AC magnetic susceptibility measurements of Bi (Pb) – Sr – Ca- Cu- O superconductor in DC magnetic fields

Abstract

In this work a Bi based superconductor with the composition Bii.e -Pfeo.4 Srz Cai Cus Oy was prepared using sol-gel method and AC Magnetic Susceptibility measurements \'(T) and x"(T) were carried out on the sample in the temperature range from 4-2 K to 120 K in both zero and applied dc magnetic fields. The ac Hartshorn bridge was used to measure the ac susceptibility of the sample. From x '(T) data in zero field the onset superconducting transition temperature of the sample was found to be 107.5 K. A single drop in the x'(T) data suggests that the sample has only one superconducting phase which is identified as Bi-2223. A small kink was observed in the x'(T) at a temperature of 105.6 K due to the weak link coupling between the superconducting grains. The X"(T) data in zero dc field shows an intergrain peak at a temperature of 100 K indicating that the maximum energy dissipation and the penetration of the ac field and the shielding current into the center of the sample take place at this temperature. In the dc applied magnetic fileds the x'(T) and the \"(T) data show broad transitions and broad peaks respectively indicating that the magnetic fields suppressed superconductivity of the sample. The intergrain peaks in x"(T) were found to shift to low temperatures with incrasing dc magnetic fields. In low dc magnetic fields two drops were observed in \'(T) data which are attributed to the superconducting grains and the weak links in the sample. In high magnetic field x '(T) data shows only one single drop suggesting that the magnetic filed simultaneously penetrated into the superconducting grains and the weak links. The high magnetic fields also shifted the superconducting transition temperature of the sample to lower temperatures.