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  • 251.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Iusan, Diana
    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.
    Roy, P.
    Radboud Univ Nijmegen, Inst Mol & Mat, Heyendaalseweg 135, NL-6525 AJ Nijmegen, Netherlands.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Lohstroh, W.
    Tech Univ Munich, Heinz Maier Leibnitz Zentrum MLZ, Garching Bei Munchen, Lichtenbergstr, D-185748 Garching, Germany.
    Mutka, H.
    Inst Laue Langevin, BP 156, F-38042 Grenoble 9, France.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Deen, P. P.
    European Spallat Source ESS ERIC, Box 176, SE-22100 Lund, Sweden;Univ Copenhagen, Nanosci Ctr, Niels Bohr Inst, DK-2100 Copenhagen O, Denmark.
    Magnetocaloric effect in Fe2P: Magnetic and phonon degrees of freedom2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 17, article id 174437Article in journal (Refereed)
    Abstract [en]

    Devices based on magnetocaloric materials provide great hope for environmentally friendly and energy efficient cooling that does not rely on the use of harmful gasses. Fe2P based compounds are alloys that have shown great potential for magnetocaloric devices. The magnetic behavior in Fe2P is characterized by a strong magnetocaloric effect that coexists with a first-order magnetic transition (FOMT). Neutron diffraction and inelastic scattering, Mossbauer spectroscopy, and first-principles calculations have been used to determine the structural and magnetic state of Fe2P around the FOMT. The results reveal that ferromagnetic moments in the ordered phase are perturbed at the FOMT such that the moments cant away from the principle direction within a small temperature region. The acoustic-phonon modes reveal a temperature-dependent nonzero energy gap in the magnetically ordered phase that falls to zero at the FOMT. The interplay between the FOMT and the phonon energy gap indicates hybridization between magnetic modes strongly affected by spin-orbit coupling and phonon modes leading to magnon-phonon quasiparticles that drive the magnetocaloric effect.

  • 252.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Delczeg-Czirjak, Erna Krisztina
    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 Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic and mechanical effects of Mn substitutions in AlFe2B22019In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 482, p. 54-60Article in journal (Refereed)
    Abstract [en]

    The mechanical and magnetic properties of the newly discovered MAB-phase class of materials based upon AlFe2B2 were investigated. The samples were synthesised from stoichiometric amounts of all constituent elements. X-ray diffraction shows that the main phase is orthorhombic with an elongated b-axis, similar to AlFe2B2. The low hardness and visual inspection of the samples after deformation indicate that these compounds are deformed via a delamination process. When substituting iron in AlFe2B2 with manganese, the magnetism in the system goes from being ferro- to antiferromagnetic via a disordered ferrimagnetic phase exhibited by AlFeMnB2. Density functional theory calculations indicate a weakening of the magnetic interactions among the transitions metal ions as iron is substituted by manganese in AlFe2B2. The Mn-Mn exchange interactions in AlMn2B2 are found to be very small.

  • 253.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Delczeg-Czirjak, Erna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergqvist, Lars
    Hansen, Thomas C.
    Beran, Premysl
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic structure of the magnetocaloric compound AlFe2B22016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 654, p. 784-791Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be - 1.3 J/K kg at the magnetic transition temperature.

  • 254.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Beran, Premysl
    ASCR, Inst Nucl Phys, Hlavni 130, Rez 25068, Czech Republic.
    Vennström, Marie
    AB Sandvik Mat Technol, SE-81181 Sandviken, Sweden.
    Danielsson, Therese
    Etteplan Sweden AB, SE-17154 Solna, Sweden.
    Ronneteg, Sabina
    AB Sandvik Mat Technol, SE-81181 Sandviken, Sweden.
    Höglin, Viktor
    Scienta Sauna Syst AB, SE-75228 Uppsala, Sweden.
    Lindell, David
    Swerea KIMAB AB, Box 7047, SE-16407 Kista, Sweden.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    André, Gilles
    CEA Saclay, LLB, F-91191 Gif Sur Yvette, France.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Low temperature magneto-structural transitions in Mn3Ni20P62016In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 237, p. 343-348Article in journal (Refereed)
    Abstract [en]

    Abstract X-ray and neutron powder diffraction has been used to determine the crystal and magnetic structure of Mn3Ni20P6. The crystal structure can be described as cubic with space group Fm 3 ¯ m (225) without any nuclear phase transformation within studied temperature interval from room temperature down to 4 K. The magnetic structure of Mn3Ni20P6 is complex with two independent magnetic positions for the Mn atoms and the compound passes three successive magnetic phase transitions during cooling. At 30 K the spins of the Mn atoms on the Wyckoff 4a site (Mn1) order to form a primitive cubic antiferromagnetic structure with propagation vector k=(0 0 1). Between 29 and 26 K the Mn atoms on the Wyckoff 8c site (Mn2) order independently on already ordered Mn1 magnetic structure forming a commensurate antiferromagnetic structure with propagation vector k=(0 0 ½) and below 26 K, both Mn positions order to form an incommensurate helical structure with propagation vector k=(0 0 ~0.45). Magnetization vs. temperature curve of Mn3Ni20P6 shows a steep increase indicating some magnetic ordering below 230 K and a sharp field dependent anomaly in a narrow temperature range around 30 K.

  • 255.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kontos, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hansen, Thomas C.
    Balmes, Olivier
    Martinez-Casado, Francisco Javier
    Matej, Zdenek
    Beran, Premysl
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetostructural transition in Fe5SiB2 observed with neutron diffraction2016In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 235, p. 113-118Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structure of Fe5SiB2 has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropy energy constant has been estimated to 03 MJ/m(3) at 300 K.

  • 256.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nonnet, Elise
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Werwinski, Miroslaw
    Institute of Molecular Physics, Polish Academy of Sciences.
    Edström, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Department of Materials Theory, ETH Zürich.
    Rusz, Jan
    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.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of cobalt substitution on the magnetic properties of Fe5PB22018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 2, p. 777-784Article in journal (Refereed)
    Abstract [en]

    In this study the effects of cobalt substitutions in Fe5PB2 have been studied. An increased cobalt content reduces the magnetic exchange interactions. This has been concluded from a large, linear decrease in both the Curie temperature as well as the saturated magnetic moment. At high cobalt concentrations, cobalt prefers to order at the M(2) position in the crystal structure. A tunable Curie transition like this shows some prerequisites for magnetic cooling applications.

    The substitutional effects of cobalt in (Fe1–xCox)5PB2 have been studied with respect to crystalline structure and chemical order with X-ray diffraction and Mössbauer spectroscopy. The magnetic properties have been determined from magnetic measurements, and density functional theory calculations have been performed for the magnetic properties of both the end compounds, as well as the chemically disordered intermediate compounds. The crystal structure of (Fe1–xCox)5PB2 is tetragonal (space group I4/mcm) with two different metal sites, with a preference for cobalt atoms in the M(2) position (4c) at higher cobalt contents. The substitution also affects the magnetic properties with a decrease of the Curie temperature (TC) with increasing cobalt content, from 622 to 152 K for Fe5PB2 and (Fe0.3Co0.7)5PB2, respectively. Thus, the Curie temperature is dependent on composition, and it is possible to tune TC to a temperature near room temperature, which is one prerequisite for magnetic cooling materials.

