  The possibility of using exchange bias in ferromagnetic-antiferromagnetic
system to over come the effect of superparamagnetism in small cobalt
nanoparticles is explored. We have prepared Co-Cr2O3 nanocomposite powders
using a chemical method. It is shown that in this system the effect of
superparamagnetism in cobalt nanoparticles could be overcome. The
superparamagnetic blocking temperature of 3 nm cobalt particles has been
increased to above room temperature. The choice of Cr2O3 is vital as its TN is
higher compared to other antiferromagnetic materials used for this purpose such
as CoO. The field cooled and zero field cooled hysteresis measurements of the
samples confirm the existence of exchange bias interaction in this system.
