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  • 1.
    Beran, P.
    et al.
    Nucl Phys Inst ACSR, Rez, Czech Republic..
    Ivanov, Sergey A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Ctr Mat Sci, Moscow 105064, Russia..
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Middey, S.
    Indian Assoc Cultivat Sci, Ctr Adv Mat, Kolkata 700032, India..
    Nag, A.
    Indian Assoc Cultivat Sci, Dept Mat Sci, Kolkata 700032, India..
    Sarma, D. D.
    Indian Assoc Cultivat Sci, Ctr Adv Mat, Kolkata 700032, India.;Indian Inst Sci, Solid State & Struct Chem Unit, Bangalore 560012, Karnataka, India.;CSIR, NISE, New Delhi 110001, India..
    Ray, S.
    Indian Assoc Cultivat Sci, Ctr Adv Mat, Kolkata 700032, India.;Indian Assoc Cultivat Sci, Dept Mat Sci, Kolkata 700032, India..
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Neutron powder diffraction study of Ba3ZnRu2-xIrxO9 (x=0, 1, 2) with 6H-type perovskite structure2015In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 50, p. 58-64Article in journal (Refereed)
    Abstract [en]

    The triple perovskites Ba3ZnRu2-xIrxO9 with x = 0, 1, and 2 are insulating compounds in which Ru(Ir) cations form a dimer state. Polycrystalline samples of these materials were studied using neutron powder diffraction (NPD) at 10 and 295 K. No structural transition nor evidence of long range magnetic order was observed within the investigated temperature range. The results from structural refinements of the NPD data and its polyhedral analysis are presented, and discussed as a function of Ru/Ir content.

  • 2. Eriksson, A K
    et al.
    Tran, T
    Saxin, S
    Svensson, G
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eriksson, S-G
    Knee, C S
    Effets of A-site substitution on the structure and magnetic properties of Bi0.15Sr0.85-yAeyCo1-xFexO3-o2009In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 11, no 11, p. 1945-1954Article in journal (Refereed)
    Abstract [en]

    The effects of partial substitution of Sr2+ by Ca2+ and Ba2+ on the   A-site of oxygen-deficient perovskites,   Bi(0.15)Sr(0.85-y)Ae(y)Co(1-x)FeO(3-delta), where y = 0.28 for Ae = Ba   and y = 0.17 for Ae = Ca, and 0.0 <= x <= 1.0, have been investigated.   The differing ionic size of the Ca2+ and Ba2+ cations influences both   the crystal structure and the properties of the materials. The smaller   Ca2+ cation favoured formation of an oxygen vacancy ordered perovskite   superstructure (14/mmm, a = 2ap, c = 4a(p)), meanwhile the presence of   the larger Ba2+ cation promoted a disordered simple cubic structure (Pm   (3) over barm, a = ap) that was also found for all Fe containing   samples, i.e. x >= 0.25. The samples were studied with PXRD, NPD, TGA,   electron microscopy and magnetic susceptibility measurements. All   as-prepared samples exhibited long range G-type antiferromagnetic   ordering. The effect of oxygen annealing was dramatic for the   Bi0.15Sr0.68Ca0.17Co1-xFexO3-delta series, with a disappearance of   magnetic order for x >= 0.25 linked to increasing spin-glass   properties. The oxygen content of the   Bi0.15Sr0.57Ba0.28Co1-xFexO3-delta as-prepared materials was generally   higher than their Ca substituted counterparts, and the long range   antiferromagnetic order was more resistant to oxygen annealing.

  • 3.
    Isberg, Jan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Gabrysch, Markus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Majdi, Saman
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kovi, Kiran Kumar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Twitchen, Daniel
    Element Six Ltd, Ascot Berkshire, UK.
    On the transition between space-charge-free and space-charge-limited conduction in diamond2011In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 13, no 5, p. 1065-1067Article in journal (Refereed)
    Abstract [en]

    Carrier transport in a high-purity single-crystalline CVD diamond sample was studied using the Time-of-Flight technique with optical UV excitation. By varying the intensity of the optical excitation over four orders of magnitude, the transition between space-charge-free and space-charge-limited hole conduction in diamond is directly observed. Experimentally, we find that even a relatively small injected charge appreciably affects the drift velocity measurements. To achieve a relative error in drift velocity less than 1%, the injected charge has to be less than 0.01 CU, where C is the sample capacitance and U the applied bias.

