Characterization of Au–YBa 2Cu 3O 7− y composites by paraconductivity analysis with a short-wavelength cutoff

Abstract

Bulk composites of Au–YBa 2Cu 3O 7− y are characterized by means of paraconductivity analyses by taking account of a short-wavelength cutoff in the fluctuation spectrum. General expressions for the Aslamazov–Larkin, Maki–Thompson and density of state terms are derived in the momentum-cutoff regime, which are found to describe fairly well observed paraconductivity at overall temperatures investigated. From the theoretical fittings, we estimate several parameters, including the anisotropy parameter, fluctuation amplitude, scattering lifetime, and phase-breaking time. A normalized absorption of AC susceptibility is also investigated. It is found that many of these parameters exhibit rapid variations with a small amount of gold, which may be attributed to enhanced disorder upon doping, while behavior in those parameters at higher doping levels is related to a percolative nature of the composites. We could observe evidence of a pronounced two-dimensional character due perhaps to better crystallinity upon Au doping.