Magnetic properties of FePt and FePt–Al₂O₃ granular films by post annealing

FePt and FePt–Al₂O₃ alloy thin films were prepared by rf magnetron sputtering system, then post annealed in vacuum. The as-deposited films were in disordered state and the ordered L1₀ structure was obtained by post annealing. The temperature for L1₀ structure of FePt and FePt–Al₂O₃ films was about 400 and 550 °C, respectively. The effect of film thickness on magnetic properties was studied. The coercivity decreased rapidly from 8 to 1.5 kOe at the thickness below 10 nm for the FePt L1₀ films. The decrease of coercivity is due the diffusion and compositional deviation. The surface roughness is as low as 0.3 nm for FePt–Al₂O₃ films with coercivity of about 3.3 kOe. © 2003 American Institute of Physics.