The effects of exchange bias on Fe-Co/MgO magnetic nanoparticles with core/shell morphology.

The effects of exchange bias on core/shell structured nanoparticles are analyzed. Nanoparticles are integrated with high moment Fe-Co crystallites covered epitaxially with MgO shells. It is observed that the coercive field H(C)(FeCo)>H(C)(Co)>H(C)(Fe); however, the exchange bias field H(E) of the Co sample is higher than that of the FeCo one, while H(E)=0 for the Fe sample. It is suggested that the exchange bias is induced by the formation of a (Co, Mg)O solid solution. In fact, we show that it is possible to modify the exchange bias properties by manipulating the level of Mg dusting at the interface, as recently reported for thin films.