Fish-Tail effect and irreversibility field of (Cu,C)Ba2Ca3Cu4O x -(LiF) y superconductor

Abstract

Addition of (LiF) y≤0.15 , and of proper amount of (AgO) z=0.45-0.8 as oxidizing agent, to (Cu,C)Ba 2 Ca 3 Cu 4 O 10+δ superconductor is useful to control and to shift the doping characteristics (hole density and distribution, and level of disorder) into the region where the irreversible properties, i.e. fish-tail effect (FTE) and irreversibility field H irr are improved. Among notable effects are the development of the second magnetization peak with a higher amplitude J c, max and the enhancement of H irr at high temperatures, above a certain value T * which depends on both y LiF and z AgO . The best results are obtained for the sample with y LiF =0.1 and z AgO =0.73. This sample preserves its single phase Cu,C-1234 composition. The influence on the FTE and H irr of the interplay between doping characteristics, controlled by LiF and AgO content, is discussed.