Search Results - (Author, Cooperation:T. M. Johnston)

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  1. 1
    Staff View
    Publication Date:
    2015-11-19
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2015-05-08
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract Muon spin relaxation has been observed in both the normal and superconducting states of Rb3C60 (T c=29.3K). The field dependence of theT 1 spin relaxation rate is due to muonium undergoing spin-exchange scattering with conduction electrons, making this the first observation of muonium in a metal. The temperature dependence ofT 1 −1 shows a Hebel-Slichter coherence peak just belowT c which is not seen in13C spin relaxation. The peak can be fit assuming spin relaxation due to interaction with the quasiparticle excitations of a BCS superconductor provided the density of states is broadened relative to that of BCS. Such fits yield a value for the zero temperature energy gap, Δ0/k B , of 53(4)K, consistent with weak-coupling BCS.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02068935

    Articles: DFG German National Licenses
  4. 4
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract Transverse-field (TF) and longitudinal-field (LF)μ + SR measurements have been made on conducting GaAs∶Si (n-type ≈ 1018 cm−3) and GaAs∶Zn (p-type ≈ 1019 cm−3) from 20 mK to 200 K. At low temperatures in GaAs∶Si, the frequency spectra show a large diamagnetic signal as well as broad lines due to bond-centered muonium (Mu BC ). This broadening is attributed to spin exchange interactions with charge carriers in impurity bands. Only the diamagnetic signal is observed in GaAs∶Zn. The field dependence of the TF diamagnetic relaxation rate at 5 K can be explained by the combined electric quadrupolar and Zeeman interaction between the muon and the surrounding nuclei and the temperature scan at TF=1.5 T indicates that the mechanisms responsible for the broadening are temperature independent. The candidates for the diamagnetic species are discussed in view of these results.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02068959

    Articles: DFG German National Licenses
  5. 5
    Staff View
    ISSN:
    1572-9540
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Physics
    Notes:
    Abstract We report longitudinal fieldμSR 1/T 1 measurements in Si from room temperature to 850 K. The data in pure Si and Si∶B (p-type) can be explained in a two-state model where muonium cycles between its positive and neutral charge states. Within this model, the average muon-electron hyperfine parameter in the neutral state is consistent with muonium at the tetrahedral interstitial site, indicating that at the highest temperatures measured, neutral muonium spends a significant amount of time away from the bond centered site, the calculated potential minimum. Although this is also true for Si∶P (n-type) at high temperatures, the data in the region between 300–450 K indicates that at least one other state is involved in the dynamics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF02068965

    Articles: DFG German National Licenses