CoPt-ZnOx/ Ag複合磁記錄薄膜之顯微結構與磁性質研究

Abstract

In this study, the CoPt, CoPt/ Ag, CoPt/ ZnOx, (CoPt/ ZnOx)n, (CoPt)y-(ZnOx)1-y, and (CoPt)y-(ZnOx)1-y/ Ag films were deposited on glass substrates at room temperature by dc magnetron sputtering. The effects of Ag underlayer, ZnOx underlayer, ZnOx addition, and process parameters on the microstructure, magnetic properties, and magnetic easy axis of the film were investigated. The ordering temperature of CoPt films could be reduced from 600~700℃ to 500~600℃ as Ag underlayer was introduced. The introduction of Ag underlayer could promote the out-of-plane magnetic properties of CoPt films.The out-of-plane coercivity, in-plane coercivity, out-of-plane squareness and in-plane squareness values of Co56.42Pt43.58 (20 nm)/ Ag (30 nm) film which annealed at 700℃ for 30 minutes are 17.6 kOe, 15.4 kOe, 0.85 and 0.51, respectively. The CoPt/ ZnOx multilayer with ZnOx sputtering power density, 2.81 watt/ cm2, showed out-of-plane magnetic anisotropy after annealing at 700℃ for 30 minutes, and (CoPt/ ZnOx)3 multilayer also presented the out-of-plane magnetic anisotropy after annealing at 700℃ for 30 minutes. The ZnO target and the CoPt target were co-sputtered to form the granular CoPt films. The high ordering of (CoPt)75-(ZnOx)25 film could be obtained after annealing at 700℃ for 30 min. It suggests that ZnOx additives would leave vacancies and defects after annealing, which provides the diffusion path of Co and Pt atoms and improves the ordering of CoPt films. Finally, the 30 nm-Ag layer was introduced under the (CoPt)y-(ZnOx)1-y film and then annealed at 700℃ for 30 min. The larger out-of-plane coercivity of (CoPt)95-(ZnOx)5/ Ag film could be obtained because of the decrease of the exchange coupling. Besides, the ZnOx would precipitate at the grain boundaries of CoPt and Ag layers as the content of ZnOx additive increased to 50 vol%, which could isolate the CoPt and Ag grains and inhibit the grain growth of CoPt. ZnOx would reduce the epitaxial effect between CoPt and Ag layers and lead (CoPt)50-(ZnOx)50/ Ag film to the random orientation.