  • 257.
    Chafai, A.
    et al.
    Univ Moulay Ismail, Fac Sci, Phys Dept, LP2MS,Unite Associee,CNRST,URAC 08, BP 11201, Meknes, Morocco.
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Moulay Ismail, Fac Sci, Phys Dept, LP2MS,Unite Associee,CNRST,URAC 08, BP 11201, Meknes, Morocco.
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Univ Moulay Ismail, Fac Sci, Phys Dept, LP2MS,Unite Associee,CNRST,URAC 08, BP 11201, Meknes, Morocco;Max Planck Inst Phys Complexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany;U.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Univ, Dept Phys & Astron, Condensed MatterTheory Grp, S-75120 Uppsala, Sweden.
    Linear and nonlinear optical properties of donors inside a CdSe/ZnTe core/shell nanodot: Role of size modulation2019In: RESULTS IN PHYSICS, ISSN 2211-3797, Vol. 14, article id 102414Article in journal (Refereed)
    Abstract [en]

    The optical absorption coefficient (OAC) and the refractive index (RI), related to a confined donor, were theoretically investigated by the mean of the density matrix formalism. In order to obtain the 1s - 1p donor transition energy a variational calculation, within the context of the effective-mass approach, was deployed. Our numerical results exhibit the possibility to modulate the electronic and optical properties of confined donors by tailoring the inner and outer radii of the core/shell heterodot. Further, we have obtained that the nanodot size shrinking leads, for very small values of core radius, to reduce the magnitude of the total absorption coefficient resonance peak. It was also obtained that the resonance peak position of the absorption coefficient is redshifted with increasing the core radius for a fixed shell thickness. The same situation occurs when reducing the thickness of the shell material for a fixed core size.

  • 258.
    Chakarov, D V
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hellsing, B
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Photos induced desorption and intercalation of potassium atoms deposited on graphite(0001)1996In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 106, p. 186-192Article in journal (Refereed)
    Abstract [en]

    In addition to the photodesorption phenomenon previously observed for single K atoms from a graphite surface covered with a monolayer of potassium we present new results related to the photon stimulated interaction of potassium with graphite, which concerns alternative routes for energy relaxation of the photo excited K adatoms: photoinduced intercalation. The desorption yield has a threshold at h omega approximate to 3 eV and a maximum at h omega(max) approximate to 4.9 eV, Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photo active. The proposed mechanism includes attachment of photo-generated hot electrons to the K 4s adsorbate resonance of energy E(res). Assuming an analogous excitation process we discuss different mechanisms for the K photo intercalation and possible applications of the photon stimulated doping of carboneous materials at low temperature.

  • 259.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    HELLSING, B
    Chalmers University of Technology.
    ZHDANOV, VP
    Chalmers University of Technology.
    KASEMO, B
    Chalmers University of Technology.
    PHOTOSTIMULATED DESORPTION OF METAL ADATOMS - POTASSIUM ON GRAPHITE1994In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 311, no 3, p. L724-L730Article in journal (Refereed)
    Abstract [en]

    Photodesorption is observed of single K atoms from a graphite surface covered with less than 1 monolayer of potassium. The desorption cross section has a threshold at homegaBAR almost-equal-to 3 eV and a maximum at homega(max)BAR almost-equal-to 4.9 eV. Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photoactive. The proposed mechanism includes attachment of hot electrons, photoexcited in the bulk, to the K4s adsorbate resonance of energy E(res). The band structure of graphite causes a narrow energy distribution of hot electrons, which yields homega(max)BAR almost-equal-to 2E(res).

  • 260.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    INTERACTION OF WATER WITH POTASSIUM ON GRAPHITE - A HREELS STUDY1993In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 64-5, p. 279-285Article in journal (Refereed)
    Abstract [en]

    Water and coadsorbed water + potassium on the basal plane of graphite were studied with high resolution electron energy loss spectroscopy (HREELS) at 85 K and after stepwise annealing up to 500 K. Water adsorbs non-dissociatively on both clean and potassium precovered surface at 85 K. The vibration spectra, together with thermal desorption spectroscopy (TDS) reveal a series of reactions within the coadsorbed layer leading to the formation of KOH, KH, and KOx and volatile products. Eventually a precursor to CO2 formation, of yet unindentified composition and observed also in K + O-2 coadsorption studies on graphite, is observed at approximate to 27 meV.

  • 261.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    WATER-ADSORPTION AND COADSORPTION WITH POTASSIUM ON GRAPHITE(0001)1995In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 11, no 4, p. 1201-1214Article in journal (Refereed)
    Abstract [en]

    Water and water coadsorbed with potassium on the basal plane of graphite were studied with thermal desorption spectroscopy (TDS) and high-resolution electron energy loss spectroscopy (HREELS) in the temperature range 85-900 K. Water alone adsorbs nondissociatively on the clean graphite surface at 85 K, forming hydrogen bonded aggregates. Its structure depends both on the coverage and on substrate temperature. With increasing coverage at 85 K(0.5-1.0 monolayer (ML)) the libration mode at similar to 86 meV shows a rapid upward shift, indicating a phase transition from a 2D to a 3D structure. The transition can also be induced by annealing the low coverage structure. Water coadsorption with potassium is nonreactive or reactive, depending on temperature and potassium coverage. The nonreactive coadsorption at T-s = 85 K occurs only below a critical potassium coverage of BK less than or equal to 0.3 ML. It is characterized by substantial symmetry changes of the adsorbed water molecules, compared to the pure water adsorption, and is attributed to formation of hydrated-ion species on the surface. The surface solvation number at the lowest K coverage is three to four H2O molecules per potassium atom. K and H2O react at submonolayer coverages at 120-160 K to form surface KOH, KH, KxOy, and volatile products. The surface species gradually transforms/decomposes at elevated temperatures (200-500 K) to first form potassium-oxygen complexes that then serve as precursors to graphite oxidation to CO2 at similar to 750 K.

  • 262.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    WATER-ADSORPTION ON GRAPHITE(0001)1995In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 46, no 8-10, p. 1109-1112Article in journal (Refereed)
    Abstract [en]

    Wafer adsorption on the clean graphite (0001) surface has been studied by high-resolution electron-energy-loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). At 85 K H2O adsorbs non-dissociatively forming hydrogen-bonded aggregates. The structure and the growth mode of water clusters depend on the substrate temperature and the coverage. At all coverages, above a few per cent of a monolayer (ML), the desorption is characterized by zero-order kinetics, while the HREEL spectra reveal a threshold coverage approximately 1 ML when the average co-ordination of the H2O molecules changes. Isothermal measurements of the desorption rate and HREELS measurements at elevated temperatures suggest an irreversible phase transition from amorphous to crystalline ice at approximately 135 K.

