  We report observation of more than an order of magnitude jump in saturation
magnetization in BiFeO$_3$/Ag nanocomposite at room temperature compared to
what is observed in bare BiFeO$_3$ nanoparticles. Using transmission electron
microscopy together with energy dispersive x-ray spectra (which maps the
element concentration across the BiFeO$_3$/Ag interface) and x-ray
photoelectron spectroscopy, we show that both the observed specific
self-assembly pattern of BiFeO$_3$ and Ag nanoparticles and the charge transfer
between Ag and O are responsible for such an enormous rise in room-temperature
magnetization. The BiFeO$_3$/Ag nanocomposites, therefore, could prove to be
extremely useful for a variety of applications including biomedical.
