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  • 1
    Electronic Resource
    Electronic Resource
    ( Sr / Ca ) 14 Cu 24 O 41 spin ladders studied by NMR under pressure (2001)
    Springer
    The European physical journal 24 (2001), S. 443-456 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.25.Ha Magnetic properties – 74.72.Jt Other cuprates – 76.60.Cq Chemical and Knight shifts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: 63Cu-NMR measurements have been performed on two-leg hole-doped spin ladders Sr14-xCaxCu24O41 single crystals 0 ? x ? 12 at several pressures up to the pressure domain where the stabilization of a superconducting ground state can be achieved. The data reveal a marked decrease of the spin gap derived from Knight shift measurements upon Ca substitution and also under pressure and confirm the onset of low lying spin excitations around P c as previously reported. The spin gap in Sr 2 Ca 12 Cu 24 O 41 is strongly reduced above 20 kbar. However, the data of an experiment performed at P = 36 kbar where superconductivity has been detected at 6.7 K by an inductive technique have shown that a significant amount of spin excitations remains gapped at 80 K when superconductivity sets in. The standard relaxation model with two and three-magnon modes explains fairly well the activated relaxation data in the intermediate temperature regime corresponding to gapped spin excitations using the spin gap data derived from Knight shift experiments. The data of Gaussian relaxation rates of heavily doped samples support the limitation of the coherence length at low temperature by the average distance between doped holes. We discuss the interplay between superconductivity and the spin gap and suggest that these new results support the exciting prospect of superconductivity induced by the interladder tunneling of preformed pairs as long as the pressure remains lower than the pressure corresponding to the maximum of the superconducting critical temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10051-001-8697-y
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  • 2
    Electronic Resource
    Electronic Resource
    An NMR approach to the superconducting regime of the spin ladder compound Sr Ca Cu O (2000)
    Springer
    The European physical journal 13 (2000), S. 417-420 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.72.Jt Other cuprates - 74.25.Ha Magnetic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: 63Cu-NMR experiments of Knight shift and relaxation time T1 have been performed on the two-leg spin ladders of a Sr2Ca12Cu24O41 single crystal at several pressures up to the critical pressure for the stabilization of a superconducting ground state. The data confirm the onset of low-lying spin excitations at observed previously [Science 279, 345 (1998)] and reveal a marked decrease of the spin gap under pressures above 20 kbar although a significant fraction of the spin excitations remains gapped at kbar. A comparison between NMR and transport data under pressure suggests that the depression of the spin gap can be ascribed to an increase in the interladder exchange coupling, possibly mediated by the ladder-chain interaction along the b-direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050052
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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