Oxygen implanted Ni/NiO exchange bias system: fabrication, structure and magnetic property

Ion implantation is used to build a nanometer scale anti-ferromagnetic (AFM) cluster embedded exchange bias (EB) system. Ni film with a thickness of 100 nm is deposited on the Si (100) substrate using magnetron sputtering, 140 keV O+ is chosen to implant into the Ni film to form NiO AFM clusters, of which the size is estimated by X-ray diffraction based on synchrotron radiation (SR-XRD). By measuring hysteresis loop after field-cooling, significant shifts of loop along the applied field are observed. By increasing the implantation dose up to 3 x 10(17)/cm2 and annealing samples in N2 atmosphere, we discuss the origin of EB effect observed and the size confinement effect which lowers down the Néel temperature (T(N)) of NiO cluster to below room temperature.