Effect of composition on L10 ordering in FePt and FePtCu thin films

FePt and FePtCu thin films with a fixed thickness of 50 nm have been prepared by magnetron Sputtering. The atomic ratio of Fe to Pt atoms was accurately controlled by dc co-sputtering. After vacuum annealing for 20 min at 350 degrees C, a coercive force of about 605 kA m(-1) is obtained in the Fe52Pt48 thin films with an ordering parameter around 0.87. The ordering parameter of the L1(0) phase is not enhanced by the addition of Cu to Fe52Pt48 films. On the contrary, the ordering process is improved by the addition of Cu to the Pt-rich or stoichiometric thin films. To keep the ordering of FePt films at a low annealing temperature, the lower the Fe content, the more addition of Cu is needed. It is found that the L 10 phase can be obtained after annealing at 350 degrees C for 20 min only for films with the ratio of (FeCu) to Pt being in the range of 1.1-1.2.