Field-cooling dependence of exchange bias in a granular system of Fe nanoparticles embedded in an Fe oxide matrix

The exchange bias properties of a granular system composed of Fe nanoparticles (mean size similar to6 nm) embedded in an Fe oxide matrix have been studied. The effect of the cooling field on the exchange field, coercivity and remanent magnetization at T=5 K has been investigated. The observed variations are explained in terms of interfacial exchange coupling between a ferromagnetic phase (the Fe particles) and a disordered magnetic phase (the oxide matrix), whose spin configuration is strongly affected by the cooling field.