Magnetic Properties of YBCO-PST Composites

Abstract

The magnetic properties of granular superconductor-insulator composites were investigated. The composites were random composition of the YBa2 Cu3 O 7-δ (YBCO) high-temperature superconductor and Pb(Sc0.sTa0.5)O3 (PST) ferroelectric insulator. The composites exhibited lower superconducting volume ratio than the YBCO content. For samples with YBCO content low enough no global (the whole sample) and local (separated grains) superconductivity was observed. The observed decay of the superconductivity, lowering of the critical temperature, and the increase in number of paramagnetic centres as PST content increases are explained assuming reaction among YBCO and PST phases and possible formation of an additional ones, which did not exist in the initial powders.

Microwave absorption in carbon-doped YNi4B superconductors

“…Usually, the initial non-linear limit is ascribed to contribution of intergranular magnetisation to the total one due to intergranular current circulation. In the intermediate fields the intergranular currents vanish and the linear MðHÞ limit is observed [10]. The decline from linearity in the higher fields originates from field penetration towards the grains above the lower critical field H c1 :…”

“…The slope of the linear part of MðHÞ plot in the intermediate field range allows one to determine the percentage of the superconducting fraction: f ¼ 800pa=3 (%), where a is the slope [10]. Here, the demagnetising factors of the superconducting inclusions n and of the sample N equal to that of a sphere n ¼ N ¼ 1=3 were assumed.…”