The study of microstructures and magnetic properties of Co100-xPtx and Co100-xPtx/Ag alloy thin films
Date Issued
2010
Date
2010
Author(s)
Wu, Meng-Shiuan
Abstract
The magnetic properties and microstructure of 25-nm-thick Co100-xPtx ( x = 20~70 ) alloy thin films grown on glass substrate as well as on 30~150 nm Ag under layer were investigated. These metal films were deposited by DC sputtering at a base pressure about 5×10-7 torr.
The Co-rich CoPt single-layer alloy thin film with hcp phase after annealing at 300℃ shows large hysteresis loop and better out-of-plane magnetic properties. CoPt single-layer alloy thin film with L10 phase after annealing at 700℃ shows better magnetic properties. For Pt-rich CoPt single-layer alloy thin film with fcc phase after annealing at 500℃ shows better magnetic properties.
After 300℃ post vacuum annealing, the phase of Co-rich CoPt/Ag(30~150 nm) alloy thin film will change from hcp to fcc and magnetic properties become worse than Co-rich CoPt single-layer alloy thin film. After 600℃ post vacuum annealing, CoPt/Ag(30~150 nm) alloy thin film shows L10 hard magnetic phase and out-of-plane magnetic anisotropy. The ordering temperature is 100℃lower than that of CoPt single-layer alloy thin film after inducing Ag under layer. The 700℃ annealed CoPt(25 nm)/Ag(30 nm) thin film improves magnetic properties, Hc⊥ = 16.6 kOe, Hc// = 10.5 kOe, S⊥= 0.87, and S// = 0.4 . After 700℃ post vacuum annealing, Pt-rich CoPt/Ag alloy thin film shows out-of-plane magnetic anisotropy by segregation of small Co-rich and Pt-rich CoPt grains on the grain boundary of Ag3Pt, those have the same lattice structure but different lattice parameter, and the stress of lattice mismatch breaks the symmetry of the cubic phase, so, presenting uniaxial magnetic anisotropy . The magnetic properties of 700℃ annealed Pt-rich CoPt/Ag(150 nm) alloy thin film are Hc⊥= 6.8 kOe, Hc// = 5.3 kOe, S⊥ = 0.75, and S// = 0.48 .
Subjects
magnetic properties and microstructure
Type
thesis
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