Magnetic hysteresis of the critical current density of polycrystalline (Bi-Pb)-Sr-Ca-Cu-O superconductors: a fingerprint of the intragranular and intergranular flux trapping

The hysteretic behavior of the superconducting critical current density J(c )(B-u) dependence under low applied magnetic fields (B-a < 50 mT) of polycr ystalline Bi1.64Pb0.36Sr2Ca2CU3Oy. samples was investigated. All the sample s were prepared from the same powder but subjected to different pressures r anging from 40 to 250 MPa before the last heat treatment. The samples were characterized by scanning electron microscopy and X-ray powder diffraction analysis. The magnetic behavior of the superconducting grains was studied b y measuring magnetization versus applied magnetic field in powder samples. The J(c)(B-a) data are discussed within the scenario of the three-level sup erconducting system. (C) 2001 Published by Elsevier Science B.V.