Nobuhiro Katayama

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.

C-axis oriented L10 phase FePt thin films by plasma-assisted diffusion

L10 phase FePt thin films with different crystal orientation have been prepared by deposition of Fe and Pt separately from the corresponding targets using dc magnetron sputtering and in situ substrate heating. The codiffusion of the Fe and Pt atoms are attributed by the surface bombardment from high energy ions in plasma. The transformation temperature for L10 phase FePt is as low as 250°C by this technique. The crystal orientation of the obtained FePt films with L10 structure is determined by the orientation of the initial Fe layer.