The effect of Al2O3 insertions on the thermal stability and microstructure of Co/Pt multilayers

This study systematically investigates the effect of Al2O3 insertions on the thermal stability of [Pt(1)/Al2O3(t)/Co(0.4)]3 films (unit: nm). The interdiffusion of Pt and Co was limited by inserting a thin Al2O3 at the Pt/Co interface for film after annealing. The increased perpendicular magnetic anisotropy (PMA) and decreased coercivity (Hc) were observed for the films with Al2O3 insertions after annealing at 400°C. X-ray diffraction results show that CoPt3(111) is formed. Simultaneously, oxygen from the Al2O3 insertions combined with Co to form Co oxides that strengthened the PMA. The annealed film with the Al2O3 insertions has better CoPt3(111) crystallinity, lower Hc, and higher amount of Co oxides than those without Al2O3 insertions. To meet the application requirements for magnetic tunnel junction electrodes, it is critical to maintain strong PMA during the 400°C-annealing process, which can be achieved by inserting Al2O3 between the [Pt/Co]n multilayers.