Effect of ion irradiation on magnetic property of exchange coupled interfacial structures of Fe/NiO and NiO/Fe on Si substrates

The role of defects on the magnetic behaviour of exchange coupled interfacial structures of Fe/NiO and NiO/Fe on Si substrates has been studied. For introduction of defects in the structures, swift (～ 100 MeV) heavy ion irradiation has been used, which is known to cause structural and microstructural modifications. In our earlier study [Srivastava, N; Srivastava, P.C. J. Appl. Phys. 2012, 111, 123909] on similar structures, the significant magnetic behaviour (of exchange bias (EB) and coercivity) for Fe/NiO/nSi interfacial structure was observed and discussed in the realm of interfacial structural modification in the antiferromagnetic layer of the structure. The irradiated interfacial structures have been characterized from X-ray diffraction and M–H characteristics. Structural investigation has shown the formation of various silicide and oxide phases due to the irradiation-induced interfacial intermixing. A significant enhancement in EB field and coercivity has been observed for Fe/NiO/nSi interfacial structure on the irradiation (as compared to unirradiated ones). The observed enhanced EB and coercivity on the irradiation has been understood due to the creation of domain wall pinning centres across the interface as a result of ion irradiation. Moreover, the present study confirms the role of defects in the antiferromagnetic layer to cause the significant change in EB and coercivity. The observation supports the domain state model of EB in the exchange-coupled structures.