Enhancement in ordering of Fe50Pt50 film caused by Cr and Cu additives

A 100-nm-thick Fe50Pt50 film with high coercivity was fabricated by magnetron sputtering. On introducing a Cr top/bottom layer, the ordering temperature (Tor) of the film decreased considerably from 500 to 380 deg. C. On introducing both Cr top/bottom layer and a 0.2-nm-thick Cu interlayer, the Tor decreased even further to 340 deg. C. During the annealing process, the number of Cr atoms diffused into the Fe50Pt50 layer increased. This increased the Fe diffusivity, lowering the Tor in the process. The diffusion of the additive and the effects of annealing were verified by selected-area electron diffraction observations and by investigating the temperature dependence of the magnetization. The superlattice structure of the ordered Fe50Pt50 film containing Cr and Cu additives was confirmed by the transmission electronic microscopy. Because of the Cr and Cu additives, the average grain size in the ordered Fe50Pt50 film increased slightly; however, the coercivity of the ordered Fe50Pt50 film is improved considerably.