Superconducting fluctuation conductivity in (SN)<sub>x</sub>: temperature and magnetic field dependence
P Barrett; W G Herrenden-Harker; M G Priestley; E Z da Silva; P Barrett; H.H. Wills Phys. Lab., Univ. of Bristol, Bristol, UK; W G Herrenden-Harker; H.H. Wills Phys. Lab., Univ. of Bristol, Bristol, UK; M G Priestley; H.H. Wills Phys. Lab., Univ. of Bristol, Bristol, UK; E Z da Silva; H.H. Wills Phys. Lab., Univ. of Bristol, Bristol, UK
Журнал:
Journal of Physics F: Metal Physics
Дата:
1981-04-01
Аннотация:
Fluctuations into the superconducting state in (SN)<sub>x</sub> were investigated as a function of temperature and magnetic field. It was found that the fluctuation conductivity as a function of temperature at constant magnetic field for H//b (the fibre axis) was consistent with the dependence of sigma <sub>f</sub>=C((T-T<sub>c</sub>)/T<sub>c</sub>)<sup>-3/2</sup> predicted by da Silva and Gyorffy (SG) (1979) for a single anisotropic fibre. The values of C in zero field, together with the parallel critical field H<sub>c2</sub>//(0) and an estimate of the ratio of the electronic diffusion constants D/sub ////D<sub>perpendicular to </sub> approximately=20, taken from the optical data of Geserich et al. (1977) were used to derive the microscopic parameters in the SG theory. The sample of highest conductivity gave a fibre radius r<sub>0</sub>=74+or-6 AA, D/sub ///=280+or-40 cm<sup>2</sup> s<sup>-1</sup>, and D<sub>perpendicular to </sub>=14+or-2 cm<sup>2</sup> s<sup>-1</sup>. An extension of the SG theory predicted the magnetic field dependence of the fluctuation conductivity to be sigma <sub>f</sub> varies as ((H-H<sub>c2</sub>)/H<sub>c2</sub>)<sup>-3/2</sup>. The authors estimate the superconducting coherence lengths to be xi /sub ///(0) approximately=5500 AA and xi <sub>perpendicular to </sub>(0) approximately=1200 AA, for the above sample.
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