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 Mn_xO_y/Ni₈₀Fe₂₀ bilayers. A Mn_xO_y/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 Mn_xO_y/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 Mn_xO_y/Ni₈₀Fe₂₀ bilayer.