  • 4.
    Ivanov, Sergey A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar Puri, Anil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bush, A. A.
    Ottosson, Mikael
    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.
    Temperature evolution of structural and magnetic properties of stoichiometric LiCu2O2: Correlation of thermal expansion coefficient and magnetic order2014In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 34, p. 97-101Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent crystallographic and magnetic studies on stoichiometric single crystals of LiCu2O2 are reported. The temperature dependence of the lattice parameters was extracted from X-ray powder diffractograms collected on crushed single crystals, from 12 K to 295 K. The magnetic properties are similar to earlier findings demonstrating antiferromagnetic ordering below 25 K. Evidence of magnetoelastic coupling is observed in the thermal expansion along the c-direction; not only at the low temperature antiferromagnetic transitions, but an anomalous behavior of the thermal expansion indicate magnetoelastic coupling also to the magnetic ordering related to a weak spontaneous magnetic moment appearing at 150 K. Ac-susceptibility measurements at different frequencies and superposed dc-fields are employed to further characterize this magnetic anomaly.

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

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

  • 6.
    Ivanov, Sergey A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahu, J. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Voronkova, V. I.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Structure and magnetism in hexagonal tungsten bronze metal oxides AM(1/3)W(8/3)O(9) (A-K, Rb, Cs; M-Cr, Fe)2015In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 40, p. 44-49Article in journal (Refereed)
    Abstract [en]

    The structure and magnetic properties of hexagonal tungsten bronzes AM(1/3)W(8/3)O(9) (A-K+, Rb+, Cs+; M- Cr3+, Fe3+) have been investigated. Pure ceramic samples were synthesized by solid-state reaction. The samples have been studied by X-ray powder diffraction in combination with magnetic measurements. The compounds crystallize in hexagonal space group P6(3)/mcm. The substitution of magnetic ions into the WO6 octahedra yields dilute antiferromagnetic Cr3+-O2--Cr3+(or Fe3+-O2--Fe3+) superexchange interaction causing the appearance of short-range magnetic order at low temperatures. The antiferromagnetic character of the interaction is supported by negative values of the derived Curie-Weiss temperatures, qCW. The magnitude of qCW is found to decrease with increasing ionic radius of the A cation. 

  • 7.
    Ivanov, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tellgren, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Ericsson, T
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Korchagina, S.K.
    Rybakova, L.F.
    Hewat, A
    Influence of PbZrO3 doping on the structural and magnetic properties of BiFeO32008In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 10, no 12, p. 1875-1885Article in journal (Refereed)
    Abstract [en]

    Solid solutions of the perovskites (1 - x)BiFeO3-xPbZrO3 with x ranging from 0 to 0.2 were synthesized by solid-state reaction in an attempt to find magnetoelectric materials, in which ferroelectricity and ferromagnetism coexist. These complex perovskites have been studied by X-ray and neutron powder diffractions, magnetic and Mössbauer spectroscopic measurements. All samples are single phase with rhombohedrally distorted perovskite structure. The field and temperature dependences of the magnetization of (1 - x)BiFeO3-xPbZrO3 samples showed antiferromagnetic behavior with Neel temperatures, TN = 635 K (x = 0.1) and 500 K (x = 0.2); a weak ferromagnetic moment appeared at TN in both samples reaching about 0.01 μB/Fe at low temperature for the x = 0.1 sample. Mössbauer spectra also support the existence of the magnetic order and are consistent with the presence of high-spin Fe3+ cations located in the octahedral B-site position. Rietveld refinements of neutron powder diffraction data collected at different temperatures, between 10 and 700 K, have been carried out. The structure of these compounds is a rhombohedrally distorted perovskite (space group R3c) within the whole temperature interval. The Bi/Pb and Fe/Zr ions were found to be disordered over the perovskite A- and B-sites, respectively. Neutron diffraction patterns showed evidence of a long-range magnetic ordering below TN with a G-type antiferromagnetic arrangement of the magnetic moments of Fe3+ cations in the B-site. The effect of PbZrO3 doping on BiFeO3 results in a noticeable lattice expansion and a significant decrease of TN. The factors governing the observed structural and magnetic properties of (1 - x)BiFeO3-xPbZrO3 are discussed and compared with those of pure BiFeO3.

  • 8.
    Ivanov, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tellgren, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Ritter, C.
    Magnetoelectric perovskite (Bi0.5Pb0.5)(Fe0.5Zr0.5)O3: Preparation, structural and magnetic properties2010In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 12, no 1, p. 115-122Article in journal (Refereed)
    Abstract [en]

    The perovskite (Bi0.5Pb0.5)(Fe0.5Zr0.5)O3 was synthesized by solid-state reaction in an attempt to find magnetoelectric materials, in which ferroelectricity and ferromagnetism coexist. This complex perovskite has been studied by X-ray and neutron powder diffraction in combination with magnetic measurements. The compound crystallizes in the orthorhombic space group Pbam with a √2ap, b 2√2ap and c 2ap (with ap 4.057 Å). The field and temperature dependence of the magnetization combined with neutron diffraction data showed antiferromagnetic behavior with the Neel temperature, TN 450 K. Rietveld refinements of neutron powder diffraction data collected at different temperatures, between 10 and 700 K, have been carried out in order to extract information about the thermal evolution of the nuclear and magnetic structures. A distorted orthorhombic perovskite structure was found within the whole temperature interval. The Bi/Pb and Fe/Zr ions were found to be partially ordered over the perovskite A-site and disordered over the B-site. The neutron diffraction patterns of the (Bi0.5Pb0.5)(Fe0.5Zr0.5)O3 sample showed evidence of a long-range magnetic ordering below TN with a propagation vector k = (0,0,0) and an antiferromagnetic arrangement of the magnetic moments of the Fe3+ cations in the B-site. This is consistent with an Ay-type magnetic structure. The factors governing the structural and magnetic properties of (1 − x)BiFeO3xPbZrO3 solid solutions are discussed and compared with those of pure BiFeO3 and PbZrO3. A solid solution strategy for developing magnetoelectric properties in BiFeO3-based compounds is described, with the aim of realizing both a spontaneous polarization and magnetization at room temperature.

