-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of wurtzite-GaN investigated by N 1s soft x-ray absorption spectroscopy and N K, Ga M1, and Ga M2,3 emission spectroscopy is compared to that of pure Ga. The measurements are interpreted by calculated spectra using first-principles density-functional theory DFT including dipole transition matrix elements and additional on-site Coulomb interaction WC-GGA+U. TheGa 4p-N 2p and Ga 4s-N 2p hybridization and chemical bond regions are identified at the top of the valence band between −1.0 and −2.0 and further down between −5.5 and −6.5 eV, respectively. In addition, N 2s-N 2p-Ga 4s and N 2s-N 2p-Ga 3d hybridization regions occur at the bottom of the valence band between −13 and −15 eV, and between −17.0 and −18.0 eV, respectively. A bandlike satellite feature is also found around −10 eV in the Ga M1 and Ga M2,3 emission from GaN, but is absent in pure Ga and the calculated ground-state spectra. The difference between the identified spectroscopic features of GaN and Ga are discussed in relation to the various hybridization regions calculated within band-structure methods.

  • 46.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nilsson, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Weinelt, M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Angular-dependent resonant-photoemission processes at the 2p thresholds in nickel metal1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 4, p. 2436-2440Article in journal (Refereed)
    Abstract [en]

    Angle-resolved valence-band resonant-photoemission of nickel metal has been measured close to the 2p core-level thresholds with synchrotron radiation. The well-known 6-eV correlation satellite has an intensity enhancement of about two orders of magnitude at resonance. The angular dependence of the photoemission intensity has been studied as function of photon energy and provides unambiguous evidence for interference effects all the way up to the resonance maximum. The observation of different angular asymmetries, β, for the valence band and the satellite is discussed in connection to the origin of the resonant-photoemission process and the character of the satellite.  

  • 47.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Palmquist, Jens-Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Mattesini, M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Wilhelmsson, O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Eklund, P
    Högberg, H
    Hultman, L
    Jansson, U
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Electronic structure investigation of Ti3AlC2, Ti3SiC2, and Ti3GeC2 by soft x-ray emission spectroscopy2005In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 72, no 24, article id 245101Article in journal (Refereed)
    Abstract [en]

    The electronic structures of epitaxially grown films of Ti3AlC2, Ti3SiC2, and Ti3GeC2 have been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured high-resolution Ti L, C K, Al L, Si L, and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L emission of Ti3AlC2. As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2, respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.

  • 48.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Föhlisch, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Wassdahl, N
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nilsson, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    X-ray fluorescence spectra of metals excited below threshold2003In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 68, no 4, article id 045119Article in journal (Refereed)
    Abstract [en]

    X-ray scattering spectra of Cu and Ni metals have been measured using monochromatic synchrotron radiation tuned from far above to more than 10 eV below threshold. Energy conservation in the scattering process is found to be sufficient to explain the modulation of the spectral shape, neglecting momentum conservation and channel interference. At excitation energies close to and above threshold, the emission spectra map the occupied local partial density of states. For the subthreshold excitations, the high-energy flank of the inelastic scattering exhibits a Raman-type linear dispersion, and an asymmetric low-energy tail develops. For excitation far below threshold the emission spectra are proportional to a convolution of the occupied and unoccupied local partial densities of states.

  • 49.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Wassdahl, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nilsson, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Föhlisch, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel1998In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 58, no 7, p. 3677-3681Article in journal (Refereed)
    Abstract [en]

    The excitation energy dependence of the three-hole satellites in the L3-M45M45 andL2-M45M45 Auger spectra of nickel metal has been measured using synchrotron radiation. The satellite behavior in the nonradiative emission spectra at the L3 and L2thresholds is compared and the influence of the Coster-Kronig channel explored. The three-hole satellite intensity at the L3 Auger emission line reveals a peak structure at 5 eV above the L3 threshold attributed to resonant processes at the 2p53d9 shake-up threshold. This is discussed in connection with the 6-eV feature in the x-ray-absorption spectrum.

  • 50.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Wassdahl, Nial
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Energy dependence of Cu L2,3 satellites using synchrotron excited x-ray-emission spectroscopy1997In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 56, no 19, p. 12238-12242Article in journal (Refereed)
    Abstract [en]

    The L2,3 x-ray emission of Cu metal has been measured using monochromatic synchrotron radiation. The self-absorption effect in the spectra is shown to be very small in our experimental geometry. From the quantitative analysis of spectra recorded at different excitation energies, the L3/L2 emission intensity ratio and the partial Auger width are extracted. High-energy satellite features on the L3 emission line are separated by a subtraction procedure. The satellite intensity is found to be slowly increasing for excitation energies between the L3, L2, and L1 core-level thresholds due to shake-up and shake-off transitions. As the excitation energy passes the L2 threshold, a step of rapidly increasing satellite intensity of the L3 emission is found due to additional Coster-Kronig processes.

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