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Implication for phase separation in an overdoped Y-Ca-Ba-Cu-O superconducting system♣

E. NAZAROVA1, A. ZALESKI2, A. ZAHARIEV1, K. BUCHKOV1,* , V. KOVACHEV1

Affiliation

  1. Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
  2. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw, Poland

Abstract

A series of polycrystalline, oxygenated Y1-x CaxBa2 Cu 3O 7-δ (x=0; 0.025; 0.05; 0.1 and 0.2) samples is investigated by XRD and magnetic measurements. It is established that increasing Ca content leads to T c suppression, thus supporting the sample overdoping. The width of magnetization loops (ΔM(H) T=const) is reduced. However ΔM(H)T=const is a measure of the intragranular critical current in a magnetic field. Its suppression may indicate a decrease in the pinning ability of the material and/or the quality of the superconducting condensate. The main pinning centers in Y1-xCaxBa 2Cu3 O 7-δ are the oxygen vacancies, but their amount increases with x. Therefore, ΔM(H) T=const reduction suggests that phase separation appeares and the number of Cooper pairs decreases when the overdoping is stronger. This assumption is also supported by an observed degradation of the Meissner volume fraction with increasing carrier concentration, which obviously excludes the role of the magnetic field..

Keywords

Y(Ca)BCO, Overdoping, Hysteresis, Phase separation.

Submitted at: Nov. 5, 2008
Accepted at: Oct. 3, 2009

Citation

E. NAZAROVA, A. ZALESKI, A. ZAHARIEV, K. BUCHKOV, V. KOVACHEV, Implication for phase separation in an overdoped Y-Ca-Ba-Cu-O superconducting system♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 10, pp. 1545-1548 (2009)