Effects of Pauli paramagnetism on superconducting fluctuations

Abstract

We discuss the effects of the Pauli paramagnetism on the excess conductivity σfl due to fluctuations of the superconducting order parameter. We derived a formula for σfl for a thin film placed in a magnetic field of an arbitrary orientation α. It was found that σfl has a universal behavior as a function of some parameterp which depends on α and ΔH=H-H c. If ΔH is kept constant and σfl is measured as a function of α, in the absence of the Pauli paramagnetism σfl is maximum when the field is parallel to the film and is minimum when the field is perpendicular. But in high field superconductors due to the effect of the Pauli paramagnetism σfl becomes maximum at some intermediate field orientation. We also discussed the excess conductivity in magnetic alloys in which impurity spins are aligned by an external magnetic field. It was shown that in this case one should expect, with certain strengths of the external field, the excess conductivity which is non-monotonic in temperature.