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 t(_Pt) 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 P_t(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 t_Pt 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.