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

Abstract

The Co-rich type Co–Pt alloy thin films were deposited on various thicknesses of Pt underlayer ( $t_{\mathrm {Pt}}$ ) 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 Pt(111) underlayer. At $t_{\mathrm {Pt}} = 5$ nm, very small Pt grains induced multiple orientations in Co–Pt films, and then showed the longitudinal magnetic anisotropy (LMA). At $t_{\mathrm {Pt}} = 10$ 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 $t_{\mathrm {Pt}}$ 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 $t_{\mathrm {Pt}} = 10$ nm is due to the existence of the column-like structure and strong hcp(002) orientations.