Analysis of fluctuation conductivity in melt-textured YBa 2Cu 3O 7− y superconductors with Ag-doping

Abstract

The difference in the properties between Ag-doped and undoped YBa 2Cu 3O 7− y (YBCO) melt-textured samples was investigated by fluctuation-conductivity analysis. The temperature dependence of the resistance in those samples was measured. Data about the dimensionality and amplitude of the fluctuation were obtained by analyzing the fluctuation conductivity on the basis of the Aslamazov–Larkin theory. The fluctuation conductivity of the undoped sample shows three-dimensional behavior in the mean-field region (MFR) with a one-dimensional (1D) character at further higher temperature. The effect of a small amount of Ag addition is manifested on a fractal conduction behavior in the 1D region of the undoped sample. Upon further Ag-doping, the conduction behavior is two-dimensional in the MFR with evidence for a rapid suppression of the short-wavelength fluctuation. The conduction behavior is discussed on the relevance to structural features of melt-textured YBCO samples with and without Ag-doping.