| The multilayer films of Fe/Pt, Dy/Pt and Dy/Fe/Pt have been deposited by DC magnetron sputtering, and then the FePt Dy-Pt and Dy-FePt alloy films have been composited by annealing under high vacuum environment. The phase structure, composition, phase transformation and magnetic properties of these films were investigated by XRD, SEM, EDAX and magnetic measurement techniques. The influencing factors of magnetic properties have been also discussed in this paper.In the research of the thickness of Pt buffer-layer, it was found that: the temperature of the phase transition from disorder to order of FePt alloy films reduces obviously and the grain size decrease with the increase in thickness of Pt buffer-layer; the c/a ratio of the lattice parameter decreases and the parameter of the degree of order S increases gradually with the increasing thickness of the Pt buffer-layer. The coercivity of the samples annealed at 425℃increases from 398K at t=0nm to 523KA/m at t=8.6nm (close to the value of 500℃annealed sample), i.e. the average chang rate is 14.53kA/m/nm. On the contrary, the ordering temperature and the remnant magnetism ratio decrease.In the research of the Fe50-0.5xPt50-0.5xDyx(X=0,0.5,1.0,1.5,2.0) alloy films, it was found that: with the addition of Dy, the solid solution of FePt was formed , the lattice parameter were increased, and the average grain size of FePt alloy films with FCT structure decreases obviously because that the growth of grains was inhibited significantly with the introduction of Dy. The coercivity of films enhances with increase of Dy content, it reaches the maximum Hc=903KA/m, when the Dy concentration is increased to 1.5at.%, and then decrease. At the same time, the coercivity also increases linearly with the annealing time increasing; it reaches the maximum when the annealing time is 200 h.Researching on the Dy-Pt alloy films, it was found that: the periodic layered structures along thickness direction were observed in the as-deposited Dy/Pt films. With the annealing temperature increasing, the compounds of DyPt, DyPt2 and DyPt3 are formed successively at temperature ranging from 300℃to 350℃, where the compound DyPt3 was formed after annealing at 400℃. Then the composition reaction DyPt + DyPt3→2DyPt2 took place at 500℃, and the compounds DyPt and DyPt3 have transformed completely into the DyPt2 compound after annealing at 500℃for 1h. In the research of the Dy3Pt4 alloy films, the compound of Dy3Pt4 preferred orientation along [211] has been formed after annealing at 400℃for 1h, but it gradually decomposes to DyPt and DyPt2 after annealing at 550℃for 1h, and nearly complete decomposition after annealing at 550℃for 7 days.
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