Exchange bias in Co-Cr2O3 nanocomposites

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.