  The ceramic pellets of the nominal compositions
Bi$_{0.7}$Ba$_{0.3}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.00-0.20) were prepared
initially by standard solid state reaction technique. The pellets were then
ground into micrometer-sized powders and mixed with isopropanol in an
ultrasonic bath to prepare nanoparticles. The X-ray diffraction patterns
demonstrate the presence of a significant number of impurity phases in bulk
powder materials. Interestingly, these secondary phases were completely removed
due to the sonication of these bulk powder materials for 60 minutes. The field
and temperature dependent magnetization measurements exhibited significant
difference between the magnetic properties of the bulk materials and their
corresponding nanoparticles. We anticipate that the large difference in the
magnetic behavior may be associated with the presence and absence of secondary
impurity phases in the bulk materials and their corresponding nanoparticles,
respectively. The leakage current density of the bulk materials was also found
to suppress in the ultrasonically prepared nanoparticles compared to that of
bulk counterparts.