  • 9. Linton, Peter
    et al.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Alfredsson, Viveka
    Evolution of structure and composition during the synthesis of mesoporous silica SBA-15 studied by small-angle neutron scattering2011In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 13, no 4, p. 793-799Article in journal (Refereed)
    Abstract [en]

    In-situ time-resolved small-angle neutron scattering (SANS) has been applied for the study of the formation of mesoporous silica SBA-15. The advantage of neutron scattering, compared to X-ray scattering, is the possibility to contrast match i.e. highlight certain parts of the sample. Three different solvents with different scattering contrasts were used for each synthesis. Three different silica sources (tetramethyl orthosilicate, tetraethyl orthosilicate and tetrapropyl orthosilicate) were used and in three cases salts (sodium chloride or sodium bromide) were added prior to addition of the silica source. Hence, the effect of the silica sources and of the salts, on the formation of SBA-15 was investigated. The main focus was on the evolution of the ordered hexagonal structure i.e. investigation of the (10) Bragg peak. In synchrotron SAXS measurements the intensity of the (10) Bragg peak continuously increases during the measurement. However, in the SANS measurements the (10) Bragg peak area decreases with time. The decrease of the (10) peak is highly dependent on the solvent, a larger fraction of D2O in the solvent results in a bigger reduction. The decrease is also more pronounced when salt is present in the synthesis. The reduction of intensity reflects the chemistry in the wall and is explained by the compositional change in the wall during the maturation of the hexagonal order.

  • 10. Srivastava, Anurag
    et al.
    Tyagi, Neha
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    First-principles study of structural and electronic properties of gallium based nanowires2013In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 23, p. 35-41Article in journal (Refereed)
    Abstract [en]

    Structural stability and electronic properties of GaX (X = N, P, As and Sb) nanowires have been investigated using first-principles based density function theory approach. Out of linear, zigzag, square and hexagon shaped configuration, the square shaped geometry is energetically most stable. The computation of lattice parameters, bulk modulus and pressure derivatives for these Ga based nanowires observes the highest bulk modulus for hexagonal shaped GaN nanowire amongst all, suggest the mechanical strength of this geometry. Electronic band structures analysis shows the semiconducting as well as metallic behavior of these nanowires.

  • 11.
    Tellgren, Roland
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ivanov, Sergey
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Dept Inorgan Mat, Ctr Mat Sci, Moscow 105064, Russia.
    Bush, A. A.
    Moscow Technol Univ, RU-119434 Moscow, Russia..
    Kumar, P. Anil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Substitution mechanism and structural study of Ag-doped LiCu2O22017In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 70, p. 36-40Article in journal (Refereed)
    Abstract [en]

    Plate-like stoichiometric crystals of Ag-doped LiCu2O2 have been grown by slowly cooling Li2CO3 center dot 4(1 - x)CuO center dot 4xAgNO(3) (0 <= x <= 0.5) melts. X-ray single crystal diffraction has shown that the crystals are isostructural with LiCu2O2 and contain around 5 at % Ag (relative to the Cu atoms). The addition of silver to lithium cuprate crystals significantly increases their electrical conductivity but has little effect on the temperature behavior of their magnetic moment. The possible substitution mechanism is determined which supports Ag+ <-> Cu+, rather than Ag+ <-> Li+ in the Ag-doped LiCu2O2 crystals.

  • 12. Werheit, H.
    et al.
    Filipov, V.
    Kuhlmann, U.
    Dose, T.
    Lundström, T.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fe-doped beta-Rhombohedral boron: Structural changes at the p-type/n-type transition2015In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 47, p. 7-12Article in journal (Refereed)
    Abstract [en]

    n-type beta-rhombohedral boron is e.g. obtained by interstitial doping with Fe atoms exceeding 2.45 at.%. The spectra of Raman- and IR-active phonons have been measured up to the solubility limit of similar to 4 at.%. Numerous significant discontinuities in the spectra indicate structural changes at the p/n-transition. These might be restricted to specific elements of the structure, as the lattice parameters vary continuously, thus indicating that the overall structure remains largely unchanged.

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