IRREVERSIBILITY LINES OF HGBA2CUO4+DELTA WITH DIFFERENT OXYGEN CONTENTS

Single phase HgBa2CuO4+delta samples were annealed in flowing oxygen g as or in flowing argon gas. Oxygen contents of both samples determined by iodometric titrations indicate that the samples annealed in oxygen gas and in argon gas were respectively in over-doped and in under-dop ed region. Both samples were respectively grain-aligned in magnetic fi elds. Hysteresis loops for grain-aligned over-doped and under-doped sa mples were measured in applied fields parallel and perpendicular to th e c-axis. Region where irreversibility lines of over-doped sample was located was found to be higher than that of under-doped sample. Irreve rsibility line of over-doped sample was found to be higher than that o f YBa2Cu3O6.6. Anisotropy of irreversibility lines of both samples wer e found to be smaller than that of Y-123 superconductors.