The effects of Co-metal clusters on exchange bias for Co-doped NiO/FeNi bilayers

Co-doped NiO inhomogeneous films were synthesized by sputtering metallic Co chips and NiO together and the exchange bias of bilayers Co-doped NiO/FeNi was investigated. When Co content was up to 25.2%, the exchange bias field HE at the room temperature increased to the maximum which was about three times compared to the undoped-bilayers. With further increase of Co content, the exchange bias field HE and blocking temperature TB decreased. Analysis suggests that the configuration of nanometer-sized Co-metal clusters enchased into NiO matrix played an important role in the change of magnetic behavior for the bilayers.