Observation of Paramagnetic Meissner Effect in Niobium Disks

Abstract
For several superconducting niobium disks, the dc field-cooled magnetization (FCM) shows a paramagnetic response below their superconducting transition temperature Tc9.2K when the applied magnetic filed is normal to the disk. At 8.6 K, the FCM reaches a maximum in fields of 5 to 10 Oe and becomes diamagnetic for fields larger than 20 Oe. This FCM behavior is qualitatively similar to the paramagnetic Meissner effect (PME) recently observed in high- Tc cuprate superconductors. Various surface treatments to the Nb disks result in changes in both the zero-field-cooled magnetization and the FCM, including the disappearance of the PME.