AC SUSCEPTIBILITY OF A PARAMAGNETIC MEISSNER EFFECT SAMPLE

The dynamic magnetic properties of a granular Bi2Sr2CaCu2O8 sample tha t displays the paramagnetic Meissner effect have been studied by low f ield ac susceptibility measurements. The frequency and field dependenc e of the in-phase and out-of-phase components of the susceptibility sh ow a spontaneous creation of an increasing number of microscopically g iant magnetic moments in the sample with decreasing temperature below T-c. The magnetic response of the sample can be explained by a superpo sition of shielding and flux expulsion from individual grains and a po larisation of spontaneous moments by the applied magnetic field. The p olarisation mechanism is the thermal activation over energy barriers s eparating the up and down directions of the magnetic moments. From our experimental data, the size of the thermally active magnetic moments is estimated to be 10(7)-10(8) mu(B). (C) 1998 Elsevier Science B.V.