Controlling the magnetic reversal mechanism of exchange biased MnxOy/Ni80Fe20 bilayers through O+ implantation
This work investigates the different magnetic reversal mechanisms of as-grown and oxygen-ion (O+) implanted MnxOy/Ni80Fe20 bilayers. A MnxOy/Ni80Fe20 bilayer was prepared by ion-beam sputter deposition in an Ar+ atmosphere using a partially oxidised Mn target. Oxygen implantations were then performed using 8 keV O+ ions at fluences of 1016, 1017 and 1018 ions/cm2 to modify the exchange bias strength at the MnxOy/Ni80Fe20 interface. The magnetic, crystallographic and chemical properties of the bilayers before and after O+ implantation were studied using transmission electron microscopy, X-ray reflectometry, magnetometry and polarised neutron reflectometry. The results show an overall improved exchange bias and coercivity for the O+ implanted bilayers. The 1017 ions/cm2 implanted sample shows the greatest improvement in exchange bias and was further studied for its detailed spin-reversal behaviour using polarised neutron reflectometry. Data analysis in the magnetically-trained state reveals a coexistence of coherent rotational and non-coherent magnetic spin reversal in the as-grown sample and a solely coherent spin rotation reversal mechanism for the O+ implanted MnxOy/Ni80Fe20 bilayer.