Fluctuation-Enhanced Diamagnetism in Superconductors above the Transition Temperature

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Abstract
A theory which describes small-amplitude fluctuations of arbitrary spatial extent in a super-conductor has been used to calculate the magnetization in a magnetic field above the transition temperature. The calculations agree quite well with the experimental data. Analytical and numerical work indicates that corrections to the electromagnetic properties because of the large size of the fluctuating pairs play an essential role. The effect of impurity scattering has also been included. For moderately small impurity concentrations, agreement is obtained with a semiempirical suggestion due to Gollub, Beasley, and Tinkham, that a universal behavior should occur in terms of an appropriately scaled magnetic field. Deviations from this behavior are predicted at higher impurity concentrations.