Abstract
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2-x Ru (x) O7-delta, (Tl, Pb)/Sr-1212, with 0.0 a parts per thousand currency sign x a parts per thousand currency sign 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement of the phase formation, superconducting transition temperature T (c) and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120-290 K) for all prepared samples. The number of spins N participating in the resonance and the paramagnetic susceptibility chi were calculated as a function of both Ru-content and temperature. N and chi increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E (a) was calculated as a function of the Ru-content. The temperature dependence of chi was fitted according to Curie-Weiss type of magnetic behavior. Curie constant C, Curie temperature theta, the effective magnetic moment mu and the electronic specific heat gamma were estimated as a function of the Ru-content.