  • 263.
    Chakravorty, Manotosh
    et al.
    SN Bose Natl Ctr Basic Sci, Dept Condensed Matter Phys & Mat Sci, Block JD,Sect 3, Kolkata 700098, W Bengal, India..
    Raychaudhuri, A. K.
    SN Bose Natl Ctr Basic Sci, Dept Condensed Matter Phys & Mat Sci, Block JD,Sect 3, Kolkata 700098, W Bengal, India..
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Proposed Bose-Einstein condensation of magnons in nanostructured films of Gd at low temperature and its manifestations in electrical resistivity and magnetoresistance2017In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 25, article id 255701Article in journal (Refereed)
    Abstract [en]

    In this paper we report the observation of a proposed Bose-Einstein condensation (BEC) of magnons in a temperature range of around 15-20 K in nanostructured films of Gd with grain sizes that are much larger than the size range where superparamagentism is expected. The observation was carried out using magnetic as well as high precision resistivity and magnetoresistance (MR) measurements performed to low temperatures. We observe that the experimental observations depend crucially on one parameter, namely softening of the spin wave stiffness parameter D at BEC and the resistivity as well as MR can be related quantitatively to magnetic measurements through the temperature variation of the constant D in the vicinity of the transition. This paper establishes that the BEC reported before in nanocrystalline Gd can be extended to a somewhat larger size range.

  • 264. Chao, K. S.
    et al.
    Huang, D. J.
    Okamoto, J.
    Lin, H.-J.
    Kaneko, Y.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wu, W. B.
    Tokura, Y.
    Chen, C. T.
    Orbital Ordering of Manganites from Resonant Soft X-ray Scattering2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 310, p. 819-Article in journal (Refereed)
  • 265. Chatzigeorgiou, E
    et al.
    Århammar, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Gråsjö, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Resonant Inelastic X-ray Scattering on Mesoporous Magnesium Carbonate2019In: The 40th International Conference on Vacuum Ultraviolet and X-ray Physics, San Fransisco, 2019Conference paper (Refereed)
  • 266. Chen, H.-P.
    et al.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmera, G.
    On the "Cracking" Experiments in the Paper "A Directional Coupler Attack against the Kish Key Distribution System" by Gunn, Allison and Abbott2014In: Metrology and Measurement Systems (Metrol. Meas. Syst.), ISSN p-ISSN: 0860-8229, Vol. XXI, p. 389-400Article in journal (Refereed)
  • 267. Chen, H.-P.
    et al.
    Kish, L.-B.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmera, G.
    Do Electromagnetic Waves Exist in a Short Cable? What Does Physics Say?2014In: Fluctuation and Noise Letters, ISSN 0219-4775, Vol. 13, no 1450016, p. 1-13Article in journal (Refereed)
  • 268. Chen, Hsien-Pu
    et al.
    Kish, Laszlo B.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmera, G.
    On The "Cracking" Scheme in The Paper "A Directional Coupler Attack Against the Kish Key Distribution System" by Gunn, Allison And Abbott2014In: METROLOGY AND MEASUREMENT SYSTEMS, ISSN 0860-8229, Vol. 21, no 3, p. 389-400Article in journal (Refereed)
    Abstract [en]

    Recently, Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law-Johnson-noise (KLJN) secure key distribution. We proved in a former paper [Fluct. Noise Lett. 13 (2014) 1450016] that GAA's mathematical model is unphysical. Here we analyze GAA's cracking scheme and show that, in the case of a loss-free cable, it provides less eavesdropping information than in the earlier (Bergou)-Scheuer-Yariv mean-square-based attack [Kish LB, Scheuer J, Phys. Lett. A 374:2140-2142 (2010)], while it offers no information in the case of a lossy cable. We also investigate GAA's claim to be experimentally capable of distinguishing-using statistics over a few correlation times only-the distributions of two Gaussian noises with a relative variance difference of less than 10(-8). Normally such distinctions would require hundreds of millions of correlations times to be observable. We identify several potential experimental artifacts as results of poor KLJN design, which can lead to GAA's assertions: deterministic currents due to spurious harmonic components caused by ground loops, DC offset, aliasing, non-Gaussian features including non-linearities and other non-idealities in generators, and the time-derivative nature of GAA's scheme which tends to enhance all of these artifacts.

  • 269. Chen, Hsien-Pu
    et al.
    Kish, Laszlo B.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmera, Gabor
    Do Electromagnetic Waves Exist in a Short Cable at Low Frequencies?: What Does Physics Say?2014In: Fluctuation and Noise Letters, ISSN 0219-4775, E-ISSN 1793-6780, Vol. 13, no 2, p. 1450016-Article in journal (Refereed)
    Abstract [en]

    We refute a physical model, recently proposed by Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf], to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law-Johnson-noise (KLJN) secure key distribution. Their model, and its theoretical underpinnings, is found to be fundamentally flawed because their assumption of electromagnetic waves violates not only the wave equation but also the second law of thermodynamics, the principle of detailed balance, Boltzmann's energy equipartition theorem, and Planck's formula by implying infinitely strong blackbody radiation. We deduce the correct mathematical model of the GAA scheme, which is based on impedances at the quasi-static limit. Mathematical analysis and simulation results confirm our approach and prove that GAA's experimental interpretation is incorrect too.

  • 270.
    Cheung, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tillämpning och simulering av naturlig ventilation: Potential för utnyttjande i kontorsrum2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mechanical ventilation is the most common type of

    ventilation in newly constructed office buildings. There

    has been an interest to utilize natural ventilation

    instead of mechanical ventilation among architects and

    HVAC consultants in recent years. This is due to the

    size of mechanical ventilation systems, which are

    space consuming. The mechanical ventilation system is

    also complex and requires maintenance. Furthermore,

    the fan uses a considerable amount of energy. Natural

    ventilation is an alternative not affecting the rentable

    floor space. The basic idea of natural ventilation is to

    use a technique where natural forces such as wind and

    thermal gradients fully handle the ventilation.

    The software program IDA ICE was used to simulate

    the natural ventilation by advanced window control in

    offices and to investigate if natural ventilation is a

    good option to conventional systems regarding indoor

    climate and energy use. The indoor temperature and

    the concentration of carbon dioxide control the

    window opening. A CAC (Clean Air Control)- sensor

    was also used instead of a traditional CO2-sensor,

    which is a sensor that regulates the airflow according

    to the level of air pollution.

