Paramagnetic Meissner effect in MgB2

We observed the paramagnetic Meissner effect (PME) in MgB2 pellets after cooling in low fields of less than 1 Oe. As external magnetic field increases, the paramagnetic response of the sample decreases and disappears completely at 1 Oe. Effect of gamma irradiation on magnetic properties of MgB2 has been investigated at low fields. In irradiated samples, the magnitude of the PME was found to be lower. To understand that whether this effect is of geometrical origin (so called flux compression model) or whether it is intrinsic to the material (e.g., pi-junctions), measurements were performed with two samples having different geometries. Our results showed that paramagnetic response did not change as the geometry changes. (C) 2004 Elsevier B.V. All rights reserved.