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(μs) at 77K and room tempreture. The samples which Cu molar ratio, X was changed from 2.5 to 3.5 in YBa Cu O7-δ were used to study Cu molar ratio dependence on μs in Cu-O chains. The samples which pelet forming pressure were varied from 400 to 800kg/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<X<3.5 indicate antiferromagnetism at room temprature. The antiferromagnetism was the strongest at X=3.0 which was most suitable composition for high-Tc superconductors and this sample showed the highest Tc end and Jc.
