Effect of Ag Segregation on Reversal Behavior of (FePt)77 Ag23 Alloy Thin Films

Effect of Ag segregation on magnetic and structural properties of (FePt)₇₇ Ag₂₃ single-layer films were studied. Thin films were first sputtered on the heated glass substrates and cooled to room temperature, a post annealing at temperatures (Tp) from 200 degC to 400 degC for 60 min was then applied. Ll₀ structure formed as substrate temperature (T_s) equals to 600 degC and 700 degC. For those ordered films, Ag was observed to precipitate as particles on the film surface and grow with the increasing T_s. After post annealing at 400 degC for 60min, those silver particles dissolved into the film, leading to changes in reversal behavior. The optimum condition is obtained in the T_s=600degC, T_p=400degC sample. Drastic reduction in coercive squareness ratio (from >0.8 to 0.41) and enhanced coercivity (from 4.7 to 6.4 kOe) indicate the reversal behavior alters from cooperative to independent. Negative deltaM curve suggests that this independent rotation results from the reduction of exchange interactions