Enhanced Perpendicular Magnetic Anisotropy of Co-Rich Type Co–Pt Film by Inserting Pt Underlayer

The Co-rich type Co-Pt alloy thin films were deposited on various thicknesses of Pt underlayer (tPt) on glass substrates at room temperature. It was observed that the magnetic properties, microstructures, and phase structures of Co-Pt films were significantly affected by Pt(111) underlayer. At t_Pt = 5 nm, very small Pt grains induced multiple orientations in Co-Pt films, and then showed the longitudinal magnetic anisotropy (LMA). At t_Pt = 10 nm, columnar Co-Pt grains with hcp(002) orientation grew on a single Pt(111) grain, leading c-axis to be normal to the plane. The perpendicular magnetic anisotropy (PMA) of the film was enhanced. Further increase the tPt above 20 nm, Co-Pt grains exhibited hcp(100) orientation and the LMA is dominated again. In this paper, strong relationship between microstructures and magnetic properties in Co-Pt/Pt bilayer films was observed. The enhanced PMA in the Co-Pt/Pt bilayer film at t_Pt = 10 nm is due to the existence of the column-like structure and strong hcp(002) orientations.