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.