Magnetic field dependence of the precursor diamagnetism in La superconductors with magnetic Pr impurities

Abstract

The interplay between fluctuating Cooper pairs and magnetic impurities in conventional BCS low-Tc superconductors has been studied through measurements of the magnetic field dependence of the fluctuation diamagnetism (FD) above Tc in lanthanum with praseodymium impurities. These measurements provide a crucial confirmation of our previous observation [Europhys. Lett. 73, 587 (2006)] that in the dilute impurity regime the FD increases almost linearly with the concentration of magnetic impurities. This striking effect is attributed to a variation due to the presence of the fluctuating Cooper pairs of the coupling between magnetic impurities. To describe these results at a phenomenological level, we propose a Gaussian Ginzburg-Landau model for the FD which includes an indirect contribution proportional to both the impurities concentration and the Cooper pairs density. Our approach is able to explain simultaneously the FD increase due to magnetic impurities and its decrease with the application of large magnetic fields.

arXiv comment7 pages (2 columns), 5 figures

References in corpus (5)

• A Common Thread: the pairing interaction for the unconventional superconductors
• On the consequences of the uncertainty principle on the superconducting fluctuations well inside the normal state
• Spin screening of magnetic moments in superconductors
• Observation of enhanced fluctuation diamagnetism in lanthanum superconductors with dilute magnetic impurities
• Precursor superconducting diamagnetism in YBa2Cu3O7-d with in-plane or intercalated magnetic impurities

Cited by in corpus (1)

• Two types of superconducting pairs in stripe-ordered La${}_{2-x}$Ba${}_x$CuO${}_4$ ($x=1/8$): evidence from the resistivity measurements