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 the Bi2Sr2CaCu2O8 system on the ac susceptibility. The mean grain size of the samples was determined by powder x-ray diffraction (XRD). The results showed that unlike the usual polycrystalline high-temperature superconductors, our present samples with small grain sizes displayed paramagnetism, and the paramagnetism became weaker and weaker by increasing the grain size. The peculiar paramagnetic properties of out samples was thought to be caused by the small grain size effect like other nanocrystalline materials.