Reduction of grain size and ordering temperature in L10 FePt thin films

Single-layer polycrystalline Fe₅₂Pt₄₈ alloy thin films were deposited on preheated natural-oxidized (100) silicon wafer b y conventional sputtering method at room temperature. The as-deposited films are soft fcc FePt phase. After suitable temperature annealing and furnace cooling, the as-deposited films are transformed from disordered soft fcc FePt phase into ordered fct L1₀ FePt phase. The ordering temperature of L1₀ FePt phase could be reduced to about 350°C by preheating substrate to 300°C followed by furnace cooling treatment. The grain size of FePt was found to decrease as the ordering temperature of L1₀ FePt phase was reduced. After annealing at 350°C for 1 h, the in-plane coercivity (H_c´´) of the 100-nm Fe₅₂Pt₄₈ alloy thin film is about 6 kOe, and the average grain size is about 6 nm.