The field dependence of the magnetization above the transition temperature Tc in MgB₂ is shown to evidence a diamagnetic contribution consistent with superconducting fluctuations reflecting both the σ and π bands. In particular, the upturn field Hup in the magnetization curve, related to the incipient effect of the magnetic field in quenching the fluctuating pairs, displays a double structure, in correspondence to two correlation lengths. The experimental findings are satisfactorily described by the extension to the diamagnetism of a recent theory for paraconductivity, in the framework of a zero-dimensional model for the fluctuating superconducting droplets above Tc.
@article{arxiv.cond-mat/0501244,
title = {Two-bands effect on the superconducting fluctuating diamagnetism in MgB₂},
author = {L. Romano' and A. Lascialfari and A. Rigamonti and I. Zucca},
journal= {arXiv preprint arXiv:cond-mat/0501244},
year = {2009}
}