Exchange bias in Co-Cr2O3 nanocomposites

The possibility of using exchange bias in a ferromagnetic-antiferromagnetic system to overcome the effect of superparamagnetism in small ferromagnetic nanoparticles is explored. We have prepared Co-Cr2O3 nanocomposite powders using a chemical method and shown that the effect of superparamagnetism in cobalt nanoparticles could be overcome using exchange bias between Co and Cr2O3. The superparamagnetic blocking temperature of 3 nm cobalt particles has been increased to above room temperature. The choice of Cr2O3 is vital as its T-N 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. (c) 2007 American Institute of Physics.