    The results show that natural ventilation with advanced

    window control cannot always achieve the regulatory

    requirements for the highest carbon dioxide content of

    1000 ppm, since the airflow is not sufficient. On these

    occasions a fan is required to provide a good indoor

    climate. An interesting observation is that the energy

    use for heating is only 38% larger for the office rooms

    with natural ventilation compared with mechanically

    ventilated offices. Even though the heat energy are

    released to the outdoor environment and not

    recovered in the naturally ventilated room.

  • 271. Chi, S.
    et al.
    Ye, F.
    Dai, P.
    Fernandez-Baca, J. A.
    Huang, Q.
    Lynn, J. W.
    Plummer, E. W.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kaneko, Y.
    Tokura, Y.
    Effect of antiferromagnetic spin correlations on lattice distortion and charge ordering in Pr0.5Ca1.5MnO42007In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 104, no 10, p. 10796-Article in journal (Refereed)
  • 272. CHIRWA, M
    et al.
    LUNDGREN, 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.
    BECKMAN, O
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    MAGNETIC SPECIFIC-HEAT OF FEF2 NEAR TN1980In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 15-8, p. 457-458Article in journal (Refereed)
  • 273. Choudhury, D.
    et al.
    Mandal, P.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hazarika, A.
    Rajan, S.
    Sundaresan, A.
    Waghmare, U. V.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarma, Dipankar Das
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Near-Room-Temperature Colossal Magnetodielectricity and Multiglass Properties in Partially Disordered La2NiMnO62012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 12, p. 127201-Article in journal (Refereed)
    Abstract [en]

    We report magnetic, dielectric, and magnetodielectric responses of the pure monoclinic bulk phase of partially disordered La2NiMnO6, exhibiting a spectrum of unusual properties and establish that this compound is an intrinsically multiglass system with a large magnetodielectric coupling (8%-20%) over a wide range of temperatures (150-300 K). Specifically, our results establish a unique way to obtain colossal magnetodielectricity, independent of any striction effects, by engineering the asymmetric hopping contribution to the dielectric constant via the tuning of the relative-spin orientations between neighboring magnetic ions in a transition-metal oxide system. We discuss the role of antisite (Ni-Mn) disorder in emergence of these unusual properties.

  • 274.
    Choudhury, Debraj
    et al.
    Solid State and Structural Chemistry Unit, and Department of Physics, at Indian Institute of Science, Bangalore, Indien.
    Mukherjee, S
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Indien.
    Mandal, P
    Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Indien.
    Sundaresan, A
    Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Indien.
    Waghamare, U V
    Theoretical Science Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Indien.
    Bhattacharjee, Satadeep
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Eriksson, Olle
    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.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sharma, Ajay
    Department of Physics, Indian Institute of Science, Bangalore, Indien.
    Bhat, S V
    Department of Physics, Indian Institute of Science, Bangalore, Indien.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Sarma, Dipankar Das
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Tuning of dielectric properties and magnetism of SrTiO3 by site-specific doping of Mn2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 12, p. 125124-Article in journal (Refereed)
    Abstract [en]

    Combining experiments with first-principles calculations, we show that site-specific doping of Mn into SrTiO(3) has a decisive influence on the dielectric properties of these doped systems. We find that phonon contributions to the dielectric constant invariably decrease sharply on doping at any site. However, a sizable, random dipolar contribution only for Mn at the Sr site arises from a strong off-centric displacement of Mn in spite of Mn being in a non-d(0) state; this leads to a large dielectric constant at higher temperatures and gives rise to a relaxor ferroelectric behavior at lower temperatures. We also investigate magnetic properties in detail and critically reevaluate the possibility of a true multiglass state in such systems.

  • 275.
    Christians, Gabriel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Prognostisering av Fjärrvärmebehov: -En jämförelse av fastigheter med olikastor varmvattenanvändning2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to investigate the differences in diurnal and annual use of districtheating for two kind of heat users with different amount of warm water usage. Thefirst user is a hotel including spa facilities that uses a large amount of warm water, thesecond user is an office building that has a very low usage of warm water.The aim is to develop and validate methods for forecasting district heat use onvarious timescales. The average daily temperature for each month is shown to benormally distributed and average temperatures are therefore suitable for long-termforecasting. It is also shown that there is a clear linear relationship between lowerout-door temperature and higher use of district heating power. The thesis shows thatthe hotel will have a different power signature for their district heating compared tothe office that use a relative low amount of warm water.Short term forecasts, with a horizon of 10 days, are made for both the hotel andoffice building. As a result of the forecasts it is shown that the it is easier todetermine when the peak district heating power outtake will occur for the buildingwith a high amount of domestic hot water usage. However, forecasts for total diurnalheat use are equally accurate for the investigated buildings

  • 276.
    Cindemir, Umut
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thin films for indoor air monitoring: Measurements of Volatile Organic Compounds2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Volatile organic compounds (VOCs) in the indoor air have adverse effects on the dwellers residing in a building or a vehicle. One of these effects is called sick building syndrome (SBS). SBS refers to situations in which the users of a building develop acute health effects and discomfort depending on the time they spend inside some buildings without having any specific illness. Furthermore, monitoring volatile organic compounds could lead to early diagnosis of specific illnesses through breath analysis. Among those VOCs formaldehyde, acetaldehyde can be listed.

    In this thesis, VOC detecting thin film sensors have been investigated. Such sensors have been manufactured using semiconducting metal oxides, ligand activated gold nanoparticles and Graphene/TiO2 mixtures. Advanced gas deposition unit, have been used to produce NiO thin films and Au nanoparticles. DC magnetron sputtering has been used to produce InSnO and VO2 thin film sensors. Graphene/TiO2 sensors have been manufactured using doctor-blading.

    While presenting the results, first, material characterization details are presented for each sensor, then, gas sensing results are presented. Morphologies, crystalline structures and chemical properties have been analyzed using scanning electron microscopy, X-ray diffraction and X-ray photo electron spectroscopy. Furthermore, more detailed analyses have been performed on NiO samples using extended X-ray absorption fine structure method and N2 adsorption measurements. Gas sensing measurements were focused on monitoring formaldehyde and acetaldehyde. However, responses ethanol and methane were measured in some cases to monitor selectivity. Graphene/TiO2 samples were used to monitor NO2 and NH3. For NiO thin film sensors and Au nano particles, fluctuation enhanced gas sensing is also presented in addition to conductometric measurements. 

  • 277.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lansåker, Pia C.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sputter-Deposited Indium-Tin Oxide Thin Films for Acetaldehyde Gas Sensing2016In: Coatings, ISSN 2079-6412, Vol. 6, no 2, article id 19Article in journal (Refereed)
    Abstract [en]

    Reactive dual-target DC magnetron sputtering was used to prepare In-Sn oxide thin films with a wide range of compositions. The films were subjected to annealing post-treatment at 400 degrees C or 500 degrees C for different periods of time. Compositional and structural characterizations were performed by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Rutherford backscattering and scanning electron microscopy. Films were investigated for gas sensing at 200 degrees C by measuring their resistance response upon exposure to acetaldehyde mixed with synthetic air. We found that the relative indium-to-tin content was very important and that measurable sensor responses could be recorded at acetaldehyde concentrations down to 200 ppb, with small resistance drift between repeated exposures, for both crystalline SnO2-like films and for amorphous films consisting of about equal amounts of In and Sn. We also demonstrated that it is not possible to prepare crystalline sensors with intermediate indium-to-tin compositions by sputter deposition and post-annealing up to 500 degrees C.

