MAGNETIZATION STUDIES OF NEAR-ROOM-TEMPERATURE FLUX-TRAPPING PHENOMENON IN CUO-BASED MATERIALS

DC magnetization studies on a variety of ceramic and crystalline YBaCu O samples indicate a superconducting-like flux-trappinig behavior occu rring at similar temperatures as zero-resistance transition temperatur es observed near room temperature. The flux-trapping behavior is exemp lified by diamagnetic-like deviations from a positive magnetic backgro und in the zero-field-cooled magnetization, by a divergence between th e zero-field-cooled and field-cooled magnetization data, or by a posit ive Meissner effect in the field-cooled magnetization. These behaviors are consistent with a high-T(c) (> 250 K) superconducting phase in an inhomogeneous superconductor where the superconducting regions exist as defect structures or surface coatings and whose volume fraction is less than a few percent.