AC MAGNETIC SUSCEPTIBILITY INVESTIGATION OF THE INTERGRAIN VORTEX PINNING INVOLVING Er IONS IN BULK (Bi1.6Pb0.4)(Sr1.8Ba0.2)(Ca1-xErx)2Cu3Oy SUPERCONDUCTOR

Abstract

Bulk superconducting samples with composition ( Bi 1.6 Pb 0.4)( Sr 1.8 Ba 0.2)( Ca 1-x Er x)2 Cu 3 O y (0 ≤ x ≤ 0.02 Er ) were prepared by conventional solid-state reaction. X-ray diffraction confirmed that with increasing Er concentration, the volume fraction of 2223 phase decreases. The intergranular vortex dynamics (and the effective pinning barrier) of the bulk system have been investigated by ac susceptibility as a function of temperature, frequency and ac field amplitude. The effect of Er ion on the intergrain vortex pinning was characterized quantitatively by using a flux diffusion model in which the effective pinning barrier depends nonlinearly on the current density.