B. Graneli

University of Zurich, Zürich, Zurich, Switzerland

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Publications (12)24.93 Total impact

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    ABSTRACT: The effect of pressure on the copper and praseodymium magnetic order in the system Nd(1-x)$Pr(x)Ba2Cu3$O7 with x=0.3, 0.5, 0.7, and 1 was investigated by means of the muon spin rotation (muSR) technique. It was found that the effect of pressure on the Neel temperatures of both copper and praseodymium is positive for the whole range of Pr concentrations (0.3<x<1) studied. These findings are in contrast with a number of previous reports and clarify some of the puzzles related to the effect of pressure on superconductivity and magnetism in the praseodymium-substituted R}(1-x)$Pr(x)Ba2Cu3O7 systems, where R is a rare earth element.
    Physical review. B, Condensed matter 11/2012; 87(5). · 3.66 Impact Factor
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    ABSTRACT: A detailed zero and transverse field (ZF&TF) muon spin rotation (muSR) investigation of magnetism and the magneto-electric coupling in Cu2OSeO3 is reported. An internal magnetic field B_int(T=0) = 85.37(25) mT was found, in agreement with a ferrimagnetic state below Tc = 57.0(1) K. The temperature dependence of the magnetic order parameter is well described by the relation B_int = B(0)(1-(T/Tc)^2)^b with an effective exponent b = 0.39(1) which is close to the critical exponent B ~ 1/3 for a three dimensional (3D) magnetic system. Just above Tc the muon relaxation rate follows the power low \lambda (T)\propto (T/Tc - 1)^\omega with \omega = 1.06(9), which is characteristic for 3D ferromagnets. Measurements of B_int(T) with and without an applied electrostatic field E = 1.66 x 10^5 V/m suggest a possible electric field effect of magnitude \Delta Bv = Bv(0 V)-Bv(500 V) = - 0.4(4) mT.
    Physical review. B, Condensed matter 05/2011; 84. · 3.66 Impact Factor
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    ABSTRACT: Zeeman perturbed nuclear quadrupole resonance was applied to evaluate weak magnetic fields in the context of orbital currents in cuprate superconductors. The magnetic environment of the barium atom in c-axis oriented powder samples of YBa(2)Cu(4)O(8) was investigated in the pseudogap phase at 90 K. No evidence for orbital currents was found: any static and dynamic field must be less than 0.07 and 0.7 mT, respectively.
    Physical Review Letters 03/2011; 106(9):097003. · 7.73 Impact Factor
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    ABSTRACT: We investigated the superconducting state of the noncentrosymmetric superconductors Li2Pd x Pt3−x B with superconducting transition temperature T c=5.16(8) K (x=2.25), 3.56(8) K (x=1.5) and 2.60 K (x=0) by means of muon-spin rotation (μSR) and specific heat experiments. The μSR relaxation rate σ sc was found to be constant at low temperatures for all the compounds. Data taken at different magnetic fields show that the magnetic penetration depth λ is field-independent for Li2Pd2.25Pt0.75B and Li2Pt3B. The electronic contribution to the specific heat measured in Li2Pd1.5Pt1.5B and Li2Pt3B increases exponentially at the lowest temperatures. These features suggest that the whole family of Li2Pd x Pt3−x B comprises single-gap s-wave superconductors across the entire doping regime.
    J. Supercond. Nov. Magn. 22, 337-342 (2009). 01/2009; 22:337.
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    ABSTRACT: We investigated the superconducting state of the noncentrosymmetric superconductors Li2Pd x Pt3−x B with superconducting transition temperature T c=5.16(8) K (x=2.25), 3.56(8) K (x=1.5) and 2.60 K (x=0) by means of muon-spin rotation (μSR) and specific heat experiments. The μSR relaxation rate σ sc was found to be constant at low temperatures for all the compounds. Data taken at different magnetic fields show that the magnetic penetration depth λ is field-independent for Li2Pd2.25Pt0.75B and Li2Pt3B. The electronic contribution to the specific heat measured in Li2Pd1.5Pt1.5B and Li2Pt3B increases exponentially at the lowest temperatures. These features suggest that the whole family of Li2Pd x Pt3−x B comprises single-gap s-wave superconductors across the entire doping regime.
    Journal of Superconductivity and Novel Magnetism 01/2009; 22(4):337-342. · 0.93 Impact Factor
