Effects of Thickness Ratio of Co to Pt Layer on Magnetic Properties and Microstructure of [Co/Pt]n Multilayer Films

[Co/Pt]_n multilayer films were deposited on a glass substrate with a Pt underlayer by an alternative sputtering method. The effect of overall multilayer [CoPt]n thickness and the relative thickness of Co to Pt layers on the structural and magnetic properties were investigated. First, the thickness ratio of Co to Pt layers (Co:Pt = 4:3, 1:1, and 3:4) in [Co/Pt]n multilayer films was varied. Higher coercivity and out-of-plane squareness were found for the [Co_{1 nm}/Pt_{0.75 nm}]_n and [Co_{1 nm}/P_{t1 nm}]_n multilayer films. The total thickness of multilayers was varied from 3.5 to 8 nm. When the Co to Pt layers thickness ratio was changed to 3:4, the magnetic performance was declined. Furthermore, the thickness ratio of Co to Pt layers was kept constant to 1:1, and the Co and Pt layer thickness in [C_{ox nm}/P_{tx nm}]_n film was varied. The highest coercivity of 2.1 kOe was obtained in the [Co_0.5/Pt_0.5]₄ film. The magnetic properties were decreased with further increase in the Co and Pt layer thickness. In this paper, we demonstrated that [Co/Pt]n multilayer films with the suitable thickness ratio of Co to Pt layers are beneficial to prepare CoPt thin films with perpendicular magnetic anisotropy.