  • 278.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, José Amenedo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sputter deposited thermochromic VO2 thin films for acetaldehyde and formaldehyde sensing.2014In: 5th International Symposium on Transparent Conductive Materials, 12-17 October 2014, Chania, Crete, Greece, 2014Conference paper (Other academic)
  • 279.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Calavia, R.
    Llobet, E.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ionescu, R.
    Gold Nanoparticle Thin Film Sensors for Formaldehyde Detection2014Conference paper (Refereed)
  • 280.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterization of nanocrystalline-nanoporous nickel oxide thin films prepared by reactive advanced gas deposition2019In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 227, p. 98-104Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline-nanoporous Ni oxide is of much interest for gas sensors and other applications. Reactive advanced gas deposition (AGD) stands out as a particularly promising technique for making thin films of this material owing to the techniques ability to separate between the growth of individual nanoparticles and their subsequent deposition to create a consolidated material on a substrate. Here we report on the characterization of Ni oxide films, made by reactive AGD, by several methods. X-ray diffractometry showed that the films had a face centered cubic NiO structure, and scanning electron microscopy indicated a compact nanoparticulate composition. X-ray photoelectron spectroscopy showed the presence of Ni3+ and demonstrated that these states became less prominent upon heat treatment in air. Extended x-ray absorption fine structure analysis elucidated the local atomic structure; in particular, data on interatomic distances and effects of annealing on local disorder showed that the Ni oxide nanoparticles crystallize upon annealing while maintaining their nanoparticle morphology, which is a crucial feature for reproducible fabrication of Ni oxide thin films for gas sensors. Importantly, several techniques demonstrated that grain growth remained modest for annealing temperatures as high as 400 degrees C for 1700-nm-thick films. The present article is a sequel to an earlier one [U. Cindemir et al., Sensors and Actuators B 242 (2017) 132-139] in which we reported on fluctuation-enhanced and conductometric gas sensing with Ni oxide films prepared by AGD.

  • 281.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnar, Niklasson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Porous Nickel Oxide Film Sensor for Formaldehyde2014In: INERA Workshop: Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices / Parallel session of the 18th International School on Condensed Matter Physics, 2014, p. UNSP 012012-Conference paper (Refereed)
    Abstract [en]

    Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 degrees C.

  • 282.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Porous Nickel Oxide Sensor for Formaldehyde Detection2014In: European Materials Society (E-MRS) Spring Meeting, Lille, France, May 26-30, 2014.: Symposium B: Advanced functional materials for environmental monitoring and applications., 2014Conference paper (Other academic)
    Abstract [en]

    Formaldehyde is a volatile organic compound, which is a harmful indoor pollutant, causing sick building syndrome (SBS) and is released from household and building materials. Since higher concentrations of formaldehyde are considered to be carcinogenic, monitoring them indoors is of great importance. Advanced gas deposition has here been used to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes, and a resistive heater at the opposite face. The morphology of the films was investigated with scanning electron microscopy, and the porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. The particle size was found to be less than 10 nm, as determined by x-ray diffraction. X-ray photoelectron spectroscopy of the NiO films was also done. Gas sensing measurements were done using a total gas flow rate of 200 ml/min. Resistivity values of sensors were recorded with formaldehyde diluted in synthetic air. Sensor resistances were recorded at 50 ppm, 25ppm, 10ppm and 5 ppm formaldehyde concentration. NiO films showed promising formaldehyde gas sensing properties implying lower levels of detection limit.

  • 283.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Trawka, Maciej
    Gdansk University of Technology, Gdansk, Poland.
    Smulko, Janusz
    Gdansk University of Technology, Gdansk, poland.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Fluctuation-enhanced and conductometric gas sensing with nanocrystalline NiO thin films: A comparison2017In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 242, p. 132-139Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline thin films of NiO were prepared by advanced reactive gas deposition, and their responses to formaldehyde, ethanol and methane gases were studied via fluctuation-enhanced and conductometric methods Thin films with thicknesses in the 200–1700-nm range were investigated in as-deposited form and after annealing at 400 and 500◦C. Morphological and structural analyses showed porous deposits with NiO nanocrystals having face-centered cubic structure. Quantitative changes in frequency-dependent resistance fluctuations as well as in DC resistance were recorded upon exposure to formaldehyde, ethanol and methane at 200◦C. The response to formaldehyde was higher than that to ethanol while the response to methane was low, which indicates that the NiO films exhibit significant selectivity towards different gaseous species. These results can be reconciled with the fact that formaldehyde has a nucleophilic group, ethanol is an electron scavenger, and methane is hard to either reduce or oxidize. The gas-induced variations in DC resistance and resistance fluctuations were in most cases similar and consistent.

  • 284.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Trawka, Maciej
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, Gdansk, Poland.
    Smulko, Janusz M.
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, Gdansk, Poland.
    Nickel oxide thin film sensor for fluctuation-enhanced gas sensing of formaldehyde2015In: 2015 IEEE Sensors, 2015Conference paper (Refereed)
    Abstract [en]

    Nanocrystalline nickel-oxide-based thin films were prepared by advanced reactive gas deposition, and the response of these films to formaldehyde was studied by fluctuation-enhanced sensing. Morphological and structural analyses showed porous deposits of nickel oxide particles with face-centered cubic structure. Resistance fluctuations were measured upon exposure to ethanol, formaldehyde and methane at 200 degrees C. Power density spectra were used to quantify the response. The response to formaldehyde was higher than to ethanol at 200 degrees C, and no significant response was observed for methane thus demonstrating some gas-species selectivity.

  • 285.
    Ciuciulkaite, Agne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Östman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Verschuuren, Marc A.
    Philips Res Labs, High Tech Campus 4, Eindhoven, Netherlands.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Collective magnetization dynamics in nanoarrays of thin FePd disks2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 18, article id 184415Article in journal (Refereed)
    Abstract [en]

    We report on the magnetization dynamics of a square array of mesoscopic disks, fabricated from an iron palladium alloy film. The dynamics properties were explored using ferromagnetic resonance measurements and micromagnetic simulations. The obtained spectra exhibit features resulting from the interactions between the disks, with a clear dependence on both temperature and the direction of the externally applied field. We demonstrate a qualitative agreement between the measured and calculated spectra. Furthermore, we calculated the mode profiles of the standing spin waves excited during time-dependent magnetic field excitations. The resulting maps confirm that the features appearing in the ferromagnetic resonance absorption spectra originate from the temperature- and directional-dependent interdisk interactions.

