Critical Conductivity Fluctuations of [Formula Omitted] Single Crystal

• Published in: IEEE transactions on magnetics Vol. 49; no. 8; p. 4638
• Main Authors: Hneda, Marlon Luiz, Vieira, Valdemar das Neves, Berchon, Luciano da Silva, Costa, Rosangela Menegotto
• Format: Journal Article
• Language: English
• Published: New York The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 01-08-2013
• Subjects: Magnetic fields; Magnetism; Superconductivity
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2013.2254472

We have studied experimentally the in-plane conductivity fluctuations, [Formula Omitted], of a [Formula Omitted] [Formula Omitted] single crystal. Different DC magnetic fields [Formula Omitted] and current densities [Formula Omitted] intensities were applied parallel to the [Formula Omitted] (ab) planes at [Formula Omitted] field-current configuration. Close to the superconducting transition, the data reveal the occurrence of a genuine critical regime, where the associated critical exponent is consistent with the predictions of the 3D-XY universality class with model-E dynamics. Decreasing further the temperature towards the transition temperature, [Formula Omitted], our results systematically show very small exponent values that could be associated to the occurrence of a supercritical regime beyond the 3D-XY scaling. This regime can be interpreted as revealing an ultimate first order character of the superconducting transition driven by antiferromagnetic fluctuations related to the pseudogap phenomenon. The data show that the applied magnetic fields cause an increase in the average exponent related to the supercritical scaling. Unlike the magnetic field, the current density does not affect the supercritical regime. The results indicated that the trivalent Fe doping in [Formula Omitted] improves the stability of the beyond 3D-XY conductivity fluctuation regime to [Formula Omitted]. Also, a further approach towards the first order transition behavior is observed.