Low-temperature ordering and enhanced coercivity of L1-FePt thin film promoted by a Bi underlayer

Abstract

We have studied L10-FePt thin films with a Bi underlayer. Experimental results show that the ordering temperature of the L10-FePt film can be lowered down to 300–350°C and the in-plane coercivity HC of the film is obviously enhanced by introduction of a Bi underlayer. After annealing at 400°C for 20min, a Bi∕FePt film realizes a HC of 13.5kOe and the ratio of the remnant magnetization Mr to the saturation one MS of as high as 0.93. The reduction of the ordering temperature and the enhanced magnetic properties of L10-FePt films can be understood by considering the large diffusivities of Fe and Pt associated with Bi diffusion.