  • 286.
    Claesson, Emma
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Analys av sorptiv kylning i industri- och kontorsbyggnader2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Energy efficiency is important both to reduce costs and to reduce greenhouse gas emissions in the atmosphere. Reducing costs will also help maintain business competitiveness.

    Scania in Södertälje is a company where the optimization of energy use is an ongoing and continual process. One area with potential to make energy and cost savings is the effectiveness of the ventilation systems in offices and industrial premises at Scania. During the summer months an increased demand for cooling occurs, leading to increased ventilation and a peak in district cooling system usage. Sorptive cooling is a technology where the supplied air is cooled by applying external heat. This technique involves a reduction in electricity consumption compared to electrically-powered cooling machines and does not affect the district cooling system usage. It was therefore of interest to investigate if sorptive cooling would be an energy efficient and viable solution for Scania in the future.

    This investigation shows that sorptive cooling requires more power than a conventional ventilation system. Despite the fact that Scania has access to free heat during the summer months, the study shows that sorptive cooling would not be economically viable to install in the industrial premises, where no cooling systems currently exist. However, compared to an electrically-powered cooling machine, sorptive cooling is anyway more energy efficient. The conclusion is that sorptive cooling is a viable solution for the offices, but not for the industrial premises at Scania in Södertälje

  • 287.
    Coll, M.
    et al.
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Fontcuberta, J.
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Althammer, M.
    Bayer Akad Wissensch, Walther Meissner Inst, D-85748 Garching, Germany;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany.
    Bibes, M.
    Univ Paris Sud, Univ Paris Saclay, Thales, Unite Mixte Phys,CNRS, F-91767 Palaiseau, France.
    Boschker, H.
    Max Planck Inst Solid State Res, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Calleja, A.
    OXOLUTIA SL, Avda Castell Barbera 26,Tellers 13,Nau 1, Barcelona 08210, Spain.
    Cheng, G.
    Univ Sci & Technol China, CAS Key Lab Microscale Magnet Resonance, Hefei 230026, Anhui, Peoples R China;Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Anhui, Peoples R China;Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA;Pittsburgh Quantum Inst, Pittsburgh, PA 15260 USA.
    Cuoco, M.
    Univ Salerno, CNR SPIN, IT-84084 Fisciano, SA, Italy;Univ Salerno, Dipartimento Fis ER Caianiello, IT-84084 Fisciano, SA, Italy.
    Dittmann, R.
    Forschungszentrum Julich, Peter Grunberg Inst PGI 7, D-52425 Julich, Germany.
    Dkhil, B.
    Univ Paris Saclay, CNRS UMR 8580, Cent Supelec, Lab Struct Proprietes & Modelisat Solides, F-91190 Gif Sur Yvette, France.
    El Baggari, I
    Cornell Univ, Dept Phys, Ithaca, NY 14853 USA.
    Fanciulli, M.
    Univ Milano Bicocca, Dept Mat Sci, Milan, Italy.
    Fina, I
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Fortunato, E.
    Univ NOVA Lisboa UNL, FCT, Dept Ciencia Mat, CENIMAT i3N, Lisbon, Portugal;CEMOP UNINOVA, P-2829516 Caparica, Portugal.
    Frontera, C.
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Fujita, S.
    Kyoto Univ, Kyoto 6158520, Japan.
    Garcia, V
    Univ Paris Sud, Univ Paris Saclay, Thales, Unite Mixte Phys,CNRS, F-91767 Palaiseau, France.
    Goennenwein, S. T. B.
    Tech Univ Dresden, Inst Festkorperphys, D-01062 Dresden, Germany;Tech Univ Dresden, Ctr Transport & Devices Emergent Mat, D-01062 Dresden, Germany.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Grollier, J.
    Univ Paris Sud, Univ Paris Saclay, Thales, Unite Mixte Phys,CNRS, F-91767 Palaiseau, France.
    Gross, R.
    Bayer Akad Wissensch, Walther Meissner Inst, D-85748 Garching, Germany;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany;NIM, D-80799 Munich, Germany.
    Hagfeldt, A.
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland.
    Herranz, G.
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Hono, K.
    NIMS, Res Ctr Magnet & Spintron Mat, 1-2-1 Sengen, Tsukuba, Ibaraki 3050047, Japan.
    Houwman, E.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands.
    Huijben, M.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands.
    Kalaboukhov, A.
    Chalmers Univ Technol, Dept Microtechnol & Nanosci, MC2, Gothenburg, Sweden.
    Keeble, D. J.
    Univ Dundee, Sch Sci & Engn, Carnegie Lab Phys, SUPA, Dundee DD1 4HN, Scotland.
    Koster, G.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands.
    Kourkoutis, L. F.
    Kavli Inst Cornell Nanoscale Sci, Ithaca, NY 14853 USA;Cornell Univ, Sch Appl & Engn Phys, Ithaca, NY 14853 USA.
    Levy, J.
    Bayer Akad Wissensch, Walther Meissner Inst, D-85748 Garching, Germany;Pittsburgh Quantum Inst, Pittsburgh, PA 15260 USA.
    Lira-Cantu, M.
    CSIC, Catalan Inst Nanosci & Nanotechnol ICN2, Campus UAB, E-08193 Barcelona, Spain;BIST, Campus UAB, E-08193 Barcelona, Spain.
    MacManus-Driscoll, J. L.
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England.
    Mannhart, Jochen
    Max Planck Inst Solid State Res, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Martins, R.
    Univ Milano Bicocca, Dept Mat Sci, Milan, Italy;IMM CNR, MDM Lab, Agrate Brianza, Italy.
    Menzel, S.
    Pittsburgh Quantum Inst, Pittsburgh, PA 15260 USA.
    Mikolajick, T.
    NaMLab gGmbH, Noethnitzer Str 64, D-01187 Dresden, Germany;Tech Univ Dresden, Chair Nanoelect Mat, D-01062 Dresden, Germany.
    Napari, M.
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England.
    Nguyen, M. D.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Paillard, C.
    Univ Arkansas, Phys Dept, Fayetteville, AR 72701 USA.
    Panigrahi, S.
    Univ NOVA Lisboa UNL, FCT, Dept Ciencia Mat, CENIMAT i3N, Lisbon, Portugal;CEMOP UNINOVA, P-2829516 Caparica, Portugal.
    Rijnders, G.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands.
    Sanchez, F.
    CSIC, Inst Ciencia Mat Barcelona ICMAB, Campus UAB, Cerdanyola Del Valles 08193, Catalonia, Spain.
    Sanchis, P.
    Univ Politecn Valencia, Nanophoton Technol Ctr, Camino Vera S-N, E-46022 Valencia, Spain.
    Sanna, S.
    Tech Univ Denmark, Dept Energy Storage & Convers, DK-4000 Roskilde, Denmark.
    Schlom, D. G.
    Cornell Univ, Dept Phys, Lab Atom & Solid State Phys, Ithaca, NY 14853 USA;Cornell Univ, Dept Mat Sci & Engn, Ithaca, NY 14853 USA.
    Schroeder, U.
    NaMLab gGmbH, Noethnitzer Str 64, D-01187 Dresden, Germany.
    Shen, K. M.
    Kavli Inst Cornell Nanoscale Sci, Ithaca, NY 14853 USA;Cornell Univ, Dept Phys, Lab Atom & Solid State Phys, Ithaca, NY 14853 USA.
    Siemon, A.
    Rhein Westfal TH Aachen, Inst Werkstoffe Elektrotech IWE 2, D-52066 Aachen, Germany.
    Spreitzer, M.
    Jozef Stefan Inst, Adv Mat Dept, Jamova Cesta 39, Ljubljana 1000, Slovenia.
    Sukegawa, H.
    NIMS, Res Ctr Magnet & Spintron Mat, 1-2-1 Sengen, Tsukuba, Ibaraki 3050047, Japan.
    Tamayo, R.
    OXOLUTIA SL, Avda Castell Barbera 26,Tellers 13,Nau 1, Barcelona 08210, Spain.
    van den Brink, J.
    IFW Dresden, Inst Theoret Solid State Phys, Helm Holtzstr 20, D-01069 Dresden, Germany.
    Pryds, N.
    Tech Univ Denmark, Dept Energy Storage & Convers, DK-4000 Roskilde, Denmark.
    Granozio, F. Miletto
    CNR SPIN, Naples Unit, Complesso Univ Monte St Angelo,Via Cinthia, IT-80126 Naples, Italy.
    Towards Oxide Electronics: a Roadmap2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 482, p. 1-93Article in journal (Refereed)
    Abstract [en]

