ANOMALOUS MAGNETIZATION OF MELT-GROWN SMBA2CU3O7-DELTA

A single grain chosen from a melt-grown SmBa2Cu3O7-delta sample was gr ound into a cylinder 4 mm long and 1.5 mm in diameter with the c-axis of the grain perpendicular to the axis of the cylinder. Magnetization curves show a peak at intermediate fields. This phenomenon has been at tributed to field induced pinning by weak superconducting oxygen defic ient regions. The temperature and angular dependence of the field, H(m ax), at which a peak occurs in the M-H loops was measured in a vibrati ng sample magnetometer. H(max) shifts from 0.7 to 11 T at 55 K as the angle theta between the external field and the c-axis varies from 0 to 90-degrees. As expected from the field induced pinning model, we foun d that the field at which all weak regions become normal has the same angular dependence as that for H(c2) in anisotropic superconductors.