Abhaengigkeit des elektrischen Widerstandes der CuO_2-Ebenen von Sauerstoffordnung und Druck in RBa_2Cu_3O_x mit (R = Y, Nd)

In this work the influence of the charge carrier concentration on the electrical resistivity of the CuO_2 planes carrying the superconductivity in YBa_2Cu_3O_x and NdBa_2Cu_3O_x was examined between 300 K and the onset of superconductivity at T_c. The charge carrier concentration n_h of the CuO_2 planes was adjusted by variation of the oxygen content in the CuO chains and by pressure-induced charge transfer from the chains to the planes. To avoid a contribution of the CuO chains to the resistivity #rho# of the planes, single crystals had to be detwinned and were electrically contacted by a wire-bonding technique afterwards. Correlations between T_c(n_h) and #rho#(n_h) point to peculiarities in the electron-system. Similar correlations have been observed in the superconducting materials La_1_._6_-_xNd_0_._4Sr_xCuO_4 and La_2_-_xSr_xCuO_4 for which stripes of spins and charges could be established. The electrical behaviour of YBa_2Cu_3O_x and NdBa_2Cu_3O_x also suggests a spin-charge separation. (orig.)Available from TIB Hannover: ZA5141(6926) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman