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 ∼6 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.