Magnetic permeability and antiferromagnetism of YBCO superconductors.

Abstract

It is wellknown that Cu-O chains indicate superexchange interaction which is the origin of antiferromagnetism. YBCO perovskite has the chains which also originates high-Tc superconductivity. So we focused to the magnetism of superconducting samples at normal conductivity state and cleared the correlation between the antiferromagnetism and the high-Tc superconductivity. To investigate the antiferromagnetism, the experiments were carried out by measuring the relative magnetic permeability at 77K and room temperature. The samples which Cu molar ration, X was changed from 2.5 to 3.5 in Y Ba Cu O7-8 were used to study Cu molar ratio dependence on mu, in Cu-O chains. The samples which pelet forming pressure were varied from 400 to 800 kg/cm2 were used in this study. Perfect diamagnetism was observed in each sample at 77K, except sample of X=2.5 which showed a value of about 1. The samples of 2.8