CORRELATION OF GRAIN-SIZE AND AC SUSCEPTIBILITY IN THE BI2SR2CACU2O8 SYSTEM

Here we report the influence of small grain size (from 9-125 nm) of th e Bi2Sr2CaCu2O8 system on the ac susceptibility. The mean grain size o f the samples was determined by powder x-ray diffraction (XRD). The re sults showed that unlike the usual polycrystalline high-temperature su perconductors, our present samples with small grain sizes displayed pa ramagnetism, and the paramagnetism became weaker and weaker by increas ing the grain size. The peculiar paramagnetic properties of out sample s was thought to be caused by the small grain size effect like other n anocrystalline materials.