Oxygen-stoichiometry-dependent microstructural and magnetic properties of CoPt thin films capped with ion-beam-assisted deposited TiOx layers

► CoPt/TiOx bilayers exhibited different microstructures as the oxygen content varied. ► Highest coercivity of 405 Oe was observed with 30% O2/Ar ratio during IBAD. ► The L10 phase CoPt growth can be enhanced by optimizing the O2 ratio during IBAD.