    At the end of a rush lasting over half a century, in which CMOS technology has been experiencing a constant and breathtaking increase of device speed and density, Moore's law is approaching the insurmountable barrier given by the ultimate atomic nature of matter. A major challenge for 21st century scientists is finding novel strategies, concepts and materials for replacing silicon-based CMOS semiconductor technologies and guaranteeing a continued and steady technological progress in next decades. Among the materials classes candidate to contribute to this momentous challenge, oxide films and heterostructures are a particularly appealing hunting ground. The vastity, intended in pure chemical terms, of this class of compounds, the complexity of their correlated behaviour, and the wealth of functional properties they display, has already made these systems the subject of choice, worldwide, of a strongly networked, dynamic and interdisciplinary research community. Oxide science and technology has been the target of a wide four-year project, named Towards Oxide-Based Electronics (TO-BE), that has been recently running in Europe and has involved as participants several hundred scientists from 29 EU countries. In this review and perspective paper, published as a final deliverable of the TO-BE Action, the opportunities of oxides as future electronic materials for Information and Communication Technologies ICT and Energy are discussed. The paper is organized as a set of contributions, all selected and ordered as individual building blocks of a wider general scheme. After a brief preface by the editors and an introductory contribution, two sections follow. The first is mainly devoted to providing a perspective on the latest theoretical and experimental methods that are employed to investigate oxides and to produce oxide-based films, heterostructures and devices. In the second, all contributions are dedicated to different specific fields of applications of oxide thin films and heterostructures, in sectors as data storage and computing, optics and plasmonics, magnonics, energy conversion and harvesting, and power electronics.

  • 288.
    Costa, M T J
    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.
    Bergman, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Venezuela, P
    Instituto de Fisica, Universidade Federal Fluminense.
    Nordblad, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Klintenberg, M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, O
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    On the large magnetic anisotropy of Fe2PManuscript (preprint) (Other academic)
  • 289.
    Costa, Marcio
    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.
    Bergman, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Venezuela, P.
    Instituto de Física, Universidade Federal Fluminense, Rio de Janeiro, Brasilien.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Klintenberg, Mattias
    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.
    Large magnetic anisotropy of Fe2P investigated via ab initio density functional theory calculations2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 8, p. 085125-Article in journal (Refereed)
    Abstract [en]

    We present an investigation of the large magnetic anisotropy of Fe2P, based on ab initio density functional theory calculations, with a full-potential linear muffin-tin orbital basis. We obtain a uniaxial magnetic anisotropy energy (MAE) of 664 mu eV/f.u., which is in decent agreement with experimental observations. Based on a band structure analysis the microscopic origin of the large magnetic anisotropy is explained. We also show that by straining the crystal structure, the MAE can be enhanced further.

  • 290. Cregg, P. J.
    et al.
    Garcia-Palacios, J. L.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Partition functions of classical Heisenberg spin chains with arbitrary and different exchange2008In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, Vol. 41, no 43, p. 435202-Article in journal (Refereed)
    Abstract [en]

    The classical Heisenberg model has been effective in modelling exchange interactions in molecular magnets. In this model, the partition function is important as it allows the calculation of the magnetization and susceptibility. For an ensemble of N-spin sites, this typically involves integrals in 2N dimensions. Here, for two-, three- and four- spin nearest neighbour open linear Heisenberg chains these integrals are reduced to sums of known functions, using a result due to Gegenbauer. For the case of the three- and four- spin chains, the sums are equivalent in form to the results of Joyce. The general result for an N-spin chain is also obtained.

  • 291. Cregg, P J
    et al.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Comment on 'Analytical results for a Bessel function times Legendre polynomials class integrals'2007In: Journal of physics. A, Mathematical and theoretical, ISSN 1751-8113, Vol. 40, no 46, p. 14029-14031Article in journal (Refereed)
    Abstract [en]

    A result is obtained, stemming from Gegenbauer, where the products of certainBessel functions and exponentials are expressed in terms of an infinite seriesof spherical Bessel functions and products of associated Legendre functions.Closed form solutions for integrals involving Bessel functions times associatedLegendre functions times exponentials, recently elucidated by Neves et al(J. Phys. A: Math. Gen. 39 L293), are then shown to result directly from theorthogonality properties of the associated Legendre functions. This result offersgreater flexibility in the treatment of classical Heisenberg chains and may doso in other problems such as occur in electromagnetic diffraction theory.