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    ABSTRACT: We investigated the superconducting state of the noncentrosymmetric superconductors Li$_2$Pd$_x$Pt$_{3-x}$B with superconducting transition temperature $T_c$= 5.16(8) K ($x$=2.25), 3.56(8) K ($x=1.5$) and 2.60 K ($x=0$) by means of muon-spin rotation ($\mu$SR) and specific heat experiments. The $\mu$SR relaxation rate $\sigma_{sc}$ was found to be constant at low temperatures for all the compounds. Data taken at different magnetic fields show that the magnetic penetration depth $\lambda$ is field-independent for Li$_2$Pd$_{2.25}$Pt$_{0.75}$B and Li$_2$Pt$_{3}$B. The electronic contribution to the specific heat measured in Li$_2$Pd$_{1.5}$Pt$_{1.5}$B and Li$_2$Pt$_{3}$B increases exponentially at the lowest temperatures. These features suggest that the {\it whole family} of Li$_2$Pd$_x$Pt$_{3-x}$B are single-gap s-wave superconductors across the entire doping regime.
    10/2007;
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    ABSTRACT: A re-investigation of the structure of beta-LiNaSO4 has been made by means of high resolution neutron powder diffraction. A comparison is made with the original single crystal X-ray measurement. Implications on the conduction mechanism and possible explanations for the differences observed in a NMR investigation are discussed.
    Physica B Condensed Matter 01/1992; 180:612-616. · 1.28 Impact Factor
  • B.-E. Mellander, B. Granéli, J. Roos
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    ABSTRACT: The ionic conductivity of single crystal LiNaSO4 has been investigated for crystal orientation parallel to the a- and c-axis using complex impedancè spectroscopy. The temperature range from 25°C up to the solid-solid phase transition temperature 518°C has been studied. For ionic transport along the c-axis direction the ionic conductivity is only slightly larger than for transport in a direction perpendicular to the c-axis. The results of this study are compared to results for NMR measurements.
    Solid State Ionics 01/1990; s 40–41:162–164. · 2.05 Impact Factor
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    ABSTRACT: The intermetallic compound β-LiAl contains relatively high concentrations of constitutional vacancies on the Li sublattice for Li deficient compositions. Neutron diffraction measurements on a Li0.486Al0.514 single crystal show that these vacancies order on every tenth (840) plane at 97K. This vacancy ordering is responsible for the “100K” anomaly observed in several physical properties.
    Solid State Communications 02/1983; 45(8):721–724. · 1.53 Impact Factor
  • R DEJUS, K SKOLD, B GRANELI
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    ABSTRACT: A novel technique for tracer diffusion measurements in solids is described. The technique is based on neutron activation of nuclei in a thin slice in the middle of the sample and the subsequent determination of the activity profile through nondestructive γ-scanning. As the active nuclei are produced within the sample and the activity profile is measured nondestructively all handling of radioactive material, except in the bulk form present in the sample, is eliminated. Also, as the entire experiment can be carried out with the sample enclosed in a sealed container, exposure of the sample to the atmosphere is avoided at all stages. The technique is limited to ionic species for which isotopes with appropriate nuclear properties, such as neutron activation cross-section and radioactive decay schemes, are available. However, this includes Cu, Ag and Na and the method is therefore applicable to a large number of fast ionic conductors. The technique is described in some detail and is illustrated by the results obtained for Cu+ diffusion in CuI, which are the first results ever obtained for this important model system. The present results for the diffusion coefficient imply the need to modify the interaction potentials used in recent Molecular Dynamics (MD) calculations on this system (1). In particular, the difference in diffusion rate between the γ-phase and the α-phase is much larger than predicted from the MD results.
    Solid State Ionics 01/1980; 1:327-336. · 2.05 Impact Factor
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    ABSTRACT: By combining 7Li and 23Na NMR results we have started to investigate the dynamics of (1−x))Li2SO4·xNa2SO4 systems especially the interdependence of Li and Na motions. We report preliminary results. Up to 750 K no essential exchange of Li ions between trigonal and monoclinic phases takes place (on the NMR time scale). In LiNaSO4 measurements of the different line widths and of the averaging of the electric field gradients at the Na and Li sites as a function of temperature allow to distinguish between the onset of Li and Na motion. The complicated behavior of the spin-lattice relaxation reflects the different dynamics of Li and Na ions.
    Solid State Ionics s 28–30:1287–1289. · 2.05 Impact Factor