Exchange-coupled FeNi-X (X = CuO, NiO, and CoO) nanocomposites prepared via ball milling

Exchange-coupled magnetic nanocomposite powders were obtained by mechanically milling ferromagnetic (FM)-antiferromagnetic (AFM) powders. A shift in the field-cooled (FC) hysteresis loop and the coercivity enhancement of the FM phase ensuing from exchange bias anisotropy was observed. The blocking temperature (TB) in all composites was found to be much lower than the Neel temperature (T-N) of the AFM phases. A model based on Preisach hysteresis was used to calculate the interfacial energy between FM and AFM particles. The calculated interfacial energies were highest for FM-CoO and lowest for FM-CuO composites. These values are in good agreement with those reported for polycrystalline AFM thin films.