  • 292. Cregg, PJ
    et al.
    Garcia-Palacios, J L
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Murphy, K
    Low-field susceptibility of classical Heisenberg chains with arbitrary and different nearest-neighbour exchange2008In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 20, p. 2041204119-Article in journal (Refereed)
    Abstract [en]

    Interest in molecular magnets continues to grow, offering a link between the atomic and nanoscale properties. The classical Heisenberg model has been effective in modelling exchange interactions in such systems. In this, the magnetization and susceptibility are calculated through the partition function, where the Hamiltonian contains both Zeeman and exchange energy. For an ensemble of N spins, this requires integrals in 2N dimensions. For two, three and four spin nearest-neighbour chains these integrals reduce to sums of known functions. For the case of the three and four spin chains, the sums are equivalent to results of Joyce. Expanding these sums, the effect of the exchange on the linear susceptibility appears as Langevin functions with exchange term arguments. These expressions are generalized here to describe an N spin nearest-neighbour chain, where the exchange between each pair of nearest neighbours is different and arbitrary. For a common exchange constant, this reduces to the result of Fisher. The high-temperature expansion of the Langevin functions for the different exchange constants leads to agreement with the appropriate high-temperature quantum formula of Schmidt et al, when the spin number is large. Simulations are presented for open linear chains of three, four and five spins with up to four different exchange constants, illustrating how the exchange constants can be retrieved successfully.

  • 293. Crema, L.
    et al.
    Bozzoli, A.
    Alberti, F.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hesse, S.
    Hislop, D.
    Rivolta, B.
    Luminari, M.
    Restall, B.
    Novel m-CHP generation from small scale Concentrated Solar Power2012In: World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conference, 2012, p. 735-742Conference paper (Refereed)
    Abstract [en]

    The paper describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. The actual marketable solar systems for domestic and distributed applications (PV and Solar thermal) suffer of notable limitation: i) the low overall (electrical) efficiency of PV systems create a small collected energy from available space, sometimes restricted in surface to few square meters, ii) the stagnation temperatures on solar thermal collectors actually limiting the diffusion of solar thermal systems, iii) fixed and not retrofittable systems may generate energy in intermittent way not aligned with the auto consumption profile of domestic spaces.

  • 294.
    Dahbi, Mohammed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Wikberg, J. Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Saadoune, Ismael
    LCME, FST Marrakech, University Cadi Ayyad, Marocko.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrochemical behavior of LiNi1-y-zCoyMnzO2 probed through structural and magnetic properties2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 2, p. 023904-Article in journal (Refereed)
    Abstract [en]

    We have investigated LixNi1-y-zCoyMnzO2 compounds with y = 1/3, 0.25, 0.2, 0.1 and z = 1/3, 0.2, 0.1, 0.05 in order to study the influence of Ni and Mn concentration, cationic disorder, and crystallite size on the magnetic and charge/discharge behavior. The samples have been studied by means of x-ray diffraction, scanning electron microscopy, voltammetry, cycling capacity, and magnetometry. The discharge capacity increases with increasing Ni concentration as does the number of ferromagnetic interactions. With higher Mn concentration a higher capacity is observed together with formation of strong antiferromagnetic interactions driving the magnetic frustration to lower temperatures. Our results show that for sufficiently low Co concentrations a stable and magnetically more ordered structure can be obtained with excellent electrochemical properties, although a relatively large amount of Ni is present.

  • 295. Dahbi, Mohammed
    et al.
    Wikberg, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Saadoune, Ismael
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    A delithiated LiNi0.65Co0.25Mn0.10O2 electrode material: A structural, magnetic and electrochemical study2009In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, no 11, p. 3211-3217Article in journal (Refereed)
    Abstract [en]

    A crystalline LiNi0.65Co0.25Mn0.10O2 electrode material was synthesized by the combustion method at 900 °C for 1 h. Rietveld refinement shows less than 3% of Li/Ni disorder in the structure. Lithium extraction involves only the Ni2+/Ni4+ redox couple while Co3+ and Mn4+ remain electrochemically inactive. No structural transition was detected during cycling in the whole composition range 0 < x < 1.0. Furthermore, the hexagonal cell volume changes by only 3% when all lithium was removed indicating a good mechanical stability of the studied compound. LiNi0.65Co0.25Mn0.10O2 has a discharge capacity of 150 mAh/g in the voltage range 2.5–4.5 V, but the best electrochemical performance was obtained with an upper cut-off potential of 4.3 V. Magnetic measurements reveal competing antiferromagnetic and ferromagnetic interactions – varying in strength as a function of lithium content – yielding a low temperature magnetically frustrated state. The evolution of the magnetic properties with lithium content confirms the preferential oxidation of Ni ions compared to Co3+ and Mn4+ during the delithiation process.

  • 296.
    Dalslet, Bjarke Thomas
    et al.
    Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Lyngby, Danmark.
    Damsgaard, Christian Danvad
    Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Lyngby, Danmark.
    Donolato, Marco
    LNESS Dipartimento di Fisica, Politecnico di Milano, Como, Italien.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hansen, Mikkel Fougt
    Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Lyngby, Danmark.
    Bead magnetorelaxometry with an on-chip magnetoresistive sensor2011In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 11, no 2, p. 296-302Article in journal (Refereed)
    Abstract [en]

    Magnetorelaxometry measurements on suspensions of magnetic beads are demonstrated using a planar Hall effect sensor chip embedded in a microfluidic system. The alternating magnetic field used for magnetizing the beads is provided by the sensor bias current and the complex magnetic susceptibility spectra are recorded as the 2nd harmonic of the sensor response. The complex magnetic susceptibility signal appears when a magnetic bead suspension is injected, it scales with the bead concentration, and it follows the Cole-Cole expression for Brownian relaxation. The complex magnetic susceptibility signal resembles that from conventional magnetorelaxometry done on the same samples apart from an offset in Brownian relaxation frequency. The time dependence of the signal can be rationalized as originating from sedimented beads.

  • 297. Dam, B.
    et al.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pemble, M.
    Rougier, A.
    Chromogenic Materials and Devices2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 143, p. 591-640Article in journal (Refereed)
  • 298. Dam, B
    et al.
    Granqvist, CG
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pemble, M
    Rougier, A
    Preface2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 143, p. 591-Article in journal (Refereed)
  • 299.
    de la Torre, Teresa Zardan Gomez
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Göransson, Jenny
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Molecular diagnostics using magnetic nanobeads2010In: / [ed] Goll G., Lohneysen H.V., Loidl A., Pruschke T., Richter M., Schultz L., Surgers C., Wosnitza J, 2010, Vol. 200, p. 122011-Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the volume-amplified magnetic nanobead detection assay with respect to bead size, bead concentration and bead oligonucleotide surface coverage in order to improve the understanding of the underlying microscopic mechanisms. It has been shown that: (i) the immobilization efficiency of the beads depends on the surface coverage of oligonucleotides, (ii) by using lower amounts of probe-tagged beads, detection sensitivity can be improved and (iii) using small enough beads enables both turn-off and turn-on detection. Finally, biplex detection was demonstrated.

  • 300. De Toro, J. A.
    et al.
    Lee, S. S.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Normile, P. S.
    Salazar, D.
    Cheong, J. L.
    Muñiz, P.
    Riveiro, J. M.
    Hillenkamp, M.
    Tamion, A.
    Tournus, F.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ideal superspin glass behaviour in a random-close-packed ensemble of maghemite nanoparticles2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 521, no 1, p. 012011-Article in journal (Refereed)
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